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Convert nethost to C - #129828

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elinor-fung merged 12 commits into
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elinor-fung:nethost-to-c
Jul 2, 2026
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Convert nethost to C#129828
elinor-fung merged 12 commits into
dotnet:mainfrom
elinor-fung:nethost-to-c

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@elinor-fungelinor-fung commented Jun 25, 2026•
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Convert nethost to C. This builds on #128420 and #129480 to fully convert nethost so it compiles and links as C-only — no C++ runtime dependency.

cc @dotnet/appmodel @AaronRobinsonMSFT

  • pal
    • Add a C pal_get_loaded_library (look up an already-loaded library without loading it). The C++ pal::get_loaded_library now delegates to it.
  • fxr_resolver
    • Convert the last C++-only piece, try_get_existing_fxr, to C.
    • Remove the thin C++ wrappers in fxr_resolver.cpp
    • Move load_fxr_and_get_delegate (used by comhost and ijwhost) into its own header load_fxr_and_get_delegate.h
  • nethost
    • Replace nethost.cpp with nethost.c using the shared host bits that have been converted to C. The RAII error_writer_scope_t is replaced by manual save/restore of the error writer.
  • Build
    • Split hostmisc into C/C++ sources and add a C-only hostmisc_c object library

linux x64 Release

BinaryBaselinePRΔ bytesΔ %
libnethost.a2,743,470532,650-2,210,820-80.6%
libnethost.so43,37635,072-8,304-19.1%

macOS arm64 Release

BinaryBaselinePRΔ bytesΔ %
libnethost.a1,097,312268,360−828,952−75.5%
libnethost.dylib92,36889,088−3,280−3.6%

windows x64 Release

BinaryBaselinePRΔ bytesΔ %
libnethost.lib2,951,1761,677,420−1,273,756−43.2%
nethost.dll71,16856,832−14,336−20.1%

Note

This PR description was drafted by GitHub Copilot.

elinor-fungand others added 5 commits June 23, 2026 14:51
@elinor-fung
Add C pal_get_loaded_library
2340343
Add a C implementation of looking up an already-loaded library in the
current process, so callers that need to reuse an existing hostfxr (e.g.
nethost) can do so without the C++ pal:: surface.
- Add a pal_dll_t typedef and pal_get_loaded_library declaration in pal.h.
- Implement pal_get_loaded_library in pal.unix.c (dlopen RTLD_NOLOAD,
dladdr to resolve the path, and the /proc/self/maps fallback) and
pal.windows.c (GetModuleHandleW + a shared get_module_file_name helper
factored out of pal_get_own_executable_path).
- Repoint the C++ pal::get_loaded_library wrappers at the new C function,
removing the old C++ implementations and the proc-maps helper.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Convert fxr_resolver_try_get_existing_fxr to C
ec86642
Now that pal_get_loaded_library is available in C, move the last
fxr_resolver function that was still C++-only into fxr_resolver.c.
Add fxr_resolver_try_get_existing_fxr (declaration in fxr_resolver.h,
implementation in fxr_resolver.c) and make the C++
fxr_resolver::try_get_existing_fxr wrapper delegate to it. Drop the file
comment noting that try_get_existing_fxr had to stay in C++.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Convert nethost to C
61fde33
Rewrite nethost.cpp as nethost.c using the C host APIs: trace_* for
tracing, fxr_resolver_try_get_existing_fxr / try_get_path_from_dotnet_root
/ try_get_path for resolution, and utils_get_directory. The RAII
error_writer_scope_t is replaced by saving and restoring the previous
error writer manually around the call, and pal::string_t buffers become
manually-managed pal_char_t* allocations.
Update nethost/CMakeLists.txt to build nethost.c. The compiled nethost
code is now C-only.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Remove the C++ fxr_resolver wrappers
190e36a
fxr_resolver.cpp held thin C++ wrappers (marshalling pal::string_t to and
from the pal_char_t* C API) over the fxr_resolver_* functions in
fxr_resolver.c. Remove them and have the remaining C++ callers use the C
API directly:
- hostfxr_resolver.cpp uses fxr_search_location and fxr_resolver_try_get_path
directly (with direct utils.h/error_codes.h includes that were previously
pulled in transitively through fxr_resolver.h).
- The load_fxr_and_get_delegate template (used by ijwhost and comhost) moves
to its own header, load_fxr_and_get_delegate.h, and calls the C resolver
functions. Its fxr handle is typed as pal_dll_t.
fxr_resolver.h is now a pure C header and fxr_resolver is C-only (no
fxr_resolver.cpp), which also drops it from the static singlefilehost
sources.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Link nethost against a C-only hostmisc
9189c4b
nethost's own code is C, and after the previous change fxr_resolver is
C-only too, but nethost still linked the full hostmisc (which includes C++
translation units). That gave the nethost targets a C++ linker language, so
the clang++ driver added a dependency on the C++ runtime (libc++) and
libnethost.a embedded the unused C++ objects.
Split the hostmisc sources into C_SOURCES/CXX_SOURCES and add hostmisc_c, an
object library built from just the C sources. hostmisc and hostmisc::public
are unchanged for the C++ consumers (apphost, hostfxr, hostpolicy, etc.).
Point nethost/libnethost at hostmisc_c (+ minipal_objects, which object
libraries don't propagate transitively). The nethost targets now compile no
C++, link with the C driver, and have no libc++ dependency; libnethost.a
shrinks substantially by dropping the embedded C++ objects.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
CopilotAI review requested due to automatic review settings June 25, 2026 00:06
CopilotAI reviewed Jun 25, 2026
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Pull request overview

This PR completes the nethost conversion to C-only by rewriting nethost in C, moving remaining fxr_resolver functionality to the C surface, and adding a C PAL helper to detect an already-loaded hostfxr without introducing a C++ runtime dependency.

Changes:

  • Replaced nethost.cpp with nethost.c, switching to the C host APIs and manually saving/restoring the trace error writer.
  • Added C pal_get_loaded_library (and pal_dll_t) and routed the existing C++ pal::get_loaded_library through it.
  • Removed fxr_resolver.cpp and moved the delegate-loading template to load_fxr_and_get_delegate.h; updated C++ callers to use the C fxr_resolver_* APIs directly.
Show a summary per file
FileDescription
src/native/corehost/nethost/nethost.cppRemoved C++ implementation of get_hostfxr_path.
src/native/corehost/nethost/nethost.cNew C implementation of get_hostfxr_path using C host APIs.
src/native/corehost/nethost/CMakeLists.txtSwitched nethost sources to C and updated link deps to hostmisc_c.
src/native/corehost/load_fxr_and_get_delegate.hNew header containing the load_fxr_and_get_delegate C++ template previously in fxr_resolver.h.
src/native/corehost/ijwhost/ijwhost.cppUpdated include to use load_fxr_and_get_delegate.h.
src/native/corehost/comhost/comhost.cppUpdated include to use load_fxr_and_get_delegate.h.
src/native/corehost/hostmisc/pal.hAdded pal_dll_t and the C pal_get_loaded_library declaration.
src/native/corehost/hostmisc/pal.windows.cAdded pal_get_loaded_library implementation and refactored module-path helper.
src/native/corehost/hostmisc/pal.windows.cppC++ pal::get_loaded_library now delegates to pal_get_loaded_library.
src/native/corehost/hostmisc/pal.unix.cAdded pal_get_loaded_library implementation (dlopen RTLD_NOLOAD + dladdr, with /proc/self/maps fallback).
src/native/corehost/hostmisc/pal.unix.cppC++ pal::get_loaded_library now delegates to pal_get_loaded_library.
src/native/corehost/hostmisc/CMakeLists.txtSplit hostmisc C vs C++ sources and introduced hostmisc_c object library.
src/native/corehost/fxr_resolver.hRemoved C++ wrapper surface; added C fxr_resolver_try_get_existing_fxr.
src/native/corehost/fxr_resolver.cppRemoved thin C++ wrapper implementation.
src/native/corehost/fxr_resolver.cAdded C implementation of fxr_resolver_try_get_existing_fxr.
src/native/corehost/CMakeLists.txtUpdated fxr_resolver interface target to stop compiling fxr_resolver.cpp.
src/native/corehost/apphost/static/CMakeLists.txtDropped ../../fxr_resolver.cpp from sources.
src/native/corehost/apphost/standalone/hostfxr_resolver.cppSwitched from C++ wrappers to C fxr_resolver_try_get_path API.
src/installer/managed/Microsoft.NET.HostModel/AppHost/HostWriter.csUpdated comment to match renamed enum reference (fxr_search_location).

Copilot's findings

  • Files reviewed: 19/19 changed files
  • Comments generated: 4

Comment threadsrc/native/corehost/nethost/nethost.c
Comment threadsrc/native/corehost/hostmisc/pal.unix.c
Comment threadsrc/native/corehost/fxr_resolver.c Outdated
Comment threadsrc/native/corehost/fxr_resolver.c
@elinor-fung
Address PR review feedback
a525dd7
- nethost.c: use %zu (not %d) for the size_t in the invalid-size trace.
- pal.unix.c: bound the /proc/self/maps %s read with an explicit field
width so a pathological line can't overflow the buffer.
- fxr_resolver.c: initialize *out_fxr in fxr_resolver_try_get_existing_fxr,
and drop the stale fxr_resolver.cpp reference from the file comment.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
This was referenced Jun 25, 2026
Open
Closed
@elinor-fung
elinor-fung marked this pull request as ready for review June 25, 2026 20:16
CopilotAI review requested due to automatic review settings June 25, 2026 20:16
@elinor-fung
Drop single-field find_max_version_context_t wrapper
3ce2f43
It only held a c_fx_ver_t, so pass the c_fx_ver_t directly as the
pal_readdir_onlydirectories context instead of wrapping it.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
CopilotAI reviewed Jun 25, 2026
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Copilot's findings

  • Files reviewed: 19/19 changed files
  • Comments generated: 0 new

CopilotAI review requested due to automatic review settings June 25, 2026 20:26
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Copilot's findings

  • Files reviewed: 19/19 changed files
  • Comments generated: 1

Comment threadsrc/native/corehost/hostmisc/pal.unix.c
@elinor-fung
Potential fix for pull request finding
9179007
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
CopilotAI review requested due to automatic review settings June 25, 2026 20:38
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Copilot's findings

  • Files reviewed: 19/19 changed files
  • Comments generated: 1

Comment threadsrc/native/corehost/nethost/CMakeLists.txt
@build-analysisbuild-analysisBot mentioned this pull request Jun 26, 2026
Closed
AaronRobinsonMSFT
AaronRobinsonMSFT reviewed Jun 30, 2026
View reviewed changes
Comment threadsrc/native/corehost/apphost/standalone/hostfxr_resolver.cpp Outdated
Comment threadsrc/native/corehost/hostmisc/pal.unix.c
Comment threadsrc/native/corehost/nethost/nethost.c Outdated
Comment threadsrc/native/corehost/nethost/nethost.c Outdated
@elinor-fung@AaronRobinsonMSFT
Apply suggestions from code review
c6e1062
Co-authored-by: Aaron R Robinson <arobins@microsoft.com>
CopilotAI review requested due to automatic review settings June 30, 2026 15:27
@elinor-fung
Scope hostfxr_resolver raw path pointers to their lifetime
129203b
In hostfxr_resolver_t's constructor, wrap the dotnet_root/fxr_path raw
pointers in a block so they go out of scope right after they are freed,
preventing later dangling-pointer use. The rest of the constructor only
needs the resolved flag and the assigned members.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Copilot's findings

  • Files reviewed: 19/19 changed files
  • Comments generated: 0 new

CopilotAI review requested due to automatic review settings June 30, 2026 15:35
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Copilot's findings

  • Files reviewed: 19/19 changed files
  • Comments generated: 2

Comment threadsrc/native/corehost/load_fxr_and_get_delegate.h
Comment threadsrc/native/corehost/fxr_resolver.h Outdated
@elinor-fung
Potential fix for pull request finding
0a52486
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
CopilotAI review requested due to automatic review settings July 1, 2026 20:06
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Copilot's findings

  • Files reviewed: 19/19 changed files
  • Comments generated: 1

Comment threadsrc/native/corehost/load_fxr_and_get_delegate.h
AaronRobinsonMSFT
AaronRobinsonMSFT reviewed Jul 1, 2026
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Comment threadsrc/native/corehost/load_fxr_and_get_delegate.h Outdated
@elinor-fung@AaronRobinsonMSFT
Apply suggestions from code review
c6f2953
Co-authored-by: Aaron R Robinson <arobins@microsoft.com>
Co-authored-by: Elinor Fung <elfung@microsoft.com>
CopilotAI review requested due to automatic review settings July 1, 2026 22:48
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Copilot's findings

