Differential D7635 Diff 23953 src/secp256k1/src/assumptions.h

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src/secp256k1/src/assumptions.h

	/**********************************************************************			/**********************************************************************
	* Copyright (c) 2020 Pieter Wuille *			* Copyright (c) 2020 Pieter Wuille *
	* 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.*
	**********************************************************************/			**********************************************************************/

	#ifndef SECP256K1_ASSUMPTIONS_H			#ifndef SECP256K1_ASSUMPTIONS_H
	#define SECP256K1_ASSUMPTIONS_H			#define SECP256K1_ASSUMPTIONS_H

				#include <limits.h>

	#include "util.h"			#include "util.h"

	/* This library, like most software, relies on a number of compiler implementation defined (but not undefined)			/* This library, like most software, relies on a number of compiler implementation defined (but not undefined)
	behaviours. Although the behaviours we require are essentially universal we test them specifically here to			behaviours. Although the behaviours we require are essentially universal we test them specifically here to
	reduce the odds of experiencing an unwelcome surprise.			reduce the odds of experiencing an unwelcome surprise.
	*/			*/

	struct secp256k1_assumption_checker {			struct secp256k1_assumption_checker {
	/* This uses a trick to implement a static assertion in C89: a type with an array of negative size is not			/* This uses a trick to implement a static assertion in C89: a type with an array of negative size is not
	allowed. */			allowed. */
	int dummy_array[(			int dummy_array[(
	/* Bytes are 8 bits. */			/* Bytes are 8 bits. */
	CHAR_BIT == 8 &&			(CHAR_BIT == 8) &&

				/* No integer promotion for uint32_t. This ensures that we can multiply uintXX_t values where XX >= 32
				without signed overflow, which would be undefined behaviour. */
				(UINT_MAX <= UINT32_MAX) &&

	/* Conversions from unsigned to signed outside of the bounds of the signed type are			/* Conversions from unsigned to signed outside of the bounds of the signed type are
	implementation-defined. Verify that they function as reinterpreting the lower			implementation-defined. Verify that they function as reinterpreting the lower
	bits of the input in two's complement notation. Do this for conversions:			bits of the input in two's complement notation. Do this for conversions:
	- from uint(N)_t to int(N)_t with negative result			- from uint(N)_t to int(N)_t with negative result
	- from uint(2N)_t to int(N)_t with negative result			- from uint(2N)_t to int(N)_t with negative result
	- from int(2N)_t to int(N)_t with negative result			- from int(2N)_t to int(N)_t with negative result
	- from int(2N)_t to int(N)_t with positive result */			- from int(2N)_t to int(N)_t with positive result */
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