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From: Fangrui Song <>
Cc: Fangrui Song <>
Subject: [musl] [PATCH] Use __builtin_FILE/__builtin_LINE if available
Date: Fri, 17 Feb 2023 17:33:33 -0800	[thread overview]
Message-ID: <> (raw)

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(); }' >
    cat > B.ccm <<'eof'
    #include <assert.h>
    export module B; export inline void foo() { assert(1); }
    cat > C.ccm <<'eof'
    #include <assert.h>
    export module C; export inline void foo() { assert(1); }
    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=. 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
 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)))
+#define assert(x) ((void)((x) || (__assert_fail(#x, __FILE__, __LINE__, __func__),0)))
 #define assert(x) ((void)((x) || (__assert_fail(#x, __FILE__, __LINE__, __func__),0)))

             reply	other threads:[~2023-02-18  1:34 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-02-18  1:33 Fangrui Song [this message]
2023-02-18  2:03 ` Rich Felker
2023-02-18  2:53   ` Fangrui Song
2023-02-18 12:17     ` Jon Chesterfield
2023-02-21 19:09       ` Fangrui Song
2023-02-27 22:26         ` Szabolcs Nagy
2023-03-02  8:19           ` Fangrui Song
     [not found]           ` <>
2023-03-05  3:23             ` Zhihao Yuan
2023-02-21 19:45       ` Jeffrey Walton

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