fd_write crash on send_downstream() when updating to latest Viceroy #5

Closed
Closed
fd_write crash on send_downstream() when updating to latest Viceroy#5

Description

@erikrose
erikrose
opened on Aug 29, 2025

I was hoping to update to the latest Viceroy WITs and get off the sunfishcode/sync-wit branch, but this happens when serving a request:

% make serve
rm -rf hello_compute
componentize-py -d wit -w compute bindings hello_compute
componentize-py -d wit -w compute componentize --stub-wasi app -o app.wasm
Component built successfully
viceroy --adapt app.wasm
2025-08-29T16:46:00.920215Z ERROR WebAssembly trapped: error while executing at wasm backtrace:
0: 0x1143b98 - wit-component:adapter:wasi_snapshot_preview1!<wasm function 28>
1: 0x28fd0c5 - wit-component:shim!adapt-wasi_snapshot_preview1-fd_write
2: 0x1216612 - libcomponentize_py_runtime.so!wasi::lib_generated::fd_write::h16f1318d12ef7a07
3: 0x1207310 - libcomponentize_py_runtime.so!std::io::Write::write_all::hcae5d5a17ded01cf
4: 0x11ff50f - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::_$u7b$$u7b$closure$u7d$$u7d$::h9b174c565bf11cf0 (.llvm.10071916962893096014)
5: 0x11ff3c4 - libcomponentize_py_runtime.so!std::thread::current::try_with_current::hb3d871380377cf67
6: 0x120d9e2 - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::h6f239d02db0f481d
7: 0x120c7aa - libcomponentize_py_runtime.so!std::panicking::default_hook::he8216edd979025aa
8: 0x120e1d3 - libcomponentize_py_runtime.so!std::panicking::rust_panic_with_hook::h02d894de16d94192
9: 0x11f9d92 - libcomponentize_py_runtime.so!std::panicking::begin_panic_handler::_$u7b$$u7b$closure$u7d$$u7d$::he125d401eefa4f33
10: 0x11f9cf3 - libcomponentize_py_runtime.so!std::sys::backtrace::__rust_end_short_backtrace::h31a9416a2c4ea1cb
11: 0x120db45 - libcomponentize_py_runtime.so!__rustc::rust_begin_unwind
12: 0x122f16e - libcomponentize_py_runtime.so!core::panicking::panic_fmt::h52dbee1629029330
13: 0x124e734 - libcomponentize_py_runtime.so!core::result::unwrap_failed::h68b1db2abd074508
14: 0x1186bf0 - libcomponentize_py_runtime.so!componentize-py#ToCanonString
15: 0x28e15c9 - libcomponentize_py_bindings.so!fastly:api/http-resp#header-append-import
16: 0x28e56d7 - libcomponentize_py_bindings.so!componentize-py#CallIndirect
17: 0x185f3 - <unknown>!<wasm function 484>
18: 0x118acc4 - libcomponentize_py_runtime.so!componentize_py_runtime::_$LT$impl$u20$componentize_py_runtime..call_import..MakeDef$GT$::_PYO3_DEF::trampoline::h88da0896868f0eed
19: 0x1417d72 - cfunction_vectorcall_FASTCALL_KEYWORDS
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/methodobject.c:438:24
20: 0x13bb483 - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
21: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
22: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
23: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
24: 0x13babcb - _PyObject_FastCallDictTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:133:15
25: 0x13bbc35 - _PyObject_Call_Prepend
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:508:24
26: 0x143d0c9 - slot_tp_call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/typeobject.c:8769:15
27: 0x13baac3 - _PyObject_MakeTpCall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:240:18
28: 0x13bb46e - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:90:16
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
29: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
30: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
31: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
32: 0x13bdf7a - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- method_vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/classobject.c:91:18
33: 0x13bb30c - _PyVectorcall_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:271:16
34: 0x13bb6ef - _PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:354:16
35: 0x13bb789 - PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:379:12
36: 0x181c9 - <unknown>!<wasm function 406>
37: 0x118b45c - libcomponentize_py_runtime.so!pyo3::call::PyCallArgs::call_method_positional::hf0c9fd3e2a3bd359 (.llvm.11185300699313483585)
38: 0x11857ab - libcomponentize_py_runtime.so!componentize-py#Dispatch
39: 0x28e5648 - libcomponentize_py_bindings.so!fastly:api/reactor#serve-export
Caused by:
wasm trap: wasm `unreachable` instruction executed
2025-08-29T16:46:00.922327Z ERROR There was an error handling the request error while executing at wasm backtrace:
0: 0x1143b98 - wit-component:adapter:wasi_snapshot_preview1!<wasm function 28>
1: 0x28fd0c5 - wit-component:shim!adapt-wasi_snapshot_preview1-fd_write
2: 0x1216612 - libcomponentize_py_runtime.so!wasi::lib_generated::fd_write::h16f1318d12ef7a07
3: 0x1207310 - libcomponentize_py_runtime.so!std::io::Write::write_all::hcae5d5a17ded01cf
4: 0x11ff50f - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::_$u7b$$u7b$closure$u7d$$u7d$::h9b174c565bf11cf0 (.llvm.10071916962893096014)
5: 0x11ff3c4 - libcomponentize_py_runtime.so!std::thread::current::try_with_current::hb3d871380377cf67
6: 0x120d9e2 - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::h6f239d02db0f481d
7: 0x120c7aa - libcomponentize_py_runtime.so!std::panicking::default_hook::he8216edd979025aa
8: 0x120e1d3 - libcomponentize_py_runtime.so!std::panicking::rust_panic_with_hook::h02d894de16d94192
9: 0x11f9d92 - libcomponentize_py_runtime.so!std::panicking::begin_panic_handler::_$u7b$$u7b$closure$u7d$$u7d$::he125d401eefa4f33
10: 0x11f9cf3 - libcomponentize_py_runtime.so!std::sys::backtrace::__rust_end_short_backtrace::h31a9416a2c4ea1cb
11: 0x120db45 - libcomponentize_py_runtime.so!__rustc::rust_begin_unwind
12: 0x122f16e - libcomponentize_py_runtime.so!core::panicking::panic_fmt::h52dbee1629029330
13: 0x124e734 - libcomponentize_py_runtime.so!core::result::unwrap_failed::h68b1db2abd074508
14: 0x1186bf0 - libcomponentize_py_runtime.so!componentize-py#ToCanonString
15: 0x28e15c9 - libcomponentize_py_bindings.so!fastly:api/http-resp#header-append-import
16: 0x28e56d7 - libcomponentize_py_bindings.so!componentize-py#CallIndirect
17: 0x185f3 - <unknown>!<wasm function 484>
18: 0x118acc4 - libcomponentize_py_runtime.so!componentize_py_runtime::_$LT$impl$u20$componentize_py_runtime..call_import..MakeDef$GT$::_PYO3_DEF::trampoline::h88da0896868f0eed
19: 0x1417d72 - cfunction_vectorcall_FASTCALL_KEYWORDS
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/methodobject.c:438:24
20: 0x13bb483 - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
21: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
22: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
23: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
24: 0x13babcb - _PyObject_FastCallDictTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:133:15
25: 0x13bbc35 - _PyObject_Call_Prepend
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:508:24
26: 0x143d0c9 - slot_tp_call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/typeobject.c:8769:15
27: 0x13baac3 - _PyObject_MakeTpCall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:240:18
28: 0x13bb46e - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:90:16
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
29: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
30: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
31: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
32: 0x13bdf7a - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- method_vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/classobject.c:91:18
33: 0x13bb30c - _PyVectorcall_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:271:16
34: 0x13bb6ef - _PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:354:16
35: 0x13bb789 - PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:379:12
36: 0x181c9 - <unknown>!<wasm function 406>
37: 0x118b45c - libcomponentize_py_runtime.so!pyo3::call::PyCallArgs::call_method_positional::hf0c9fd3e2a3bd359 (.llvm.11185300699313483585)
38: 0x11857ab - libcomponentize_py_runtime.so!componentize-py#Dispatch
39: 0x28e5648 - libcomponentize_py_bindings.so!fastly:api/reactor#serve-export

I commented out chunks of app.py to reduce it, finally narrowing it down to send_downstream(). You can construct params to send_downstream() just fine, but actually calling it crashes. Perhaps it now calls fd_write() where it didn't before. Putting this aside for now.

