macos: workaround AppleClang compiler strrchr optimization bug

Apple shipped a clang built for macOS with an optimization enabled
that is not available on macOS. This compiler error may then be faced:

  ld: Undefined symbols:
	_memrchr, referenced from:
	    name_read(char const*) in map.cpp.o

This is a compiler error:

> On Mac OSX (macOS version 12.4, sdk version 12.1) llvm can replace call
> to strrchr() with call to memrchr() when string length is known at
> compile time. This results in link error, because memrchr is not present
> in libSystem.
> -- https://github.com/llvm/llvm-project/issues/62254

We workaround this by making the string length not known at build time
on macOS to avoid triggering the unavailable compiler optimization.

diff --git a/libs/uniquenames.h b/libs/uniquenames.h
index 9f89ba4556bdc2352517946c3eadf3f6b8d1a04c..7ef0755e3a6e62f91ec7028d9ccd5af5c2f1225c 100644 (file)
--- a/libs/uniquenames.h
+++ b/libs/uniquenames.h
@@ -106,9 +106,34 @@ inline void name_write( char* buffer, name_t name ){
 
 inline name_t name_read( const char* name ){
        const char* end = name + strlen( name );
+
+#if GDEF_OS_MACOS
+       /* HACK: Apple shipped a clang built for macOS with an optimization enabled
+       that is not available on macOS. This compiler error may then be faced:
+
+         ld: Undefined symbols:
+           _memrchr, referenced from:
+               name_read(char const*) in map.cpp.o
+
+       This is a compiler error:
+
+       > On Mac OSX (macOS version 12.4, sdk version 12.1) llvm can replace call
+       > to strrchr() with call to memrchr() when string length is known at
+       > compile time. This results in link error, because memrchr is not present
+       > in libSystem.
+       > -- https://github.com/llvm/llvm-project/issues/62254
+
+       We workaround this by making the string length not known at build time
+       on macOS to avoid triggering the unavailable compiler optimization. */
+
+       const char* volatile numbers = "1234567890";
+#else
+       const char* numbers = "1234567890";
+#endif
+
        for ( const char* p = end; end != name; --p )
        {
-               if ( strrchr( "1234567890", *p ) == NULL ) {
+               if ( strrchr( numbers, *p ) == NULL ) {
                        break;
                }
                end = p;