From ba5d72d62659f9305d2be30b2ac89ce9480a0e78 Mon Sep 17 00:00:00 2001 From: Tim Ruffing Date: Mon, 8 Jan 2024 15:55:05 +0100 Subject: [PATCH] assumptions: Use new STATIC_ASSERT macro This also splits the big "&&" expression into separate expressions. If we ever see an assertion fail, the error message will tell it precisely which one failed. --- src/assumptions.h | 100 ++++++++++++++++++++++++---------------------- 1 file changed, 52 insertions(+), 48 deletions(-) diff --git a/src/assumptions.h b/src/assumptions.h index 8ed04209e..796100535 100644 --- a/src/assumptions.h +++ b/src/assumptions.h @@ -19,65 +19,69 @@ reduce the odds of experiencing an unwelcome surprise. */ -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 - allowed. */ - int dummy_array[( - /* Bytes are 8 bits. */ - (CHAR_BIT == 8) && +#if defined(__has_attribute) +# if __has_attribute(__unavailable__) +__attribute__((__unavailable__("Don't call this function. It only exists because STATIC_ASSERT cannot be used outside a function."))) +# endif +#endif +static void secp256k1_assumption_checker(void) { + /* Bytes are 8 bits. */ + STATIC_ASSERT(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) && + /* 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. */ + STATIC_ASSERT(UINT_MAX <= UINT32_MAX); - /* Conversions from unsigned to signed outside of the bounds of the signed type are - implementation-defined. Verify that they function as reinterpreting the lower - 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(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 */ + /* Conversions from unsigned to signed outside of the bounds of the signed type are + implementation-defined. Verify that they function as reinterpreting the lower + 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(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 */ - /* To int8_t. */ - ((int8_t)(uint8_t)0xAB == (int8_t)-(int8_t)0x55) && - ((int8_t)(uint16_t)0xABCD == (int8_t)-(int8_t)0x33) && - ((int8_t)(int16_t)(uint16_t)0xCDEF == (int8_t)(uint8_t)0xEF) && - ((int8_t)(int16_t)(uint16_t)0x9234 == (int8_t)(uint8_t)0x34) && + /* To int8_t. */ + STATIC_ASSERT(((int8_t)(uint8_t)0xAB == (int8_t)-(int8_t)0x55)); + STATIC_ASSERT((int8_t)(uint16_t)0xABCD == (int8_t)-(int8_t)0x33); + STATIC_ASSERT((int8_t)(int16_t)(uint16_t)0xCDEF == (int8_t)(uint8_t)0xEF); + STATIC_ASSERT((int8_t)(int16_t)(uint16_t)0x9234 == (int8_t)(uint8_t)0x34); - /* To int16_t. */ - ((int16_t)(uint16_t)0xBCDE == (int16_t)-(int16_t)0x4322) && - ((int16_t)(uint32_t)0xA1B2C3D4 == (int16_t)-(int16_t)0x3C2C) && - ((int16_t)(int32_t)(uint32_t)0xC1D2E3F4 == (int16_t)(uint16_t)0xE3F4) && - ((int16_t)(int32_t)(uint32_t)0x92345678 == (int16_t)(uint16_t)0x5678) && + /* To int16_t. */ + STATIC_ASSERT((int16_t)(uint16_t)0xBCDE == (int16_t)-(int16_t)0x4322); + STATIC_ASSERT((int16_t)(uint32_t)0xA1B2C3D4 == (int16_t)-(int16_t)0x3C2C); + STATIC_ASSERT((int16_t)(int32_t)(uint32_t)0xC1D2E3F4 == (int16_t)(uint16_t)0xE3F4); + STATIC_ASSERT((int16_t)(int32_t)(uint32_t)0x92345678 == (int16_t)(uint16_t)0x5678); - /* To int32_t. */ - ((int32_t)(uint32_t)0xB2C3D4E5 == (int32_t)-(int32_t)0x4D3C2B1B) && - ((int32_t)(uint64_t)0xA123B456C789D012ULL == (int32_t)-(int32_t)0x38762FEE) && - ((int32_t)(int64_t)(uint64_t)0xC1D2E3F4A5B6C7D8ULL == (int32_t)(uint32_t)0xA5B6C7D8) && - ((int32_t)(int64_t)(uint64_t)0xABCDEF0123456789ULL == (int32_t)(uint32_t)0x23456789) && + /* To int32_t. */ + STATIC_ASSERT((int32_t)(uint32_t)0xB2C3D4E5 == (int32_t)-(int32_t)0x4D3C2B1B); + STATIC_ASSERT((int32_t)(uint64_t)0xA123B456C789D012ULL == (int32_t)-(int32_t)0x38762FEE); + STATIC_ASSERT((int32_t)(int64_t)(uint64_t)0xC1D2E3F4A5B6C7D8ULL == (int32_t)(uint32_t)0xA5B6C7D8); + STATIC_ASSERT((int32_t)(int64_t)(uint64_t)0xABCDEF0123456789ULL == (int32_t)(uint32_t)0x23456789); - /* To int64_t. */ - ((int64_t)(uint64_t)0xB123C456D789E012ULL == (int64_t)-(int64_t)0x4EDC3BA928761FEEULL) && + /* To int64_t. */ + STATIC_ASSERT((int64_t)(uint64_t)0xB123C456D789E012ULL == (int64_t)-(int64_t)0x4EDC3BA928761FEEULL); #if defined(SECP256K1_INT128_NATIVE) - ((int64_t)(((uint128_t)0xA1234567B8901234ULL << 64) + 0xC5678901D2345678ULL) == (int64_t)-(int64_t)0x3A9876FE2DCBA988ULL) && - (((int64_t)(int128_t)(((uint128_t)0xB1C2D3E4F5A6B7C8ULL << 64) + 0xD9E0F1A2B3C4D5E6ULL)) == (int64_t)(uint64_t)0xD9E0F1A2B3C4D5E6ULL) && - (((int64_t)(int128_t)(((uint128_t)0xABCDEF0123456789ULL << 64) + 0x0123456789ABCDEFULL)) == (int64_t)(uint64_t)0x0123456789ABCDEFULL) && + STATIC_ASSERT((int64_t)(((uint128_t)0xA1234567B8901234ULL << 64) + 0xC5678901D2345678ULL) == (int64_t)-(int64_t)0x3A9876FE2DCBA988ULL); + STATIC_ASSERT(((int64_t)(int128_t)(((uint128_t)0xB1C2D3E4F5A6B7C8ULL << 64) + 0xD9E0F1A2B3C4D5E6ULL)) == (int64_t)(uint64_t)0xD9E0F1A2B3C4D5E6ULL); + STATIC_ASSERT(((int64_t)(int128_t)(((uint128_t)0xABCDEF0123456789ULL << 64) + 0x0123456789ABCDEFULL)) == (int64_t)(uint64_t)0x0123456789ABCDEFULL); - /* To int128_t. */ - ((int128_t)(((uint128_t)0xB1234567C8901234ULL << 64) + 0xD5678901E2345678ULL) == (int128_t)(-(int128_t)0x8E1648B3F50E80DCULL * 0x8E1648B3F50E80DDULL + 0x5EA688D5482F9464ULL)) && + /* To int128_t. */ + STATIC_ASSERT((int128_t)(((uint128_t)0xB1234567C8901234ULL << 64) + 0xD5678901E2345678ULL) == (int128_t)(-(int128_t)0x8E1648B3F50E80DCULL * 0x8E1648B3F50E80DDULL + 0x5EA688D5482F9464ULL)); #endif - /* Right shift on negative signed values is implementation defined. Verify that it - acts as a right shift in two's complement with sign extension (i.e duplicating - the top bit into newly added bits). */ - ((((int8_t)0xE8) >> 2) == (int8_t)(uint8_t)0xFA) && - ((((int16_t)0xE9AC) >> 4) == (int16_t)(uint16_t)0xFE9A) && - ((((int32_t)0x937C918A) >> 9) == (int32_t)(uint32_t)0xFFC9BE48) && - ((((int64_t)0xA8B72231DF9CF4B9ULL) >> 19) == (int64_t)(uint64_t)0xFFFFF516E4463BF3ULL) && + /* Right shift on negative signed values is implementation defined. Verify that it + acts as a right shift in two's complement with sign extension (i.e duplicating + the top bit into newly added bits). */ + STATIC_ASSERT((((int8_t)0xE8) >> 2) == (int8_t)(uint8_t)0xFA); + STATIC_ASSERT((((int16_t)0xE9AC) >> 4) == (int16_t)(uint16_t)0xFE9A); + STATIC_ASSERT((((int32_t)0x937C918A) >> 9) == (int32_t)(uint32_t)0xFFC9BE48); + STATIC_ASSERT((((int64_t)0xA8B72231DF9CF4B9ULL) >> 19) == (int64_t)(uint64_t)0xFFFFF516E4463BF3ULL); #if defined(SECP256K1_INT128_NATIVE) - ((((int128_t)(((uint128_t)0xCD833A65684A0DBCULL << 64) + 0xB349312F71EA7637ULL)) >> 39) == (int128_t)(((uint128_t)0xFFFFFFFFFF9B0674ULL << 64) + 0xCAD0941B79669262ULL)) && + STATIC_ASSERT((((int128_t)(((uint128_t)0xCD833A65684A0DBCULL << 64) + 0xB349312F71EA7637ULL)) >> 39) == (int128_t)(((uint128_t)0xFFFFFFFFFF9B0674ULL << 64) + 0xCAD0941B79669262ULL)); #endif - 1) * 2 - 1]; -}; + + /* This function is not supposed to be called. */ + VERIFY_CHECK(0); +} #endif /* SECP256K1_ASSUMPTIONS_H */