  • Files reviewed: 19/19 changed files
  • Comments generated: 0 new

This was referenced Jul 2, 2026
Open
Closed
@elinor-fung
elinor-fung merged commit ad0692a into dotnet:mainJul 2, 2026
173 checks passed
@elinor-fung
elinor-fung deleted the nethost-to-c branch July 2, 2026 17:13
@dotnet-maestrodotnet-maestroBot mentioned this pull request Jul 3, 2026
Merged
@dotnet-milestone-botdotnet-milestone-botBot added this to the 11.0-preview7 milestone Jul 3, 2026
eiriktsarpalis pushed a commit that referenced this pull request Jul 15, 2026
@elinor-fung
@AaronRobinsonMSFT@eiriktsarpalis
Convert nethost to C (#129828)
6c8fdf9
Convert `nethost` to C. This builds on #128420 and #129480 to fully
convert `nethost` so it compiles and links as C-only — no C++ runtime
dependency.
- **pal**
- Add a C `pal_get_loaded_library` (look up an already-loaded library
without loading it). The C++ `pal::get_loaded_library` now delegates to
it.
- **fxr_resolver** - Convert the last C++-only piece, `try_get_existing_fxr`, to C.
- Remove the thin C++ wrappers in `fxr_resolver.cpp`
- Move `load_fxr_and_get_delegate` (used by `comhost` and `ijwhost`)
into its own header `load_fxr_and_get_delegate.h`
- **nethost**
- Replace `nethost.cpp` with `nethost.c` using the shared host bits that
have been converted to C. The RAII `error_writer_scope_t` is replaced by
manual save/restore of the error writer.
- **Build**
- Split `hostmisc` into C/C++ sources and add a C-only `hostmisc_c`
object library
**linux x64 Release**
| Binary | Baseline | PR | Δ bytes | Δ % |
|---|---|---|---|---|
| `libnethost.a` | 2,743,470 | 532,650 | -2,210,820 | -80.6% |
| `libnethost.so` | 43,376 | 35,072 | -8,304 | -19.1% |
**macOS arm64 Release**
| Binary | Baseline | PR | Δ bytes | Δ % |
|---|---:|---:|---:|---:|
| `libnethost.a` | 1,097,312 | 268,360 | −828,952 | −75.5% |
| `libnethost.dylib` | 92,368 | 89,088 | −3,280 | −3.6% |
**windows x64 Release**
| Binary | Baseline | PR | Δ bytes | Δ % |
|---|--:|--:|--:|--:|
| `libnethost.lib` | 2,951,176 | 1,677,420 | −1,273,756 | −43.2% |
| `nethost.dll` | 71,168 | 56,832 | −14,336 | −20.1% |
---------
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Aaron R Robinson <arobins@microsoft.com>
@github-actionsgithub-actionsBot locked and limited conversation to collaborators Aug 3, 2026
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Status: Done

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Convert nethost to C by elinor-fung · Pull Request #129828 · dotnet/runtime · GitHub
Skip to content
Convert nethost to C - #129828
Merged
elinor-fung merged 12 commits into
dotnet:mainfrom 
elinor-fung:nethost-to-c
Jul 2, 2026
Merged
Convert nethost to C#129828
elinor-fung merged 12 commits into
dotnet:mainfrom 
elinor-fung:nethost-to-c
Conversation
@elinor-fung
@elinor-fungelinor-fung
commented
Jun 25, 2026•

edited

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Convert nethost to C. This builds on #128420 and #129480 to fully convert nethost so it compiles and links as C-only — no C++ runtime dependency.
cc @dotnet/appmodel @AaronRobinsonMSFT
  • pal
    • Add a C pal_get_loaded_library (look up an already-loaded library without loading it). The C++ pal::get_loaded_library now delegates to it.
  • fxr_resolver
    • Convert the last C++-only piece, try_get_existing_fxr, to C.
    • Remove the thin C++ wrappers in fxr_resolver.cpp
    • Move load_fxr_and_get_delegate (used by comhost and ijwhost) into its own header load_fxr_and_get_delegate.h
  • nethost
    • Replace nethost.cpp with nethost.c using the shared host bits that have been converted to C. The RAII error_writer_scope_t is replaced by manual save/restore of the error writer.
  • Build
    • Split hostmisc into C/C++ sources and add a C-only hostmisc_c object library
linux x64 Release
BinaryBaselinePRΔ bytesΔ %
libnethost.a2,743,470532,650-2,210,820-80.6%
libnethost.so43,37635,072-8,304-19.1%
macOS arm64 Release
BinaryBaselinePRΔ bytesΔ %
libnethost.a1,097,312268,360−828,952−75.5%
libnethost.dylib92,36889,088−3,280−3.6%
windows x64 Release
BinaryBaselinePRΔ bytesΔ %
libnethost.lib2,951,1761,677,420−1,273,756−43.2%
nethost.dll71,16856,832−14,336−20.1%
Note
This PR description was drafted by GitHub Copilot.
elinor-fungand others
added 5 commits
June 23, 2026 14:51
@elinor-fung
Add C pal_get_loaded_library
2340343
Add a C implementation of looking up an already-loaded library in the
current process, so callers that need to reuse an existing hostfxr (e.g.
nethost) can do so without the C++ pal:: surface.
- Add a pal_dll_t typedef and pal_get_loaded_library declaration in pal.h.
- Implement pal_get_loaded_library in pal.unix.c (dlopen RTLD_NOLOAD,
dladdr to resolve the path, and the /proc/self/maps fallback) and
pal.windows.c (GetModuleHandleW + a shared get_module_file_name helper
factored out of pal_get_own_executable_path).
- Repoint the C++ pal::get_loaded_library wrappers at the new C function,
removing the old C++ implementations and the proc-maps helper.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Convert fxr_resolver_try_get_existing_fxr to C
ec86642
Now that pal_get_loaded_library is available in C, move the last
fxr_resolver function that was still C++-only into fxr_resolver.c.
Add fxr_resolver_try_get_existing_fxr (declaration in fxr_resolver.h,
implementation in fxr_resolver.c) and make the C++
fxr_resolver::try_get_existing_fxr wrapper delegate to it. Drop the file
comment noting that try_get_existing_fxr had to stay in C++.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Convert nethost to C
61fde33
Rewrite nethost.cpp as nethost.c using the C host APIs: trace_* for
tracing, fxr_resolver_try_get_existing_fxr / try_get_path_from_dotnet_root
/ try_get_path for resolution, and utils_get_directory. The RAII
error_writer_scope_t is replaced by saving and restoring the previous
error writer manually around the call, and pal::string_t buffers become
manually-managed pal_char_t* allocations.
Update nethost/CMakeLists.txt to build nethost.c. The compiled nethost
code is now C-only.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Remove the C++ fxr_resolver wrappers
190e36a
fxr_resolver.cpp held thin C++ wrappers (marshalling pal::string_t to and
from the pal_char_t* C API) over the fxr_resolver_* functions in
fxr_resolver.c. Remove them and have the remaining C++ callers use the C
API directly:
- hostfxr_resolver.cpp uses fxr_search_location and fxr_resolver_try_get_path
directly (with direct utils.h/error_codes.h includes that were previously
pulled in transitively through fxr_resolver.h).
- The load_fxr_and_get_delegate template (used by ijwhost and comhost) moves
to its own header, load_fxr_and_get_delegate.h, and calls the C resolver
functions. Its fxr handle is typed as pal_dll_t.
fxr_resolver.h is now a pure C header and fxr_resolver is C-only (no
fxr_resolver.cpp), which also drops it from the static singlefilehost
sources.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Link nethost against a C-only hostmisc
9189c4b
nethost's own code is C, and after the previous change fxr_resolver is
C-only too, but nethost still linked the full hostmisc (which includes C++
translation units). That gave the nethost targets a C++ linker language, so
the clang++ driver added a dependency on the C++ runtime (libc++) and
libnethost.a embedded the unused C++ objects.
Split the hostmisc sources into C_SOURCES/CXX_SOURCES and add hostmisc_c, an
object library built from just the C sources. hostmisc and hostmisc::public
are unchanged for the C++ consumers (apphost, hostfxr, hostpolicy, etc.).
Point nethost/libnethost at hostmisc_c (+ minipal_objects, which object
libraries don't propagate transitively). The nethost targets now compile no
C++, link with the C driver, and have no libc++ dependency; libnethost.a
shrinks substantially by dropping the embedded C++ objects.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Pull request overview
This PR completes the nethost conversion to C-only by rewriting nethost in C, moving remaining fxr_resolver functionality to the C surface, and adding a C PAL helper to detect an already-loaded hostfxr without introducing a C++ runtime dependency.
Changes:
  • Replaced nethost.cpp with nethost.c, switching to the C host APIs and manually saving/restoring the trace error writer.
  • Added C pal_get_loaded_library (and pal_dll_t) and routed the existing C++ pal::get_loaded_library through it.
  • Removed fxr_resolver.cpp and moved the delegate-loading template to load_fxr_and_get_delegate.h; updated C++ callers to use the C fxr_resolver_* APIs directly.
Show a summary per file
FileDescription
src/native/corehost/nethost/nethost.cppRemoved C++ implementation of get_hostfxr_path.
src/native/corehost/nethost/nethost.cNew C implementation of get_hostfxr_path using C host APIs.
src/native/corehost/nethost/CMakeLists.txtSwitched nethost sources to C and updated link deps to hostmisc_c.
src/native/corehost/load_fxr_and_get_delegate.hNew header containing the load_fxr_and_get_delegate C++ template previously in fxr_resolver.h.
src/native/corehost/ijwhost/ijwhost.cppUpdated include to use load_fxr_and_get_delegate.h.
src/native/corehost/comhost/comhost.cppUpdated include to use load_fxr_and_get_delegate.h.
src/native/corehost/hostmisc/pal.hAdded pal_dll_t and the C pal_get_loaded_library declaration.
src/native/corehost/hostmisc/pal.windows.cAdded pal_get_loaded_library implementation and refactored module-path helper.
src/native/corehost/hostmisc/pal.windows.cppC++ pal::get_loaded_library now delegates to pal_get_loaded_library.
src/native/corehost/hostmisc/pal.unix.cAdded pal_get_loaded_library implementation (dlopen RTLD_NOLOAD + dladdr, with /proc/self/maps fallback).
src/native/corehost/hostmisc/pal.unix.cppC++ pal::get_loaded_library now delegates to pal_get_loaded_library.
src/native/corehost/hostmisc/CMakeLists.txtSplit hostmisc C vs C++ sources and introduced hostmisc_c object library.
src/native/corehost/fxr_resolver.hRemoved C++ wrapper surface; added C fxr_resolver_try_get_existing_fxr.
src/native/corehost/fxr_resolver.cppRemoved thin C++ wrapper implementation.
src/native/corehost/fxr_resolver.cAdded C implementation of fxr_resolver_try_get_existing_fxr.
src/native/corehost/CMakeLists.txtUpdated fxr_resolver interface target to stop compiling fxr_resolver.cpp.
src/native/corehost/apphost/static/CMakeLists.txtDropped ../../fxr_resolver.cpp from sources.
src/native/corehost/apphost/standalone/hostfxr_resolver.cppSwitched from C++ wrappers to C fxr_resolver_try_get_path API.
src/installer/managed/Microsoft.NET.HostModel/AppHost/HostWriter.csUpdated comment to match renamed enum reference (fxr_search_location).
Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 4
Comment threadsrc/native/corehost/nethost/nethost.c
Comment threadsrc/native/corehost/hostmisc/pal.unix.c
Comment threadsrc/native/corehost/fxr_resolver.c
Outdated

Comment threadsrc/native/corehost/fxr_resolver.c
@elinor-fung
Address PR review feedback
a525dd7
- nethost.c: use %zu (not %d) for the size_t in the invalid-size trace.
- pal.unix.c: bound the /proc/self/maps %s read with an explicit field
width so a pathological line can't overflow the buffer.
- fxr_resolver.c: initialize *out_fxr in fxr_resolver_try_get_existing_fxr,
and drop the stale fxr_resolver.cpp reference from the file comment.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

This was referenced Jun 25, 2026

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elinor-fung
marked this pull request as ready for review
June 25, 2026 20:16
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@elinor-fung
Drop single-field find_max_version_context_t wrapper
3ce2f43
It only held a c_fx_ver_t, so pass the c_fx_ver_t directly as the
pal_readdir_onlydirectories context instead of wrapping it.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 0 new
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Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 1
Comment threadsrc/native/corehost/hostmisc/pal.unix.c
@elinor-fung
Potential fix for pull request finding
9179007
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Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 1
Comment threadsrc/native/corehost/nethost/CMakeLists.txt
@build-analysisbuild-analysisBot
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Comment threadsrc/native/corehost/apphost/standalone/hostfxr_resolver.cpp
Outdated

Comment threadsrc/native/corehost/hostmisc/pal.unix.c
Comment threadsrc/native/corehost/nethost/nethost.c
Outdated

Comment threadsrc/native/corehost/nethost/nethost.c
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Apply suggestions from code review
c6e1062
Co-authored-by: Aaron R Robinson <arobins@microsoft.com>
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@elinor-fung
Scope hostfxr_resolver raw path pointers to their lifetime
129203b
In hostfxr_resolver_t's constructor, wrap the dotnet_root/fxr_path raw
pointers in a block so they go out of scope right after they are freed,
preventing later dangling-pointer use. The rest of the constructor only
needs the resolved flag and the assigned members.
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Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 0 new
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Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 2
Comment threadsrc/native/corehost/load_fxr_and_get_delegate.h
Comment threadsrc/native/corehost/fxr_resolver.h
Outdated

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Potential fix for pull request finding
0a52486
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Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 1
Comment threadsrc/native/corehost/load_fxr_and_get_delegate.h
AaronRobinsonMSFT
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Apply suggestions from code review
c6f2953
Co-authored-by: Aaron R Robinson <arobins@microsoft.com>
Co-authored-by: Elinor Fung <elfung@microsoft.com>
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Copilot's findings
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  • Comments generated: 0 new

