Re: gcc behavior of init priority of .ctors and .dtors section

On 5/16/24 4:05 PM, Lorenzo Salvadore wrote:
> On Thursday, May 16th, 2024 at 20:26, Konstantin Belousov <kostikbel@gmail.com> wrote:
>>> gcc13 from ports
>>> `# gcc ctors.c && ./a.out init 1 init 2 init 5 init 4 init 3 main fini 3 fini 4 fini 5 fini 2 fini 1`
>>>
>>> The above order is not expected. I think clang's one is correct.
>>>
>>> Further hacking with readelf shows that clang produces the right order of
>>> section .rela.ctors but gcc does not.
>>>
>>> ```
>>> # clang -fno-use-init-array -c ctors.c && readelf -r ctors.o | grep 'Relocation section with addend (.rela.ctors)' -A5 > clang.txt
>>> # gcc -c ctors.c && readelf -r ctors.o | grep 'Relocation section with addend (.rela.ctors)' -A5 > gcc.txt
>>> # diff clang.txt gcc.txt
>>> 3,5c3,5
>>> < 000000000000 000800000001 R_X86_64_64 0000000000000060 init_65535_2 + 0
>>> < 000000000008 000700000001 R_X86_64_64 0000000000000040 init + 0
>>> < 000000000010 000600000001 R_X86_64_64 0000000000000020 init_65535 + 0
>>> ---
>>>
>>>> 000000000000 000600000001 R_X86_64_64 0000000000000011 init_65535 + 0
>>>> 000000000008 000700000001 R_X86_64_64 0000000000000022 init + 0
>>>> 000000000010 000800000001 R_X86_64_64 0000000000000033 init_65535_2 + 0
>>>> ```
>>>
>>> The above show clearly gcc produces the wrong order of section `.rela.ctors`.
>>>
>>> Is that expected behavior ?
>>>
>>> I have not tried Linux version of gcc.
>>
>> Note that init array vs. init function behavior is encoded by a note added
>> by crt1.o. I suspect that the problem is that gcc port is built without
>> --enable-initfini-array configure option.
> 
> Indeed, support for .init_array and .fini_array has been added to the GCC ports
> but is present in the *-devel ports only for now. I will
> soon proceed to enable it for the GCC standard ports too. lang/gcc14 is soon
> to be added to the ports tree and will have it since the beginning.
> 
> If this is indeed the issue, switching to a -devel GCC port should fix it.

FWIW, the devel/freebsd-gcc* ports have passed this flag to GCC's configure
for a long time (since we made the switch in clang).

-- 
John Baldwin