The C++17 standard requires the default implementation for
allocator_traits::max_size to return SIZE_MAX / sizeof(value_type).
That causes GCC to warn because the value could be larger than can
sensibly be passed to malloc. This patch changes the new_allocator and
malloc_allocator max_size() members to use PTRDIFF_MAX instead of
SIZE_MAX (and because they define it, the allocator_traits default isn't
used). This also changes vector::max_size to impose a sensible limit
using PTRDIFF_MAX for cases where the value from the allocator or
allocator_traits is not sensible.
PR libstdc++/87544
* include/bits/stl_vector.h (vector::_S_max_size): Limit size to
PTRDIFF_MAX / sizeof(value_type).
* include/ext/malloc_allocator.h (malloc_allocator::max_size):
Likewise.
* include/ext/new_allocator.h (new_allocator::max_size): Likewise.
* testsuite/23_containers/vector/allocator/minimal.cc: Adjust
expected value for max_size().
* testsuite/23_containers/vector/capacity/87544.cc: New test.
Tested x86_64-linux, committed to trunk.
commit 57daf3cdf2668f944417cc4550faec588f83a790
Author: Jonathan Wakely <jwak...@redhat.com>
Date: Wed Oct 10 15:23:12 2018 +0100
PR libstdc++/87544 limit max_size() to PTRDIFF_MAX / sizeof(T)
The C++17 standard requires the default implementation for
allocator_traits::max_size to return SIZE_MAX / sizeof(value_type).
That causes GCC to warn because the value could be larger than can
sensibly be passed to malloc. This patch changes the new_allocator and
malloc_allocator max_size() members to use PTRDIFF_MAX instead of
SIZE_MAX (and because they define it, the allocator_traits default isn't
used). This also changes vector::max_size to impose a sensible limit
using PTRDIFF_MAX for cases where the value from the allocator or
allocator_traits is not sensible.
PR libstdc++/87544
* include/bits/stl_vector.h (vector::_S_max_size): Limit size to
PTRDIFF_MAX / sizeof(value_type).
* include/ext/malloc_allocator.h (malloc_allocator::max_size):
Likewise.
* include/ext/new_allocator.h (new_allocator::max_size): Likewise.
* testsuite/23_containers/vector/allocator/minimal.cc: Adjust
expected value for max_size().
* testsuite/23_containers/vector/capacity/87544.cc: New test.
diff --git a/libstdc++-v3/include/bits/stl_vector.h
b/libstdc++-v3/include/bits/stl_vector.h
index 47856473107..37607417d08 100644
--- a/libstdc++-v3/include/bits/stl_vector.h
+++ b/libstdc++-v3/include/bits/stl_vector.h
@@ -1726,7 +1726,11 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
static size_type
_S_max_size(const _Tp_alloc_type& __a) _GLIBCXX_NOEXCEPT
{
- const size_t __diffmax = __gnu_cxx::__numeric_traits<ptrdiff_t>::__max;
+ // std::distance(begin(), end()) cannot be greater than PTRDIFF_MAX,
+ // and realistically we can't store more than PTRDIFF_MAX/sizeof(T)
+ // (even if std::allocator_traits::max_size says we can).
