176 lines
6.9 KiB
C++
176 lines
6.9 KiB
C++
/* Copyright (c) 2017, Google Inc.
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*
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* Permission to use, copy, modify, and/or distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
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* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
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* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
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* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
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#include <limits.h>
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#include <stdint.h>
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#include <type_traits>
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#include <gtest/gtest.h>
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#include "test/test_util.h"
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template <typename T>
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static void CheckRepresentation(T value) {
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SCOPED_TRACE(value);
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// Convert to the corresponding two's-complement unsigned value. We use an
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// unsigned value so the right-shift below has defined value. Right-shifts of
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// negative numbers in C are implementation defined.
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//
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// If |T| is already unsigned, this is a no-op, as desired.
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//
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// If |T| is signed, conversion to unsigned is defined to repeatedly add or
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// subtract (numerically, not within |T|) one more than the unsigned type's
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// maximum value until it fits (this must be a power of two). This is the
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// conversion we want.
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using UnsignedT = typename std::make_unsigned<T>::type;
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UnsignedT value_u = static_cast<UnsignedT>(value);
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EXPECT_EQ(sizeof(UnsignedT), sizeof(T));
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// Integers must be little-endian.
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uint8_t expected[sizeof(UnsignedT)];
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for (size_t i = 0; i < sizeof(UnsignedT); i++) {
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expected[i] = static_cast<uint8_t>(value_u);
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// Divide instead of right-shift to appease compilers that warn if |T| is a
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// char. The explicit cast is also needed to appease MSVC if integer
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// promotion happened.
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value_u = static_cast<UnsignedT>(value_u / 256);
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}
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EXPECT_EQ(0u, value_u);
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// Check that |value| has the expected representation.
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EXPECT_EQ(Bytes(expected),
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Bytes(reinterpret_cast<const uint8_t *>(&value), sizeof(value)));
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}
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TEST(CompilerTest, IntegerRepresentation) {
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EXPECT_EQ(8, CHAR_BIT);
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EXPECT_EQ(0xff, static_cast<int>(UCHAR_MAX));
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// uint8_t is assumed to be unsigned char. I.e., casting to uint8_t should be
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// as good as unsigned char for strict aliasing purposes.
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uint8_t u8 = 0;
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unsigned char *ptr = &u8;
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(void)ptr;
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// Sized integers have the expected size.
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EXPECT_EQ(1u, sizeof(uint8_t));
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EXPECT_EQ(2u, sizeof(uint16_t));
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EXPECT_EQ(4u, sizeof(uint32_t));
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EXPECT_EQ(8u, sizeof(uint64_t));
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// size_t does not exceed uint64_t.
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EXPECT_LE(sizeof(size_t), 8u);
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// int must be 32-bit or larger.
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EXPECT_LE(0x7fffffff, INT_MAX);
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EXPECT_LE(0xffffffffu, UINT_MAX);
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CheckRepresentation(static_cast<signed char>(127));
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CheckRepresentation(static_cast<signed char>(1));
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CheckRepresentation(static_cast<signed char>(0));
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CheckRepresentation(static_cast<signed char>(-1));
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CheckRepresentation(static_cast<signed char>(-42));
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CheckRepresentation(static_cast<signed char>(-128));
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CheckRepresentation(static_cast<int>(INT_MAX));
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CheckRepresentation(static_cast<int>(0x12345678));
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CheckRepresentation(static_cast<int>(1));
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CheckRepresentation(static_cast<int>(0));
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CheckRepresentation(static_cast<int>(-1));
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CheckRepresentation(static_cast<int>(-0x12345678));
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CheckRepresentation(static_cast<int>(INT_MIN));
