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extern C functions need to be C-unwind in Rust 1.81.0 #584

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asomers opened this issue Jun 22, 2024 · 0 comments · Fixed by #585
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extern C functions need to be C-unwind in Rust 1.81.0 #584

asomers opened this issue Jun 22, 2024 · 0 comments · Fixed by #585
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asomers commented Jun 22, 2024

A recent change to rustc (rust-lang/rust#74990) changed the behavior of unwinding from a Rust function across an extern C ABI change. Now, that will cause an abort. This is causing Mockall's CI tests to fail. The possible solutions are either:

  • Require users to specify extern C-unwind instead. This is annoying for users, and it might not be correct for all non-mock functions.
  • Automatically define the mock functions as C-unwind. This is much better. However, it causes two new problems:
    • A function pointer to the original C function will now have a different type from a function pointer to the mock function, because the ABI is part of the function pointer's type.
    • C-unwind does not yet work for variadic functions.
  • Somehow figure out how to make Mockall work with panic=abort. It's not a problem, as long as no tests are should_panic and no tests ever fail 😉 .
@asomers asomers added the bug Something isn't working label Jun 22, 2024
asomers added a commit that referenced this issue Jun 22, 2024
@asomers
Use the C-unwind ABI instead of C when mocking extern C functions
0e12d52 
Begining within Rust 1.81
(rust-lang/rust#74990) Rust will abort when
attempting to unwind a panic across an "extern C" boundary.  Previously
it was technically UB, but it worked and Mockall relied on it.  Now,
unwinding across such a boundary requires the "extern C-unwind" ABI.
Use that ABI in the generated code.

However, don't use that ABI when mocking a C variadic function.  That
doesn't work, due to rust-lang/rust#126836 .

Fixes #584
@asomers asomers mentioned this issue Jun 22, 2024
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Use the C-unwind ABI instead of C when mocking extern C functions asomers/mockall
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