https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71960
--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jonathan Wakely <r...@gcc.gnu.org>: https://gcc.gnu.org/g:10f51543bb81cc953792270b40a9c812049e8b4c commit r11-2971-g10f51543bb81cc953792270b40a9c812049e8b4c Author: Jonathan Wakely <jwak...@redhat.com> Date: Tue Sep 1 20:52:26 2020 +0100 libstdc++: Add compile-time checks to__glibcxx_assert [PR 71960] This change evaluates __glibcxx_assert checks unconditionally when a function is being constant evaluated (when std::is_constant_evaluated() is true). If the check fails, compilation will fail with an error. If the function isn't being constant evaluated, the normal runtime check will be done if enabled by _GLIBCXX_ASSERTIONS or _GLIBCXX_DEBUG, the same as before. Tangentially, the __glibcxx_assert and _GLIBCXX_PARALLEL_ASSERT macros are changed to expand to 'do { } while (false)' when assertions are disabled, instead of expanding to nothing. This avoids -Wempty-body warnings when a disabled assertion is used in an 'if' or 'else' statement e.g. if constexpr (/* precondition is testable */) __glibcxx_assert(precondition); a.C:9:27: warning: suggest braces around empty body in an âifâ statement [-Wempty-body] 9 | __glibcxx_assert(precondition); | ^ libstdc++-v3/ChangeLog: PR libstdc++/71960 * include/bits/c++config (__glibcxx_assert_impl): Remove do-while so that uses of the macro need to add it. (__glibcxx_assert): Rename macro for runtime assertions to __glibcxx_assert_2. (__glibcxx_assert_1): Define macro for constexpr assertions. (__glibcxx_assert): Define macro for constexpr and runtime assertions. * include/bits/range_access.h (ranges::advance): Remove redundant precondition checks during constant evaluation. * include/parallel/base.h (_GLIBCXX_PARALLEL_ASSERT): Always use do-while in macro expansion. * include/std/ranges (iota_view::iota_view(W, B)): Remove redundant braces.
