[Bug c/40179] Incorrectly use Built-in function to replace the normal function with flag -O1

["baichangjun at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #2 from baichangjun at gmail dot com  2009-05-17 23:08 -------
It is not expected. I have done some tests with gcc i386, x86_64, amd64 and
powerpc version. only i386 compiler replaces strlen by builtin function. the
other compilers gave a warning msg: "warning: conflicting types for built-in
function 'strlen'", and chose the correct strlen function in test.c.

test result in x86_64 system:
Target: x86_64-linux-gnu
gcc version 4.2.4 (Ubuntu 4.2.4-1ubuntu4)

$ cat test.c
int strlen(char *p)
{
        return 0;
}
main()
{
        return strlen(0);
}
$ gcc -S -O1 test.c
test.c:2: warning: conflicting types for built-in function 'strlen'
$ cat test.s 
        .file   "test.c"
        .text
.globl strlen
        .type   strlen, @function
strlen:
.LFB2:
        movl    $0, %eax
        ret
.LFE2:
        .size   strlen, .-strlen
.globl main
        .type   main, @function
main:
.LFB3:
        movl    $0, %edi
        call    strlen
        rep ; ret
.LFE3:
        .size   main, .-main
.......
        .ident  "GCC: (GNU) 4.2.4 (Ubuntu 4.2.4-1ubuntu4)"
        .section        .note.GNU-stack,"",@progbits
$ 


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40179