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Fix incorrect clashing_extern_declarations warnings. - #73990

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jumbatm:clashing-extern-decl
Jul 30, 2020
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Fix incorrect clashing_extern_declarations warnings.#73990
bors merged 6 commits into
rust-lang:masterfrom
jumbatm:clashing-extern-decl

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@jumbatm

@jumbatmjumbatm commented Jul 3, 2020•
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Fixes#73735, fixes#73872.

Fix clashing_extern_declarations warning for #[repr(transparent)] structs and safely-FFI-convertible enums, and not warning for clashes of struct members of different types, but the same size.

r? @nagisa

@rust-highfiverust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jul 3, 2020
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jumbatmforce-pushed the clashing-extern-decl branch 2 times, most recently from ee6f54b to b9efacfCompareJuly 3, 2020 12:43
teymour-aldridge
teymour-aldridge reviewed Jul 3, 2020
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Comment threadsrc/librustc_lint/builtin.rs Outdated
Comment threadsrc/librustc_lint/builtin.rs Outdated
Comment threadsrc/librustc_lint/types.rs Outdated
Comment threadsrc/librustc_lint/types.rs Outdated
Comment threadsrc/test/ui/lint/clashing-extern-fn.rs Outdated
Comment threadsrc/test/ui/lint/clashing-extern-fn.rs Outdated
nagisa
nagisa reviewed Jul 4, 2020
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Comment threadsrc/librustc_lint/builtin.rs Outdated
Comment threadsrc/librustc_lint/builtin.rs Outdated
Comment threadsrc/librustc_lint/builtin.rs Outdated
Comment threadsrc/librustc_lint/builtin.rs Outdated
Comment threadsrc/librustc_lint/builtin.rs Outdated
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jumbatmforce-pushed the clashing-extern-decl branch 3 times, most recently from d22ea6a to 7bba12bCompareJuly 4, 2020 07:32
nagisa
nagisa reviewed Jul 4, 2020
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jumbatmforce-pushed the clashing-extern-decl branch from 7bba12b to d283429CompareJuly 4, 2020 12:08
nagisa
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davidtwco
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@jumbatm

jumbatm commented Jul 5, 2020

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I'm still working on getting is_repr_nullable_ptr returning the type that's FFI-safe to use, but in the meantime, I've got a working (but quite awkward) solution where the caller optionally passes a type to check against.

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jumbatmforce-pushed the clashing-extern-decl branch 2 times, most recently from 136fe20 to f84b951CompareJuly 7, 2020 13:41
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jumbatm commented Jul 7, 2020

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Alright, this good for re-review -- I have repr_nullable_ptr returning the corresponding FFI-safe type as I mentioned earlier.

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jumbatmforce-pushed the clashing-extern-decl branch from f84b951 to c9ccc99CompareJuly 8, 2020 21:42
nagisa
nagisa reviewed Jul 11, 2020
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nagisa commented Jul 11, 2020

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Broadly lgtm, left 2 minor comments, r=me once resolved.

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jumbatmforce-pushed the clashing-extern-decl branch from c9ccc99 to 68b8a09CompareJuly 13, 2020 15:00
@jumbatm

jumbatm commented Jul 14, 2020•
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The changes have been applied. This is good to go.

e: Oops, had some unstaged formatting changes. This will be good to go once CI passes.

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jumbatmforce-pushed the clashing-extern-decl branch from 68b8a09 to 9182910CompareJuly 14, 2020 06:30
@jumbatm

jumbatm commented Jul 14, 2020

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Note that I've also added a few additional commits; they fix an assertion failure and false negative I noticed while working on this.

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bors commented Jul 14, 2020

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☔ The latest upstream changes (presumably #74342) made this pull request unmergeable. Please resolve the merge conflicts.

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jumbatmforce-pushed the clashing-extern-decl branch from 470d759 to da009d5CompareJuly 15, 2020 07:32
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bors commented Jul 18, 2020

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☔ The latest upstream changes (presumably #74468) made this pull request unmergeable. Please resolve the merge conflicts.

