https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93923
Bug ID: 93923
Summary: [Regression 10] std::is_copy_constructible raises
compilation error
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: laurent.stacul at gmail dot com
Target Milestone: ---
Hello,
The following code does not compile anymore with gcc 10 although it works in
9.2, 9.2, 8.x.
#include <type_traits>
#include <initializer_list>
class A;
template<typename T>
struct B {
template<
class... Args,
std::enable_if_t<std::is_constructible<T, Args...>::value, int> = 0 >
B(Args && ... args) {}
};
struct A {
A(const B<A>& b) {}
};
int main(int argc, const char *argv[])
{
static_assert(std::is_copy_constructible<A>::value);
return 0;
}
Compiling with the HEAD of gcc 10 I have the following error:
$ g++ is_constructible.cpp
[jobs: 0][history: 5132]
In file included from is_constructible.cpp:1:
/remote/tools/Linux/2.6/1A/toolchain/x86_64-v20.0.10/include/c++/10.0.1/type_traits:
In instantiation of ‘struct std::is_constructible<A, const A&>’:
is_constructible.cpp:10:75: required by substitution of ‘template<class ...
Args, typename std::enable_if<std::is_constructible<A, Args ...>::value,
int>::type <anonymous> > B<A>::B(Args&& ...) [with Args = {const A&}; typename
std::enable_if<std::is_constructible<A, Args ...>::value, int>::type
<anonymous> = <missing>]’
/remote/tools/Linux/2.6/1A/toolchain/x86_64-v20.0.10/include/c++/10.0.1/type_traits:901:30:
required from ‘struct std::__is_constructible_impl<A, const A&>’
/remote/tools/Linux/2.6/1A/toolchain/x86_64-v20.0.10/include/c++/10.0.1/type_traits:930:12:
required from ‘struct std::__is_copy_constructible_impl<A, true>’
/remote/tools/Linux/2.6/1A/toolchain/x86_64-v20.0.10/include/c++/10.0.1/type_traits:936:12:
required from ‘struct std::is_copy_constructible<A>’
is_constructible.cpp:21:48: required from here
/remote/tools/Linux/2.6/1A/toolchain/x86_64-v20.0.10/include/c++/10.0.1/type_traits:906:12:
error: invalid use of incomplete type ‘struct std::__is_constructible_impl<A,
const A&>’
906 | struct is_constructible
| ^~~~~~~~~~~~~~~~
/remote/tools/Linux/2.6/1A/toolchain/x86_64-v20.0.10/include/c++/10.0.1/type_traits:900:12:
note: declaration of ‘struct std::__is_constructible_impl<A, const A&>’
900 | struct __is_constructible_impl
| ^~~~~~~~~~~~~~~~~~~~~~~
This is true in any standard versions (-std=c/gnu++14, c/gnu++17, c/gnu++2a,
c++20).
System information
$ gcc --version
gcc (GCC) 10.0.1 20200220 (experimental)
Copyright (C) 2020 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ uname -a
Linux ncerndobedev6196 4.12.14-95.45-default #1 SMP Wed Dec 11 13:09:13 UTC
2019 (12c8180) x86_64 x86_64 x86_64 GNU/Linux
