[musl] [PATCH] Use __builtin_FILE/__builtin_LINE if available

[Fangrui Song <i@maskray.me>]

C++ inline functions are requred to have exact same sequence of tokens
in every translation unit, but __FILE__ and __LINE__ may expand to
different tokens. The ODR violatioin is usually benign, but it can lead
to errors when C++20 modules are used.

    echo 'import B; import C; int main() { foo(); }' > A.cc
    cat > B.ccm <<'eof'
    module;
    #include <assert.h>
    export module B; export inline void foo() { assert(1); }
    eof
    cat > C.ccm <<'eof'
    module;
    #include <assert.h>
    export module C; export inline void foo() { assert(1); }
    eof
    clang -std=c++20 --precompile B.ccm -o B.pcm
    clang -std=c++20 --precompile C.ccm -o C.pcm
    clang -std=c++20 -fprebuilt-module-path=. A.cc B.pcm C.pcm -o A

    /tmp/d/C.ccm:3:37: error: 'foo' has different definitions in different modules; definition in module 'C' first difference is function body
    export module C; export inline void foo() { assert(1); }
                            ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~
    /tmp/d/B.ccm:3:37: note: but in 'B' found a different body
    export module B; export inline void foo() { assert(1); }
                            ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~

Fix this by preferring __builtin_FILE/__builtin_LINE which do not need
preprocessing.
---
 include/assert.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/include/assert.h b/include/assert.h
index d14ec94e..b209c2ae 100644
--- a/include/assert.h
+++ b/include/assert.h
@@ -4,6 +4,12 @@
 
 #ifdef NDEBUG
 #define	assert(x) (void)0
+#elif defined(__has_builtin)
+#if __has_builtin(__builtin_FILE)
+#define assert(x) ((void)((x) || (__assert_fail(#x, __builtin_FILE(), __builtin_LINE(), __func__),0)))
+#else
+#define assert(x) ((void)((x) || (__assert_fail(#x, __FILE__, __LINE__, __func__),0)))
+#endif
 #else
 #define assert(x) ((void)((x) || (__assert_fail(#x, __FILE__, __LINE__, __func__),0)))
 #endif
-- 
2.39.GIT