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/* Copyright (C) 2022-2023 Free Software Foundation, Inc.
This file is part of GDB.
This program 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 of the License, or
(at your option) any later version.
This program 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 program. If not, see <http://www.gnu.org/licenses/>. */
#ifndef COMMON_GDB_CHECKED_DYNAMIC_CAST_H
#define COMMON_GDB_CHECKED_DYNAMIC_CAST_H
#include "gdbsupport/traits.h"
namespace gdb
{
/* This function can be used in place of static_cast when casting between
pointers of polymorphic types. The benefit of using this call is that,
when compiling in developer mode, dynamic_cast will be used to validate
the cast. This use of dynamic_cast is why this function will only
work for polymorphic types.
In non-developer (i.e. production) builds, the dynamic_cast is replaced
with a static_cast which is usually significantly faster. */
template<typename T, typename V>
T
checked_static_cast (V *v)
{
/* We only support casting to pointer types. */
static_assert (std::is_pointer<T>::value, "target must be a pointer type");
/* Check for polymorphic types explicitly in case we're in release mode. */
static_assert (std::is_polymorphic<V>::value, "types must be polymorphic");
/* Figure out the type that T points to. */
using T_no_P = typename std::remove_pointer<T>::type;
/* In developer mode this cast uses dynamic_cast to confirm at run-time
that the cast from V* to T is valid. However, we can catch some
mistakes at compile time, this assert prevents anything other than
downcasts, or casts to same type. */
static_assert (std::is_base_of<V, T_no_P>::value
|| std::is_base_of<T_no_P, V>::value,
"types must be related");
#ifdef DEVELOPMENT
if (v == nullptr)
return nullptr;
T result = dynamic_cast<T> (v);
gdb_assert (result != nullptr);
#else
T result = static_cast<T> (v);
#endif
return result;
}
/* Same as the above, but to cast from a reference type to another. */
template<typename T, typename V, typename = gdb::Requires<std::is_reference<T>>>
T
checked_static_cast (V &v)
{
static_assert (std::is_reference<T>::value, "target must be a reference type");
using T_no_R = typename std::remove_reference<T>::type;
using T_P = typename std::add_pointer<T_no_R>::type;
using V_no_R = typename std::remove_reference<V>::type;
return *checked_static_cast<T_P, V_no_R> (&v);
}
}
#endif /* COMMON_GDB_CHECKED_DYNAMIC_CAST_H */
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