@jumbatm
jumbatmforce-pushed the clashing-extern-decl branch from da009d5 to cfcb282CompareJuly 18, 2020 21:46
@jumbatm
jumbatmforce-pushed the clashing-extern-decl branch from cfcb282 to 004c1c1CompareJuly 30, 2020 11:57
jumbatmand others added 6 commits July 30, 2020 21:59
@jumbatm
Add additional clashing_extern_decl cases.
4da72f5
@jumbatm
Don't emit clashing decl lint for FFI-safe enums.
3eaead7
An example of an FFI-safe enum conversion is when converting
Option<NonZeroUsize> to usize. Because the Some value must be non-zero,
rustc can use 0 to represent the None variant, making this conversion is
safe. Furthermore, it can be relied on (and removing this optimisation
already would be a breaking change).
@jumbatm@teymour-aldridge
Apply suggested wording changes from code review.
5e52edc
Co-authored-by: Teymour Aldridge <42674621+teymour-aldridge@users.noreply.github.com>
@jumbatm
Address code review comments.
060666d
- Make `is_repr_nullable_ptr` freestanding again to avoid usage of
ImproperCTypesVisitor in ClashingExternDeclarations (and don't
accidentally revert the ParamEnv::reveal_all() fix from a week earlier)
- Revise match condition for 1 Adt, 1 primitive
- Generalise check for non-null type so that it would also work for
ranges which exclude any single value (all bits set, for example)
- Make is_repr_nullable_ptr return the representable type instead of
just a boolean, to avoid adding an additional, independent "source of
truth" about the FFI-compatibility of Option-like enums. Also, rename to
`repr_nullable_ptr`.
@jumbatm
Handle structs with zst members.
30a6f57
@jumbatm
Fix missed same-sized member clash in ClashingExternDeclarations.
0bd292d
@jumbatm
jumbatmforce-pushed the clashing-extern-decl branch from 004c1c1 to 0bd292dCompareJuly 30, 2020 12:35
@jumbatm

jumbatm commented Jul 30, 2020

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I've just done another rebase -- @nagisa, are you available to review and approve? I'd like to get this merged soon so that these fixes can be backported to beta, and so I can try a crater check run with this lint as deny-by-default.

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nagisa commented Jul 30, 2020

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@bors r+

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bors commented Jul 30, 2020

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📌 Commit 0bd292d has been approved by nagisa

@borsbors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jul 30, 2020
@nagisanagisa added beta-nominated Nominated for backporting to the compiler in the beta channel. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Jul 30, 2020
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bors commented Jul 30, 2020

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⌛ Testing commit 0bd292d with merge 6b09c37...

@pnkfelix

pnkfelix commented Jul 30, 2020

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discussed at T-compiler meeting.

We decided the complexity of this PR, weighed against the bug it fixes, does not warrant a backport.

However, we agreed that a PR that just changed the lint on beta to be allow-by-default would be a reasonable thing to put on the beta branch.

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pnkfelix commented Jul 30, 2020

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@rustbot modify labels: -beta-nominated

@rustbotrustbot removed the beta-nominated Nominated for backporting to the compiler in the beta channel. label Jul 30, 2020
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☀️ Test successful - checks-actions, checks-azure
Approved by: nagisa
Pushing 6b09c37 to master...

@borsbors added the merged-by-bors This PR was explicitly merged by bors. label Jul 30, 2020
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bors merged commit 6b09c37 into rust-lang:masterJul 30, 2020
@borsbors mentioned this pull request Jul 30, 2020
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Auto merge ofrust-lang#74966- jumbatm:allow-clashing-extern-decl, r…
32c481e
…=Mark-Simulacrum
[beta] Make ClashingExternDeclarations Allow by default.
As per rust-lang#73990 (comment), this PR changes `clashing_extern_declarations` to allow-by-default to sidestep current false positives & negatives on the beta branch.
Note that the changes to fix the issue properly have been merged to master (see rust-lang#73990), but those changes will have to arrive on the next release train.
@Mark-SimulacrumMark-Simulacrum mentioned this pull request Aug 24, 2020
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@matthiaskrgrmatthiaskrgr mentioned this pull request Sep 7, 2023
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@cuvipercuviper added this to the 1.47.0 milestone May 2, 2024
RalfJung
RalfJung reviewed Sep 21, 2024
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Comment threadsrc/librustc_lint/types.rs
/// can, return the the type that `ty` can be safely converted to, otherwise return `None`.
/// Currently restricted to function pointers, boxes, references, `core::num::NonZero*`,
/// `core::ptr::NonNull`, and `#[repr(transparent)]` newtypes.
/// FIXME: This duplicates code in codegen.

@RalfJungRalfJungSep 21, 2024

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Does anyone involved still remember which code in codegen this duplicates? The comment as-is is unfortunately not very helpful since it is unclear where that duplication is.

@RalfJungRalfJungSep 21, 2024

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Ah never mind, this comment predates this PR, it just got moved here.

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clashing_extern_declarations misses clashes of same-sized members of structs Incorrect clashing_extern_decl warning in nightly

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