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      Skip to content
      fd_write crash on send_downstream() when updating to latest Viceroy #5
      Closed
      Closed
      fd_write crash on send_downstream() when updating to latest Viceroy#5
      Description
      @erikrose
      erikrose
      opened on Aug 29, 2025
      I was hoping to update to the latest Viceroy WITs and get off the sunfishcode/sync-wit branch, but this happens when serving a request:
      % make serve
rm -rf hello_compute
componentize-py -d wit -w compute bindings hello_compute
componentize-py -d wit -w compute componentize --stub-wasi app -o app.wasm
Component built successfully
viceroy --adapt app.wasm
2025-08-29T16:46:00.920215Z ERROR WebAssembly trapped: error while executing at wasm backtrace:
0: 0x1143b98 - wit-component:adapter:wasi_snapshot_preview1!<wasm function 28>
1: 0x28fd0c5 - wit-component:shim!adapt-wasi_snapshot_preview1-fd_write
2: 0x1216612 - libcomponentize_py_runtime.so!wasi::lib_generated::fd_write::h16f1318d12ef7a07
3: 0x1207310 - libcomponentize_py_runtime.so!std::io::Write::write_all::hcae5d5a17ded01cf
4: 0x11ff50f - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::_$u7b$$u7b$closure$u7d$$u7d$::h9b174c565bf11cf0 (.llvm.10071916962893096014)
5: 0x11ff3c4 - libcomponentize_py_runtime.so!std::thread::current::try_with_current::hb3d871380377cf67
6: 0x120d9e2 - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::h6f239d02db0f481d
7: 0x120c7aa - libcomponentize_py_runtime.so!std::panicking::default_hook::he8216edd979025aa
8: 0x120e1d3 - libcomponentize_py_runtime.so!std::panicking::rust_panic_with_hook::h02d894de16d94192
9: 0x11f9d92 - libcomponentize_py_runtime.so!std::panicking::begin_panic_handler::_$u7b$$u7b$closure$u7d$$u7d$::he125d401eefa4f33
10: 0x11f9cf3 - libcomponentize_py_runtime.so!std::sys::backtrace::__rust_end_short_backtrace::h31a9416a2c4ea1cb
11: 0x120db45 - libcomponentize_py_runtime.so!__rustc::rust_begin_unwind
12: 0x122f16e - libcomponentize_py_runtime.so!core::panicking::panic_fmt::h52dbee1629029330
13: 0x124e734 - libcomponentize_py_runtime.so!core::result::unwrap_failed::h68b1db2abd074508
14: 0x1186bf0 - libcomponentize_py_runtime.so!componentize-py#ToCanonString
15: 0x28e15c9 - libcomponentize_py_bindings.so!fastly:api/http-resp#header-append-import
16: 0x28e56d7 - libcomponentize_py_bindings.so!componentize-py#CallIndirect
17: 0x185f3 - <unknown>!<wasm function 484>
18: 0x118acc4 - libcomponentize_py_runtime.so!componentize_py_runtime::_$LT$impl$u20$componentize_py_runtime..call_import..MakeDef$GT$::_PYO3_DEF::trampoline::h88da0896868f0eed
19: 0x1417d72 - cfunction_vectorcall_FASTCALL_KEYWORDS
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/methodobject.c:438:24
20: 0x13bb483 - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
21: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
22: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
23: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
24: 0x13babcb - _PyObject_FastCallDictTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:133:15
25: 0x13bbc35 - _PyObject_Call_Prepend
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:508:24
26: 0x143d0c9 - slot_tp_call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/typeobject.c:8769:15
27: 0x13baac3 - _PyObject_MakeTpCall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:240:18
28: 0x13bb46e - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:90:16
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
29: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
30: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
31: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
32: 0x13bdf7a - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- method_vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/classobject.c:91:18
33: 0x13bb30c - _PyVectorcall_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:271:16
34: 0x13bb6ef - _PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:354:16
35: 0x13bb789 - PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:379:12
36: 0x181c9 - <unknown>!<wasm function 406>
37: 0x118b45c - libcomponentize_py_runtime.so!pyo3::call::PyCallArgs::call_method_positional::hf0c9fd3e2a3bd359 (.llvm.11185300699313483585)
38: 0x11857ab - libcomponentize_py_runtime.so!componentize-py#Dispatch
39: 0x28e5648 - libcomponentize_py_bindings.so!fastly:api/reactor#serve-export
Caused by:
wasm trap: wasm `unreachable` instruction executed
2025-08-29T16:46:00.922327Z ERROR There was an error handling the request error while executing at wasm backtrace:
0: 0x1143b98 - wit-component:adapter:wasi_snapshot_preview1!<wasm function 28>
1: 0x28fd0c5 - wit-component:shim!adapt-wasi_snapshot_preview1-fd_write
2: 0x1216612 - libcomponentize_py_runtime.so!wasi::lib_generated::fd_write::h16f1318d12ef7a07
3: 0x1207310 - libcomponentize_py_runtime.so!std::io::Write::write_all::hcae5d5a17ded01cf
4: 0x11ff50f - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::_$u7b$$u7b$closure$u7d$$u7d$::h9b174c565bf11cf0 (.llvm.10071916962893096014)
5: 0x11ff3c4 - libcomponentize_py_runtime.so!std::thread::current::try_with_current::hb3d871380377cf67
6: 0x120d9e2 - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::h6f239d02db0f481d
7: 0x120c7aa - libcomponentize_py_runtime.so!std::panicking::default_hook::he8216edd979025aa
8: 0x120e1d3 - libcomponentize_py_runtime.so!std::panicking::rust_panic_with_hook::h02d894de16d94192
9: 0x11f9d92 - libcomponentize_py_runtime.so!std::panicking::begin_panic_handler::_$u7b$$u7b$closure$u7d$$u7d$::he125d401eefa4f33
10: 0x11f9cf3 - libcomponentize_py_runtime.so!std::sys::backtrace::__rust_end_short_backtrace::h31a9416a2c4ea1cb
11: 0x120db45 - libcomponentize_py_runtime.so!__rustc::rust_begin_unwind
12: 0x122f16e - libcomponentize_py_runtime.so!core::panicking::panic_fmt::h52dbee1629029330
13: 0x124e734 - libcomponentize_py_runtime.so!core::result::unwrap_failed::h68b1db2abd074508
14: 0x1186bf0 - libcomponentize_py_runtime.so!componentize-py#ToCanonString
15: 0x28e15c9 - libcomponentize_py_bindings.so!fastly:api/http-resp#header-append-import
16: 0x28e56d7 - libcomponentize_py_bindings.so!componentize-py#CallIndirect
17: 0x185f3 - <unknown>!<wasm function 484>
18: 0x118acc4 - libcomponentize_py_runtime.so!componentize_py_runtime::_$LT$impl$u20$componentize_py_runtime..call_import..MakeDef$GT$::_PYO3_DEF::trampoline::h88da0896868f0eed
19: 0x1417d72 - cfunction_vectorcall_FASTCALL_KEYWORDS
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/methodobject.c:438:24
20: 0x13bb483 - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
21: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
22: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
23: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
24: 0x13babcb - _PyObject_FastCallDictTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:133:15
25: 0x13bbc35 - _PyObject_Call_Prepend
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:508:24
26: 0x143d0c9 - slot_tp_call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/typeobject.c:8769:15
27: 0x13baac3 - _PyObject_MakeTpCall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:240:18
28: 0x13bb46e - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:90:16
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
29: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
30: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
31: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
32: 0x13bdf7a - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- method_vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/classobject.c:91:18
33: 0x13bb30c - _PyVectorcall_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:271:16
34: 0x13bb6ef - _PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:354:16
35: 0x13bb789 - PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:379:12
36: 0x181c9 - <unknown>!<wasm function 406>
37: 0x118b45c - libcomponentize_py_runtime.so!pyo3::call::PyCallArgs::call_method_positional::hf0c9fd3e2a3bd359 (.llvm.11185300699313483585)
38: 0x11857ab - libcomponentize_py_runtime.so!componentize-py#Dispatch
39: 0x28e5648 - libcomponentize_py_bindings.so!fastly:api/reactor#serve-export

