Skip to content

Commit

Permalink
Merge bitcoin#15391: Add compile time verification of assumptions we'…
Browse files Browse the repository at this point in the history
…re currently making implicitly/tacitly

7cee858 Add compile time verification of assumptions we're currently making implicitly/tacitly (practicalswift)

Pull request description:

  Add compile time verification of assumptions we're currently making implicitly/tacitly.

  As suggested by @sipa in bitcoin#14239 (comment) and @MarcoFalke in bitcoin#14479 (comment).

Tree-SHA512: e68fe51164dbd3eeb76aa8a7e83dfcd3b4d5a66037c0f1822bbbd189bbe3c280e03b3b10af870880ecc09b612e62fb3d9bcd6cf1e16cb7ba818c257db0712ce4
  • Loading branch information
laanwj authored and PastaPastaPasta committed Jun 27, 2021
1 parent 395cb61 commit 2ed7317
Show file tree
Hide file tree
Showing 3 changed files with 51 additions and 0 deletions.
1 change: 1 addition & 0 deletions src/Makefile.am
Original file line number Diff line number Diff line change
Expand Up @@ -142,6 +142,7 @@ BITCOIN_CORE_H = \
coinjoin/coinjoin-util.h \
coins.h \
compat.h \
compat/assumptions.h \
compat/byteswap.h \
compat/endian.h \
compat/sanity.h \
Expand Down
49 changes: 49 additions & 0 deletions src/compat/assumptions.h
Original file line number Diff line number Diff line change
@@ -0,0 +1,49 @@
// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2019 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

// Compile-time verification of assumptions we make.

#ifndef BITCOIN_COMPAT_ASSUMPTIONS_H
#define BITCOIN_COMPAT_ASSUMPTIONS_H

#include <limits>

// Assumption: We assume that the macro NDEBUG is not defined.
// Example(s): We use assert(...) extensively with the assumption of it never
// being a noop at runtime.
#if defined(NDEBUG)
# error "Bitcoin cannot be compiled without assertions."
#endif

// Assumption: We assume the floating-point types to fulfill the requirements of
// IEC 559 (IEEE 754) standard.
// Example(s): Floating-point division by zero in ConnectBlock, CreateTransaction
// and EstimateMedianVal.
static_assert(std::numeric_limits<float>::is_iec559, "IEEE 754 float assumed");
static_assert(std::numeric_limits<double>::is_iec559, "IEEE 754 double assumed");

// Assumption: We assume eight bits per byte (obviously, but remember: don't
// trust -- verify!).
// Example(s): Everywhere :-)
static_assert(std::numeric_limits<unsigned char>::digits == 8, "8-bit byte assumed");

// Assumption: We assume floating-point widths.
// Example(s): Type punning in serialization code (ser_{float,double}_to_uint{32,64}).
static_assert(sizeof(float) == 4, "32-bit float assumed");
static_assert(sizeof(double) == 8, "64-bit double assumed");

// Assumption: We assume integer widths.
// Example(s): GetSizeOfCompactSize and WriteCompactSize in the serialization
// code.
static_assert(sizeof(short) == 2, "16-bit short assumed");
static_assert(sizeof(int) == 4, "32-bit int assumed");

// Some important things we are NOT assuming (non-exhaustive list):
// * We are NOT assuming a specific value for sizeof(std::size_t).
// * We are NOT assuming a specific value for std::endian::native.
// * We are NOT assuming a specific value for std::locale("").name().
// * We are NOT assuming a specific value for std::numeric_limits<char>::is_signed.

#endif // BITCOIN_COMPAT_ASSUMPTIONS_H
1 change: 1 addition & 0 deletions src/util.h
Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@

#include <attributes.h>
#include <compat.h>
#include <compat/assumptions.h>
#include <fs.h>
#include <logging.h>
#include <sync.h>
Expand Down

0 comments on commit 2ed7317

Please sign in to comment.