This was referenced Jul 2, 2026

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merged commit ad0692a
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@elinor-fung
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Convert nethost to C (#129828)
6c8fdf9
Convert `nethost` to C. This builds on #128420 and #129480 to fully
convert `nethost` so it compiles and links as C-only — no C++ runtime
dependency.
- **pal**
- Add a C `pal_get_loaded_library` (look up an already-loaded library
without loading it). The C++ `pal::get_loaded_library` now delegates to
it.
- **fxr_resolver** - Convert the last C++-only piece, `try_get_existing_fxr`, to C.
- Remove the thin C++ wrappers in `fxr_resolver.cpp`
- Move `load_fxr_and_get_delegate` (used by `comhost` and `ijwhost`)
into its own header `load_fxr_and_get_delegate.h`
- **nethost**
- Replace `nethost.cpp` with `nethost.c` using the shared host bits that
have been converted to C. The RAII `error_writer_scope_t` is replaced by
manual save/restore of the error writer.
- **Build**
- Split `hostmisc` into C/C++ sources and add a C-only `hostmisc_c`
object library
**linux x64 Release**
| Binary | Baseline | PR | Δ bytes | Δ % |
|---|---|---|---|---|
| `libnethost.a` | 2,743,470 | 532,650 | -2,210,820 | -80.6% |
| `libnethost.so` | 43,376 | 35,072 | -8,304 | -19.1% |
**macOS arm64 Release**
| Binary | Baseline | PR | Δ bytes | Δ % |
|---|---:|---:|---:|---:|
| `libnethost.a` | 1,097,312 | 268,360 | −828,952 | −75.5% |
| `libnethost.dylib` | 92,368 | 89,088 | −3,280 | −3.6% |
**windows x64 Release**
| Binary | Baseline | PR | Δ bytes | Δ % |
|---|--:|--:|--:|--:|
| `libnethost.lib` | 2,951,176 | 1,677,420 | −1,273,756 | −43.2% |
| `nethost.dll` | 71,168 | 56,832 | −14,336 | −20.1% |
---------
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Aaron R Robinson <arobins@microsoft.com>
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Convert nethost to C by elinor-fung · Pull Request #129828 · dotnet/runtime · GitHub
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Convert nethost to C - #129828
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Convert nethost to C#129828
elinor-fung merged 12 commits into
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Convert nethost to C. This builds on #128420 and #129480 to fully convert nethost so it compiles and links as C-only — no C++ runtime dependency.
cc @dotnet/appmodel @AaronRobinsonMSFT
  • pal
    • Add a C pal_get_loaded_library (look up an already-loaded library without loading it). The C++ pal::get_loaded_library now delegates to it.
  • fxr_resolver
    • Convert the last C++-only piece, try_get_existing_fxr, to C.
    • Remove the thin C++ wrappers in fxr_resolver.cpp
    • Move load_fxr_and_get_delegate (used by comhost and ijwhost) into its own header load_fxr_and_get_delegate.h
  • nethost
    • Replace nethost.cpp with nethost.c using the shared host bits that have been converted to C. The RAII error_writer_scope_t is replaced by manual save/restore of the error writer.
  • Build
    • Split hostmisc into C/C++ sources and add a C-only hostmisc_c object library
linux x64 Release
BinaryBaselinePRΔ bytesΔ %
libnethost.a2,743,470532,650-2,210,820-80.6%
libnethost.so43,37635,072-8,304-19.1%
macOS arm64 Release
BinaryBaselinePRΔ bytesΔ %
libnethost.a1,097,312268,360−828,952−75.5%
libnethost.dylib92,36889,088−3,280−3.6%
windows x64 Release
BinaryBaselinePRΔ bytesΔ %
libnethost.lib2,951,1761,677,420−1,273,756−43.2%
nethost.dll71,16856,832−14,336−20.1%
Note
This PR description was drafted by GitHub Copilot.
elinor-fungand others
added 5 commits
June 23, 2026 14:51
@elinor-fung
Add C pal_get_loaded_library
2340343
Add a C implementation of looking up an already-loaded library in the
current process, so callers that need to reuse an existing hostfxr (e.g.
nethost) can do so without the C++ pal:: surface.
- Add a pal_dll_t typedef and pal_get_loaded_library declaration in pal.h.
- Implement pal_get_loaded_library in pal.unix.c (dlopen RTLD_NOLOAD,
dladdr to resolve the path, and the /proc/self/maps fallback) and
pal.windows.c (GetModuleHandleW + a shared get_module_file_name helper
factored out of pal_get_own_executable_path).
- Repoint the C++ pal::get_loaded_library wrappers at the new C function,
removing the old C++ implementations and the proc-maps helper.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Convert fxr_resolver_try_get_existing_fxr to C
ec86642
Now that pal_get_loaded_library is available in C, move the last
fxr_resolver function that was still C++-only into fxr_resolver.c.
Add fxr_resolver_try_get_existing_fxr (declaration in fxr_resolver.h,
implementation in fxr_resolver.c) and make the C++
fxr_resolver::try_get_existing_fxr wrapper delegate to it. Drop the file
comment noting that try_get_existing_fxr had to stay in C++.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Convert nethost to C
61fde33
Rewrite nethost.cpp as nethost.c using the C host APIs: trace_* for
tracing, fxr_resolver_try_get_existing_fxr / try_get_path_from_dotnet_root
/ try_get_path for resolution, and utils_get_directory. The RAII
error_writer_scope_t is replaced by saving and restoring the previous
error writer manually around the call, and pal::string_t buffers become
manually-managed pal_char_t* allocations.
Update nethost/CMakeLists.txt to build nethost.c. The compiled nethost
code is now C-only.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Remove the C++ fxr_resolver wrappers
190e36a
fxr_resolver.cpp held thin C++ wrappers (marshalling pal::string_t to and
from the pal_char_t* C API) over the fxr_resolver_* functions in
fxr_resolver.c. Remove them and have the remaining C++ callers use the C
API directly:
- hostfxr_resolver.cpp uses fxr_search_location and fxr_resolver_try_get_path
directly (with direct utils.h/error_codes.h includes that were previously
pulled in transitively through fxr_resolver.h).
- The load_fxr_and_get_delegate template (used by ijwhost and comhost) moves
to its own header, load_fxr_and_get_delegate.h, and calls the C resolver
functions. Its fxr handle is typed as pal_dll_t.
fxr_resolver.h is now a pure C header and fxr_resolver is C-only (no
fxr_resolver.cpp), which also drops it from the static singlefilehost
sources.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Link nethost against a C-only hostmisc
9189c4b
nethost's own code is C, and after the previous change fxr_resolver is
C-only too, but nethost still linked the full hostmisc (which includes C++
translation units). That gave the nethost targets a C++ linker language, so
the clang++ driver added a dependency on the C++ runtime (libc++) and
libnethost.a embedded the unused C++ objects.
Split the hostmisc sources into C_SOURCES/CXX_SOURCES and add hostmisc_c, an
object library built from just the C sources. hostmisc and hostmisc::public
are unchanged for the C++ consumers (apphost, hostfxr, hostpolicy, etc.).
Point nethost/libnethost at hostmisc_c (+ minipal_objects, which object
libraries don't propagate transitively). The nethost targets now compile no
C++, link with the C driver, and have no libc++ dependency; libnethost.a
shrinks substantially by dropping the embedded C++ objects.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
CopilotAI
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Pull request overview
This PR completes the nethost conversion to C-only by rewriting nethost in C, moving remaining fxr_resolver functionality to the C surface, and adding a C PAL helper to detect an already-loaded hostfxr without introducing a C++ runtime dependency.
Changes:
  • Replaced nethost.cpp with nethost.c, switching to the C host APIs and manually saving/restoring the trace error writer.
  • Added C pal_get_loaded_library (and pal_dll_t) and routed the existing C++ pal::get_loaded_library through it.
  • Removed fxr_resolver.cpp and moved the delegate-loading template to load_fxr_and_get_delegate.h; updated C++ callers to use the C fxr_resolver_* APIs directly.
Show a summary per file
FileDescription
src/native/corehost/nethost/nethost.cppRemoved C++ implementation of get_hostfxr_path.
src/native/corehost/nethost/nethost.cNew C implementation of get_hostfxr_path using C host APIs.
src/native/corehost/nethost/CMakeLists.txtSwitched nethost sources to C and updated link deps to hostmisc_c.
src/native/corehost/load_fxr_and_get_delegate.hNew header containing the load_fxr_and_get_delegate C++ template previously in fxr_resolver.h.
src/native/corehost/ijwhost/ijwhost.cppUpdated include to use load_fxr_and_get_delegate.h.
src/native/corehost/comhost/comhost.cppUpdated include to use load_fxr_and_get_delegate.h.
src/native/corehost/hostmisc/pal.hAdded pal_dll_t and the C pal_get_loaded_library declaration.
src/native/corehost/hostmisc/pal.windows.cAdded pal_get_loaded_library implementation and refactored module-path helper.
src/native/corehost/hostmisc/pal.windows.cppC++ pal::get_loaded_library now delegates to pal_get_loaded_library.
src/native/corehost/hostmisc/pal.unix.cAdded pal_get_loaded_library implementation (dlopen RTLD_NOLOAD + dladdr, with /proc/self/maps fallback).
src/native/corehost/hostmisc/pal.unix.cppC++ pal::get_loaded_library now delegates to pal_get_loaded_library.
src/native/corehost/hostmisc/CMakeLists.txtSplit hostmisc C vs C++ sources and introduced hostmisc_c object library.
src/native/corehost/fxr_resolver.hRemoved C++ wrapper surface; added C fxr_resolver_try_get_existing_fxr.
src/native/corehost/fxr_resolver.cppRemoved thin C++ wrapper implementation.
src/native/corehost/fxr_resolver.cAdded C implementation of fxr_resolver_try_get_existing_fxr.
src/native/corehost/CMakeLists.txtUpdated fxr_resolver interface target to stop compiling fxr_resolver.cpp.
src/native/corehost/apphost/static/CMakeLists.txtDropped ../../fxr_resolver.cpp from sources.
src/native/corehost/apphost/standalone/hostfxr_resolver.cppSwitched from C++ wrappers to C fxr_resolver_try_get_path API.
src/installer/managed/Microsoft.NET.HostModel/AppHost/HostWriter.csUpdated comment to match renamed enum reference (fxr_search_location).
Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 4
Comment threadsrc/native/corehost/nethost/nethost.c
Comment threadsrc/native/corehost/hostmisc/pal.unix.c
Comment threadsrc/native/corehost/fxr_resolver.c
Outdated

Comment threadsrc/native/corehost/fxr_resolver.c
@elinor-fung
Address PR review feedback
a525dd7
- nethost.c: use %zu (not %d) for the size_t in the invalid-size trace.
- pal.unix.c: bound the /proc/self/maps %s read with an explicit field
width so a pathological line can't overflow the buffer.
- fxr_resolver.c: initialize *out_fxr in fxr_resolver_try_get_existing_fxr,
and drop the stale fxr_resolver.cpp reference from the file comment.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

