https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93989
Bug ID: 93989
Summary: [c++20] Error initializing trivial types in constexpr
constructor
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: kingoipo at gmail dot com
Target Milestone: ---
In trying to implement p0980r1, I encountered the following error when calling
the constexpr basic_string(const _Alloc& __a) constructor:
/home/oipo-unencrypted/Programming/gcc/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/copy_assign_constexpr.cc:
In function ‘consteval void test01()’:
/home/oipo-unencrypted/Programming/gcc/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/copy_assign_constexpr.cc:37:
error: ‘test_type{std::__cxx11::basic_string<char, std::char_traits<char>,
__gnu_test::constexpr_allocator<char>
>::_Alloc_hider{__gnu_test::constexpr_allocator<char>{1}, ((char*)(&
v1.std::__cxx11::basic_string<char, std::char_traits<char>,
__gnu_test::constexpr_allocator<char>
>::<anonymous>.std::__cxx11::basic_string<char, std::char_traits<char>,
__gnu_test::constexpr_allocator<char> >::<unnamed union>::_M_local_buf))}, 0,
std::__cxx11::basic_string<char, std::char_traits<char>,
__gnu_test::constexpr_allocator<char> >::<unnamed union>{char [16]{0}}}’ is not
a constant expression
/home/oipo-unencrypted/Programming/gcc/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/copy_assign_constexpr.cc:37:
error: ‘std::__cxx11::basic_string<char, std::char_traits<char>,
__gnu_test::constexpr_allocator<char> >(a1)’ is not a constant expression
because it refers to an incompletely initialized variable
This is reproducible by checking out the code from https://github.com/Oipo/gcc
and running the new libstdc++3 testcase
https://github.com/Oipo/gcc/blob/master/libstdc%2B%2B-v3/testsuite/21_strings/basic_string/allocator/char/copy_assign_constexpr.cc
. This can be done with "make -jN check-target-libstdc++-v3".
A noteworthy extra change is the introduction of a constexpr_allocator in
testsuite_allocator.h.
Apologies for not being able to make a smaller reproducible case.
