From c9dce3b15e89e851f59ebe9e8879c8f3a620311a Mon Sep 17 00:00:00 2001 From: Jonathan Wakely Date: Wed, 17 Jun 2020 20:53:45 +0100 Subject: [PATCH] libstdc++: Handle non-integral sizes in std::uninitialized_fill_n The std::uninitialized_fill_n algorithm uses sd::fill_n for trivial types, but that algorithm has a stronger requirement that the Size parameter is convertible to an integral type. As the new test shows, there are types which are valid for std::uninitialized_fill_n but which produce a different result when converted to an integral type, or cannot be converted at all. Only use the std::fill_n optimization when the Size type is already an integral type. The std::__uninitialized_default_n extension has the same problem, and so does C++17's std::uninitialized_value_construct_n which uses it. * include/bits/stl_uninitialized.h (uninitialized_fill_n): Only use std::fill_n when the size is an integral type. (__uninitialized_default_n): Likewise. * testsuite/20_util/specialized_algorithms/uninitialized_default_n/sizes.cc: New test. * testsuite/20_util/specialized_algorithms/uninitialized_fill_n/sizes.cc: New test. * testsuite/20_util/specialized_algorithms/uninitialized_value_construct_n/sizes.cc: New test. --- libstdc++-v3/include/bits/stl_uninitialized.h | 26 ++++--- .../uninitialized_default_n/sizes.cc | 72 ++++++++++++++++++ .../uninitialized_fill_n/sizes.cc | 62 ++++++++++++++++ .../uninitialized_value_construct_n/sizes.cc | 73 +++++++++++++++++++ 4 files changed, 224 insertions(+), 9 deletions(-) create mode 100644 libstdc++-v3/testsuite/20_util/specialized_algorithms/uninitialized_default_n/sizes.cc create mode 100644 libstdc++-v3/testsuite/20_util/specialized_algorithms/uninitialized_fill_n/sizes.cc create mode 100644 libstdc++-v3/testsuite/20_util/specialized_algorithms/uninitialized_value_construct_n/sizes.cc diff --git a/libstdc++-v3/include/bits/stl_uninitialized.h b/libstdc++-v3/include/bits/stl_uninitialized.h index 3109a89462d..3771ddfd973 100644 --- a/libstdc++-v3/include/bits/stl_uninitialized.h +++ b/libstdc++-v3/include/bits/stl_uninitialized.h @@ -273,19 +273,26 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { typedef typename iterator_traits<_ForwardIterator>::value_type _ValueType; + + // Trivial types do not need a constructor to begin their lifetime, + // so try to use std::fill_n to benefit from its memmove optimization. + // For arbitrary class types and floating point types we can't assume + // that __n > 0 and std::__size_to_integer(__n) > 0 are equivalent, + // so only use std::fill_n when _Size is already an integral type. #if __cplusplus < 201103L - const bool __assignable = true; + const bool __can_fill = __is_integer<_Size>::__value; #else - // Trivial types can have deleted copy constructor, but the std::fill + // Trivial types can have deleted copy constructor, but the std::fill_n // optimization that uses memmove would happily "copy" them anyway. static_assert(is_constructible<_ValueType, const _Tp&>::value, "result type must be constructible from input type"); - // Trivial types can have deleted assignment, so using std::fill - // would be ill-formed. Require assignability before using std::fill: - const bool __assignable = is_copy_assignable<_ValueType>::value; + // Trivial types can have deleted assignment, so using std::fill_n + // would be ill-formed. Require assignability before using std::fill_n: + constexpr bool __can_fill + = __and_, is_copy_assignable<_ValueType>>::value; #endif - return __uninitialized_fill_n<__is_trivial(_ValueType) && __assignable>:: + return __uninitialized_fill_n<__is_trivial(_ValueType) && __can_fill>:: __uninit_fill_n(__first, __n, __x); } @@ -615,11 +622,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { typedef typename iterator_traits<_ForwardIterator>::value_type _ValueType; - // trivial types can have deleted assignment - const bool __assignable = is_copy_assignable<_ValueType>::value; + // See uninitialized_fill_n for the conditions for using std::fill_n. + constexpr bool __can_fill + = __and_, is_copy_assignable<_ValueType>>::value; return __uninitialized_default_n_1<__is_trivial(_ValueType) - && __assignable>:: + && __can_fill>:: __uninit_default_n(__first, __n); } diff --git a/libstdc++-v3/testsuite/20_util/specialized_algorithms/uninitialized_default_n/sizes.cc b/libstdc++-v3/testsuite/20_util/specialized_algorithms/uninitialized_default_n/sizes.cc new file mode 100644 index 00000000000..1bb4c6a9fb1 --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/specialized_algorithms/uninitialized_default_n/sizes.cc @@ -0,0 +1,72 @@ +// Copyright (C) 2020 Free Software Foundation, Inc. +// +// This file is part of the GNU ISO C++ Library. This library is free +// software; you can redistribute it and/or modify it under the +// terms of the GNU General Public License as published by the +// Free Software Foundation; either version 3, or (at your option) +// any later version. + +// This library is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU General Public License for more details. + +// You should have received a copy