This was referenced Jun 25, 2026

Open


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@elinor-fung
elinor-fung
marked this pull request as ready for review
June 25, 2026 20:16
CopilotAI
review requested due to automatic review settings
June 25, 2026 20:16
@elinor-fung
Drop single-field find_max_version_context_t wrapper
3ce2f43
It only held a c_fx_ver_t, so pass the c_fx_ver_t directly as the
pal_readdir_onlydirectories context instead of wrapping it.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Comment threadsrc/native/corehost/hostmisc/pal.unix.c
@elinor-fung
Potential fix for pull request finding
9179007
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Comment threadsrc/native/corehost/nethost/CMakeLists.txt
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Comment threadsrc/native/corehost/apphost/standalone/hostfxr_resolver.cpp
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Comment threadsrc/native/corehost/hostmisc/pal.unix.c
Comment threadsrc/native/corehost/nethost/nethost.c
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Comment threadsrc/native/corehost/nethost/nethost.c
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@elinor-fung
Scope hostfxr_resolver raw path pointers to their lifetime
129203b
In hostfxr_resolver_t's constructor, wrap the dotnet_root/fxr_path raw
pointers in a block so they go out of scope right after they are freed,
preventing later dangling-pointer use. The rest of the constructor only
needs the resolved flag and the assigned members.
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Comment threadsrc/native/corehost/load_fxr_and_get_delegate.h
Comment threadsrc/native/corehost/fxr_resolver.h
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Comment threadsrc/native/corehost/load_fxr_and_get_delegate.h
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@elinor-fung
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Convert nethost to C (#129828)
6c8fdf9
Convert `nethost` to C. This builds on #128420 and #129480 to fully
convert `nethost` so it compiles and links as C-only — no C++ runtime
dependency.
- **pal**
- Add a C `pal_get_loaded_library` (look up an already-loaded library
without loading it). The C++ `pal::get_loaded_library` now delegates to
it.
- **fxr_resolver** - Convert the last C++-only piece, `try_get_existing_fxr`, to C.
- Remove the thin C++ wrappers in `fxr_resolver.cpp`
- Move `load_fxr_and_get_delegate` (used by `comhost` and `ijwhost`)
into its own header `load_fxr_and_get_delegate.h`
- **nethost**
- Replace `nethost.cpp` with `nethost.c` using the shared host bits that
have been converted to C. The RAII `error_writer_scope_t` is replaced by
manual save/restore of the error writer.
- **Build**
- Split `hostmisc` into C/C++ sources and add a C-only `hostmisc_c`
object library
**linux x64 Release**
| Binary | Baseline | PR | Δ bytes | Δ % |
|---|---|---|---|---|
| `libnethost.a` | 2,743,470 | 532,650 | -2,210,820 | -80.6% |
| `libnethost.so` | 43,376 | 35,072 | -8,304 | -19.1% |
**macOS arm64 Release**
| Binary | Baseline | PR | Δ bytes | Δ % |
|---|---:|---:|---:|---:|
| `libnethost.a` | 1,097,312 | 268,360 | −828,952 | −75.5% |
| `libnethost.dylib` | 92,368 | 89,088 | −3,280 | −3.6% |
**windows x64 Release**
| Binary | Baseline | PR | Δ bytes | Δ % |
|---|--:|--:|--:|--:|
| `libnethost.lib` | 2,951,176 | 1,677,420 | −1,273,756 | −43.2% |
| `nethost.dll` | 71,168 | 56,832 | −14,336 | −20.1% |
---------
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Co-authored-by: Aaron R Robinson <arobins@microsoft.com>
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Convert nethost to C by elinor-fung · Pull Request #129828 · dotnet/runtime · GitHub
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Convert nethost to C - #129828
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Convert nethost to C#129828
elinor-fung merged 12 commits into
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@elinor-fungelinor-fung
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Convert nethost to C. This builds on #128420 and #129480 to fully convert nethost so it compiles and links as C-only — no C++ runtime dependency.
cc @dotnet/appmodel @AaronRobinsonMSFT
  • pal
    • Add a C pal_get_loaded_library (look up an already-loaded library without loading it). The C++ pal::get_loaded_library now delegates to it.
  • fxr_resolver
    • Convert the last C++-only piece, try_get_existing_fxr, to C.
    • Remove the thin C++ wrappers in fxr_resolver.cpp
    • Move load_fxr_and_get_delegate (used by comhost and ijwhost) into its own header load_fxr_and_get_delegate.h
  • nethost
    • Replace nethost.cpp with nethost.c using the shared host bits that have been converted to C. The RAII error_writer_scope_t is replaced by manual save/restore of the error writer.
  • Build
    • Split hostmisc into C/C++ sources and add a C-only hostmisc_c object library
linux x64 Release
BinaryBaselinePRΔ bytesΔ %
libnethost.a2,743,470532,650-2,210,820-80.6%
libnethost.so43,37635,072-8,304-19.1%
macOS arm64 Release
BinaryBaselinePRΔ bytesΔ %
libnethost.a1,097,312268,360−828,952−75.5%
libnethost.dylib92,36889,088−3,280−3.6%
windows x64 Release
BinaryBaselinePRΔ bytesΔ %
libnethost.lib2,951,1761,677,420−1,273,756−43.2%
nethost.dll71,16856,832−14,336−20.1%
Note
This PR description was drafted by GitHub Copilot.
elinor-fungand others
added 5 commits
June 23, 2026 14:51
@elinor-fung
Add C pal_get_loaded_library
2340343
Add a C implementation of looking up an already-loaded library in the
current process, so callers that need to reuse an existing hostfxr (e.g.
nethost) can do so without the C++ pal:: surface.
- Add a pal_dll_t typedef and pal_get_loaded_library declaration in pal.h.
- Implement pal_get_loaded_library in pal.unix.c (dlopen RTLD_NOLOAD,
dladdr to resolve the path, and the /proc/self/maps fallback) and
pal.windows.c (GetModuleHandleW + a shared get_module_file_name helper
factored out of pal_get_own_executable_path).
- Repoint the C++ pal::get_loaded_library wrappers at the new C function,
removing the old C++ implementations and the proc-maps helper.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Convert fxr_resolver_try_get_existing_fxr to C
ec86642
Now that pal_get_loaded_library is available in C, move the last
fxr_resolver function that was still C++-only into fxr_resolver.c.
Add fxr_resolver_try_get_existing_fxr (declaration in fxr_resolver.h,
implementation in fxr_resolver.c) and make the C++
fxr_resolver::try_get_existing_fxr wrapper delegate to it. Drop the file
comment noting that try_get_existing_fxr had to stay in C++.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Convert nethost to C
61fde33
Rewrite nethost.cpp as nethost.c using the C host APIs: trace_* for
tracing, fxr_resolver_try_get_existing_fxr / try_get_path_from_dotnet_root
/ try_get_path for resolution, and utils_get_directory. The RAII
error_writer_scope_t is replaced by saving and restoring the previous
error writer manually around the call, and pal::string_t buffers become
manually-managed pal_char_t* allocations.
Update nethost/CMakeLists.txt to build nethost.c. The compiled nethost
code is now C-only.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Remove the C++ fxr_resolver wrappers
190e36a
fxr_resolver.cpp held thin C++ wrappers (marshalling pal::string_t to and
from the pal_char_t* C API) over the fxr_resolver_* functions in
fxr_resolver.c. Remove them and have the remaining C++ callers use the C
API directly:
- hostfxr_resolver.cpp uses fxr_search_location and fxr_resolver_try_get_path
directly (with direct utils.h/error_codes.h includes that were previously
pulled in transitively through fxr_resolver.h).
- The load_fxr_and_get_delegate template (used by ijwhost and comhost) moves
to its own header, load_fxr_and_get_delegate.h, and calls the C resolver
functions. Its fxr handle is typed as pal_dll_t.
fxr_resolver.h is now a pure C header and fxr_resolver is C-only (no
fxr_resolver.cpp), which also drops it from the static singlefilehost
sources.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Link nethost against a C-only hostmisc
9189c4b
nethost's own code is C, and after the previous change fxr_resolver is
C-only too, but nethost still linked the full hostmisc (which includes C++
translation units). That gave the nethost targets a C++ linker language, so
the clang++ driver added a dependency on the C++ runtime (libc++) and
libnethost.a embedded the unused C++ objects.
Split the hostmisc sources into C_SOURCES/CXX_SOURCES and add hostmisc_c, an
object library built from just the C sources. hostmisc and hostmisc::public
are unchanged for the C++ consumers (apphost, hostfxr, hostpolicy, etc.).
Point nethost/libnethost at hostmisc_c (+ minipal_objects, which object
libraries don't propagate transitively). The nethost targets now compile no
C++, link with the C driver, and have no libc++ dependency; libnethost.a
shrinks substantially by dropping the embedded C++ objects.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Pull request overview
This PR completes the nethost conversion to C-only by rewriting nethost in C, moving remaining fxr_resolver functionality to the C surface, and adding a C PAL helper to detect an already-loaded hostfxr without introducing a C++ runtime dependency.
Changes:
  • Replaced nethost.cpp with nethost.c, switching to the C host APIs and manually saving/restoring the trace error writer.
  • Added C pal_get_loaded_library (and pal_dll_t) and routed the existing C++ pal::get_loaded_library through it.
  • Removed fxr_resolver.cpp and moved the delegate-loading template to load_fxr_and_get_delegate.h; updated C++ callers to use the C fxr_resolver_* APIs directly.
Show a summary per file
FileDescription
src/native/corehost/nethost/nethost.cppRemoved C++ implementation of get_hostfxr_path.
src/native/corehost/nethost/nethost.cNew C implementation of get_hostfxr_path using C host APIs.
src/native/corehost/nethost/CMakeLists.txtSwitched nethost sources to C and updated link deps to hostmisc_c.
src/native/corehost/load_fxr_and_get_delegate.hNew header containing the load_fxr_and_get_delegate C++ template previously in fxr_resolver.h.
src/native/corehost/ijwhost/ijwhost.cppUpdated include to use load_fxr_and_get_delegate.h.
src/native/corehost/comhost/comhost.cppUpdated include to use load_fxr_and_get_delegate.h.
src/native/corehost/hostmisc/pal.hAdded pal_dll_t and the C pal_get_loaded_library declaration.
src/native/corehost/hostmisc/pal.windows.cAdded pal_get_loaded_library implementation and refactored module-path helper.
src/native/corehost/hostmisc/pal.windows.cppC++ pal::get_loaded_library now delegates to pal_get_loaded_library.
src/native/corehost/hostmisc/pal.unix.cAdded pal_get_loaded_library implementation (dlopen RTLD_NOLOAD + dladdr, with /proc/self/maps fallback).
src/native/corehost/hostmisc/pal.unix.cppC++ pal::get_loaded_library now delegates to pal_get_loaded_library.
src/native/corehost/hostmisc/CMakeLists.txtSplit hostmisc C vs C++ sources and introduced hostmisc_c object library.
src/native/corehost/fxr_resolver.hRemoved C++ wrapper surface; added C fxr_resolver_try_get_existing_fxr.
src/native/corehost/fxr_resolver.cppRemoved thin C++ wrapper implementation.
src/native/corehost/fxr_resolver.cAdded C implementation of fxr_resolver_try_get_existing_fxr.
src/native/corehost/CMakeLists.txtUpdated fxr_resolver interface target to stop compiling fxr_resolver.cpp.
src/native/corehost/apphost/static/CMakeLists.txtDropped ../../fxr_resolver.cpp from sources.
src/native/corehost/apphost/standalone/hostfxr_resolver.cppSwitched from C++ wrappers to C fxr_resolver_try_get_path API.
src/installer/managed/Microsoft.NET.HostModel/AppHost/HostWriter.csUpdated comment to match renamed enum reference (fxr_search_location).
Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 4
Comment threadsrc/native/corehost/nethost/nethost.c
Comment threadsrc/native/corehost/hostmisc/pal.unix.c
Comment threadsrc/native/corehost/fxr_resolver.c
Outdated

Comment threadsrc/native/corehost/fxr_resolver.c
@elinor-fung
Address PR review feedback
a525dd7
- nethost.c: use %zu (not %d) for the size_t in the invalid-size trace.
- pal.unix.c: bound the /proc/self/maps %s read with an explicit field
width so a pathological line can't overflow the buffer.
- fxr_resolver.c: initialize *out_fxr in fxr_resolver_try_get_existing_fxr,
and drop the stale fxr_resolver.cpp reference from the file comment.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

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marked this pull request as ready for review
June 25, 2026 20:16
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Drop single-field find_max_version_context_t wrapper
3ce2f43
It only held a c_fx_ver_t, so pass the c_fx_ver_t directly as the
pal_readdir_onlydirectories context instead of wrapping it.
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  • Comments generated: 0 new
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Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 1
Comment threadsrc/native/corehost/hostmisc/pal.unix.c
@elinor-fung
Potential fix for pull request finding
9179007
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Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 1
Comment threadsrc/native/corehost/nethost/CMakeLists.txt
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Comment threadsrc/native/corehost/apphost/standalone/hostfxr_resolver.cpp
Outdated