      I commented out chunks of app.py to reduce it, finally narrowing it down to send_downstream(). You can construct params to send_downstream() just fine, but actually calling it crashes. Perhaps it now calls fd_write() where it didn't before. Putting this aside for now.
      Activity
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          Skip to content
          fd_write crash on send_downstream() when updating to latest Viceroy #5
          Closed
          Closed
          fd_write crash on send_downstream() when updating to latest Viceroy#5
          Description
          @erikrose
          erikrose
          opened on Aug 29, 2025
          I was hoping to update to the latest Viceroy WITs and get off the sunfishcode/sync-wit branch, but this happens when serving a request:
          % make serve
rm -rf hello_compute
componentize-py -d wit -w compute bindings hello_compute
componentize-py -d wit -w compute componentize --stub-wasi app -o app.wasm
Component built successfully
viceroy --adapt app.wasm
2025-08-29T16:46:00.920215Z ERROR WebAssembly trapped: error while executing at wasm backtrace:
0: 0x1143b98 - wit-component:adapter:wasi_snapshot_preview1!<wasm function 28>
1: 0x28fd0c5 - wit-component:shim!adapt-wasi_snapshot_preview1-fd_write
2: 0x1216612 - libcomponentize_py_runtime.so!wasi::lib_generated::fd_write::h16f1318d12ef7a07
3: 0x1207310 - libcomponentize_py_runtime.so!std::io::Write::write_all::hcae5d5a17ded01cf
4: 0x11ff50f - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::_$u7b$$u7b$closure$u7d$$u7d$::h9b174c565bf11cf0 (.llvm.10071916962893096014)
5: 0x11ff3c4 - libcomponentize_py_runtime.so!std::thread::current::try_with_current::hb3d871380377cf67
6: 0x120d9e2 - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::h6f239d02db0f481d
7: 0x120c7aa - libcomponentize_py_runtime.so!std::panicking::default_hook::he8216edd979025aa
8: 0x120e1d3 - libcomponentize_py_runtime.so!std::panicking::rust_panic_with_hook::h02d894de16d94192
9: 0x11f9d92 - libcomponentize_py_runtime.so!std::panicking::begin_panic_handler::_$u7b$$u7b$closure$u7d$$u7d$::he125d401eefa4f33
10: 0x11f9cf3 - libcomponentize_py_runtime.so!std::sys::backtrace::__rust_end_short_backtrace::h31a9416a2c4ea1cb
11: 0x120db45 - libcomponentize_py_runtime.so!__rustc::rust_begin_unwind
12: 0x122f16e - libcomponentize_py_runtime.so!core::panicking::panic_fmt::h52dbee1629029330
13: 0x124e734 - libcomponentize_py_runtime.so!core::result::unwrap_failed::h68b1db2abd074508
14: 0x1186bf0 - libcomponentize_py_runtime.so!componentize-py#ToCanonString
15: 0x28e15c9 - libcomponentize_py_bindings.so!fastly:api/http-resp#header-append-import
16: 0x28e56d7 - libcomponentize_py_bindings.so!componentize-py#CallIndirect
17: 0x185f3 - <unknown>!<wasm function 484>
18: 0x118acc4 - libcomponentize_py_runtime.so!componentize_py_runtime::_$LT$impl$u20$componentize_py_runtime..call_import..MakeDef$GT$::_PYO3_DEF::trampoline::h88da0896868f0eed
19: 0x1417d72 - cfunction_vectorcall_FASTCALL_KEYWORDS
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/methodobject.c:438:24
20: 0x13bb483 - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
21: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
22: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
23: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
24: 0x13babcb - _PyObject_FastCallDictTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:133:15
25: 0x13bbc35 - _PyObject_Call_Prepend
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:508:24
26: 0x143d0c9 - slot_tp_call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/typeobject.c:8769:15
27: 0x13baac3 - _PyObject_MakeTpCall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:240:18
28: 0x13bb46e - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:90:16
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
29: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
30: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
31: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
32: 0x13bdf7a - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- method_vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/classobject.c:91:18
33: 0x13bb30c - _PyVectorcall_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:271:16
34: 0x13bb6ef - _PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:354:16
35: 0x13bb789 - PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:379:12
36: 0x181c9 - <unknown>!<wasm function 406>
37: 0x118b45c - libcomponentize_py_runtime.so!pyo3::call::PyCallArgs::call_method_positional::hf0c9fd3e2a3bd359 (.llvm.11185300699313483585)
38: 0x11857ab - libcomponentize_py_runtime.so!componentize-py#Dispatch
39: 0x28e5648 - libcomponentize_py_bindings.so!fastly:api/reactor#serve-export
Caused by:
wasm trap: wasm `unreachable` instruction executed
2025-08-29T16:46:00.922327Z ERROR There was an error handling the request error while executing at wasm backtrace:
0: 0x1143b98 - wit-component:adapter:wasi_snapshot_preview1!<wasm function 28>
1: 0x28fd0c5 - wit-component:shim!adapt-wasi_snapshot_preview1-fd_write
2: 0x1216612 - libcomponentize_py_runtime.so!wasi::lib_generated::fd_write::h16f1318d12ef7a07
3: 0x1207310 - libcomponentize_py_runtime.so!std::io::Write::write_all::hcae5d5a17ded01cf
4: 0x11ff50f - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::_$u7b$$u7b$closure$u7d$$u7d$::h9b174c565bf11cf0 (.llvm.10071916962893096014)
5: 0x11ff3c4 - libcomponentize_py_runtime.so!std::thread::current::try_with_current::hb3d871380377cf67
6: 0x120d9e2 - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::h6f239d02db0f481d
7: 0x120c7aa - libcomponentize_py_runtime.so!std::panicking::default_hook::he8216edd979025aa
8: 0x120e1d3 - libcomponentize_py_runtime.so!std::panicking::rust_panic_with_hook::h02d894de16d94192
9: 0x11f9d92 - libcomponentize_py_runtime.so!std::panicking::begin_panic_handler::_$u7b$$u7b$closure$u7d$$u7d$::he125d401eefa4f33
10: 0x11f9cf3 - libcomponentize_py_runtime.so!std::sys::backtrace::__rust_end_short_backtrace::h31a9416a2c4ea1cb
11: 0x120db45 - libcomponentize_py_runtime.so!__rustc::rust_begin_unwind
12: 0x122f16e - libcomponentize_py_runtime.so!core::panicking::panic_fmt::h52dbee1629029330
13: 0x124e734 - libcomponentize_py_runtime.so!core::result::unwrap_failed::h68b1db2abd074508
14: 0x1186bf0 - libcomponentize_py_runtime.so!componentize-py#ToCanonString
15: 0x28e15c9 - libcomponentize_py_bindings.so!fastly:api/http-resp#header-append-import
16: 0x28e56d7 - libcomponentize_py_bindings.so!componentize-py#CallIndirect
17: 0x185f3 - <unknown>!<wasm function 484>
18: 0x118acc4 - libcomponentize_py_runtime.so!componentize_py_runtime::_$LT$impl$u20$componentize_py_runtime..call_import..MakeDef$GT$::_PYO3_DEF::trampoline::h88da0896868f0eed
19: 0x1417d72 - cfunction_vectorcall_FASTCALL_KEYWORDS
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/methodobject.c:438:24
20: 0x13bb483 - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
21: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
22: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
23: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
24: 0x13babcb - _PyObject_FastCallDictTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:133:15
25: 0x13bbc35 - _PyObject_Call_Prepend
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:508:24
26: 0x143d0c9 - slot_tp_call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/typeobject.c:8769:15
27: 0x13baac3 - _PyObject_MakeTpCall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:240:18
28: 0x13bb46e - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:90:16
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
29: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
30: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
31: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
32: 0x13bdf7a - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- method_vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/classobject.c:91:18
33: 0x13bb30c - _PyVectorcall_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:271:16
34: 0x13bb6ef - _PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:354:16
35: 0x13bb789 - PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:379:12
36: 0x181c9 - <unknown>!<wasm function 406>
37: 0x118b45c - libcomponentize_py_runtime.so!pyo3::call::PyCallArgs::call_method_positional::hf0c9fd3e2a3bd359 (.llvm.11185300699313483585)
38: 0x11857ab - libcomponentize_py_runtime.so!componentize-py#Dispatch
39: 0x28e5648 - libcomponentize_py_bindings.so!fastly:api/reactor#serve-export

          I commented out chunks of app.py to reduce it, finally narrowing it down to send_downstream(). You can construct params to send_downstream() just fine, but actually calling it crashes. Perhaps it now calls fd_write() where it didn't before. Putting this aside for now.
          Activity
          Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
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          Metadata
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(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

