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From: Jonathan Wakely <redi@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r12-4140] libstdc++: Disable std::string{, _view} construction from nullptr (P2166R1) Date: Mon, 4 Oct 2021 14:23:54 +0000 (GMT) [thread overview] Message-ID: <20211004142354.D7E3D3858D28@sourceware.org> (raw) https://gcc.gnu.org/g:cf876562c592193732f869e9f96034a42d0fad89 commit r12-4140-gcf876562c592193732f869e9f96034a42d0fad89 Author: Jonathan Wakely <jwakely@redhat.com> Date: Fri Oct 1 21:27:24 2021 +0100 libstdc++: Disable std::string{,_view} construction from nullptr (P2166R1) Implement this C++23 feature. Because construction from a null pointer is undefined, we can implement it for C++11 and up, turning undefined behaviour into a compilation error. libstdc++-v3/ChangeLog: * include/bits/basic_string.h (basic_string(nullptr_t)): Define as deleted. (operator=(nullptr_t)): Likewise. * include/bits/cow_string.h (basic_string(nullptr_t)): Likewise. (operator=(nullptr_t)): Likewise. * include/std/string_view (basic_string_view(nullptr_t)): Likewise. * testsuite/21_strings/basic_string/cons/char/nullptr.cc: New test. * testsuite/21_strings/basic_string_view/cons/char/nonnull.cc: Change dg-warning to dg-error. * testsuite/21_strings/basic_string_view/cons/wchar_t/nonnull.cc: Likewise. Diff: --- libstdc++-v3/include/bits/basic_string.h | 2 ++ libstdc++-v3/include/bits/cow_string.h | 3 +++ libstdc++-v3/include/std/string_view | 2 ++ libstdc++-v3/testsuite/21_strings/basic_string/cons/char/nullptr.cc | 4 ++++ .../testsuite/21_strings/basic_string_view/cons/char/nonnull.cc | 2 +- .../testsuite/21_strings/basic_string_view/cons/wchar_t/nonnull.cc | 2 +- 6 files changed, 13 insertions(+), 2 deletions(-) diff --git a/libstdc++-v3/include/bits/basic_string.h b/libstdc++-v3/include/bits/basic_string.h index 24c454d863a..68c388408f0 100644 --- a/libstdc++-v3/include/bits/basic_string.h +++ b/libstdc++-v3/include/bits/basic_string.h @@ -623,6 +623,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11 _M_construct(__str.begin(), __str.end()); } + basic_string(nullptr_t) = delete; + basic_string& operator=(nullptr_t) = delete; #endif // C++11 /** diff --git a/libstdc++-v3/include/bits/cow_string.h b/libstdc++-v3/include/bits/cow_string.h index ba4a8cc2e98..f0540128364 100644 --- a/libstdc++-v3/include/bits/cow_string.h +++ b/libstdc++-v3/include/bits/cow_string.h @@ -667,6 +667,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION else _M_dataplus._M_p = _S_construct(__str.begin(), __str.end(), __a); } + + basic_string(nullptr_t) = delete; + basic_string& operator=(nullptr_t) = delete; #endif // C++11 /** diff --git a/libstdc++-v3/include/std/string_view b/libstdc++-v3/include/std/string_view index d8cbee9bee0..996b03f9346 100644 --- a/libstdc++-v3/include/std/string_view +++ b/libstdc++-v3/include/std/string_view @@ -168,6 +168,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION #endif // C++23 #endif // C++20 + basic_string_view(nullptr_t) = delete; + constexpr basic_string_view& operator=(const basic_string_view&) noexcept = default; diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/cons/char/nullptr.cc b/libstdc++-v3/testsuite/21_strings/basic_string/cons/char/nullptr.cc new file mode 100644 index 00000000000..fdb24aeeb89 --- /dev/null +++ b/libstdc++-v3/testsuite/21_strings/basic_string/cons/char/nullptr.cc @@ -0,0 +1,4 @@ +// { dg-do compile { target c++11 } } +#include <string> + +std::string s = nullptr; // { dg-error "deleted" "P2166R1" } diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/cons/char/nonnull.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/cons/char/nonnull.cc index b33af088a3d..f42f95e2fdd 100644 --- a/libstdc++-v3/testsuite/21_strings/basic_string_view/cons/char/nonnull.cc +++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/cons/char/nonnull.cc @@ -25,5 +25,5 @@ test01() { std::string_view s((const char*)nullptr); // { dg-warning "\\\[-Wnonnull" } std::string_view t((char*)nullptr); // { dg-warning "\\\[-Wnonnull" } - std::string_view u(nullptr); // { dg-warning "\\\[-Wnonnull" } + std::string_view u(nullptr); // { dg-error "deleted" } } diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/cons/wchar_t/nonnull.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/cons/wchar_t/nonnull.cc index 4c1013177eb..e480f7c4923 100644 --- a/libstdc++-v3/testsuite/21_strings/basic_string_view/cons/wchar_t/nonnull.cc +++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/cons/wchar_t/nonnull.cc @@ -25,5 +25,5 @@ test01() { std::wstring_view s((const wchar_t*)nullptr); // { dg-warning "\\\[-Wnonnull" } std::wstring_view t((wchar_t*)nullptr); // { dg-warning "\\\[-Wnonnull" } - std::wstring_view u(nullptr); // { dg-warning "\\\[-Wnonnull" } + std::wstring_view u(nullptr); // { dg-error "deleted" } }
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