Comment threadsrc/native/corehost/hostmisc/pal.unix.c
Comment threadsrc/native/corehost/nethost/nethost.c
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Comment threadsrc/native/corehost/nethost/nethost.c
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Apply suggestions from code review
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Co-authored-by: Aaron R Robinson <arobins@microsoft.com>
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@elinor-fung
Scope hostfxr_resolver raw path pointers to their lifetime
129203b
In hostfxr_resolver_t's constructor, wrap the dotnet_root/fxr_path raw
pointers in a block so they go out of scope right after they are freed,
preventing later dangling-pointer use. The rest of the constructor only
needs the resolved flag and the assigned members.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Copilot's findings
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  • Comments generated: 0 new
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Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 2
Comment threadsrc/native/corehost/load_fxr_and_get_delegate.h
Comment threadsrc/native/corehost/fxr_resolver.h
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Potential fix for pull request finding
0a52486
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Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 1
Comment threadsrc/native/corehost/load_fxr_and_get_delegate.h
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Convert nethost to C (#129828)
6c8fdf9
Convert `nethost` to C. This builds on #128420 and #129480 to fully
convert `nethost` so it compiles and links as C-only — no C++ runtime
dependency.
- **pal**
- Add a C `pal_get_loaded_library` (look up an already-loaded library
without loading it). The C++ `pal::get_loaded_library` now delegates to
it.
- **fxr_resolver** - Convert the last C++-only piece, `try_get_existing_fxr`, to C.
- Remove the thin C++ wrappers in `fxr_resolver.cpp`
- Move `load_fxr_and_get_delegate` (used by `comhost` and `ijwhost`)
into its own header `load_fxr_and_get_delegate.h`
- **nethost**
- Replace `nethost.cpp` with `nethost.c` using the shared host bits that
have been converted to C. The RAII `error_writer_scope_t` is replaced by
manual save/restore of the error writer.
- **Build**
- Split `hostmisc` into C/C++ sources and add a C-only `hostmisc_c`
object library
**linux x64 Release**
| Binary | Baseline | PR | Δ bytes | Δ % |
|---|---|---|---|---|
| `libnethost.a` | 2,743,470 | 532,650 | -2,210,820 | -80.6% |
| `libnethost.so` | 43,376 | 35,072 | -8,304 | -19.1% |
**macOS arm64 Release**
| Binary | Baseline | PR | Δ bytes | Δ % |
|---|---:|---:|---:|---:|
| `libnethost.a` | 1,097,312 | 268,360 | −828,952 | −75.5% |
| `libnethost.dylib` | 92,368 | 89,088 | −3,280 | −3.6% |
**windows x64 Release**
| Binary | Baseline | PR | Δ bytes | Δ % |
|---|--:|--:|--:|--:|
| `libnethost.lib` | 2,951,176 | 1,677,420 | −1,273,756 | −43.2% |
| `nethost.dll` | 71,168 | 56,832 | −14,336 | −20.1% |
---------
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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, 'i');
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var __re = new RegExp('^' + "youtube\\.com" + '
Convert nethost to C by elinor-fung · Pull Request #129828 · dotnet/runtime · GitHub
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Convert nethost to C - #129828
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Convert nethost to C#129828
elinor-fung merged 12 commits into
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Convert nethost to C. This builds on #128420 and #129480 to fully convert nethost so it compiles and links as C-only — no C++ runtime dependency.
cc @dotnet/appmodel @AaronRobinsonMSFT
  • pal
    • Add a C pal_get_loaded_library (look up an already-loaded library without loading it). The C++ pal::get_loaded_library now delegates to it.
  • fxr_resolver
    • Convert the last C++-only piece, try_get_existing_fxr, to C.
    • Remove the thin C++ wrappers in fxr_resolver.cpp
    • Move load_fxr_and_get_delegate (used by comhost and ijwhost) into its own header load_fxr_and_get_delegate.h
  • nethost
    • Replace nethost.cpp with nethost.c using the shared host bits that have been converted to C. The RAII error_writer_scope_t is replaced by manual save/restore of the error writer.
  • Build
    • Split hostmisc into C/C++ sources and add a C-only hostmisc_c object library
linux x64 Release
BinaryBaselinePRΔ bytesΔ %
libnethost.a2,743,470532,650-2,210,820-80.6%
libnethost.so43,37635,072-8,304-19.1%
macOS arm64 Release
BinaryBaselinePRΔ bytesΔ %
libnethost.a1,097,312268,360−828,952−75.5%
libnethost.dylib92,36889,088−3,280−3.6%
windows x64 Release
BinaryBaselinePRΔ bytesΔ %
libnethost.lib2,951,1761,677,420−1,273,756−43.2%
nethost.dll71,16856,832−14,336−20.1%
Note
This PR description was drafted by GitHub Copilot.
elinor-fungand others
added 5 commits
June 23, 2026 14:51
@elinor-fung
Add C pal_get_loaded_library
2340343
Add a C implementation of looking up an already-loaded library in the
current process, so callers that need to reuse an existing hostfxr (e.g.
nethost) can do so without the C++ pal:: surface.
- Add a pal_dll_t typedef and pal_get_loaded_library declaration in pal.h.
- Implement pal_get_loaded_library in pal.unix.c (dlopen RTLD_NOLOAD,
dladdr to resolve the path, and the /proc/self/maps fallback) and
pal.windows.c (GetModuleHandleW + a shared get_module_file_name helper
factored out of pal_get_own_executable_path).
- Repoint the C++ pal::get_loaded_library wrappers at the new C function,
removing the old C++ implementations and the proc-maps helper.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Convert fxr_resolver_try_get_existing_fxr to C
ec86642
Now that pal_get_loaded_library is available in C, move the last
fxr_resolver function that was still C++-only into fxr_resolver.c.
Add fxr_resolver_try_get_existing_fxr (declaration in fxr_resolver.h,
implementation in fxr_resolver.c) and make the C++
fxr_resolver::try_get_existing_fxr wrapper delegate to it. Drop the file
comment noting that try_get_existing_fxr had to stay in C++.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Convert nethost to C
61fde33
Rewrite nethost.cpp as nethost.c using the C host APIs: trace_* for
tracing, fxr_resolver_try_get_existing_fxr / try_get_path_from_dotnet_root
/ try_get_path for resolution, and utils_get_directory. The RAII
error_writer_scope_t is replaced by saving and restoring the previous
error writer manually around the call, and pal::string_t buffers become
manually-managed pal_char_t* allocations.
Update nethost/CMakeLists.txt to build nethost.c. The compiled nethost
code is now C-only.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Remove the C++ fxr_resolver wrappers
190e36a
fxr_resolver.cpp held thin C++ wrappers (marshalling pal::string_t to and
from the pal_char_t* C API) over the fxr_resolver_* functions in
fxr_resolver.c. Remove them and have the remaining C++ callers use the C
API directly:
- hostfxr_resolver.cpp uses fxr_search_location and fxr_resolver_try_get_path
directly (with direct utils.h/error_codes.h includes that were previously
pulled in transitively through fxr_resolver.h).
- The load_fxr_and_get_delegate template (used by ijwhost and comhost) moves
to its own header, load_fxr_and_get_delegate.h, and calls the C resolver
functions. Its fxr handle is typed as pal_dll_t.
fxr_resolver.h is now a pure C header and fxr_resolver is C-only (no
fxr_resolver.cpp), which also drops it from the static singlefilehost
sources.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Link nethost against a C-only hostmisc
9189c4b
nethost's own code is C, and after the previous change fxr_resolver is
C-only too, but nethost still linked the full hostmisc (which includes C++
translation units). That gave the nethost targets a C++ linker language, so
the clang++ driver added a dependency on the C++ runtime (libc++) and
libnethost.a embedded the unused C++ objects.
Split the hostmisc sources into C_SOURCES/CXX_SOURCES and add hostmisc_c, an
object library built from just the C sources. hostmisc and hostmisc::public
are unchanged for the C++ consumers (apphost, hostfxr, hostpolicy, etc.).
Point nethost/libnethost at hostmisc_c (+ minipal_objects, which object
libraries don't propagate transitively). The nethost targets now compile no
C++, link with the C driver, and have no libc++ dependency; libnethost.a
shrinks substantially by dropping the embedded C++ objects.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Pull request overview
This PR completes the nethost conversion to C-only by rewriting nethost in C, moving remaining fxr_resolver functionality to the C surface, and adding a C PAL helper to detect an already-loaded hostfxr without introducing a C++ runtime dependency.
Changes:
  • Replaced nethost.cpp with nethost.c, switching to the C host APIs and manually saving/restoring the trace error writer.
  • Added C pal_get_loaded_library (and pal_dll_t) and routed the existing C++ pal::get_loaded_library through it.
  • Removed fxr_resolver.cpp and moved the delegate-loading template to load_fxr_and_get_delegate.h; updated C++ callers to use the C fxr_resolver_* APIs directly.
Show a summary per file
FileDescription
src/native/corehost/nethost/nethost.cppRemoved C++ implementation of get_hostfxr_path.
src/native/corehost/nethost/nethost.cNew C implementation of get_hostfxr_path using C host APIs.
src/native/corehost/nethost/CMakeLists.txtSwitched nethost sources to C and updated link deps to hostmisc_c.
src/native/corehost/load_fxr_and_get_delegate.hNew header containing the load_fxr_and_get_delegate C++ template previously in fxr_resolver.h.
src/native/corehost/ijwhost/ijwhost.cppUpdated include to use load_fxr_and_get_delegate.h.
src/native/corehost/comhost/comhost.cppUpdated include to use load_fxr_and_get_delegate.h.
src/native/corehost/hostmisc/pal.hAdded pal_dll_t and the C pal_get_loaded_library declaration.
src/native/corehost/hostmisc/pal.windows.cAdded pal_get_loaded_library implementation and refactored module-path helper.
src/native/corehost/hostmisc/pal.windows.cppC++ pal::get_loaded_library now delegates to pal_get_loaded_library.
src/native/corehost/hostmisc/pal.unix.cAdded pal_get_loaded_library implementation (dlopen RTLD_NOLOAD + dladdr, with /proc/self/maps fallback).
src/native/corehost/hostmisc/pal.unix.cppC++ pal::get_loaded_library now delegates to pal_get_loaded_library.
src/native/corehost/hostmisc/CMakeLists.txtSplit hostmisc C vs C++ sources and introduced hostmisc_c object library.
src/native/corehost/fxr_resolver.hRemoved C++ wrapper surface; added C fxr_resolver_try_get_existing_fxr.
src/native/corehost/fxr_resolver.cppRemoved thin C++ wrapper implementation.
src/native/corehost/fxr_resolver.cAdded C implementation of fxr_resolver_try_get_existing_fxr.
src/native/corehost/CMakeLists.txtUpdated fxr_resolver interface target to stop compiling fxr_resolver.cpp.
src/native/corehost/apphost/static/CMakeLists.txtDropped ../../fxr_resolver.cpp from sources.
src/native/corehost/apphost/standalone/hostfxr_resolver.cppSwitched from C++ wrappers to C fxr_resolver_try_get_path API.
src/installer/managed/Microsoft.NET.HostModel/AppHost/HostWriter.csUpdated comment to match renamed enum reference (fxr_search_location).
Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 4
Comment threadsrc/native/corehost/nethost/nethost.c
Comment threadsrc/native/corehost/hostmisc/pal.unix.c
Comment threadsrc/native/corehost/fxr_resolver.c
Outdated

Comment threadsrc/native/corehost/fxr_resolver.c
@elinor-fung
Address PR review feedback
a525dd7
- nethost.c: use %zu (not %d) for the size_t in the invalid-size trace.
- pal.unix.c: bound the /proc/self/maps %s read with an explicit field
width so a pathological line can't overflow the buffer.
- fxr_resolver.c: initialize *out_fxr in fxr_resolver_try_get_existing_fxr,
and drop the stale fxr_resolver.cpp reference from the file comment.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

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June 25, 2026 20:16
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Drop single-field find_max_version_context_t wrapper
3ce2f43
It only held a c_fx_ver_t, so pass the c_fx_ver_t directly as the
pal_readdir_onlydirectories context instead of wrapping it.
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Copilot's findings
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  • Comments generated: 1
Comment threadsrc/native/corehost/hostmisc/pal.unix.c
@elinor-fung
Potential fix for pull request finding
9179007
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Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 1
Comment threadsrc/native/corehost/nethost/CMakeLists.txt
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Comment threadsrc/native/corehost/apphost/standalone/hostfxr_resolver.cpp
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Comment threadsrc/native/corehost/hostmisc/pal.unix.c
Comment threadsrc/native/corehost/nethost/nethost.c
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Comment threadsrc/native/corehost/nethost/nethost.c
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@elinor-fung
Scope hostfxr_resolver raw path pointers to their lifetime
129203b
In hostfxr_resolver_t's constructor, wrap the dotnet_root/fxr_path raw
pointers in a block so they go out of scope right after they are freed,
preventing later dangling-pointer use. The rest of the constructor only
needs the resolved flag and the assigned members.
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Copilot's findings
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  • Comments generated: 0 new
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Copilot's findings
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  • Comments generated: 2
Comment threadsrc/native/corehost/load_fxr_and_get_delegate.h
Comment threadsrc/native/corehost/fxr_resolver.h
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Potential fix for pull request finding
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Copilot's findings
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  • Comments generated: 1
Comment threadsrc/native/corehost/load_fxr_and_get_delegate.h
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Co-authored-by: Aaron R Robinson <arobins@microsoft.com>
Co-authored-by: Elinor Fung <elfung@microsoft.com>
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Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 0 new

This was referenced Jul 2, 2026

Open


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@elinor-fung
elinor-fung
merged commit ad0692a
into
dotnet:mainJul 2, 2026

173 checks passed

@elinor-fung
elinor-fung
deleted the

nethost-to-c

branch
July 2, 2026 17:13
@dotnet-maestrodotnet-maestroBot
mentioned this pull request
Jul 3, 2026
 Merged