              Skip to content
              fd_write crash on send_downstream() when updating to latest Viceroy #5
              Closed
              Closed
              fd_write crash on send_downstream() when updating to latest Viceroy#5
              Description
              @erikrose
              erikrose
              opened on Aug 29, 2025
              I was hoping to update to the latest Viceroy WITs and get off the sunfishcode/sync-wit branch, but this happens when serving a request:
              % make serve
rm -rf hello_compute
componentize-py -d wit -w compute bindings hello_compute
componentize-py -d wit -w compute componentize --stub-wasi app -o app.wasm
Component built successfully
viceroy --adapt app.wasm
2025-08-29T16:46:00.920215Z ERROR WebAssembly trapped: error while executing at wasm backtrace:
0: 0x1143b98 - wit-component:adapter:wasi_snapshot_preview1!<wasm function 28>
1: 0x28fd0c5 - wit-component:shim!adapt-wasi_snapshot_preview1-fd_write
2: 0x1216612 - libcomponentize_py_runtime.so!wasi::lib_generated::fd_write::h16f1318d12ef7a07
3: 0x1207310 - libcomponentize_py_runtime.so!std::io::Write::write_all::hcae5d5a17ded01cf
4: 0x11ff50f - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::_$u7b$$u7b$closure$u7d$$u7d$::h9b174c565bf11cf0 (.llvm.10071916962893096014)
5: 0x11ff3c4 - libcomponentize_py_runtime.so!std::thread::current::try_with_current::hb3d871380377cf67
6: 0x120d9e2 - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::h6f239d02db0f481d
7: 0x120c7aa - libcomponentize_py_runtime.so!std::panicking::default_hook::he8216edd979025aa
8: 0x120e1d3 - libcomponentize_py_runtime.so!std::panicking::rust_panic_with_hook::h02d894de16d94192
9: 0x11f9d92 - libcomponentize_py_runtime.so!std::panicking::begin_panic_handler::_$u7b$$u7b$closure$u7d$$u7d$::he125d401eefa4f33
10: 0x11f9cf3 - libcomponentize_py_runtime.so!std::sys::backtrace::__rust_end_short_backtrace::h31a9416a2c4ea1cb
11: 0x120db45 - libcomponentize_py_runtime.so!__rustc::rust_begin_unwind
12: 0x122f16e - libcomponentize_py_runtime.so!core::panicking::panic_fmt::h52dbee1629029330
13: 0x124e734 - libcomponentize_py_runtime.so!core::result::unwrap_failed::h68b1db2abd074508
14: 0x1186bf0 - libcomponentize_py_runtime.so!componentize-py#ToCanonString
15: 0x28e15c9 - libcomponentize_py_bindings.so!fastly:api/http-resp#header-append-import
16: 0x28e56d7 - libcomponentize_py_bindings.so!componentize-py#CallIndirect
17: 0x185f3 - <unknown>!<wasm function 484>
18: 0x118acc4 - libcomponentize_py_runtime.so!componentize_py_runtime::_$LT$impl$u20$componentize_py_runtime..call_import..MakeDef$GT$::_PYO3_DEF::trampoline::h88da0896868f0eed
19: 0x1417d72 - cfunction_vectorcall_FASTCALL_KEYWORDS
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/methodobject.c:438:24
20: 0x13bb483 - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
21: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
22: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
23: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
24: 0x13babcb - _PyObject_FastCallDictTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:133:15
25: 0x13bbc35 - _PyObject_Call_Prepend
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:508:24
26: 0x143d0c9 - slot_tp_call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/typeobject.c:8769:15
27: 0x13baac3 - _PyObject_MakeTpCall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:240:18
28: 0x13bb46e - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:90:16
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
29: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
30: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
31: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
32: 0x13bdf7a - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- method_vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/classobject.c:91:18
33: 0x13bb30c - _PyVectorcall_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:271:16
34: 0x13bb6ef - _PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:354:16
35: 0x13bb789 - PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:379:12
36: 0x181c9 - <unknown>!<wasm function 406>
37: 0x118b45c - libcomponentize_py_runtime.so!pyo3::call::PyCallArgs::call_method_positional::hf0c9fd3e2a3bd359 (.llvm.11185300699313483585)
38: 0x11857ab - libcomponentize_py_runtime.so!componentize-py#Dispatch
39: 0x28e5648 - libcomponentize_py_bindings.so!fastly:api/reactor#serve-export
Caused by:
wasm trap: wasm `unreachable` instruction executed
2025-08-29T16:46:00.922327Z ERROR There was an error handling the request error while executing at wasm backtrace:
0: 0x1143b98 - wit-component:adapter:wasi_snapshot_preview1!<wasm function 28>
1: 0x28fd0c5 - wit-component:shim!adapt-wasi_snapshot_preview1-fd_write
2: 0x1216612 - libcomponentize_py_runtime.so!wasi::lib_generated::fd_write::h16f1318d12ef7a07
3: 0x1207310 - libcomponentize_py_runtime.so!std::io::Write::write_all::hcae5d5a17ded01cf
4: 0x11ff50f - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::_$u7b$$u7b$closure$u7d$$u7d$::h9b174c565bf11cf0 (.llvm.10071916962893096014)
5: 0x11ff3c4 - libcomponentize_py_runtime.so!std::thread::current::try_with_current::hb3d871380377cf67
6: 0x120d9e2 - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::h6f239d02db0f481d
7: 0x120c7aa - libcomponentize_py_runtime.so!std::panicking::default_hook::he8216edd979025aa
8: 0x120e1d3 - libcomponentize_py_runtime.so!std::panicking::rust_panic_with_hook::h02d894de16d94192
9: 0x11f9d92 - libcomponentize_py_runtime.so!std::panicking::begin_panic_handler::_$u7b$$u7b$closure$u7d$$u7d$::he125d401eefa4f33
10: 0x11f9cf3 - libcomponentize_py_runtime.so!std::sys::backtrace::__rust_end_short_backtrace::h31a9416a2c4ea1cb
11: 0x120db45 - libcomponentize_py_runtime.so!__rustc::rust_begin_unwind
12: 0x122f16e - libcomponentize_py_runtime.so!core::panicking::panic_fmt::h52dbee1629029330
13: 0x124e734 - libcomponentize_py_runtime.so!core::result::unwrap_failed::h68b1db2abd074508
14: 0x1186bf0 - libcomponentize_py_runtime.so!componentize-py#ToCanonString
15: 0x28e15c9 - libcomponentize_py_bindings.so!fastly:api/http-resp#header-append-import
16: 0x28e56d7 - libcomponentize_py_bindings.so!componentize-py#CallIndirect
17: 0x185f3 - <unknown>!<wasm function 484>
18: 0x118acc4 - libcomponentize_py_runtime.so!componentize_py_runtime::_$LT$impl$u20$componentize_py_runtime..call_import..MakeDef$GT$::_PYO3_DEF::trampoline::h88da0896868f0eed
19: 0x1417d72 - cfunction_vectorcall_FASTCALL_KEYWORDS
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/methodobject.c:438:24
20: 0x13bb483 - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
21: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
22: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
23: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
24: 0x13babcb - _PyObject_FastCallDictTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:133:15
25: 0x13bbc35 - _PyObject_Call_Prepend
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:508:24
26: 0x143d0c9 - slot_tp_call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/typeobject.c:8769:15
27: 0x13baac3 - _PyObject_MakeTpCall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:240:18
28: 0x13bb46e - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:90:16
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
29: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
30: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
31: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
32: 0x13bdf7a - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- method_vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/classobject.c:91:18
33: 0x13bb30c - _PyVectorcall_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:271:16
34: 0x13bb6ef - _PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:354:16
35: 0x13bb789 - PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:379:12
36: 0x181c9 - <unknown>!<wasm function 406>
37: 0x118b45c - libcomponentize_py_runtime.so!pyo3::call::PyCallArgs::call_method_positional::hf0c9fd3e2a3bd359 (.llvm.11185300699313483585)
38: 0x11857ab - libcomponentize_py_runtime.so!componentize-py#Dispatch
39: 0x28e5648 - libcomponentize_py_bindings.so!fastly:api/reactor#serve-export

              I commented out chunks of app.py to reduce it, finally narrowing it down to send_downstream(). You can construct params to send_downstream() just fine, but actually calling it crashes. Perhaps it now calls fd_write() where it didn't before. Putting this aside for now.
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

