llvm/llvm/include/llvm/ADT/Any.h

//===- Any.h - Generic type erased holder of any type -----------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
///
/// \file
///  This file provides Any, a non-template class modeled in the spirit of
///  std::any.  The idea is to provide a type-safe replacement for C's void*.
///  It can hold a value of any copy-constructible copy-assignable type
///
//===----------------------------------------------------------------------===//

#ifndef LLVM_ADT_ANY_H
#define LLVM_ADT_ANY_H

#include "llvm/ADT/STLForwardCompat.h"
#include "llvm/Support/Compiler.h"

#include <cassert>
#include <memory>
#include <type_traits>

namespace llvm {

class LLVM_EXTERNAL_VISIBILITY Any { … };

// Define the type id and initialize with a non-zero value.
// Initializing with a zero value means the variable can end up in either the
// .data or the .bss section. This can lead to multiple definition linker errors
// when some object files are compiled with a compiler that puts the variable
// into .data but they are linked to object files from a different compiler that
// put the variable into .bss. To prevent this issue from happening, initialize
// the variable with a non-zero value, which forces it to land in .data (because
// .bss is zero-initialized).
// See also https://github.com/llvm/llvm-project/issues/62270
template <typename T> char Any::TypeId<T>::Id = …;

template <class T> T any_cast(const Any &Value) { … }

template <class T> T any_cast(Any &Value) { … }

template <class T> T any_cast(Any &&Value) { … }

template <class T> const T *any_cast(const Any *Value) { … }

template <class T> T *any_cast(Any *Value) { … }

} // end namespace llvm

#endif // LLVM_ADT_ANY_H