+ const size_t __diffmax
+ = __gnu_cxx::__numeric_traits<ptrdiff_t>::__max / sizeof(_Tp);
const size_t __allocmax = _Alloc_traits::max_size(__a);
return (std::min)(__diffmax, __allocmax);
}
diff --git a/libstdc++-v3/include/ext/malloc_allocator.h
b/libstdc++-v3/include/ext/malloc_allocator.h
index 8739c1fdaa3..8eaf5d44cf7 100644
--- a/libstdc++-v3/include/ext/malloc_allocator.h
+++ b/libstdc++-v3/include/ext/malloc_allocator.h
@@ -139,7 +139,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
size_type
max_size() const _GLIBCXX_USE_NOEXCEPT
- { return size_t(-1) / sizeof(_Tp); }
+ {
+#if __PTRDIFF_MAX__ < __SIZE_MAX__
+ return size_t(__PTRDIFF_MAX__) / sizeof(_Tp);
+#else
+ return size_t(-1) / sizeof(_Tp);
+#endif
+ }
#if __cplusplus >= 201103L
template<typename _Up, typename... _Args>
diff --git a/libstdc++-v3/include/ext/new_allocator.h
b/libstdc++-v3/include/ext/new_allocator.h
index 19e7ad02e75..7c50731736b 100644
--- a/libstdc++-v3/include/ext/new_allocator.h
+++ b/libstdc++-v3/include/ext/new_allocator.h
@@ -130,7 +130,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
size_type
max_size() const _GLIBCXX_USE_NOEXCEPT
- { return size_t(-1) / sizeof(_Tp); }
+ {
+#if __PTRDIFF_MAX__ < __SIZE_MAX__
+ return size_t(__PTRDIFF_MAX__) / sizeof(_Tp);
+#else
+ return size_t(-1) / sizeof(_Tp);
+#endif
+ }
#if __cplusplus >= 201103L
template<typename _Up, typename... _Args>
diff --git a/libstdc++-v3/testsuite/23_containers/vector/allocator/minimal.cc
b/libstdc++-v3/testsuite/23_containers/vector/allocator/minimal.cc
index 7a75d9189b2..5e989b0f8c7 100644
--- a/libstdc++-v3/testsuite/23_containers/vector/allocator/minimal.cc
+++ b/libstdc++-v3/testsuite/23_containers/vector/allocator/minimal.cc
@@ -35,7 +35,7 @@ void test01()
typedef std::vector<T, alloc_type> test_type;
test_type v(alloc_type{});
v.push_back(T());
- VERIFY( v.max_size() == traits_type::max_size(v.get_allocator()) );
+ VERIFY( v.max_size() <= traits_type::max_size(v.get_allocator()) );
}
int main()
diff --git a/libstdc++-v3/testsuite/23_containers/vector/capacity/87544.cc
b/libstdc++-v3/testsuite/23_containers/vector/capacity/87544.cc
new file mode 100644
index 00000000000..f04430e1147
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/vector/capacity/87544.cc
@@ -0,0 +1,73 @@
+// Copyright (C) 2018 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
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-O2" }
+// { dg-do compile { target c++11 } }
+
+#include <cstdlib>
+#include <vector>
+
+template<class T>
+struct Alloc : public std::allocator<T>
+{
+ template<class U>
+ struct rebind { typedef Alloc<U> other; };
+
+ Alloc() : std::allocator<T>() {}
+
+ template<class U>
+ Alloc(const Alloc<U>& other) : std::allocator<T>(other) {}
+
+ T* allocate(std::size_t num, const void* = 0)
+ {
+ std::size_t size = num * sizeof(T);
+ void *result = std::malloc(size);
+ if(size>16 && (std::size_t(result) & 15)!=0) {
+ std::free(result);
+ return 0;
+ }
+ return static_cast<T*>( result );
+ }
+
+ void deallocate(T* p, std::size_t) { std::free(p); }
+};
+
+unsigned f(std::vector<int, Alloc<int> >& v)
+{
+ v.push_back(1);
+ return v.size();
+}
+
+template<class T>
+struct Alloc2 : public Alloc<T>
+{
+ template<class U>
+ struct rebind { typedef Alloc2<U> other; };
+
+ Alloc2() : Alloc<T>() {}
+
+ template<class U>
+ Alloc2(const Alloc2<U>& other) : Alloc<T>(other) {}
+
+ std::size_t max_size() const { return std::size_t(-1) / sizeof(T); }
+};
+
+unsigned g(std::vector<int, Alloc2<int> >& v)
+{
+ v.push_back(1);
+ return v.size();
+}