                  Skip to content
                  fd_write crash on send_downstream() when updating to latest Viceroy #5
                  Closed
                  Closed
                  fd_write crash on send_downstream() when updating to latest Viceroy#5
                  Description
                  @erikrose
                  erikrose
                  opened on Aug 29, 2025
                  I was hoping to update to the latest Viceroy WITs and get off the sunfishcode/sync-wit branch, but this happens when serving a request:
                  % make serve
rm -rf hello_compute
componentize-py -d wit -w compute bindings hello_compute
componentize-py -d wit -w compute componentize --stub-wasi app -o app.wasm
Component built successfully
viceroy --adapt app.wasm
2025-08-29T16:46:00.920215Z ERROR WebAssembly trapped: error while executing at wasm backtrace:
0: 0x1143b98 - wit-component:adapter:wasi_snapshot_preview1!<wasm function 28>
1: 0x28fd0c5 - wit-component:shim!adapt-wasi_snapshot_preview1-fd_write
2: 0x1216612 - libcomponentize_py_runtime.so!wasi::lib_generated::fd_write::h16f1318d12ef7a07
3: 0x1207310 - libcomponentize_py_runtime.so!std::io::Write::write_all::hcae5d5a17ded01cf
4: 0x11ff50f - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::_$u7b$$u7b$closure$u7d$$u7d$::h9b174c565bf11cf0 (.llvm.10071916962893096014)
5: 0x11ff3c4 - libcomponentize_py_runtime.so!std::thread::current::try_with_current::hb3d871380377cf67
6: 0x120d9e2 - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::h6f239d02db0f481d
7: 0x120c7aa - libcomponentize_py_runtime.so!std::panicking::default_hook::he8216edd979025aa
8: 0x120e1d3 - libcomponentize_py_runtime.so!std::panicking::rust_panic_with_hook::h02d894de16d94192
9: 0x11f9d92 - libcomponentize_py_runtime.so!std::panicking::begin_panic_handler::_$u7b$$u7b$closure$u7d$$u7d$::he125d401eefa4f33
10: 0x11f9cf3 - libcomponentize_py_runtime.so!std::sys::backtrace::__rust_end_short_backtrace::h31a9416a2c4ea1cb
11: 0x120db45 - libcomponentize_py_runtime.so!__rustc::rust_begin_unwind
12: 0x122f16e - libcomponentize_py_runtime.so!core::panicking::panic_fmt::h52dbee1629029330
13: 0x124e734 - libcomponentize_py_runtime.so!core::result::unwrap_failed::h68b1db2abd074508
14: 0x1186bf0 - libcomponentize_py_runtime.so!componentize-py#ToCanonString
15: 0x28e15c9 - libcomponentize_py_bindings.so!fastly:api/http-resp#header-append-import
16: 0x28e56d7 - libcomponentize_py_bindings.so!componentize-py#CallIndirect
17: 0x185f3 - <unknown>!<wasm function 484>
18: 0x118acc4 - libcomponentize_py_runtime.so!componentize_py_runtime::_$LT$impl$u20$componentize_py_runtime..call_import..MakeDef$GT$::_PYO3_DEF::trampoline::h88da0896868f0eed
19: 0x1417d72 - cfunction_vectorcall_FASTCALL_KEYWORDS
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/methodobject.c:438:24
20: 0x13bb483 - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
21: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
22: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
23: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
24: 0x13babcb - _PyObject_FastCallDictTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:133:15
25: 0x13bbc35 - _PyObject_Call_Prepend
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:508:24
26: 0x143d0c9 - slot_tp_call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/typeobject.c:8769:15
27: 0x13baac3 - _PyObject_MakeTpCall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:240:18
28: 0x13bb46e - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:90:16
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
29: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
30: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
31: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
32: 0x13bdf7a - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- method_vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/classobject.c:91:18
33: 0x13bb30c - _PyVectorcall_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:271:16
34: 0x13bb6ef - _PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:354:16
35: 0x13bb789 - PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:379:12
36: 0x181c9 - <unknown>!<wasm function 406>
37: 0x118b45c - libcomponentize_py_runtime.so!pyo3::call::PyCallArgs::call_method_positional::hf0c9fd3e2a3bd359 (.llvm.11185300699313483585)
38: 0x11857ab - libcomponentize_py_runtime.so!componentize-py#Dispatch
39: 0x28e5648 - libcomponentize_py_bindings.so!fastly:api/reactor#serve-export
Caused by:
wasm trap: wasm `unreachable` instruction executed
2025-08-29T16:46:00.922327Z ERROR There was an error handling the request error while executing at wasm backtrace:
0: 0x1143b98 - wit-component:adapter:wasi_snapshot_preview1!<wasm function 28>
1: 0x28fd0c5 - wit-component:shim!adapt-wasi_snapshot_preview1-fd_write
2: 0x1216612 - libcomponentize_py_runtime.so!wasi::lib_generated::fd_write::h16f1318d12ef7a07
3: 0x1207310 - libcomponentize_py_runtime.so!std::io::Write::write_all::hcae5d5a17ded01cf
4: 0x11ff50f - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::_$u7b$$u7b$closure$u7d$$u7d$::h9b174c565bf11cf0 (.llvm.10071916962893096014)
5: 0x11ff3c4 - libcomponentize_py_runtime.so!std::thread::current::try_with_current::hb3d871380377cf67
6: 0x120d9e2 - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::h6f239d02db0f481d
7: 0x120c7aa - libcomponentize_py_runtime.so!std::panicking::default_hook::he8216edd979025aa
8: 0x120e1d3 - libcomponentize_py_runtime.so!std::panicking::rust_panic_with_hook::h02d894de16d94192
9: 0x11f9d92 - libcomponentize_py_runtime.so!std::panicking::begin_panic_handler::_$u7b$$u7b$closure$u7d$$u7d$::he125d401eefa4f33
10: 0x11f9cf3 - libcomponentize_py_runtime.so!std::sys::backtrace::__rust_end_short_backtrace::h31a9416a2c4ea1cb
11: 0x120db45 - libcomponentize_py_runtime.so!__rustc::rust_begin_unwind
12: 0x122f16e - libcomponentize_py_runtime.so!core::panicking::panic_fmt::h52dbee1629029330
13: 0x124e734 - libcomponentize_py_runtime.so!core::result::unwrap_failed::h68b1db2abd074508
14: 0x1186bf0 - libcomponentize_py_runtime.so!componentize-py#ToCanonString
15: 0x28e15c9 - libcomponentize_py_bindings.so!fastly:api/http-resp#header-append-import
16: 0x28e56d7 - libcomponentize_py_bindings.so!componentize-py#CallIndirect
17: 0x185f3 - <unknown>!<wasm function 484>
18: 0x118acc4 - libcomponentize_py_runtime.so!componentize_py_runtime::_$LT$impl$u20$componentize_py_runtime..call_import..MakeDef$GT$::_PYO3_DEF::trampoline::h88da0896868f0eed
19: 0x1417d72 - cfunction_vectorcall_FASTCALL_KEYWORDS
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/methodobject.c:438:24
20: 0x13bb483 - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
21: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
22: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
23: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
24: 0x13babcb - _PyObject_FastCallDictTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:133:15
25: 0x13bbc35 - _PyObject_Call_Prepend
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:508:24
26: 0x143d0c9 - slot_tp_call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/typeobject.c:8769:15
27: 0x13baac3 - _PyObject_MakeTpCall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:240:18
28: 0x13bb46e - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:90:16
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
29: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
30: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
31: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
32: 0x13bdf7a - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- method_vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/classobject.c:91:18
33: 0x13bb30c - _PyVectorcall_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:271:16
34: 0x13bb6ef - _PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:354:16
35: 0x13bb789 - PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:379:12
36: 0x181c9 - <unknown>!<wasm function 406>
37: 0x118b45c - libcomponentize_py_runtime.so!pyo3::call::PyCallArgs::call_method_positional::hf0c9fd3e2a3bd359 (.llvm.11185300699313483585)
38: 0x11857ab - libcomponentize_py_runtime.so!componentize-py#Dispatch
39: 0x28e5648 - libcomponentize_py_bindings.so!fastly:api/reactor#serve-export

                  I commented out chunks of app.py to reduce it, finally narrowing it down to send_downstream(). You can construct params to send_downstream() just fine, but actually calling it crashes. Perhaps it now calls fd_write() where it didn't before. Putting this aside for now.
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
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})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

