1// Copyright (c) 2009-2010 Satoshi Nakamoto
2// Copyright (c) 2009-present The Bitcoin Core developers
3// Distributed under the MIT software license, see the accompanying
4// file COPYING or http://www.opensource.org/licenses/mit-license.php.
5
6// Compile-time verification of assumptions we make.
7
8#ifndef BITCOIN_COMPAT_ASSUMPTIONS_H
9#define BITCOIN_COMPAT_ASSUMPTIONS_H
10
11#include <cstddef>
12#include <limits>
13
14// Assumption: We assume the floating-point types to fulfill the requirements of
15//             IEC 559 (IEEE 754) standard.
16// Example(s): Floating-point division by zero in ConnectBlock, CreateTransaction
17//             and EstimateMedianVal.
18static_assert(std::numeric_limits<float>::is_iec559, "IEEE 754 float assumed");
19static_assert(std::numeric_limits<double>::is_iec559, "IEEE 754 double assumed");
20
21// Assumption: We assume eight bits per byte (obviously, but remember: don't
22//             trust -- verify!).
23// Example(s): Everywhere :-)
24static_assert(std::numeric_limits<unsigned char>::digits == 8, "8-bit byte assumed");
25
26// Assumption: We assume integer widths.
27// Example(s): GetSizeOfCompactSize and WriteCompactSize in the serialization
28//             code.
29static_assert(sizeof(short) == 2, "16-bit short assumed");
30static_assert(sizeof(int) == 4, "32-bit int assumed");
31static_assert(sizeof(unsigned) == 4, "32-bit unsigned assumed");
32
33// Assumption: We assume size_t to be 32-bit or 64-bit.
34// Example(s): size_t assumed to be at least 32-bit in ecdsa_signature_parse_der_lax(...).
35//             size_t assumed to be 32-bit or 64-bit in MallocUsage(...).
36static_assert(sizeof(size_t) == 4 || sizeof(size_t) == 8, "size_t assumed to be 32-bit or 64-bit");
37static_assert(sizeof(size_t) == sizeof(void*), "Sizes of size_t and void* assumed to be equal");
38
39// Some important things we are NOT assuming (non-exhaustive list):
40// * We are NOT assuming a specific value for std::endian::native.
41// * We are NOT assuming a specific value for std::locale("").name().
42// * We are NOT assuming a specific value for std::numeric_limits<char>::is_signed.
43
44#endif // BITCOIN_COMPAT_ASSUMPTIONS_H
45