Bitcoin Core  22.99.0
P2P Digital Currency
assumptions.h
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1 // Copyright (c) 2009-2010 Satoshi Nakamoto
2 // Copyright (c) 2009-2020 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 <limits>
12 
13 // Assumption: We assume that the macro NDEBUG is not defined.
14 // Example(s): We use assert(...) extensively with the assumption of it never
15 // being a noop at runtime.
16 #if defined(NDEBUG)
17 # error "Bitcoin cannot be compiled without assertions."
18 #endif
19 
20 // Assumption: We assume a C++17 (ISO/IEC 14882:2017) compiler (minimum requirement).
21 // Example(s): We assume the presence of C++17 features everywhere :-)
22 // ISO Standard C++17 [cpp.predefined]p1:
23 // "The name __cplusplus is defined to the value 201703L when compiling a C++
24 // translation unit."
25 static_assert(__cplusplus >= 201703L, "C++17 standard assumed");
26 
27 // Assumption: We assume the floating-point types to fulfill the requirements of
28 // IEC 559 (IEEE 754) standard.
29 // Example(s): Floating-point division by zero in ConnectBlock, CreateTransaction
30 // and EstimateMedianVal.
31 static_assert(std::numeric_limits<float>::is_iec559, "IEEE 754 float assumed");
32 static_assert(std::numeric_limits<double>::is_iec559, "IEEE 754 double assumed");
33 
34 // Assumption: We assume eight bits per byte (obviously, but remember: don't
35 // trust -- verify!).
36 // Example(s): Everywhere :-)
37 static_assert(std::numeric_limits<unsigned char>::digits == 8, "8-bit byte assumed");
38 
39 // Assumption: We assume integer widths.
40 // Example(s): GetSizeOfCompactSize and WriteCompactSize in the serialization
41 // code.
42 static_assert(sizeof(short) == 2, "16-bit short assumed");
43 static_assert(sizeof(int) == 4, "32-bit int assumed");
44 static_assert(sizeof(unsigned) == 4, "32-bit unsigned assumed");
45 
46 // Assumption: We assume size_t to be 32-bit or 64-bit.
47 // Example(s): size_t assumed to be at least 32-bit in ecdsa_signature_parse_der_lax(...).
48 // size_t assumed to be 32-bit or 64-bit in MallocUsage(...).
49 static_assert(sizeof(size_t) == 4 || sizeof(size_t) == 8, "size_t assumed to be 32-bit or 64-bit");
50 static_assert(sizeof(size_t) == sizeof(void*), "Sizes of size_t and void* assumed to be equal");
51 
52 // Some important things we are NOT assuming (non-exhaustive list):
53 // * We are NOT assuming a specific value for std::endian::native.
54 // * We are NOT assuming a specific value for std::locale("").name().
55 // * We are NOT assuming a specific value for std::numeric_limits<char>::is_signed.
56 
57 #endif // BITCOIN_COMPAT_ASSUMPTIONS_H