                      Skip to content
                      fd_write crash on send_downstream() when updating to latest Viceroy #5
                      Closed
                      Closed
                      fd_write crash on send_downstream() when updating to latest Viceroy#5
                      Description
                      @erikrose
                      erikrose
                      opened on Aug 29, 2025
                      I was hoping to update to the latest Viceroy WITs and get off the sunfishcode/sync-wit branch, but this happens when serving a request:
                      % make serve
rm -rf hello_compute
componentize-py -d wit -w compute bindings hello_compute
componentize-py -d wit -w compute componentize --stub-wasi app -o app.wasm
Component built successfully
viceroy --adapt app.wasm
2025-08-29T16:46:00.920215Z ERROR WebAssembly trapped: error while executing at wasm backtrace:
0: 0x1143b98 - wit-component:adapter:wasi_snapshot_preview1!<wasm function 28>
1: 0x28fd0c5 - wit-component:shim!adapt-wasi_snapshot_preview1-fd_write
2: 0x1216612 - libcomponentize_py_runtime.so!wasi::lib_generated::fd_write::h16f1318d12ef7a07
3: 0x1207310 - libcomponentize_py_runtime.so!std::io::Write::write_all::hcae5d5a17ded01cf
4: 0x11ff50f - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::_$u7b$$u7b$closure$u7d$$u7d$::h9b174c565bf11cf0 (.llvm.10071916962893096014)
5: 0x11ff3c4 - libcomponentize_py_runtime.so!std::thread::current::try_with_current::hb3d871380377cf67
6: 0x120d9e2 - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::h6f239d02db0f481d
7: 0x120c7aa - libcomponentize_py_runtime.so!std::panicking::default_hook::he8216edd979025aa
8: 0x120e1d3 - libcomponentize_py_runtime.so!std::panicking::rust_panic_with_hook::h02d894de16d94192
9: 0x11f9d92 - libcomponentize_py_runtime.so!std::panicking::begin_panic_handler::_$u7b$$u7b$closure$u7d$$u7d$::he125d401eefa4f33
10: 0x11f9cf3 - libcomponentize_py_runtime.so!std::sys::backtrace::__rust_end_short_backtrace::h31a9416a2c4ea1cb
11: 0x120db45 - libcomponentize_py_runtime.so!__rustc::rust_begin_unwind
12: 0x122f16e - libcomponentize_py_runtime.so!core::panicking::panic_fmt::h52dbee1629029330
13: 0x124e734 - libcomponentize_py_runtime.so!core::result::unwrap_failed::h68b1db2abd074508
14: 0x1186bf0 - libcomponentize_py_runtime.so!componentize-py#ToCanonString
15: 0x28e15c9 - libcomponentize_py_bindings.so!fastly:api/http-resp#header-append-import
16: 0x28e56d7 - libcomponentize_py_bindings.so!componentize-py#CallIndirect
17: 0x185f3 - <unknown>!<wasm function 484>
18: 0x118acc4 - libcomponentize_py_runtime.so!componentize_py_runtime::_$LT$impl$u20$componentize_py_runtime..call_import..MakeDef$GT$::_PYO3_DEF::trampoline::h88da0896868f0eed
19: 0x1417d72 - cfunction_vectorcall_FASTCALL_KEYWORDS
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/methodobject.c:438:24
20: 0x13bb483 - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
21: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
22: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
23: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
24: 0x13babcb - _PyObject_FastCallDictTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:133:15
25: 0x13bbc35 - _PyObject_Call_Prepend
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:508:24
26: 0x143d0c9 - slot_tp_call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/typeobject.c:8769:15
27: 0x13baac3 - _PyObject_MakeTpCall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:240:18
28: 0x13bb46e - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:90:16
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
29: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
30: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
31: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
32: 0x13bdf7a - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- method_vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/classobject.c:91:18
33: 0x13bb30c - _PyVectorcall_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:271:16
34: 0x13bb6ef - _PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:354:16
35: 0x13bb789 - PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:379:12
36: 0x181c9 - <unknown>!<wasm function 406>
37: 0x118b45c - libcomponentize_py_runtime.so!pyo3::call::PyCallArgs::call_method_positional::hf0c9fd3e2a3bd359 (.llvm.11185300699313483585)
38: 0x11857ab - libcomponentize_py_runtime.so!componentize-py#Dispatch
39: 0x28e5648 - libcomponentize_py_bindings.so!fastly:api/reactor#serve-export
Caused by:
wasm trap: wasm `unreachable` instruction executed
2025-08-29T16:46:00.922327Z ERROR There was an error handling the request error while executing at wasm backtrace:
0: 0x1143b98 - wit-component:adapter:wasi_snapshot_preview1!<wasm function 28>
1: 0x28fd0c5 - wit-component:shim!adapt-wasi_snapshot_preview1-fd_write
2: 0x1216612 - libcomponentize_py_runtime.so!wasi::lib_generated::fd_write::h16f1318d12ef7a07
3: 0x1207310 - libcomponentize_py_runtime.so!std::io::Write::write_all::hcae5d5a17ded01cf
4: 0x11ff50f - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::_$u7b$$u7b$closure$u7d$$u7d$::h9b174c565bf11cf0 (.llvm.10071916962893096014)
5: 0x11ff3c4 - libcomponentize_py_runtime.so!std::thread::current::try_with_current::hb3d871380377cf67
6: 0x120d9e2 - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::h6f239d02db0f481d
7: 0x120c7aa - libcomponentize_py_runtime.so!std::panicking::default_hook::he8216edd979025aa
8: 0x120e1d3 - libcomponentize_py_runtime.so!std::panicking::rust_panic_with_hook::h02d894de16d94192
9: 0x11f9d92 - libcomponentize_py_runtime.so!std::panicking::begin_panic_handler::_$u7b$$u7b$closure$u7d$$u7d$::he125d401eefa4f33
10: 0x11f9cf3 - libcomponentize_py_runtime.so!std::sys::backtrace::__rust_end_short_backtrace::h31a9416a2c4ea1cb
11: 0x120db45 - libcomponentize_py_runtime.so!__rustc::rust_begin_unwind
12: 0x122f16e - libcomponentize_py_runtime.so!core::panicking::panic_fmt::h52dbee1629029330
13: 0x124e734 - libcomponentize_py_runtime.so!core::result::unwrap_failed::h68b1db2abd074508
14: 0x1186bf0 - libcomponentize_py_runtime.so!componentize-py#ToCanonString
15: 0x28e15c9 - libcomponentize_py_bindings.so!fastly:api/http-resp#header-append-import
16: 0x28e56d7 - libcomponentize_py_bindings.so!componentize-py#CallIndirect
17: 0x185f3 - <unknown>!<wasm function 484>
18: 0x118acc4 - libcomponentize_py_runtime.so!componentize_py_runtime::_$LT$impl$u20$componentize_py_runtime..call_import..MakeDef$GT$::_PYO3_DEF::trampoline::h88da0896868f0eed
19: 0x1417d72 - cfunction_vectorcall_FASTCALL_KEYWORDS
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/methodobject.c:438:24
20: 0x13bb483 - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
21: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
22: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
23: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
24: 0x13babcb - _PyObject_FastCallDictTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:133:15
25: 0x13bbc35 - _PyObject_Call_Prepend
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:508:24
26: 0x143d0c9 - slot_tp_call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/typeobject.c:8769:15
27: 0x13baac3 - _PyObject_MakeTpCall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:240:18
28: 0x13bb46e - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:90:16
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
29: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
30: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
31: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
32: 0x13bdf7a - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- method_vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/classobject.c:91:18
33: 0x13bb30c - _PyVectorcall_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:271:16
34: 0x13bb6ef - _PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:354:16
35: 0x13bb789 - PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:379:12
36: 0x181c9 - <unknown>!<wasm function 406>
37: 0x118b45c - libcomponentize_py_runtime.so!pyo3::call::PyCallArgs::call_method_positional::hf0c9fd3e2a3bd359 (.llvm.11185300699313483585)
38: 0x11857ab - libcomponentize_py_runtime.so!componentize-py#Dispatch
39: 0x28e5648 - libcomponentize_py_bindings.so!fastly:api/reactor#serve-export

                      I commented out chunks of app.py to reduce it, finally narrowing it down to send_downstream(). You can construct params to send_downstream() just fine, but actually calling it crashes. Perhaps it now calls fd_write() where it didn't before. Putting this aside for now.
                      Activity
                      Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
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                      Metadata
                      Assignees
                      No one assigned
                        Labels
                        No labels
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                        Type
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                          None yet
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                          No branches or pull requests
                          Issue actions
                          
, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

                          Skip to content
                          fd_write crash on send_downstream() when updating to latest Viceroy #5
                          Closed
                          Closed
                          fd_write crash on send_downstream() when updating to latest Viceroy#5
                          Description
                          @erikrose
                          erikrose
                          opened on Aug 29, 2025
                          I was hoping to update to the latest Viceroy WITs and get off the sunfishcode/sync-wit branch, but this happens when serving a request:
                          % make serve
rm -rf hello_compute
componentize-py -d wit -w compute bindings hello_compute
componentize-py -d wit -w compute componentize --stub-wasi app -o app.wasm
Component built successfully
viceroy --adapt app.wasm
2025-08-29T16:46:00.920215Z ERROR WebAssembly trapped: error while executing at wasm backtrace:
0: 0x1143b98 - wit-component:adapter:wasi_snapshot_preview1!<wasm function 28>
1: 0x28fd0c5 - wit-component:shim!adapt-wasi_snapshot_preview1-fd_write
2: 0x1216612 - libcomponentize_py_runtime.so!wasi::lib_generated::fd_write::h16f1318d12ef7a07
3: 0x1207310 - libcomponentize_py_runtime.so!std::io::Write::write_all::hcae5d5a17ded01cf
4: 0x11ff50f - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::_$u7b$$u7b$closure$u7d$$u7d$::h9b174c565bf11cf0 (.llvm.10071916962893096014)
5: 0x11ff3c4 - libcomponentize_py_runtime.so!std::thread::current::try_with_current::hb3d871380377cf67
6: 0x120d9e2 - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::h6f239d02db0f481d
7: 0x120c7aa - libcomponentize_py_runtime.so!std::panicking::default_hook::he8216edd979025aa
8: 0x120e1d3 - libcomponentize_py_runtime.so!std::panicking::rust_panic_with_hook::h02d894de16d94192
9: 0x11f9d92 - libcomponentize_py_runtime.so!std::panicking::begin_panic_handler::_$u7b$$u7b$closure$u7d$$u7d$::he125d401eefa4f33
10: 0x11f9cf3 - libcomponentize_py_runtime.so!std::sys::backtrace::__rust_end_short_backtrace::h31a9416a2c4ea1cb
11: 0x120db45 - libcomponentize_py_runtime.so!__rustc::rust_begin_unwind
12: 0x122f16e - libcomponentize_py_runtime.so!core::panicking::panic_fmt::h52dbee1629029330
13: 0x124e734 - libcomponentize_py_runtime.so!core::result::unwrap_failed::h68b1db2abd074508
14: 0x1186bf0 - libcomponentize_py_runtime.so!componentize-py#ToCanonString
15: 0x28e15c9 - libcomponentize_py_bindings.so!fastly:api/http-resp#header-append-import
16: 0x28e56d7 - libcomponentize_py_bindings.so!componentize-py#CallIndirect
17: 0x185f3 - <unknown>!<wasm function 484>
18: 0x118acc4 - libcomponentize_py_runtime.so!componentize_py_runtime::_$LT$impl$u20$componentize_py_runtime..call_import..MakeDef$GT$::_PYO3_DEF::trampoline::h88da0896868f0eed
19: 0x1417d72 - cfunction_vectorcall_FASTCALL_KEYWORDS
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/methodobject.c:438:24
20: 0x13bb483 - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
21: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
22: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
23: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
24: 0x13babcb - _PyObject_FastCallDictTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:133:15
25: 0x13bbc35 - _PyObject_Call_Prepend
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:508:24
26: 0x143d0c9 - slot_tp_call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/typeobject.c:8769:15
27: 0x13baac3 - _PyObject_MakeTpCall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:240:18
28: 0x13bb46e - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:90:16
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
29: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
30: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
31: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
32: 0x13bdf7a - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- method_vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/classobject.c:91:18
33: 0x13bb30c - _PyVectorcall_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:271:16
34: 0x13bb6ef - _PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:354:16
35: 0x13bb789 - PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:379:12
36: 0x181c9 - <unknown>!<wasm function 406>
37: 0x118b45c - libcomponentize_py_runtime.so!pyo3::call::PyCallArgs::call_method_positional::hf0c9fd3e2a3bd359 (.llvm.11185300699313483585)
38: 0x11857ab - libcomponentize_py_runtime.so!componentize-py#Dispatch
39: 0x28e5648 - libcomponentize_py_bindings.so!fastly:api/reactor#serve-export
Caused by:
wasm trap: wasm `unreachable` instruction executed
2025-08-29T16:46:00.922327Z ERROR There was an error handling the request error while executing at wasm backtrace:
0: 0x1143b98 - wit-component:adapter:wasi_snapshot_preview1!<wasm function 28>
1: 0x28fd0c5 - wit-component:shim!adapt-wasi_snapshot_preview1-fd_write
2: 0x1216612 - libcomponentize_py_runtime.so!wasi::lib_generated::fd_write::h16f1318d12ef7a07
3: 0x1207310 - libcomponentize_py_runtime.so!std::io::Write::write_all::hcae5d5a17ded01cf
4: 0x11ff50f - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::_$u7b$$u7b$closure$u7d$$u7d$::h9b174c565bf11cf0 (.llvm.10071916962893096014)
5: 0x11ff3c4 - libcomponentize_py_runtime.so!std::thread::current::try_with_current::hb3d871380377cf67
6: 0x120d9e2 - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::h6f239d02db0f481d
7: 0x120c7aa - libcomponentize_py_runtime.so!std::panicking::default_hook::he8216edd979025aa
8: 0x120e1d3 - libcomponentize_py_runtime.so!std::panicking::rust_panic_with_hook::h02d894de16d94192
9: 0x11f9d92 - libcomponentize_py_runtime.so!std::panicking::begin_panic_handler::_$u7b$$u7b$closure$u7d$$u7d$::he125d401eefa4f33
10: 0x11f9cf3 - libcomponentize_py_runtime.so!std::sys::backtrace::__rust_end_short_backtrace::h31a9416a2c4ea1cb
11: 0x120db45 - libcomponentize_py_runtime.so!__rustc::rust_begin_unwind
12: 0x122f16e - libcomponentize_py_runtime.so!core::panicking::panic_fmt::h52dbee1629029330
13: 0x124e734 - libcomponentize_py_runtime.so!core::result::unwrap_failed::h68b1db2abd074508
14: 0x1186bf0 - libcomponentize_py_runtime.so!componentize-py#ToCanonString
15: 0x28e15c9 - libcomponentize_py_bindings.so!fastly:api/http-resp#header-append-import
16: 0x28e56d7 - libcomponentize_py_bindings.so!componentize-py#CallIndirect
17: 0x185f3 - <unknown>!<wasm function 484>
18: 0x118acc4 - libcomponentize_py_runtime.so!componentize_py_runtime::_$LT$impl$u20$componentize_py_runtime..call_import..MakeDef$GT$::_PYO3_DEF::trampoline::h88da0896868f0eed
19: 0x1417d72 - cfunction_vectorcall_FASTCALL_KEYWORDS
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/methodobject.c:438:24
20: 0x13bb483 - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
21: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
22: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
23: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
24: 0x13babcb - _PyObject_FastCallDictTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:133:15
25: 0x13bbc35 - _PyObject_Call_Prepend
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:508:24
26: 0x143d0c9 - slot_tp_call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/typeobject.c:8769:15
27: 0x13baac3 - _PyObject_MakeTpCall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:240:18
28: 0x13bb46e - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:90:16
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
29: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
30: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
31: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
32: 0x13bdf7a - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- method_vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/classobject.c:91:18
33: 0x13bb30c - _PyVectorcall_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:271:16
34: 0x13bb6ef - _PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:354:16
35: 0x13bb789 - PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:379:12
36: 0x181c9 - <unknown>!<wasm function 406>
37: 0x118b45c - libcomponentize_py_runtime.so!pyo3::call::PyCallArgs::call_method_positional::hf0c9fd3e2a3bd359 (.llvm.11185300699313483585)
38: 0x11857ab - libcomponentize_py_runtime.so!componentize-py#Dispatch
39: 0x28e5648 - libcomponentize_py_bindings.so!fastly:api/reactor#serve-export

                          I commented out chunks of app.py to reduce it, finally narrowing it down to send_downstream(). You can construct params to send_downstream() just fine, but actually calling it crashes. Perhaps it now calls fd_write() where it didn't before. Putting this aside for now.
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

