On Wed, 17 Dec 2025 at 12:38, Jonathan Wakely <[email protected]> wrote:
>
> On Wed, 17 Dec 2025 at 10:34, Tomasz Kamiński <[email protected]> wrote:
> >
> > Defining the new implementation inside the _V2 inline namespace,
> > would guaranteed TUs using old definition (GCC-15 or ones defining
> > _GLIBCXX_USE_OLD_GENERATE_CANONICAL) will observe old behavior
> > (call old implementation) when linked against TUs using new
> > implementation.
> >
> > This updates random/pr60037-neg.cc to accept static assertion
> > with a given message on any line number. Preventing need for
> > constant updates.
> >
> > libstdc++-v3/ChangeLog:
> >
> > * include/bits/random.h (generate_canonical)
> > [!_GLIBCXX_USE_OLD_GENERATE_CANONICAL]: Define inside
> > _V2 inline namespace.
> > * include/bits/random.tcc (generate_canonical)
> > [!_GLIBCXX_USE_OLD_GENERATE_CANONICAL]: Likewise.
> > * testsuite/26_numerics/random/pr60037-neg.cc: Make
> > test independed on line of which static assert is placed.
>
> "independent of line on which"
FWIW, I used this commit msg in my local commit. The extra text about
the change to the test might be worth using ... but on the other hand
it's a lot of words for a tiny change to one test!
libstdc++: Move new std::generate_canonical to inline namespace
This ensures that the new definition of std::generate_canonical has a
different mangled name from the old one, so that TUs compiled with GCC
16 will be sure to use the new definition, even if the linker also sees
a symbol instantiated from the old definition. We use the same _V2
inline namespace as used elsewhere (std::_V2::condition_variable,
std::_V2::__rotate, and std::chrono::_V2::system_clock), and use a macro
to add it conditionally so that it's not used for the ABI-unstable
gnu-versioned-namespace configuration.
We can simplify the 26_numerics/random/pr60037-neg.cc test to only use
one dg-error without a line number, so that it matches any of the three
relevant static_assert failures for this test: the one from _Adaptor in
<bits/random.h> and the ones from the new and old definitions of
std::generate_canonical in <bits/random.tcc>. Without this change, the
line number for the dg-error matching the <bits/random.tcc> error epends
on the _GLIBCXX_USE_OLD_GENERATE_CANONICAL macro, which is awkward to
depend on in the test (because DejaGnu sees all dg-error directives, it
doesn't care if they're guarded by #ifdef preprocessor checks).
libstdc++-v3/ChangeLog:
* include/bits/random.h [!_GLIBCXX_USE_OLD_GENERATE_CANONICAL]
(generate_canonical): Use inline namespace _V2.
* include/bits/random.tcc [!_GLIBCXX_USE_OLD_GENERATE_CANONICAL]
(generate_canonical): Likewise.
* testsuite/26_numerics/random/pr60037-neg.cc: Remove lineno so
that one dg-error matches both diagnostics.
