libstdc++: Begin lifetime of storage in std::vector<bool> [PR114367]

This doesn't cause a problem with GCC, but Clang correctly diagnoses a
bug in the code. The objects in the allocated storage need to begin
their lifetime before we start using them.

This change uses the allocator's construct function instead of using
std::construct_at directly, in order to support fancy pointers.

libstdc++-v3/ChangeLog:

	PR libstdc++/114367
	* include/bits/stl_bvector.h (_M_allocate): Use allocator's
	construct function to begin lifetime of words.

(cherry picked from commit 16afbd9c9c4282d56062cef95e6eccfdcf3efe03)

diff --git a/libstdc++-v3/include/bits/stl_bvector.h b/libstdc++-v3/include/bits/stl_bvector.h
index f90d3c47f3d3ee929acaf13a0bff6a0b5333e824..e1559c253d81e7616739e2fa9fdce2257f4c570b 100644 (file)
--- a/libstdc++-v3/include/bits/stl_bvector.h
+++ b/libstdc++-v3/include/bits/stl_bvector.h
@@ -629,13 +629,13 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
       _M_allocate(size_t __n)
       {
        _Bit_pointer __p = _Bit_alloc_traits::allocate(_M_impl, _S_nword(__n));
-#if __cpp_lib_is_constant_evaluated
+#if __cpp_lib_is_constant_evaluated && __cpp_constexpr_dynamic_alloc
        if (std::is_constant_evaluated())
-       {
-         __n = _S_nword(__n);
-         for (size_t __i = 0; __i < __n; ++__i)
-           __p[__i] = 0ul;
-       }
+         {
+           __n = _S_nword(__n);
+           for (size_t __i = 0; __i < __n; ++__i)
+             std::construct_at(std::to_address(__p) + __i);
+         }
 #endif
        return __p;
       }