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added this to the 11.0-preview7 milestone
Jul 3, 2026
eiriktsarpalis pushed a commit
that referenced
this pull request
Jul 15, 2026
@elinor-fung
@AaronRobinsonMSFT@eiriktsarpalis
Convert nethost to C (#129828)
6c8fdf9
Convert `nethost` to C. This builds on #128420 and #129480 to fully
convert `nethost` so it compiles and links as C-only — no C++ runtime
dependency.
- **pal**
- Add a C `pal_get_loaded_library` (look up an already-loaded library
without loading it). The C++ `pal::get_loaded_library` now delegates to
it.
- **fxr_resolver** - Convert the last C++-only piece, `try_get_existing_fxr`, to C.
- Remove the thin C++ wrappers in `fxr_resolver.cpp`
- Move `load_fxr_and_get_delegate` (used by `comhost` and `ijwhost`)
into its own header `load_fxr_and_get_delegate.h`
- **nethost**
- Replace `nethost.cpp` with `nethost.c` using the shared host bits that
have been converted to C. The RAII `error_writer_scope_t` is replaced by
manual save/restore of the error writer.
- **Build**
- Split `hostmisc` into C/C++ sources and add a C-only `hostmisc_c`
object library
**linux x64 Release**
| Binary | Baseline | PR | Δ bytes | Δ % |
|---|---|---|---|---|
| `libnethost.a` | 2,743,470 | 532,650 | -2,210,820 | -80.6% |
| `libnethost.so` | 43,376 | 35,072 | -8,304 | -19.1% |
**macOS arm64 Release**
| Binary | Baseline | PR | Δ bytes | Δ % |
|---|---:|---:|---:|---:|
| `libnethost.a` | 1,097,312 | 268,360 | −828,952 | −75.5% |
| `libnethost.dylib` | 92,368 | 89,088 | −3,280 | −3.6% |
**windows x64 Release**
| Binary | Baseline | PR | Δ bytes | Δ % |
|---|--:|--:|--:|--:|
| `libnethost.lib` | 2,951,176 | 1,677,420 | −1,273,756 | −43.2% |
| `nethost.dll` | 71,168 | 56,832 | −14,336 | −20.1% |
---------
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Aaron R Robinson <arobins@microsoft.com>
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lastUrl = location.href;
setTimeout(tryTheater, 500);
}
}, 1000);
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})();
(function(){
try {
var __m = "*";
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Convert nethost to C by elinor-fung · Pull Request #129828 · dotnet/runtime · GitHub
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Convert nethost to C - #129828
Merged
elinor-fung merged 12 commits into
dotnet:mainfrom 
elinor-fung:nethost-to-c
Jul 2, 2026
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Convert nethost to C#129828
elinor-fung merged 12 commits into
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elinor-fung:nethost-to-c
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Convert nethost to C. This builds on #128420 and #129480 to fully convert nethost so it compiles and links as C-only — no C++ runtime dependency.
cc @dotnet/appmodel @AaronRobinsonMSFT
  • pal
    • Add a C pal_get_loaded_library (look up an already-loaded library without loading it). The C++ pal::get_loaded_library now delegates to it.
  • fxr_resolver
    • Convert the last C++-only piece, try_get_existing_fxr, to C.
    • Remove the thin C++ wrappers in fxr_resolver.cpp
    • Move load_fxr_and_get_delegate (used by comhost and ijwhost) into its own header load_fxr_and_get_delegate.h
  • nethost
    • Replace nethost.cpp with nethost.c using the shared host bits that have been converted to C. The RAII error_writer_scope_t is replaced by manual save/restore of the error writer.
  • Build
    • Split hostmisc into C/C++ sources and add a C-only hostmisc_c object library
linux x64 Release
BinaryBaselinePRΔ bytesΔ %
libnethost.a2,743,470532,650-2,210,820-80.6%
libnethost.so43,37635,072-8,304-19.1%
macOS arm64 Release
BinaryBaselinePRΔ bytesΔ %
libnethost.a1,097,312268,360−828,952−75.5%
libnethost.dylib92,36889,088−3,280−3.6%
windows x64 Release
BinaryBaselinePRΔ bytesΔ %
libnethost.lib2,951,1761,677,420−1,273,756−43.2%
nethost.dll71,16856,832−14,336−20.1%
Note
This PR description was drafted by GitHub Copilot.
elinor-fungand others
added 5 commits
June 23, 2026 14:51
@elinor-fung
Add C pal_get_loaded_library
2340343
Add a C implementation of looking up an already-loaded library in the
current process, so callers that need to reuse an existing hostfxr (e.g.
nethost) can do so without the C++ pal:: surface.
- Add a pal_dll_t typedef and pal_get_loaded_library declaration in pal.h.
- Implement pal_get_loaded_library in pal.unix.c (dlopen RTLD_NOLOAD,
dladdr to resolve the path, and the /proc/self/maps fallback) and
pal.windows.c (GetModuleHandleW + a shared get_module_file_name helper
factored out of pal_get_own_executable_path).
- Repoint the C++ pal::get_loaded_library wrappers at the new C function,
removing the old C++ implementations and the proc-maps helper.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Convert fxr_resolver_try_get_existing_fxr to C
ec86642
Now that pal_get_loaded_library is available in C, move the last
fxr_resolver function that was still C++-only into fxr_resolver.c.
Add fxr_resolver_try_get_existing_fxr (declaration in fxr_resolver.h,
implementation in fxr_resolver.c) and make the C++
fxr_resolver::try_get_existing_fxr wrapper delegate to it. Drop the file
comment noting that try_get_existing_fxr had to stay in C++.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Convert nethost to C
61fde33
Rewrite nethost.cpp as nethost.c using the C host APIs: trace_* for
tracing, fxr_resolver_try_get_existing_fxr / try_get_path_from_dotnet_root
/ try_get_path for resolution, and utils_get_directory. The RAII
error_writer_scope_t is replaced by saving and restoring the previous
error writer manually around the call, and pal::string_t buffers become
manually-managed pal_char_t* allocations.
Update nethost/CMakeLists.txt to build nethost.c. The compiled nethost
code is now C-only.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Remove the C++ fxr_resolver wrappers
190e36a
fxr_resolver.cpp held thin C++ wrappers (marshalling pal::string_t to and
from the pal_char_t* C API) over the fxr_resolver_* functions in
fxr_resolver.c. Remove them and have the remaining C++ callers use the C
API directly:
- hostfxr_resolver.cpp uses fxr_search_location and fxr_resolver_try_get_path
directly (with direct utils.h/error_codes.h includes that were previously
pulled in transitively through fxr_resolver.h).
- The load_fxr_and_get_delegate template (used by ijwhost and comhost) moves
to its own header, load_fxr_and_get_delegate.h, and calls the C resolver
functions. Its fxr handle is typed as pal_dll_t.
fxr_resolver.h is now a pure C header and fxr_resolver is C-only (no
fxr_resolver.cpp), which also drops it from the static singlefilehost
sources.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Link nethost against a C-only hostmisc
9189c4b
nethost's own code is C, and after the previous change fxr_resolver is
C-only too, but nethost still linked the full hostmisc (which includes C++
translation units). That gave the nethost targets a C++ linker language, so
the clang++ driver added a dependency on the C++ runtime (libc++) and
libnethost.a embedded the unused C++ objects.
Split the hostmisc sources into C_SOURCES/CXX_SOURCES and add hostmisc_c, an
object library built from just the C sources. hostmisc and hostmisc::public
are unchanged for the C++ consumers (apphost, hostfxr, hostpolicy, etc.).
Point nethost/libnethost at hostmisc_c (+ minipal_objects, which object
libraries don't propagate transitively). The nethost targets now compile no
C++, link with the C driver, and have no libc++ dependency; libnethost.a
shrinks substantially by dropping the embedded C++ objects.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Pull request overview
This PR completes the nethost conversion to C-only by rewriting nethost in C, moving remaining fxr_resolver functionality to the C surface, and adding a C PAL helper to detect an already-loaded hostfxr without introducing a C++ runtime dependency.
Changes:
  • Replaced nethost.cpp with nethost.c, switching to the C host APIs and manually saving/restoring the trace error writer.
  • Added C pal_get_loaded_library (and pal_dll_t) and routed the existing C++ pal::get_loaded_library through it.
  • Removed fxr_resolver.cpp and moved the delegate-loading template to load_fxr_and_get_delegate.h; updated C++ callers to use the C fxr_resolver_* APIs directly.
Show a summary per file
FileDescription
src/native/corehost/nethost/nethost.cppRemoved C++ implementation of get_hostfxr_path.
src/native/corehost/nethost/nethost.cNew C implementation of get_hostfxr_path using C host APIs.
src/native/corehost/nethost/CMakeLists.txtSwitched nethost sources to C and updated link deps to hostmisc_c.
src/native/corehost/load_fxr_and_get_delegate.hNew header containing the load_fxr_and_get_delegate C++ template previously in fxr_resolver.h.
src/native/corehost/ijwhost/ijwhost.cppUpdated include to use load_fxr_and_get_delegate.h.
src/native/corehost/comhost/comhost.cppUpdated include to use load_fxr_and_get_delegate.h.
src/native/corehost/hostmisc/pal.hAdded pal_dll_t and the C pal_get_loaded_library declaration.
src/native/corehost/hostmisc/pal.windows.cAdded pal_get_loaded_library implementation and refactored module-path helper.
src/native/corehost/hostmisc/pal.windows.cppC++ pal::get_loaded_library now delegates to pal_get_loaded_library.
src/native/corehost/hostmisc/pal.unix.cAdded pal_get_loaded_library implementation (dlopen RTLD_NOLOAD + dladdr, with /proc/self/maps fallback).
src/native/corehost/hostmisc/pal.unix.cppC++ pal::get_loaded_library now delegates to pal_get_loaded_library.
src/native/corehost/hostmisc/CMakeLists.txtSplit hostmisc C vs C++ sources and introduced hostmisc_c object library.
src/native/corehost/fxr_resolver.hRemoved C++ wrapper surface; added C fxr_resolver_try_get_existing_fxr.
src/native/corehost/fxr_resolver.cppRemoved thin C++ wrapper implementation.
src/native/corehost/fxr_resolver.cAdded C implementation of fxr_resolver_try_get_existing_fxr.
src/native/corehost/CMakeLists.txtUpdated fxr_resolver interface target to stop compiling fxr_resolver.cpp.
src/native/corehost/apphost/static/CMakeLists.txtDropped ../../fxr_resolver.cpp from sources.
src/native/corehost/apphost/standalone/hostfxr_resolver.cppSwitched from C++ wrappers to C fxr_resolver_try_get_path API.
src/installer/managed/Microsoft.NET.HostModel/AppHost/HostWriter.csUpdated comment to match renamed enum reference (fxr_search_location).
Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 4
Comment threadsrc/native/corehost/nethost/nethost.c
Comment threadsrc/native/corehost/hostmisc/pal.unix.c
Comment threadsrc/native/corehost/fxr_resolver.c
Outdated

Comment threadsrc/native/corehost/fxr_resolver.c
@elinor-fung
Address PR review feedback
a525dd7
- nethost.c: use %zu (not %d) for the size_t in the invalid-size trace.
- pal.unix.c: bound the /proc/self/maps %s read with an explicit field
width so a pathological line can't overflow the buffer.
- fxr_resolver.c: initialize *out_fxr in fxr_resolver_try_get_existing_fxr,
and drop the stale fxr_resolver.cpp reference from the file comment.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

This was referenced Jun 25, 2026

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elinor-fung
marked this pull request as ready for review
June 25, 2026 20:16
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review requested due to automatic review settings
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@elinor-fung
Drop single-field find_max_version_context_t wrapper
3ce2f43
It only held a c_fx_ver_t, so pass the c_fx_ver_t directly as the
pal_readdir_onlydirectories context instead of wrapping it.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 0 new
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Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 1
Comment threadsrc/native/corehost/hostmisc/pal.unix.c
@elinor-fung
Potential fix for pull request finding
9179007
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
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Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 1
Comment threadsrc/native/corehost/nethost/CMakeLists.txt
@build-analysisbuild-analysisBot
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Comment threadsrc/native/corehost/apphost/standalone/hostfxr_resolver.cpp
Outdated

Comment threadsrc/native/corehost/hostmisc/pal.unix.c
Comment threadsrc/native/corehost/nethost/nethost.c
Outdated

Comment threadsrc/native/corehost/nethost/nethost.c
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Apply suggestions from code review
c6e1062
Co-authored-by: Aaron R Robinson <arobins@microsoft.com>
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@elinor-fung
Scope hostfxr_resolver raw path pointers to their lifetime
129203b
In hostfxr_resolver_t's constructor, wrap the dotnet_root/fxr_path raw
pointers in a block so they go out of scope right after they are freed,
preventing later dangling-pointer use. The rest of the constructor only
needs the resolved flag and the assigned members.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 0 new
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Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 2
Comment threadsrc/native/corehost/load_fxr_and_get_delegate.h
Comment threadsrc/native/corehost/fxr_resolver.h
Outdated

@elinor-fung
Potential fix for pull request finding
0a52486
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Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 1
Comment threadsrc/native/corehost/load_fxr_and_get_delegate.h
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Apply suggestions from code review
c6f2953
Co-authored-by: Aaron R Robinson <arobins@microsoft.com>
Co-authored-by: Elinor Fung <elfung@microsoft.com>
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  • Comments generated: 0 new

This was referenced Jul 2, 2026

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merged commit ad0692a
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@elinor-fung
@AaronRobinsonMSFT@eiriktsarpalis
Convert nethost to C (#129828)
6c8fdf9
Convert `nethost` to C. This builds on #128420 and #129480 to fully
convert `nethost` so it compiles and links as C-only — no C++ runtime
dependency.
- **pal**
- Add a C `pal_get_loaded_library` (look up an already-loaded library
without loading it). The C++ `pal::get_loaded_library` now delegates to
it.
- **fxr_resolver** - Convert the last C++-only piece, `try_get_existing_fxr`, to C.
- Remove the thin C++ wrappers in `fxr_resolver.cpp`
- Move `load_fxr_and_get_delegate` (used by `comhost` and `ijwhost`)
into its own header `load_fxr_and_get_delegate.h`
- **nethost**
- Replace `nethost.cpp` with `nethost.c` using the shared host bits that
have been converted to C. The RAII `error_writer_scope_t` is replaced by
manual save/restore of the error writer.
- **Build**
- Split `hostmisc` into C/C++ sources and add a C-only `hostmisc_c`
object library
**linux x64 Release**
| Binary | Baseline | PR | Δ bytes | Δ % |
|---|---|---|---|---|
| `libnethost.a` | 2,743,470 | 532,650 | -2,210,820 | -80.6% |
| `libnethost.so` | 43,376 | 35,072 | -8,304 | -19.1% |
**macOS arm64 Release**
| Binary | Baseline | PR | Δ bytes | Δ % |
|---|---:|---:|---:|---:|
| `libnethost.a` | 1,097,312 | 268,360 | −828,952 | −75.5% |
| `libnethost.dylib` | 92,368 | 89,088 | −3,280 | −3.6% |
**windows x64 Release**
| Binary | Baseline | PR | Δ bytes | Δ % |
|---|--:|--:|--:|--:|
| `libnethost.lib` | 2,951,176 | 1,677,420 | −1,273,756 | −43.2% |
| `nethost.dll` | 71,168 | 56,832 | −14,336 | −20.1% |
---------
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Aaron R Robinson <arobins@microsoft.com>
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(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
Convert nethost to C by elinor-fung · Pull Request #129828 · dotnet/runtime · GitHub
Skip to content
Convert nethost to C - #129828
Merged
elinor-fung merged 12 commits into
dotnet:mainfrom 
elinor-fung:nethost-to-c
Jul 2, 2026
Merged
Convert nethost to C#129828
elinor-fung merged 12 commits into
dotnet:mainfrom 
elinor-fung:nethost-to-c
Conversation
@elinor-fung
@elinor-fungelinor-fung
commented
Jun 25, 2026•

