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// Copyright 2019 The SwiftShader Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef sw_Memset_hpp
#define sw_Memset_hpp
#include <cstring>
#include <type_traits>
// GCC 8+ warns that
// "‘void* memset(void*, int, size_t)’ clearing an object of non-trivial type ‘T’;
// use assignment or value-initialization instead [-Werror=class-memaccess]"
// This is benign iff it happens before any of the base or member constructors are called.
#if defined(__GNUC__) && (__GNUC__ >= 8)
# pragma GCC diagnostic push
# pragma GCC diagnostic ignored "-Wclass-memaccess"
#endif
namespace sw {
// Memset<> is a helper class for clearing the memory of objects at construction.
// It is useful as the *first* base class of map keys which may contain padding
// bytes or bits otherwise left uninitialized.
template<class T>
struct Memset
{
Memset(T *object, int val)
{
static_assert(std::is_base_of<Memset<T>, T>::value, "Memset<T> must only clear the memory of a type of which it is a base class");
static_assert(!std::is_polymorphic<T>::value, "Memset<T> must not be used with classes that have virtual functions");
::memset(object, 0, sizeof(T));
}
// Don't rely on the implicitly declared copy constructor and copy assignment operator.
// They can leave padding bytes uninitialized.
Memset(const Memset &rhs)
{
::memcpy(this, &rhs, sizeof(T));
}
Memset &operator=(const Memset &rhs)
{
::memcpy(this, &rhs, sizeof(T));
return *this;
}
// The compiler won't declare an implicit move constructor and move assignment operator
// due to having a user-defined copy constructor and copy assignment operator. Delete
// them for explicitness. We always want memcpy() being called.
Memset(const Memset &&rhs) = delete;
Memset &operator=(const Memset &&rhs) = delete;
friend bool operator==(const T &a, const T &b)
{
return ::memcmp(&a, &b, sizeof(T)) == 0;
}
friend bool operator!=(const T &a, const T &b)
{
return ::memcmp(&a, &b, sizeof(T)) != 0;
}
friend bool operator<(const T &a, const T &b)
{
return ::memcmp(&a, &b, sizeof(T)) < 0;
}
};
} // namespace sw
// Restore -Wclass-memaccess
#if defined(__GNUC__) && (__GNUC__ >= 8)
# pragma GCC diagnostic pop
#endif
#endif // sw_Memset_hpp