[Bug other/101459] Mismatch in description of option "-falign-functions" between source code and documentation

ashimida at linux dot alibaba.com gcc-bugzilla@gcc.gnu.org
Thu Jul 15 07:37:10 GMT 2021


https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101459

--- Comment #3 from ashimida <ashimida at linux dot alibaba.com> ---
(In reply to Richard Biener from comment #2)
> The flag, -falign-functions is only enabled at -O2+ (but not -Os), but the
> actual alignment is recorded in the 'align_functions' data which is only
> populated when -falign-functions is specified so I think it works as
> documented.

I tested this option in gcc 7.5.0 and 9.2.0, with the source code:

int func1(void)                                                                 
{
    return 0;
}

int func2(void)
{
    return 0;
}

int main (void)
{
    return 1;
}

and the result is like:
ashimida@ubuntu:~/test1$ aarch64-linux-gnu-gcc -falign-functions=128 -O0 test.c
-o test
ashimida@ubuntu:~/test1$ readelf -s test|grep fun
    63: 0000000000000780     8 FUNC    GLOBAL DEFAULT   13 func1
    78: 0000000000000800     8 FUNC    GLOBAL DEFAULT   13 func2
ashimida@ubuntu:~/test1$ aarch64-linux-gnu-gcc -O0 test.c -o test
ashimida@ubuntu:~/test1$ readelf -s test|grep fun
    63: 00000000000006e4     8 FUNC    GLOBAL DEFAULT   13 func1
    78: 00000000000006ec     8 FUNC    GLOBAL DEFAULT   13 func2

so I think this flag is also worked at -O0


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