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From: Jonathan Wakely <redi@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r10-9831] libstdc++: Fix filesystem::path constraints for volatile [PR 100630] Date: Mon, 17 May 2021 14:01:28 +0000 (GMT) [thread overview] Message-ID: <20210517140128.C199C3838024@sourceware.org> (raw) https://gcc.gnu.org/g:4cd69a5a0dd31bc6fdef1bbabc8d6d1416014ea1 commit r10-9831-g4cd69a5a0dd31bc6fdef1bbabc8d6d1416014ea1 Author: Jonathan Wakely <jwakely@redhat.com> Date: Mon May 17 11:54:06 2021 +0100 libstdc++: Fix filesystem::path constraints for volatile [PR 100630] The constraint check for filesystem::path construction uses decltype(__is_path_src(declval<Source>())) which mean it considers conversion from an rvalue. When Source is a volatile-qualified type it cannot use is_path_src(const Unknown&) because a const lvalue reference can only bind to a non-volatile rvalue. Since the relevant path members all have a const Source& parameter, the constraint should be defined in terms of declval<const Source&>(), not declval<Source>(). This avoids the problem of volatile-qualified rvalues, because we no longer use an rvalue at all. libstdc++-v3/ChangeLog: PR libstdc++/100630 * include/bits/fs_path.h (__is_constructible_from): Test construction from a const lvalue, not an rvalue. * include/experimental/bits/fs_path.h (__is_constructible_from): Likewise. * testsuite/27_io/filesystem/path/construct/100630.cc: New test. * testsuite/experimental/filesystem/path/construct/100630.cc: New test. Diff: --- libstdc++-v3/include/bits/fs_path.h | 2 +- libstdc++-v3/include/experimental/bits/fs_path.h | 2 +- .../testsuite/27_io/filesystem/path/construct/100630.cc | 14 ++++++++++++++ .../experimental/filesystem/path/construct/100630.cc | 14 ++++++++++++++ 4 files changed, 30 insertions(+), 2 deletions(-) diff --git a/libstdc++-v3/include/bits/fs_path.h b/libstdc++-v3/include/bits/fs_path.h index 3d341916db5..6e0a85417cc 100644 --- a/libstdc++-v3/include/bits/fs_path.h +++ b/libstdc++-v3/include/bits/fs_path.h @@ -116,7 +116,7 @@ namespace __detail template<typename _Source> struct __constructible_from<_Source, void> - : decltype(__is_path_src(std::declval<_Source>(), 0)) + : decltype(__is_path_src(std::declval<const _Source&>(), 0)) { }; template<typename _Tp1, typename _Tp2 = void> diff --git a/libstdc++-v3/include/experimental/bits/fs_path.h b/libstdc++-v3/include/experimental/bits/fs_path.h index c5fc3beed1f..0a8f4eee0a1 100644 --- a/libstdc++-v3/include/experimental/bits/fs_path.h +++ b/libstdc++-v3/include/experimental/bits/fs_path.h @@ -124,7 +124,7 @@ namespace __detail template<typename _Source> struct __constructible_from<_Source, void> - : decltype(__is_path_src(std::declval<_Source>(), 0)) + : decltype(__is_path_src(std::declval<const _Source&>(), 0)) { }; template<typename _Tp1, typename _Tp2 = void, diff --git a/libstdc++-v3/testsuite/27_io/filesystem/path/construct/100630.cc b/libstdc++-v3/testsuite/27_io/filesystem/path/construct/100630.cc new file mode 100644 index 00000000000..eb8473e600e --- /dev/null +++ b/libstdc++-v3/testsuite/27_io/filesystem/path/construct/100630.cc @@ -0,0 +1,14 @@ +// { dg-options "-std=gnu++17" } +// { dg-do compile { target c++17 } } + +#include <filesystem> + +void f(bool) { } +void f(const std::filesystem::path&) { } + +void +test_100630() +{ + volatile bool b = true; + f(b); +} diff --git a/libstdc++-v3/testsuite/experimental/filesystem/path/construct/100630.cc b/libstdc++-v3/testsuite/experimental/filesystem/path/construct/100630.cc new file mode 100644 index 00000000000..b2428ff74cf --- /dev/null +++ b/libstdc++-v3/testsuite/experimental/filesystem/path/construct/100630.cc @@ -0,0 +1,14 @@ +// { dg-do compile { target c++11 } } +// { dg-require-filesystem-ts "" } + +#include <experimental/filesystem> + +void f(bool) { } +void f(const std::experimental::filesystem::path&) { } + +void +test_100630() +{ + volatile bool b = true; + f(b); +}
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