[libc] Keep headers compatible with -std=c89 mode #121981
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C89 doesn't have the `restrict` keyword. When in `-std=c89` mode, GNU-compatible compilers require the `__restrict` spelling.
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@llvm/pr-subscribers-libc Author: Roland McGrath (frobtech) ChangesC89 doesn't have the Full diff: https://github.com/llvm/llvm-project/pull/121981.diff 1 Files Affected:
diff --git a/libc/include/__llvm-libc-common.h b/libc/include/__llvm-libc-common.h
index d9d70aff771c08..c63eb134a5e5d7 100644
--- a/libc/include/__llvm-libc-common.h
+++ b/libc/include/__llvm-libc-common.h
@@ -50,7 +50,14 @@
#define __END_C_DECLS
#undef __restrict
-#define __restrict restrict // C99 and above support the restrict keyword.
+#if __STDC_VERSION__ >= 199901L
+// C99 and above support the restrict keyword.
+#define __restrict restrict
+#elif !defined(__GNUC__)
+// GNU-compatible compilers accept the __ spelling in all modes.
+// Otherwise, omit the qualifier for pure C89 compatibility.
+#define __restrict
+#endif
#undef _Noreturn
#if __STDC_VERSION__ >= 201112L
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jhuber6
approved these changes
Jan 7, 2025
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Do we need to do this for __inline__ as well? I forget if that shows up anywhere.
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lntue
approved these changes
Jan 7, 2025
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C89 doesn't have the
restrictkeyword. When in-std=c89mode, GNU-compatible compilers require the
__restrictspelling.