[llvm] Stop using __attribute__((retain)) in GCC builds (PR #133793)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-support

Author: Matthias Braun (MatzeB)

<details>
<summary>Changes</summary>

GCC sometimes produces warnings about `__attribute__((retain))` despite `__has_attribute(retain)` being 1. See: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99587

The amount of users who benefit from the attribute is probably very small compared to the amount of `-Werror` enabled builds or the desire to keep `-Wattributes` enabled in the LLVM build. So for now drop usage of the `retain` attribute in GCC builds.

---
Full diff: https://github.com/llvm/llvm-project/pull/133793.diff


1 Files Affected:

- (modified) llvm/include/llvm/Support/Compiler.h (+7) 


``````````diff
diff --git a/llvm/include/llvm/Support/Compiler.h b/llvm/include/llvm/Support/Compiler.h
index ff6f5e44ae2f1..dd70362455d89 100644
--- a/llvm/include/llvm/Support/Compiler.h
+++ b/llvm/include/llvm/Support/Compiler.h
@@ -231,8 +231,15 @@
 #endif
 
 #if __has_attribute(retain)
+#if defined(__clang__) || !defined(__GNUC__)
 #define LLVM_ATTRIBUTE_RETAIN __attribute__((__retain__))
 #else
+// See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99587
+// GCC may produce "warning: ‘retain’ attribute ignored" (despite
+// __has_attribute(retain) begin 1). For now skip the attribute on GCC.
+#define LLVM_ATTRIBUTE_RETAIN
+#endif
+#else
 #define LLVM_ATTRIBUTE_RETAIN
 #endif
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/133793