                              Skip to content
                              fd_write crash on send_downstream() when updating to latest Viceroy #5
                              Closed
                              Closed
                              fd_write crash on send_downstream() when updating to latest Viceroy#5
                              Description
                              @erikrose
                              erikrose
                              opened on Aug 29, 2025
                              I was hoping to update to the latest Viceroy WITs and get off the sunfishcode/sync-wit branch, but this happens when serving a request:
                              % make serve
rm -rf hello_compute
componentize-py -d wit -w compute bindings hello_compute
componentize-py -d wit -w compute componentize --stub-wasi app -o app.wasm
Component built successfully
viceroy --adapt app.wasm
2025-08-29T16:46:00.920215Z ERROR WebAssembly trapped: error while executing at wasm backtrace:
0: 0x1143b98 - wit-component:adapter:wasi_snapshot_preview1!<wasm function 28>
1: 0x28fd0c5 - wit-component:shim!adapt-wasi_snapshot_preview1-fd_write
2: 0x1216612 - libcomponentize_py_runtime.so!wasi::lib_generated::fd_write::h16f1318d12ef7a07
3: 0x1207310 - libcomponentize_py_runtime.so!std::io::Write::write_all::hcae5d5a17ded01cf
4: 0x11ff50f - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::_$u7b$$u7b$closure$u7d$$u7d$::h9b174c565bf11cf0 (.llvm.10071916962893096014)
5: 0x11ff3c4 - libcomponentize_py_runtime.so!std::thread::current::try_with_current::hb3d871380377cf67
6: 0x120d9e2 - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::h6f239d02db0f481d
7: 0x120c7aa - libcomponentize_py_runtime.so!std::panicking::default_hook::he8216edd979025aa
8: 0x120e1d3 - libcomponentize_py_runtime.so!std::panicking::rust_panic_with_hook::h02d894de16d94192
9: 0x11f9d92 - libcomponentize_py_runtime.so!std::panicking::begin_panic_handler::_$u7b$$u7b$closure$u7d$$u7d$::he125d401eefa4f33
10: 0x11f9cf3 - libcomponentize_py_runtime.so!std::sys::backtrace::__rust_end_short_backtrace::h31a9416a2c4ea1cb
11: 0x120db45 - libcomponentize_py_runtime.so!__rustc::rust_begin_unwind
12: 0x122f16e - libcomponentize_py_runtime.so!core::panicking::panic_fmt::h52dbee1629029330
13: 0x124e734 - libcomponentize_py_runtime.so!core::result::unwrap_failed::h68b1db2abd074508
14: 0x1186bf0 - libcomponentize_py_runtime.so!componentize-py#ToCanonString
15: 0x28e15c9 - libcomponentize_py_bindings.so!fastly:api/http-resp#header-append-import
16: 0x28e56d7 - libcomponentize_py_bindings.so!componentize-py#CallIndirect
17: 0x185f3 - <unknown>!<wasm function 484>
18: 0x118acc4 - libcomponentize_py_runtime.so!componentize_py_runtime::_$LT$impl$u20$componentize_py_runtime..call_import..MakeDef$GT$::_PYO3_DEF::trampoline::h88da0896868f0eed
19: 0x1417d72 - cfunction_vectorcall_FASTCALL_KEYWORDS
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/methodobject.c:438:24
20: 0x13bb483 - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
21: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
22: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
23: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
24: 0x13babcb - _PyObject_FastCallDictTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:133:15
25: 0x13bbc35 - _PyObject_Call_Prepend
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:508:24
26: 0x143d0c9 - slot_tp_call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/typeobject.c:8769:15
27: 0x13baac3 - _PyObject_MakeTpCall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:240:18
28: 0x13bb46e - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:90:16
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
29: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
30: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
31: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
32: 0x13bdf7a - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- method_vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/classobject.c:91:18
33: 0x13bb30c - _PyVectorcall_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:271:16
34: 0x13bb6ef - _PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:354:16
35: 0x13bb789 - PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:379:12
36: 0x181c9 - <unknown>!<wasm function 406>
37: 0x118b45c - libcomponentize_py_runtime.so!pyo3::call::PyCallArgs::call_method_positional::hf0c9fd3e2a3bd359 (.llvm.11185300699313483585)
38: 0x11857ab - libcomponentize_py_runtime.so!componentize-py#Dispatch
39: 0x28e5648 - libcomponentize_py_bindings.so!fastly:api/reactor#serve-export
Caused by:
wasm trap: wasm `unreachable` instruction executed
2025-08-29T16:46:00.922327Z ERROR There was an error handling the request error while executing at wasm backtrace:
0: 0x1143b98 - wit-component:adapter:wasi_snapshot_preview1!<wasm function 28>
1: 0x28fd0c5 - wit-component:shim!adapt-wasi_snapshot_preview1-fd_write
2: 0x1216612 - libcomponentize_py_runtime.so!wasi::lib_generated::fd_write::h16f1318d12ef7a07
3: 0x1207310 - libcomponentize_py_runtime.so!std::io::Write::write_all::hcae5d5a17ded01cf
4: 0x11ff50f - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::_$u7b$$u7b$closure$u7d$$u7d$::h9b174c565bf11cf0 (.llvm.10071916962893096014)
5: 0x11ff3c4 - libcomponentize_py_runtime.so!std::thread::current::try_with_current::hb3d871380377cf67
6: 0x120d9e2 - libcomponentize_py_runtime.so!std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::h6f239d02db0f481d
7: 0x120c7aa - libcomponentize_py_runtime.so!std::panicking::default_hook::he8216edd979025aa
8: 0x120e1d3 - libcomponentize_py_runtime.so!std::panicking::rust_panic_with_hook::h02d894de16d94192
9: 0x11f9d92 - libcomponentize_py_runtime.so!std::panicking::begin_panic_handler::_$u7b$$u7b$closure$u7d$$u7d$::he125d401eefa4f33
10: 0x11f9cf3 - libcomponentize_py_runtime.so!std::sys::backtrace::__rust_end_short_backtrace::h31a9416a2c4ea1cb
11: 0x120db45 - libcomponentize_py_runtime.so!__rustc::rust_begin_unwind
12: 0x122f16e - libcomponentize_py_runtime.so!core::panicking::panic_fmt::h52dbee1629029330
13: 0x124e734 - libcomponentize_py_runtime.so!core::result::unwrap_failed::h68b1db2abd074508
14: 0x1186bf0 - libcomponentize_py_runtime.so!componentize-py#ToCanonString
15: 0x28e15c9 - libcomponentize_py_bindings.so!fastly:api/http-resp#header-append-import
16: 0x28e56d7 - libcomponentize_py_bindings.so!componentize-py#CallIndirect
17: 0x185f3 - <unknown>!<wasm function 484>
18: 0x118acc4 - libcomponentize_py_runtime.so!componentize_py_runtime::_$LT$impl$u20$componentize_py_runtime..call_import..MakeDef$GT$::_PYO3_DEF::trampoline::h88da0896868f0eed
19: 0x1417d72 - cfunction_vectorcall_FASTCALL_KEYWORDS
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/methodobject.c:438:24
20: 0x13bb483 - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
21: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
22: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
23: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
24: 0x13babcb - _PyObject_FastCallDictTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:133:15
25: 0x13bbc35 - _PyObject_Call_Prepend
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:508:24
26: 0x143d0c9 - slot_tp_call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/typeobject.c:8769:15
27: 0x13baac3 - _PyObject_MakeTpCall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:240:18
28: 0x13bb46e - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:90:16
- PyObject_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:325:12
29: 0x14dbd2d - _PyEval_EvalFrameDefault
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/Python/bytecodes.c:2706:19
30: 0x14ddfd4 - _PyEval_EvalFrame
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_ceval.h:89:16
- _PyEval_Vector
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Python/ceval.c:1683:12
31: 0x13bb94d - _PyFunction_Vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c
32: 0x13bdf7a - _PyObject_VectorcallTstate
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Include/internal/pycore_call.h:92:11
- method_vectorcall
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/classobject.c:91:18
33: 0x13bb30c - _PyVectorcall_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:271:16
34: 0x13bb6ef - _PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:354:16
35: 0x13bb789 - PyObject_Call
at /home/runner/work/componentize-py/componentize-py/cpython/builddir/wasi/../../Objects/call.c:379:12
36: 0x181c9 - <unknown>!<wasm function 406>
37: 0x118b45c - libcomponentize_py_runtime.so!pyo3::call::PyCallArgs::call_method_positional::hf0c9fd3e2a3bd359 (.llvm.11185300699313483585)
38: 0x11857ab - libcomponentize_py_runtime.so!componentize-py#Dispatch
39: 0x28e5648 - libcomponentize_py_bindings.so!fastly:api/reactor#serve-export

                              I commented out chunks of app.py to reduce it, finally narrowing it down to send_downstream(). You can construct params to send_downstream() just fine, but actually calling it crashes. Perhaps it now calls fd_write() where it didn't before. Putting this aside for now.
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