https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112591
--- Comment #8 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Tomasz Kaminski <[email protected]>: https://gcc.gnu.org/g:09bece00d0ec981d1b0b47ba93a67a745de3f062 commit r16-5961-g09bece00d0ec981d1b0b47ba93a67a745de3f062 Author: Tomasz KamiÅski <[email protected]> Date: Mon Dec 8 08:49:45 2025 +0100 libstdc++: Refactor _Variadic_union so _Unitialized<T, false> is not needed [PR112591]. The changes the _Variadic_union implementation, in a way that the _Unitialized<T, false> partial specialization for non-trivial types is not necessary. This is simply done by separating the specialization for __trivially_destructible being true and false, and for the later defining an empty destructor (similarly as it was done using concepts). We also reduce the number of specialization of _Variadic_union, so specialization (int, int) is reused by (string, int, int) and (int, int). This is done by initialization __trivially_destructible with conjunction of is_trivially_destructible_v for remaining components. This is only necessary for non-trivial (false) specialization, as if both _First and _Rest... are trivially destructible, then _Rest must also be. The above change does not regress the fix r14-7259-g2d55d94e5df389 for template depth, and both before and after the change template depth is 266. I have added dg-options to the 87619.cc to catch future regressions. This also add test for PR112591. PR libstdc++/112591 libstdc++-v3/ChangeLog: * include/std/variant (_Variadic_union): Separate specializations for for union of only trivially destructible types (true as first template argument). Unconditionally define destructor for _Variadic_union<false, _First, _Rest...>. * testsuite/20_util/variant/87619.cc: Add limit for the template depth. * testsuite/20_util/variant/112591.cc: New test. Reviewed-by: Jonathan Wakely <[email protected]> Signed-off-by: Tomasz KamiÅski <[email protected]>