edited

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Convert nethost to C. This builds on #128420 and #129480 to fully convert nethost so it compiles and links as C-only — no C++ runtime dependency.
cc @dotnet/appmodel @AaronRobinsonMSFT
  • pal
    • Add a C pal_get_loaded_library (look up an already-loaded library without loading it). The C++ pal::get_loaded_library now delegates to it.
  • fxr_resolver
    • Convert the last C++-only piece, try_get_existing_fxr, to C.
    • Remove the thin C++ wrappers in fxr_resolver.cpp
    • Move load_fxr_and_get_delegate (used by comhost and ijwhost) into its own header load_fxr_and_get_delegate.h
  • nethost
    • Replace nethost.cpp with nethost.c using the shared host bits that have been converted to C. The RAII error_writer_scope_t is replaced by manual save/restore of the error writer.
  • Build
    • Split hostmisc into C/C++ sources and add a C-only hostmisc_c object library
linux x64 Release
BinaryBaselinePRΔ bytesΔ %
libnethost.a2,743,470532,650-2,210,820-80.6%
libnethost.so43,37635,072-8,304-19.1%
macOS arm64 Release
BinaryBaselinePRΔ bytesΔ %
libnethost.a1,097,312268,360−828,952−75.5%
libnethost.dylib92,36889,088−3,280−3.6%
windows x64 Release
BinaryBaselinePRΔ bytesΔ %
libnethost.lib2,951,1761,677,420−1,273,756−43.2%
nethost.dll71,16856,832−14,336−20.1%
Note
This PR description was drafted by GitHub Copilot.
elinor-fungand others
added 5 commits
June 23, 2026 14:51
@elinor-fung
Add C pal_get_loaded_library
2340343
Add a C implementation of looking up an already-loaded library in the
current process, so callers that need to reuse an existing hostfxr (e.g.
nethost) can do so without the C++ pal:: surface.
- Add a pal_dll_t typedef and pal_get_loaded_library declaration in pal.h.
- Implement pal_get_loaded_library in pal.unix.c (dlopen RTLD_NOLOAD,
dladdr to resolve the path, and the /proc/self/maps fallback) and
pal.windows.c (GetModuleHandleW + a shared get_module_file_name helper
factored out of pal_get_own_executable_path).
- Repoint the C++ pal::get_loaded_library wrappers at the new C function,
removing the old C++ implementations and the proc-maps helper.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Convert fxr_resolver_try_get_existing_fxr to C
ec86642
Now that pal_get_loaded_library is available in C, move the last
fxr_resolver function that was still C++-only into fxr_resolver.c.
Add fxr_resolver_try_get_existing_fxr (declaration in fxr_resolver.h,
implementation in fxr_resolver.c) and make the C++
fxr_resolver::try_get_existing_fxr wrapper delegate to it. Drop the file
comment noting that try_get_existing_fxr had to stay in C++.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Convert nethost to C
61fde33
Rewrite nethost.cpp as nethost.c using the C host APIs: trace_* for
tracing, fxr_resolver_try_get_existing_fxr / try_get_path_from_dotnet_root
/ try_get_path for resolution, and utils_get_directory. The RAII
error_writer_scope_t is replaced by saving and restoring the previous
error writer manually around the call, and pal::string_t buffers become
manually-managed pal_char_t* allocations.
Update nethost/CMakeLists.txt to build nethost.c. The compiled nethost
code is now C-only.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Remove the C++ fxr_resolver wrappers
190e36a
fxr_resolver.cpp held thin C++ wrappers (marshalling pal::string_t to and
from the pal_char_t* C API) over the fxr_resolver_* functions in
fxr_resolver.c. Remove them and have the remaining C++ callers use the C
API directly:
- hostfxr_resolver.cpp uses fxr_search_location and fxr_resolver_try_get_path
directly (with direct utils.h/error_codes.h includes that were previously
pulled in transitively through fxr_resolver.h).
- The load_fxr_and_get_delegate template (used by ijwhost and comhost) moves
to its own header, load_fxr_and_get_delegate.h, and calls the C resolver
functions. Its fxr handle is typed as pal_dll_t.
fxr_resolver.h is now a pure C header and fxr_resolver is C-only (no
fxr_resolver.cpp), which also drops it from the static singlefilehost
sources.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Link nethost against a C-only hostmisc
9189c4b
nethost's own code is C, and after the previous change fxr_resolver is
C-only too, but nethost still linked the full hostmisc (which includes C++
translation units). That gave the nethost targets a C++ linker language, so
the clang++ driver added a dependency on the C++ runtime (libc++) and
libnethost.a embedded the unused C++ objects.
Split the hostmisc sources into C_SOURCES/CXX_SOURCES and add hostmisc_c, an
object library built from just the C sources. hostmisc and hostmisc::public
are unchanged for the C++ consumers (apphost, hostfxr, hostpolicy, etc.).
Point nethost/libnethost at hostmisc_c (+ minipal_objects, which object
libraries don't propagate transitively). The nethost targets now compile no
C++, link with the C driver, and have no libc++ dependency; libnethost.a
shrinks substantially by dropping the embedded C++ objects.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Pull request overview
This PR completes the nethost conversion to C-only by rewriting nethost in C, moving remaining fxr_resolver functionality to the C surface, and adding a C PAL helper to detect an already-loaded hostfxr without introducing a C++ runtime dependency.
Changes:
  • Replaced nethost.cpp with nethost.c, switching to the C host APIs and manually saving/restoring the trace error writer.
  • Added C pal_get_loaded_library (and pal_dll_t) and routed the existing C++ pal::get_loaded_library through it.
  • Removed fxr_resolver.cpp and moved the delegate-loading template to load_fxr_and_get_delegate.h; updated C++ callers to use the C fxr_resolver_* APIs directly.
Show a summary per file
FileDescription
src/native/corehost/nethost/nethost.cppRemoved C++ implementation of get_hostfxr_path.
src/native/corehost/nethost/nethost.cNew C implementation of get_hostfxr_path using C host APIs.
src/native/corehost/nethost/CMakeLists.txtSwitched nethost sources to C and updated link deps to hostmisc_c.
src/native/corehost/load_fxr_and_get_delegate.hNew header containing the load_fxr_and_get_delegate C++ template previously in fxr_resolver.h.
src/native/corehost/ijwhost/ijwhost.cppUpdated include to use load_fxr_and_get_delegate.h.
src/native/corehost/comhost/comhost.cppUpdated include to use load_fxr_and_get_delegate.h.
src/native/corehost/hostmisc/pal.hAdded pal_dll_t and the C pal_get_loaded_library declaration.
src/native/corehost/hostmisc/pal.windows.cAdded pal_get_loaded_library implementation and refactored module-path helper.
src/native/corehost/hostmisc/pal.windows.cppC++ pal::get_loaded_library now delegates to pal_get_loaded_library.
src/native/corehost/hostmisc/pal.unix.cAdded pal_get_loaded_library implementation (dlopen RTLD_NOLOAD + dladdr, with /proc/self/maps fallback).
src/native/corehost/hostmisc/pal.unix.cppC++ pal::get_loaded_library now delegates to pal_get_loaded_library.
src/native/corehost/hostmisc/CMakeLists.txtSplit hostmisc C vs C++ sources and introduced hostmisc_c object library.
src/native/corehost/fxr_resolver.hRemoved C++ wrapper surface; added C fxr_resolver_try_get_existing_fxr.
src/native/corehost/fxr_resolver.cppRemoved thin C++ wrapper implementation.
src/native/corehost/fxr_resolver.cAdded C implementation of fxr_resolver_try_get_existing_fxr.
src/native/corehost/CMakeLists.txtUpdated fxr_resolver interface target to stop compiling fxr_resolver.cpp.
src/native/corehost/apphost/static/CMakeLists.txtDropped ../../fxr_resolver.cpp from sources.
src/native/corehost/apphost/standalone/hostfxr_resolver.cppSwitched from C++ wrappers to C fxr_resolver_try_get_path API.
src/installer/managed/Microsoft.NET.HostModel/AppHost/HostWriter.csUpdated comment to match renamed enum reference (fxr_search_location).
Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 4
Comment threadsrc/native/corehost/nethost/nethost.c
Comment threadsrc/native/corehost/hostmisc/pal.unix.c
Comment threadsrc/native/corehost/fxr_resolver.c
Outdated

Comment threadsrc/native/corehost/fxr_resolver.c
@elinor-fung
Address PR review feedback
a525dd7
- nethost.c: use %zu (not %d) for the size_t in the invalid-size trace.
- pal.unix.c: bound the /proc/self/maps %s read with an explicit field
width so a pathological line can't overflow the buffer.
- fxr_resolver.c: initialize *out_fxr in fxr_resolver_try_get_existing_fxr,
and drop the stale fxr_resolver.cpp reference from the file comment.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

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elinor-fung
marked this pull request as ready for review
June 25, 2026 20:16
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Drop single-field find_max_version_context_t wrapper
3ce2f43
It only held a c_fx_ver_t, so pass the c_fx_ver_t directly as the
pal_readdir_onlydirectories context instead of wrapping it.
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Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 0 new
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Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 1
Comment threadsrc/native/corehost/hostmisc/pal.unix.c
@elinor-fung
Potential fix for pull request finding
9179007
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Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 1
Comment threadsrc/native/corehost/nethost/CMakeLists.txt
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Comment threadsrc/native/corehost/apphost/standalone/hostfxr_resolver.cpp
Outdated

Comment threadsrc/native/corehost/hostmisc/pal.unix.c
Comment threadsrc/native/corehost/nethost/nethost.c
Outdated

Comment threadsrc/native/corehost/nethost/nethost.c
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Apply suggestions from code review
c6e1062
Co-authored-by: Aaron R Robinson <arobins@microsoft.com>
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@elinor-fung
Scope hostfxr_resolver raw path pointers to their lifetime
129203b
In hostfxr_resolver_t's constructor, wrap the dotnet_root/fxr_path raw
pointers in a block so they go out of scope right after they are freed,
preventing later dangling-pointer use. The rest of the constructor only
needs the resolved flag and the assigned members.
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Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 0 new
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Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 2
Comment threadsrc/native/corehost/load_fxr_and_get_delegate.h
Comment threadsrc/native/corehost/fxr_resolver.h
Outdated

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Potential fix for pull request finding
0a52486
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Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 1
Comment threadsrc/native/corehost/load_fxr_and_get_delegate.h
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Apply suggestions from code review
c6f2953
Co-authored-by: Aaron R Robinson <arobins@microsoft.com>
Co-authored-by: Elinor Fung <elfung@microsoft.com>
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  • Comments generated: 0 new

This was referenced Jul 2, 2026

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merged commit ad0692a
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@elinor-fung
@AaronRobinsonMSFT@eiriktsarpalis
Convert nethost to C (#129828)
6c8fdf9
Convert `nethost` to C. This builds on #128420 and #129480 to fully
convert `nethost` so it compiles and links as C-only — no C++ runtime
dependency.
- **pal**
- Add a C `pal_get_loaded_library` (look up an already-loaded library
without loading it). The C++ `pal::get_loaded_library` now delegates to
it.
- **fxr_resolver** - Convert the last C++-only piece, `try_get_existing_fxr`, to C.
- Remove the thin C++ wrappers in `fxr_resolver.cpp`
- Move `load_fxr_and_get_delegate` (used by `comhost` and `ijwhost`)
into its own header `load_fxr_and_get_delegate.h`
- **nethost**
- Replace `nethost.cpp` with `nethost.c` using the shared host bits that
have been converted to C. The RAII `error_writer_scope_t` is replaced by
manual save/restore of the error writer.
- **Build**
- Split `hostmisc` into C/C++ sources and add a C-only `hostmisc_c`
object library
**linux x64 Release**
| Binary | Baseline | PR | Δ bytes | Δ % |
|---|---|---|---|---|
| `libnethost.a` | 2,743,470 | 532,650 | -2,210,820 | -80.6% |
| `libnethost.so` | 43,376 | 35,072 | -8,304 | -19.1% |
**macOS arm64 Release**
| Binary | Baseline | PR | Δ bytes | Δ % |
|---|---:|---:|---:|---:|
| `libnethost.a` | 1,097,312 | 268,360 | −828,952 | −75.5% |
| `libnethost.dylib` | 92,368 | 89,088 | −3,280 | −3.6% |
**windows x64 Release**
| Binary | Baseline | PR | Δ bytes | Δ % |
|---|--:|--:|--:|--:|
| `libnethost.lib` | 2,951,176 | 1,677,420 | −1,273,756 | −43.2% |
| `nethost.dll` | 71,168 | 56,832 | −14,336 | −20.1% |
---------
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Aaron R Robinson <arobins@microsoft.com>
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Status: Done