of the GNU General Public License along +// with this library; see the file COPYING3. If not see +// . + +// { dg-do run { target c++11 } } + +#include +#include +#include + +struct Value +{ + int value = 0x1234; +}; + +void +test01() +{ + alignas(Value) unsigned char buf[3 * sizeof(Value) + 1]; + std::fill(std::begin(buf), std::end(buf), 0xff); + const auto p = reinterpret_cast(buf); + std::__uninitialized_default_n(p, 2.0001); + VERIFY( p[0].value == 0x1234 ); + VERIFY( p[1].value == 0x1234 ); + VERIFY( p[2].value == 0x1234 ); + VERIFY( *std::prev(std::end(buf)) == 0xff ); +} + +void +test02() +{ + // The standard only requires that n>0 and --n are valid expressions. + struct Size + { + int value; + + void operator--() { --value; } + + int operator>(void*) { return value != 0; } + }; + + alignas(Value) unsigned char buf[4 * sizeof(Value) + 1]; + std::fill(std::begin(buf), std::end(buf), 0xff); + const auto p = reinterpret_cast(buf); + Size n = {4}; + std::__uninitialized_default_n(p, n); + VERIFY( p[0].value == 0x1234 ); + VERIFY( p[1].value == 0x1234 ); + VERIFY( p[2].value == 0x1234 ); + VERIFY( p[3].value == 0x1234 ); + VERIFY( *std::prev(std::end(buf)) == 0xff ); +} + +int +main() +{ + test01(); + test02(); +} diff --git a/libstdc++-v3/testsuite/20_util/specialized_algorithms/uninitialized_fill_n/sizes.cc b/libstdc++-v3/testsuite/20_util/specialized_algorithms/uninitialized_fill_n/sizes.cc new file mode 100644 index 00000000000..eb957e148da --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/specialized_algorithms/uninitialized_fill_n/sizes.cc @@ -0,0 +1,62 @@ +// Copyright (C) 2020 Free Software Foundation, Inc. +// +// This file is part of the GNU ISO C++ Library. This library is free +// software; you can redistribute it and/or modify it under the +// terms of the GNU General Public License as published by the +// Free Software Foundation; either version 3, or (at your option) +// any later version. + +// This library is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU General Public License for more details. + +// You should have received a copy of the GNU General Public License along +// with this library; see the file COPYING3. If not see +// . + +// { dg-do run } + +#include +#include + +void +test01() +{ + int i[4] = { }; + std::uninitialized_fill_n(i, 2.0001, 0xabcd); + VERIFY( i[0] == 0xabcd ); + VERIFY( i[1] == 0xabcd ); + VERIFY( i[2] == 0xabcd ); + VERIFY( i[3] == 0 ); +} + +void +test02() +{ + // The standard only requires that n>0 and --n are valid expressions. + struct Size + { + int value; + + void operator--() { --value; } + + int operator>(void*) { return value != 0; } + }; + + int i[5] = { }; + Size n = {4}; + std::uninitialized_fill_n(i, n, 0xdcba); + VERIFY( i[0] == 0xdcba ); + VERIFY( i[1] == 0xdcba ); + VERIFY( i[2] == 0xdcba ); + VERIFY( i[3] == 0xdcba ); + VERIFY( i[4] == 0 ); +} + +int +main() +{ + test01(); + test02(); +} diff --git a/libstdc++-v3/testsuite/20_util/specialized_algorithms/uninitialized_value_construct_n/sizes.cc b/libstdc++-v3/testsuite/20_util/specialized_algorithms/uninitialized_value_construct_n/sizes.cc new file mode 100644 index 00000000000..e822b198928 --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/specialized_algorithms/uninitialized_value_construct_n/sizes.cc @@ -0,0 +1,73 @@ +// Copyright (C) 2020 Free Software Foundation, Inc. +// +// This file is part of the GNU ISO C++ Library. This library is free +// software; you can redistribute it and/or modify it under the +// terms of the GNU General Public License as published by the +// Free Software Foundation; either version 3, or (at your option) +// any later version. + +// This library is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU General Public License for more details. + +// You should have received a copy of the GNU General Public License along +// with this library; see the file COPYING3. If not see +// . + +// { dg-options "-std=gnu++17" } +// { dg-do run { target c++17 } } + +#include +#include +#include + +struct Value +{ + int value = 0x1234; +}; + +void +test01() +{ + alignas(Value) unsigned char buf[3 * sizeof(Value) + 1]; + std::fill(std::begin(buf), std::end(buf), 0xff); + const auto p = reinterpret_cast(buf); + std::uninitialized_value_construct_n(p, 2.0001); + VERIFY( p[0].value == 0x1234 ); + VERIFY( p[1].value == 0x1234 ); + VERIFY( p[2].value == 0x1234 ); + VERIFY( *std::prev(std::end(buf)) == 0xff ); +} + +void +test02() +{ + // The standard only requires that n>0 and --n are valid expressions. + struct Size + { + int value; + + void operator--() { --value; } + + int operator>(void*) { return value != 0; } + }; + + alignas(Value) unsigned char buf[4 * sizeof(Value) + 1]; + std::fill(std::begin(buf), std::end(buf), 0xff); + const auto p = reinterpret_cast(buf); + Size n = {4}; + std::uninitialized_value_construct_n(p, n); + VERIFY( p[0].value == 0x1234 ); + VERIFY( p[1].value == 0x1234 ); + VERIFY( p[2].value == 0x1234 ); + VERIFY( p[3].value == 0x1234 ); + VERIFY( *std::prev(std::end(buf)) == 0xff ); +} + +int +main() +{ + test01(); + test02(); +} -- 2.30.2