Add compile time verification of assumptions we're currently making i…

…mplicitly/tacitly

src/Makefile.am

@@ -102,6 +102,7 @@ endif
 BITCOIN_CORE_H = \
   addrdb.h \
   addrman.h \
+  assumptions.h \
   attributes.h \
   banman.h \
   base58.h \

src/assumptions.h

@@ -0,0 +1,29 @@
+// 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_ASSUMPTIONS_H
+#define BITCOIN_ASSUMPTIONS_H
+
+#include <climits>
+#include <limits>
+
+// 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 floating-point widths.
+// Example(s): Type punning in serialization code (ser_{float,double}_to_uint{32,64}).
+static_assert(sizeof(float) * CHAR_BIT == 32 && CHAR_BIT == 8, "32-bit float assumed");
+static_assert(sizeof(double) * CHAR_BIT == 64 && CHAR_BIT == 8, "64-bit double assumed");
+
+// Assumption: We assume integer widths.
+// Example(s): GetSizeOfCompactSize and WriteCompactSize in the serialization code.
+static_assert(sizeof(short) * CHAR_BIT == 16 && CHAR_BIT == 8, "16-bit short assumed");
+static_assert(sizeof(int) * CHAR_BIT == 32 && CHAR_BIT == 8, "32-bit int assumed");
+
+#endif // BITCOIN_ASSUMPTIONS_H

src/util/system.h

@@ -14,6 +14,7 @@
 #include <config/bitcoin-config.h>
 #endif
 
+#include <assumptions.h>
 #include <attributes.h>
 #include <compat.h>
 #include <fs.h>