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Convert nethost to C by elinor-fung · Pull Request #129828 · dotnet/runtime · GitHub
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Convert nethost to C - #129828
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Convert nethost to C#129828
elinor-fung merged 12 commits into
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Convert nethost to C. This builds on #128420 and #129480 to fully convert nethost so it compiles and links as C-only — no C++ runtime dependency.
cc @dotnet/appmodel @AaronRobinsonMSFT
  • pal
    • Add a C pal_get_loaded_library (look up an already-loaded library without loading it). The C++ pal::get_loaded_library now delegates to it.
  • fxr_resolver
    • Convert the last C++-only piece, try_get_existing_fxr, to C.
    • Remove the thin C++ wrappers in fxr_resolver.cpp
    • Move load_fxr_and_get_delegate (used by comhost and ijwhost) into its own header load_fxr_and_get_delegate.h
  • nethost
    • Replace nethost.cpp with nethost.c using the shared host bits that have been converted to C. The RAII error_writer_scope_t is replaced by manual save/restore of the error writer.
  • Build
    • Split hostmisc into C/C++ sources and add a C-only hostmisc_c object library
linux x64 Release
BinaryBaselinePRΔ bytesΔ %
libnethost.a2,743,470532,650-2,210,820-80.6%
libnethost.so43,37635,072-8,304-19.1%
macOS arm64 Release
BinaryBaselinePRΔ bytesΔ %
libnethost.a1,097,312268,360−828,952−75.5%
libnethost.dylib92,36889,088−3,280−3.6%
windows x64 Release
BinaryBaselinePRΔ bytesΔ %
libnethost.lib2,951,1761,677,420−1,273,756−43.2%
nethost.dll71,16856,832−14,336−20.1%
Note
This PR description was drafted by GitHub Copilot.
elinor-fungand others
added 5 commits
June 23, 2026 14:51
@elinor-fung
Add C pal_get_loaded_library
2340343
Add a C implementation of looking up an already-loaded library in the
current process, so callers that need to reuse an existing hostfxr (e.g.
nethost) can do so without the C++ pal:: surface.
- Add a pal_dll_t typedef and pal_get_loaded_library declaration in pal.h.
- Implement pal_get_loaded_library in pal.unix.c (dlopen RTLD_NOLOAD,
dladdr to resolve the path, and the /proc/self/maps fallback) and
pal.windows.c (GetModuleHandleW + a shared get_module_file_name helper
factored out of pal_get_own_executable_path).
- Repoint the C++ pal::get_loaded_library wrappers at the new C function,
removing the old C++ implementations and the proc-maps helper.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Convert fxr_resolver_try_get_existing_fxr to C
ec86642
Now that pal_get_loaded_library is available in C, move the last
fxr_resolver function that was still C++-only into fxr_resolver.c.
Add fxr_resolver_try_get_existing_fxr (declaration in fxr_resolver.h,
implementation in fxr_resolver.c) and make the C++
fxr_resolver::try_get_existing_fxr wrapper delegate to it. Drop the file
comment noting that try_get_existing_fxr had to stay in C++.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Convert nethost to C
61fde33
Rewrite nethost.cpp as nethost.c using the C host APIs: trace_* for
tracing, fxr_resolver_try_get_existing_fxr / try_get_path_from_dotnet_root
/ try_get_path for resolution, and utils_get_directory. The RAII
error_writer_scope_t is replaced by saving and restoring the previous
error writer manually around the call, and pal::string_t buffers become
manually-managed pal_char_t* allocations.
Update nethost/CMakeLists.txt to build nethost.c. The compiled nethost
code is now C-only.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Remove the C++ fxr_resolver wrappers
190e36a
fxr_resolver.cpp held thin C++ wrappers (marshalling pal::string_t to and
from the pal_char_t* C API) over the fxr_resolver_* functions in
fxr_resolver.c. Remove them and have the remaining C++ callers use the C
API directly:
- hostfxr_resolver.cpp uses fxr_search_location and fxr_resolver_try_get_path
directly (with direct utils.h/error_codes.h includes that were previously
pulled in transitively through fxr_resolver.h).
- The load_fxr_and_get_delegate template (used by ijwhost and comhost) moves
to its own header, load_fxr_and_get_delegate.h, and calls the C resolver
functions. Its fxr handle is typed as pal_dll_t.
fxr_resolver.h is now a pure C header and fxr_resolver is C-only (no
fxr_resolver.cpp), which also drops it from the static singlefilehost
sources.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@elinor-fung
Link nethost against a C-only hostmisc
9189c4b
nethost's own code is C, and after the previous change fxr_resolver is
C-only too, but nethost still linked the full hostmisc (which includes C++
translation units). That gave the nethost targets a C++ linker language, so
the clang++ driver added a dependency on the C++ runtime (libc++) and
libnethost.a embedded the unused C++ objects.
Split the hostmisc sources into C_SOURCES/CXX_SOURCES and add hostmisc_c, an
object library built from just the C sources. hostmisc and hostmisc::public
are unchanged for the C++ consumers (apphost, hostfxr, hostpolicy, etc.).
Point nethost/libnethost at hostmisc_c (+ minipal_objects, which object
libraries don't propagate transitively). The nethost targets now compile no
C++, link with the C driver, and have no libc++ dependency; libnethost.a
shrinks substantially by dropping the embedded C++ objects.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Pull request overview
This PR completes the nethost conversion to C-only by rewriting nethost in C, moving remaining fxr_resolver functionality to the C surface, and adding a C PAL helper to detect an already-loaded hostfxr without introducing a C++ runtime dependency.
Changes:
  • Replaced nethost.cpp with nethost.c, switching to the C host APIs and manually saving/restoring the trace error writer.
  • Added C pal_get_loaded_library (and pal_dll_t) and routed the existing C++ pal::get_loaded_library through it.
  • Removed fxr_resolver.cpp and moved the delegate-loading template to load_fxr_and_get_delegate.h; updated C++ callers to use the C fxr_resolver_* APIs directly.
Show a summary per file
FileDescription
src/native/corehost/nethost/nethost.cppRemoved C++ implementation of get_hostfxr_path.
src/native/corehost/nethost/nethost.cNew C implementation of get_hostfxr_path using C host APIs.
src/native/corehost/nethost/CMakeLists.txtSwitched nethost sources to C and updated link deps to hostmisc_c.
src/native/corehost/load_fxr_and_get_delegate.hNew header containing the load_fxr_and_get_delegate C++ template previously in fxr_resolver.h.
src/native/corehost/ijwhost/ijwhost.cppUpdated include to use load_fxr_and_get_delegate.h.
src/native/corehost/comhost/comhost.cppUpdated include to use load_fxr_and_get_delegate.h.
src/native/corehost/hostmisc/pal.hAdded pal_dll_t and the C pal_get_loaded_library declaration.
src/native/corehost/hostmisc/pal.windows.cAdded pal_get_loaded_library implementation and refactored module-path helper.
src/native/corehost/hostmisc/pal.windows.cppC++ pal::get_loaded_library now delegates to pal_get_loaded_library.
src/native/corehost/hostmisc/pal.unix.cAdded pal_get_loaded_library implementation (dlopen RTLD_NOLOAD + dladdr, with /proc/self/maps fallback).
src/native/corehost/hostmisc/pal.unix.cppC++ pal::get_loaded_library now delegates to pal_get_loaded_library.
src/native/corehost/hostmisc/CMakeLists.txtSplit hostmisc C vs C++ sources and introduced hostmisc_c object library.
src/native/corehost/fxr_resolver.hRemoved C++ wrapper surface; added C fxr_resolver_try_get_existing_fxr.
src/native/corehost/fxr_resolver.cppRemoved thin C++ wrapper implementation.
src/native/corehost/fxr_resolver.cAdded C implementation of fxr_resolver_try_get_existing_fxr.
src/native/corehost/CMakeLists.txtUpdated fxr_resolver interface target to stop compiling fxr_resolver.cpp.
src/native/corehost/apphost/static/CMakeLists.txtDropped ../../fxr_resolver.cpp from sources.
src/native/corehost/apphost/standalone/hostfxr_resolver.cppSwitched from C++ wrappers to C fxr_resolver_try_get_path API.
src/installer/managed/Microsoft.NET.HostModel/AppHost/HostWriter.csUpdated comment to match renamed enum reference (fxr_search_location).
Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 4
Comment threadsrc/native/corehost/nethost/nethost.c
Comment threadsrc/native/corehost/hostmisc/pal.unix.c
Comment threadsrc/native/corehost/fxr_resolver.c
Outdated

Comment threadsrc/native/corehost/fxr_resolver.c
@elinor-fung
Address PR review feedback
a525dd7
- nethost.c: use %zu (not %d) for the size_t in the invalid-size trace.
- pal.unix.c: bound the /proc/self/maps %s read with an explicit field
width so a pathological line can't overflow the buffer.
- fxr_resolver.c: initialize *out_fxr in fxr_resolver_try_get_existing_fxr,
and drop the stale fxr_resolver.cpp reference from the file comment.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

This was referenced Jun 25, 2026

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elinor-fung
marked this pull request as ready for review
June 25, 2026 20:16
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review requested due to automatic review settings
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@elinor-fung
Drop single-field find_max_version_context_t wrapper
3ce2f43
It only held a c_fx_ver_t, so pass the c_fx_ver_t directly as the
pal_readdir_onlydirectories context instead of wrapping it.
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Copilot's findings
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Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 1
Comment threadsrc/native/corehost/hostmisc/pal.unix.c
@elinor-fung
Potential fix for pull request finding
9179007
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
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Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 1
Comment threadsrc/native/corehost/nethost/CMakeLists.txt
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Comment threadsrc/native/corehost/apphost/standalone/hostfxr_resolver.cpp
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Comment threadsrc/native/corehost/hostmisc/pal.unix.c
Comment threadsrc/native/corehost/nethost/nethost.c
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Comment threadsrc/native/corehost/nethost/nethost.c
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Apply suggestions from code review
c6e1062
Co-authored-by: Aaron R Robinson <arobins@microsoft.com>
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@elinor-fung
Scope hostfxr_resolver raw path pointers to their lifetime
129203b
In hostfxr_resolver_t's constructor, wrap the dotnet_root/fxr_path raw
pointers in a block so they go out of scope right after they are freed,
preventing later dangling-pointer use. The rest of the constructor only
needs the resolved flag and the assigned members.
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Copilot's findings
  • Files reviewed: 19/19 changed files
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Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 2
Comment threadsrc/native/corehost/load_fxr_and_get_delegate.h
Comment threadsrc/native/corehost/fxr_resolver.h
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@elinor-fung
Potential fix for pull request finding
0a52486
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
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Copilot's findings
  • Files reviewed: 19/19 changed files
  • Comments generated: 1
Comment threadsrc/native/corehost/load_fxr_and_get_delegate.h
AaronRobinsonMSFT
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Apply suggestions from code review
c6f2953
Co-authored-by: Aaron R Robinson <arobins@microsoft.com>
Co-authored-by: Elinor Fung <elfung@microsoft.com>
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  • Comments generated: 0 new

This was referenced Jul 2, 2026

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@elinor-fung
elinor-fung
merged commit ad0692a
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dotnet:mainJul 2, 2026

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@elinor-fung
elinor-fung
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nethost-to-c

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July 2, 2026 17:13
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added this to the 11.0-preview7 milestone
Jul 3, 2026
eiriktsarpalis pushed a commit
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Jul 15, 2026
@elinor-fung
@AaronRobinsonMSFT@eiriktsarpalis
Convert nethost to C (#129828)
6c8fdf9
Convert `nethost` to C. This builds on #128420 and #129480 to fully
convert `nethost` so it compiles and links as C-only — no C++ runtime
dependency.
- **pal**
- Add a C `pal_get_loaded_library` (look up an already-loaded library
without loading it). The C++ `pal::get_loaded_library` now delegates to
it.
- **fxr_resolver** - Convert the last C++-only piece, `try_get_existing_fxr`, to C.
- Remove the thin C++ wrappers in `fxr_resolver.cpp`
- Move `load_fxr_and_get_delegate` (used by `comhost` and `ijwhost`)
into its own header `load_fxr_and_get_delegate.h`
- **nethost**
- Replace `nethost.cpp` with `nethost.c` using the shared host bits that
have been converted to C. The RAII `error_writer_scope_t` is replaced by
manual save/restore of the error writer.
- **Build**
- Split `hostmisc` into C/C++ sources and add a C-only `hostmisc_c`
object library
**linux x64 Release**
| Binary | Baseline | PR | Δ bytes | Δ % |
|---|---|---|---|---|
| `libnethost.a` | 2,743,470 | 532,650 | -2,210,820 | -80.6% |
| `libnethost.so` | 43,376 | 35,072 | -8,304 | -19.1% |
**macOS arm64 Release**
| Binary | Baseline | PR | Δ bytes | Δ % |
|---|---:|---:|---:|---:|
| `libnethost.a` | 1,097,312 | 268,360 | −828,952 | −75.5% |
| `libnethost.dylib` | 92,368 | 89,088 | −3,280 | −3.6% |
**windows x64 Release**
| Binary | Baseline | PR | Δ bytes | Δ % |
|---|--:|--:|--:|--:|
| `libnethost.lib` | 2,951,176 | 1,677,420 | −1,273,756 | −43.2% |
| `nethost.dll` | 71,168 | 56,832 | −14,336 | −20.1% |
---------
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Aaron R Robinson <arobins@microsoft.com>
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