With the 4.1.0 release, the following snippet does not compile with g++-10
// filename: minimal.cc
#include "gsl/gsl"
#include <iostream>
#include <memory>
int main() {
gsl::not_null<std::unique_ptr<int>> ptr = std::make_unique<int>(42);
std::cout << *ptr << std::endl;
}$ g++ minimal.cc -I GSL-4.1.0/include -std=c++20
In file included from GSL-4.1.0/include/gsl/gsl:24,
from minimal.cc:1:
GSL-4.1.0/include/gsl/pointers: In instantiation of ‘constexpr gsl::details::value_or_reference_return_t<T> gsl::not_null<T>::get() const [with T = std::unique_ptr<int>; gsl::details::value_or_reference_return_t<T> = const std::unique_ptr<int>&]’:
GSL-4.1.0/include/gsl/pointers:127:58: required from ‘constexpr decltype(auto) gsl::not_null<T>::operator*() const [with T = std::unique_ptr<int>]’
minimal.cc:7:17: required from here
GSL-4.1.0/include/gsl/pointers:120:18: error: use of deleted function ‘std::unique_ptr<_Tp, _Dp>::unique_ptr(const std::unique_ptr<_Tp, _Dp>&) [with _Tp = int; _Dp = std::default_delete<int>]’
120 | noexcept(noexcept(details::value_or_reference_return_t<T>{std::declval<T&>()}))
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/10/memory:83,
from GSL-4.1.0/include/gsl/span:28,
from GSL-4.1.0/include/gsl/algorithm:21,
from GSL-4.1.0/include/gsl/gsl:21,
from minimal.cc:1:
/usr/include/c++/10/bits/unique_ptr.h:468:7: note: declared here
468 | unique_ptr(const unique_ptr&) = delete;
| ^~~~~~~~~~$ g++ --version
g++ (Debian 10.2.1-6) 10.2.1 20210110
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This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
With the 4.1.0 release, the following snippet does not compile with g++-10
$ g++ minimal.cc -I GSL-4.1.0/include -std=c++20 In file included from GSL-4.1.0/include/gsl/gsl:24, from minimal.cc:1: GSL-4.1.0/include/gsl/pointers: In instantiation of ‘constexpr gsl::details::value_or_reference_return_t<T> gsl::not_null<T>::get() const [with T = std::unique_ptr<int>; gsl::details::value_or_reference_return_t<T> = const std::unique_ptr<int>&]’: GSL-4.1.0/include/gsl/pointers:127:58: required from ‘constexpr decltype(auto) gsl::not_null<T>::operator*() const [with T = std::unique_ptr<int>]’ minimal.cc:7:17: required from here GSL-4.1.0/include/gsl/pointers:120:18: error: use of deleted function ‘std::unique_ptr<_Tp, _Dp>::unique_ptr(const std::unique_ptr<_Tp, _Dp>&) [with _Tp = int; _Dp = std::default_delete<int>]’ 120 | noexcept(noexcept(details::value_or_reference_return_t<T>{std::declval<T&>()})) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ In file included from /usr/include/c++/10/memory:83, from GSL-4.1.0/include/gsl/span:28, from GSL-4.1.0/include/gsl/algorithm:21, from GSL-4.1.0/include/gsl/gsl:21, from minimal.cc:1: /usr/include/c++/10/bits/unique_ptr.h:468:7: note: declared here 468 | unique_ptr(const unique_ptr&) = delete; | ^~~~~~~~~~