Bitcoin Core  0.19.99
P2P Digital Currency
assumptions.h
Go to the documentation of this file.
1 // Copyright (c) 2009-2010 Satoshi Nakamoto
2 // Copyright (c) 2009-2019 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++11 (ISO/IEC 14882:2011) compiler (minimum requirement).
21 // Example(s): We assume the presence of C++11 features everywhere :-)
22 // Note: MSVC does not report the expected __cplusplus value due to legacy
23 // reasons.
24 #if !defined(_MSC_VER)
25 // ISO Standard C++11 [cpp.predefined]p1:
26 // "The name __cplusplus is defined to the value 201103L when compiling a C++
27 // translation unit."
28 static_assert(__cplusplus >= 201103L, "C++11 standard assumed");
29 #endif
30 
31 // Assumption: We assume the floating-point types to fulfill the requirements of
32 // IEC 559 (IEEE 754) standard.
33 // Example(s): Floating-point division by zero in ConnectBlock, CreateTransaction
34 // and EstimateMedianVal.
35 static_assert(std::numeric_limits<float>::is_iec559, "IEEE 754 float assumed");
36 static_assert(std::numeric_limits<double>::is_iec559, "IEEE 754 double assumed");
37 
38 // Assumption: We assume eight bits per byte (obviously, but remember: don't
39 // trust -- verify!).
40 // Example(s): Everywhere :-)
41 static_assert(std::numeric_limits<unsigned char>::digits == 8, "8-bit byte assumed");
42 
43 // Assumption: We assume floating-point widths.
44 // Example(s): Type punning in serialization code (ser_{float,double}_to_uint{32,64}).
45 static_assert(sizeof(float) == 4, "32-bit float assumed");
46 static_assert(sizeof(double) == 8, "64-bit double assumed");
47 
48 // Assumption: We assume integer widths.
49 // Example(s): GetSizeOfCompactSize and WriteCompactSize in the serialization
50 // code.
51 static_assert(sizeof(short) == 2, "16-bit short assumed");
52 static_assert(sizeof(int) == 4, "32-bit int assumed");
53 
54 // Assumption: We assume size_t to be 32-bit or 64-bit.
55 // Example(s): size_t assumed to be at least 32-bit in ecdsa_signature_parse_der_lax(...).
56 // size_t assumed to be 32-bit or 64-bit in MallocUsage(...).
57 static_assert(sizeof(size_t) == 4 || sizeof(size_t) == 8, "size_t assumed to be 32-bit or 64-bit");
58 static_assert(sizeof(size_t) == sizeof(void*), "Sizes of size_t and void* assumed to be equal");
59 
60 // Some important things we are NOT assuming (non-exhaustive list):
61 // * We are NOT assuming a specific value for std::endian::native.
62 // * We are NOT assuming a specific value for std::locale("").name().
63 // * We are NOT assuming a specific value for std::numeric_limits<char>::is_signed.
64 
65 #endif // BITCOIN_COMPAT_ASSUMPTIONS_H