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CheckRepresentation(static_cast<unsigned>(UINT_MAX));
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CheckRepresentation(static_cast<unsigned>(0x12345678));
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CheckRepresentation(static_cast<unsigned>(1));
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CheckRepresentation(static_cast<unsigned>(0));
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CheckRepresentation(static_cast<long>(LONG_MAX));
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CheckRepresentation(static_cast<long>(0x12345678));
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CheckRepresentation(static_cast<long>(1));
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CheckRepresentation(static_cast<long>(0));
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CheckRepresentation(static_cast<long>(-1));
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CheckRepresentation(static_cast<long>(-0x12345678));
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CheckRepresentation(static_cast<long>(LONG_MIN));
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CheckRepresentation(static_cast<unsigned long>(ULONG_MAX));
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CheckRepresentation(static_cast<unsigned long>(0x12345678));
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CheckRepresentation(static_cast<unsigned long>(1));
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CheckRepresentation(static_cast<unsigned long>(0));
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CheckRepresentation(static_cast<int16_t>(0x7fff));
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CheckRepresentation(static_cast<int16_t>(0x1234));
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CheckRepresentation(static_cast<int16_t>(1));
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CheckRepresentation(static_cast<int16_t>(0));
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CheckRepresentation(static_cast<int16_t>(-1));
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CheckRepresentation(static_cast<int16_t>(-0x7fff - 1));
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CheckRepresentation(static_cast<uint16_t>(0xffff));
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CheckRepresentation(static_cast<uint16_t>(0x1234));
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CheckRepresentation(static_cast<uint16_t>(1));
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CheckRepresentation(static_cast<uint16_t>(0));
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CheckRepresentation(static_cast<int32_t>(0x7fffffff));
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CheckRepresentation(static_cast<int32_t>(0x12345678));
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CheckRepresentation(static_cast<int32_t>(1));
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CheckRepresentation(static_cast<int32_t>(0));
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CheckRepresentation(static_cast<int32_t>(-1));
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CheckRepresentation(static_cast<int32_t>(-0x7fffffff - 1));
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CheckRepresentation(static_cast<uint32_t>(0xffffffff));
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CheckRepresentation(static_cast<uint32_t>(0x12345678));
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CheckRepresentation(static_cast<uint32_t>(1));
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CheckRepresentation(static_cast<uint32_t>(0));
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CheckRepresentation(static_cast<int64_t>(0x7fffffffffffffff));
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CheckRepresentation(static_cast<int64_t>(0x123456789abcdef0));
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CheckRepresentation(static_cast<int64_t>(1));
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CheckRepresentation(static_cast<int64_t>(0));
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CheckRepresentation(static_cast<int64_t>(-1));
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CheckRepresentation(static_cast<int64_t>(-0x7fffffffffffffff - 1));
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CheckRepresentation(static_cast<uint64_t>(0xffffffffffffffff));
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CheckRepresentation(static_cast<uint64_t>(0x12345678abcdef0));
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CheckRepresentation(static_cast<uint64_t>(1));
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CheckRepresentation(static_cast<uint64_t>(0));
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}
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TEST(CompilerTest, PointerRepresentation) {
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// Converting pointers to integers and doing arithmetic on those values are
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// both defined. Converting those values back into pointers is undefined,
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// but, for aliasing checks, we require that the implementation-defined
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// result of that computation commutes with pointer arithmetic.
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char chars[256];
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for (size_t i = 0; i < sizeof(chars); i++) {
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EXPECT_EQ(reinterpret_cast<uintptr_t>(chars) + i,
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reinterpret_cast<uintptr_t>(chars + i));
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}
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int ints[256];
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for (size_t i = 0; i < OPENSSL_ARRAY_SIZE(ints); i++) {
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EXPECT_EQ(reinterpret_cast<uintptr_t>(ints) + i * sizeof(int),
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reinterpret_cast<uintptr_t>(ints + i));
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}
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// nullptr must be represented by all zeros in memory. This is necessary so
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// structs may be initialized by memset(0).
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int *null = nullptr;
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uint8_t bytes[sizeof(null)] = {0};
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EXPECT_EQ(Bytes(bytes),
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Bytes(reinterpret_cast<uint8_t *>(&null), sizeof(null)));
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}
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