Re: Errors when trying to use C++ modules with cmake and GCC

[Jonathan Wakely <jwakely.gcc@gmail.com>]

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On Wed, 8 Feb 2023, 09:49 HHN, <harihara.sn@gmail.com> wrote:

> The patches suggested have worked to generate modules, there must have
> been some error on my end when i tried previously. But unfortunately when I
> try to compile HPX with these patches I face a couple of errors.
>

That's a warning, not an error.


Any help would be appreciated. I have tried to do a diff between the
> successful compile logs (G++-11) and the patches suggested and attached the
> file. grep for "/home/hhn/makes/gcc-modules-install/" might help focus on
> the warnings more easily.
>
> Just to summarise the warnings are mostly
> 1.
> /home/hhn/makes/gcc-modules-install/usr/local/include/c++/13.0.0/atomic:287:22:
> warning: ‘unsigned int __atomic_load_4(const volatile void*, int)’ writing
> 4 bytes into a region of size 0 overflows the destination
> [-Wstringop-overflow=]
>   287 |         __atomic_load(std::__addressof(_M_i), __ptr, int(__m));
>
> 2.
> /home/hhn/makes/gcc-modules-install/usr/local/include/c++/13.0.0/bits/new_allocator.h:165:33:
> note: call to ‘void operator delete(void*, std::size_t)’ here
>   165 |         _GLIBCXX_OPERATOR_DELETE(_GLIBCXX_SIZED_DEALLOC(__p, __n));
>
> On Wed, Feb 1, 2023 at 4:31 PM Jonathan Wakely <jwakely.gcc@gmail.com>
> wrote:
>
>> On Wed, 1 Feb 2023 at 10:53, HHN via Gcc-help <gcc-help@gcc.gnu.org>
>> wrote:
>> >
>> > I have been working on upgrading the HPX build system to support C++
>> > modules, while trying to experiment with GCC support for C++ modules, I
>> > keep running into this issue of unrecognized command-line options.
>> >
>> > `
>> > g++: error: unrecognized command-line option
>> > ‘-fdep-file=CMakeFiles/std_module_example.dir/t3.cxx.o.ddi’
>> > g++: error: unrecognized command-line option
>> > ‘-fdep-output=CMakeFiles/std_module_example.dir/t3.cxx.o’
>> > g++: error: unrecognized command-line option ‘-fdep-format=trtbd’
>>
>> [...]
>>
>> > I have tried this with g++ 11.3, g++ 12.1 installed using ubuntu package
>> > managers,
>>
>> As you were told in the cmake forum by Ben B., the patches to add
>> -fdep-file etc. are not yet in GCC, so of course it doesn't work with
>> releases from more than a year ago.
>>
>> > I have also tried the same using this certain patch
>> > <https://github.com/mathstuf/gcc/tree/p1689r5> as suggested by the
>> user on
>> > an online forum
>> > <https://discourse.cmake.org/t/module-support-for-g-and-clang/7367/2>.
>>
>> That user is the person who wrote the patch to add -fdep-file, so you
>> should listen to them. If it still doesn't work with that patch, then
>> you probably didn't apply the patch correctly.
>>
>> > I have also tried the same using the master
>> > <https://github.com/gcc-mirror/gcc> and devel/c++-modules
>> > <https://github.com/gcc-mirror/gcc/tree/devel/c++-modules> branch on
>> gcc
>> > repo.
>>
>> Obviously it's not going to work with those branches, because the
>> patches to add -fdep-file support are not part of GCC yet, as Ben B.
>> already told you.
>>
>> > All of them have given the same errors. Also the devel/c++-modules
>> branch
>> > compiles to g++ version of g++ (GCC) 11.0.0 20210203 (experimental)
>> > [c++-modules revision 20230201-1505], while the master branch has
>> > version g++ (GCC) 13.0.1 20230201 (experimental).
>>
>> Don't use the devel/c++-modules branch. It was used two+ years ago for
>> the initial work on modules, but the master branch now has all that
>> work and numerous improvements.
>>
>
>
> --
> Hari Hara Naveen
>