Re: [PATCH RFC] libstdc++: run testsuite with -Wabi

[Jonathan Wakely]

On Fri, 9 May 2025 at 18:13, Jonathan Wakely <jwak...@redhat.com> wrote:
>
> On Fri, 9 May 2025 at 11:19, Jonathan Wakely <jwak...@redhat.com> wrote:
> >
> > On Thu, 8 May 2025 at 20:56, Jason Merrill <ja...@redhat.com> wrote:
> > >
> > > Tested x86_64-pc-linux-gnu.  Does this make sense for trunk?
> >
> > Yes, it looks useful. I'm going to test it with my "very -std and -m32
> > and old-string ABI" test settings to be sure it doesn't cause any
> > problems.
>
> There are a few failures when using GLIBCXX_TESTSUITE_STDS=20 to run
> tests as C++20 or later:
>
> FAIL: experimental/net/internet/resolver/ops/lookup.cc  -std=gnu++23
> (test for excess errors)
> Excess errors:
> /tmp/build/x86_64-pc-linux-gnu/libstdc++-v3/include/experimental/internet:2100:
> warning: offset of
> 'std::experimental::net::v1::ip::basic_resolver<std::experimental::net::v1::ip::tcp>::_M_ctx'
> for '-std=c++20' and up changes in '-fabi-version=21' (GCC 16) [-Wabi]

We have code like this in the networking TS headers:

struct Base {
protected:
Base() = default;
~Base() = default;
};

struct Derived : Base {
void* ptr;
};

Is the warning wrong?

>
> FAIL: experimental/optional/requirements.cc  -std=gnu++20 (test for
> excess errors)
> Excess errors:
> /home/test/src/gcc/libstdc++-v3/testsuite/experimental/optional/requirements.cc:80:
> warning: offset of 'no_copy_assignment::__as_base ' base class for
> '-std=c++20' and up changes in '-fabi-version=21' (GCC 16) [-Wabi]
> /home/test/src/gcc/libstdc++-v3/testsuite/experimental/optional/requirements.cc:81:
> warning: offset of 'no_move_assignment::__as_base ' base class for
> '-std=c++20' and up changes in '-fabi-version=21' (GCC 16) [-Wabi]

This is just test code, which looks like:

struct no_move_constructor
{
  no_move_constructor() = default;
  no_move_constructor(no_move_constructor const&) = default;
  no_move_constructor& operator=(no_move_constructor const&) = default;
  no_move_constructor(no_move_constructor&&) = delete;
  no_move_constructor& operator=(no_move_constructor&&) = default;
};

struct no_move_assignment
{
  no_move_assignment() = default;
  no_move_assignment(no_move_assignment const&) = default;
  no_move_assignment& operator=(no_move_assignment const&) = default;
  no_move_assignment(no_move_assignment&&) = default;
  no_move_assignment& operator=(no_move_assignment&&) = delete;
};

struct no_move : no_move_constructor, no_move_assignment { };