[LLVMgold] Suppress -Wcast-function-type-mismatch diagnostic

[MaskRay]

llvm/cmake/modules/HandleLLVMOptions.cmake adds -Wextra.
-Wcast-function-type-mismatch was recently added to -Wextra, leading to
a warning for the get_wrap_symbols code (https://reviews.llvm.org/D44235).

Suppress the diagnostic.

[llvmbot]

@llvm/pr-subscribers-lto

Author: Fangrui Song (MaskRay)

Changes

llvm/cmake/modules/HandleLLVMOptions.cmake adds -Wextra.
-Wcast-function-type-mismatch was recently added to -Wextra, leading to
a warning for the get_wrap_symbols code (https://reviews.llvm.org/D44235).

Suppress the diagnostic.

---

Full diff: https://github.com/llvm/llvm-project/pull/89994.diff

1 Files Affected:

• (modified) llvm/tools/gold/gold-plugin.cpp (+8-2)

diff --git a/llvm/tools/gold/gold-plugin.cpp b/llvm/tools/gold/gold-plugin.cpp
index b8a33f74bd570f..b8431334f8487c 100644
--- a/llvm/tools/gold/gold-plugin.cpp
+++ b/llvm/tools/gold/gold-plugin.cpp
@@ -434,8 +434,14 @@ ld_plugin_status onload(ld_plugin_tv *tv) {
       // FIXME: When binutils 2.31 (containing gold 1.16) is the minimum
       // required version, this should be changed to:
       // get_wrap_symbols = tv->tv_u.tv_get_wrap_symbols;
-      get_wrap_symbols =
-          (ld_plugin_get_wrap_symbols)tv->tv_u.tv_message;
+#ifdef __clang__
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wcast-function-type"
+#endif
+      get_wrap_symbols = (ld_plugin_get_wrap_symbols)tv->tv_u.tv_message;
+#ifdef __clang__
+#pragma clang diagnostic pop
+#endif
       break;
     default:
       break;

[MaskRay]

@Abhinkop

[UsmanNadeem]

This change is breaking some of our build bots because -Wcast-function-type is only supported in clang 13.0+
I am not familiar with this warning but can this be fixed without suppressing the warning, like other patches e.g. #76875 and #86290

llvm/tools/gold/gold-plugin.cpp:475:32: error: unknown warning group '-Wcast-function-type', ignored [-Werror,-Wunknown-warning-option]
#pragma GCC diagnostic ignored "-Wcast-function-type"
^
1 error generated.

https://llvm.org/docs/GettingStarted.html#host-c-toolchain-both-compiler-and-standard-library lists Clang 5.0, we are using clang 12.

[MaskRay]

I think we could use a union, but the mechanism would be too heavy.

llvm.org/docs/GettingStarted.html#host-c-toolchain-both-compiler-and-standard-library lists Clang 5.0, we are using clang 12.

While we support older clang versions down to 5, we cannot support -Werror for all of them, since every version might fix some false positives present in older versions...