From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 2181) id 8774E3857B98; Tue, 6 Jun 2023 13:34:15 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 8774E3857B98 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1686058455; bh=iMonZlfYTOQlf62iahCFxuQaTh5dOtPjP+C6jWURJ0o=; h=From:To:Subject:Date:From; b=FA+n88l9Li3kh6voXTEmz0f3PJhu0/I/on4XO6PyxHd24yt7HnCQg+lTmOrHDnWk3 HCDh9oLGvQBPruGYasm8bzRP10OKm1mcTuGpsS1F/zHg/j7QTLxAdQY9YB3q6Wd1Yl UdR9aYVIAjJ2gwGz4TkZyCvIpw/GwEgxt/VZwAjg= MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="utf-8" From: Jonathan Wakely To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r13-7418] libstdc++: Fix ambiguous expression in std::array::front() [PR110139] X-Act-Checkin: gcc X-Git-Author: Jonathan Wakely X-Git-Refname: refs/heads/releases/gcc-13 X-Git-Oldrev: ad12d81e5922d0c3087f1f2569618c31e8db208c X-Git-Newrev: 32f2b0f32816af816605dbe8060fb903cf7d5603 Message-Id: <20230606133415.8774E3857B98@sourceware.org> Date: Tue, 6 Jun 2023 13:34:15 +0000 (GMT) List-Id: https://gcc.gnu.org/g:32f2b0f32816af816605dbe8060fb903cf7d5603 commit r13-7418-g32f2b0f32816af816605dbe8060fb903cf7d5603 Author: Jonathan Wakely Date: Tue Jun 6 11:38:42 2023 +0100 libstdc++: Fix ambiguous expression in std::array::front() [PR110139] For 32-bit targets using -pedantic (or using Clang) makes the expression _M_elems[0] ambiguous. The overloaded operator[] that we want to call has a size_t parameter, but 0 is type ptrdiff_t for many ILP32 targets, so using the implicit conversion from _M_elems to T* and then subscripting that is also viable. Change the 0 to (size_type)0 and also make the conversion to T* explicit, so that's it's not viable here. The latter change requires a static_cast in data() where we really do want to convert _M_elems to a pointer. libstdc++-v3/ChangeLog: PR libstdc++/110139 * include/std/array (__array_traits::operator T*()): Make conversion operator explicit. (array::front): Use size_type as subscript operand. (array::data): Use static_cast to make conversion explicit. * testsuite/23_containers/array/element_access/110139.cc: New test. (cherry picked from commit 56001fad4ecc32396beead6644906e3846244b67) Diff: --- libstdc++-v3/include/std/array | 10 +++++----- .../testsuite/23_containers/array/element_access/110139.cc | 5 +++++ 2 files changed, 10 insertions(+), 5 deletions(-) diff --git a/libstdc++-v3/include/std/array b/libstdc++-v3/include/std/array index 27354d9e3fb..70280c1beeb 100644 --- a/libstdc++-v3/include/std/array +++ b/libstdc++-v3/include/std/array @@ -69,7 +69,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // Conversion to a pointer produces a null pointer. __attribute__((__always_inline__)) - constexpr operator _Tp*() const noexcept { return nullptr; } + constexpr explicit operator _Tp*() const noexcept { return nullptr; } }; using _Is_swappable = true_type; @@ -240,7 +240,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION front() noexcept { __glibcxx_requires_nonempty(); - return _M_elems[0]; + return _M_elems[(size_type)0]; } [[__nodiscard__]] @@ -250,7 +250,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION #if __cplusplus >= 201402L __glibcxx_requires_nonempty(); #endif - return _M_elems[0]; + return _M_elems[(size_type)0]; } [[__nodiscard__]] @@ -274,12 +274,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION [[__nodiscard__, __gnu__::__const__, __gnu__::__always_inline__]] _GLIBCXX17_CONSTEXPR pointer data() noexcept - { return _M_elems; } + { return static_cast(_M_elems); } [[__nodiscard__]] _GLIBCXX17_CONSTEXPR const_pointer data() const noexcept - { return _M_elems; } + { return static_cast(_M_elems); } }; #if __cpp_deduction_guides >= 201606 diff --git a/libstdc++-v3/testsuite/23_containers/array/element_access/110139.cc b/libstdc++-v3/testsuite/23_containers/array/element_access/110139.cc new file mode 100644 index 00000000000..6f09aacf0a7 --- /dev/null +++ b/libstdc++-v3/testsuite/23_containers/array/element_access/110139.cc @@ -0,0 +1,5 @@ +// { dg-options "-pedantic" } +// { dg-do compile { target c++11 } } +#include +template class std::array; +// { dg-bogus "ambiguous overload" "" { target *-*-* } 0 }