[all-commits] [llvm/llvm-project] 78abec: [clang][Sema] Fix diagnostic for function overload...

[s-watanabe314 via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 78abeca1d88593d7f2a27f3c3e140abe77236e7e
      https://github.com/llvm/llvm-project/commit/78abeca1d88593d7f2a27f3c3e140abe77236e7e
  Author: s-watanabe314 <watanabe.shu-06 at fujitsu.com>
  Date:   2024-09-03 (Tue, 03 Sep 2024)

  Changed paths:
    M clang/docs/ReleaseNotes.rst
    M clang/lib/Sema/SemaDecl.cpp
    M clang/test/SemaCXX/extern-c.cpp

  Log Message:
  -----------
  [clang][Sema] Fix diagnostic for function overloading in extern "C" (#106033)

Fixes #80235

When trying to overload a function within `extern "C"`, the diagnostic
`functions that differ only in their return type cannot be overloaded`
is given. This diagnostic is inappropriate because overloading is
basically not allowed in the C language. However, if the redeclared
function has the `((overloadable))` attribute, it should be diagnosed as
`functions that differ only in their return type cannot be overloaded`.

This patch uses `isExternC()` to provide an appropriate diagnostic
during the diagnostic process. `isExternC()` updates the linkage
information cache internally, so calling it before merging functions can
cause clang to crash. An example is declaring `static void foo()` and
`void foo()` within an `extern "C"` block. Therefore, I decided to call
`isExternC()` after the compilation error is confirmed and select the
diagnostic message. The diagnostic message is `conflicting types for
'func'` similar to the diagnostic in C, and `functions that differ only
in their return type cannot be overloaded` if the `((overloadable))`
attribute is given.

Regression tests verify that the expected diagnostics are given when
trying to overload functions within `extern "C"` and when the
`((overloadable))` attribute is present.

---------

Co-authored-by: Sirraide <aeternalmail at gmail.com>



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