Differential D4731 Diff 14927 src/compat/assumptions.h

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src/compat/assumptions.h

	// Copyright (c) 2009-2010 Satoshi Nakamoto			// Copyright (c) 2009-2010 Satoshi Nakamoto
	// Copyright (c) 2009-2019 The Bitcoin Core developers			// Copyright (c) 2009-2019 The Bitcoin Core developers
	// Distributed under the MIT software license, see the accompanying			// Distributed under the MIT software license, see the accompanying
	// file COPYING or http://www.opensource.org/licenses/mit-license.php.			// file COPYING or http://www.opensource.org/licenses/mit-license.php.

	// Compile-time verification of assumptions we make.			// Compile-time verification of assumptions we make.

	#ifndef BITCOIN_COMPAT_ASSUMPTIONS_H			#ifndef BITCOIN_COMPAT_ASSUMPTIONS_H
	#define BITCOIN_COMPAT_ASSUMPTIONS_H			#define BITCOIN_COMPAT_ASSUMPTIONS_H

				#include <climits>
				#include <cstdint>
	#include <limits>			#include <limits>
				#include <type_traits>

	// Assumption: We assume that the macro NDEBUG is not defined.			// Assumption: We assume that the macro NDEBUG is not defined.
	// Example(s): We use assert(...) extensively with the assumption of it never			// Example(s): We use assert(...) extensively with the assumption of it never
	// being a noop at runtime.			// being a noop at runtime.
	#if defined(NDEBUG)			#if defined(NDEBUG)
	#error "Bitcoin cannot be compiled without assertions."			#error "Bitcoin cannot be compiled without assertions."
	#endif			#endif

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	static_assert(sizeof(double) == 8, "64-bit double assumed");			static_assert(sizeof(double) == 8, "64-bit double assumed");

	// Assumption: We assume integer widths.			// Assumption: We assume integer widths.
	// Example(s): GetSizeOfCompactSize and WriteCompactSize in the serialization			// Example(s): GetSizeOfCompactSize and WriteCompactSize in the serialization
	// code.			// code.
	static_assert(sizeof(short) == 2, "16-bit short assumed");			static_assert(sizeof(short) == 2, "16-bit short assumed");
	static_assert(sizeof(int) == 4, "32-bit int assumed");			static_assert(sizeof(int) == 4, "32-bit int assumed");

				// Assumption: We assume 8-bit bytes, because 32-bit int and 16-bit short are
				// assumed.
				static_assert(CHAR_BIT == 8, "8-bit bytes assumed");

				// Assumption: We assume uint8_t is an alias of unsigned char.
				// char, unsigned char, and std::byte (C++17) are the only "byte types"
				// according to the C++ Standard. "byte type" means a type that can be used to
				// observe an object's value representation. We use uint8_t everywhere to see
				// bytes, so we have to ensure that uint8_t is an alias to a "byte type".
				// http://eel.is/c++draft/basic.types
				// http://eel.is/c++draft/basic.memobj#def:byte
				// http://eel.is/c++draft/expr.sizeof#1
				// http://eel.is/c++draft/cstdint#syn
				static_assert(std::is_same<uint8_t, unsigned char>::value);

	// Some important things we are NOT assuming (non-exhaustive list):			// Some important things we are NOT assuming (non-exhaustive list):
	// * We are NOT assuming a specific value for sizeof(std::size_t).			// * We are NOT assuming a specific value for sizeof(std::size_t).
	// * We are NOT assuming a specific value for std::endian::native.			// * We are NOT assuming a specific value for std::endian::native.
	// * We are NOT assuming a specific value for std::locale("").name().			// * We are NOT assuming a specific value for std::locale("").name().
	// * We are NOT assuming a specific value for			// * We are NOT assuming a specific value for
	// std::numeric_limits<char>::is_signed.			// std::numeric_limits<char>::is_signed.

	#endif // BITCOIN_COMPAT_ASSUMPTIONS_H			#endif // BITCOIN_COMPAT_ASSUMPTIONS_H