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d134b0cae3
With -fsanitize=integer every over/under-flowing integer manipulation triggers a warning.
This is extremely useful as it allows to find some non-obvious bugs such as
for(size_t i = 0; i < N - 1; i++) { ... }
But it comes with a lot of false positives, for instance with every hash function
doing shifting on unsigned integer. Random number generators are also often detected
with this sanitizer.
This marks a few of these functions as safe in this case.
Co-authored-by: Martin Hořeňovský <martin.horenovsky@gmail.com>
79 lines
2.1 KiB
C++
79 lines
2.1 KiB
C++
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// Copyright Catch2 Authors
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// Distributed under the Boost Software License, Version 1.0.
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// (See accompanying file LICENSE.txt or copy at
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// https://www.boost.org/LICENSE_1_0.txt)
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// SPDX-License-Identifier: BSL-1.0
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#include <catch2/internal/catch_random_number_generator.hpp>
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#if defined( __clang__ )
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# define CATCH2_CLANG_NO_SANITIZE_INTEGER \
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__attribute__( ( no_sanitize( "unsigned-integer-overflow" ) ) )
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#else
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# define CATCH2_CLANG_NO_SANITIZE_INTEGER
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#endif
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namespace Catch {
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namespace {
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#if defined(_MSC_VER)
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#pragma warning(push)
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#pragma warning(disable:4146) // we negate uint32 during the rotate
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#endif
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// Safe rotr implementation thanks to John Regehr
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CATCH2_CLANG_NO_SANITIZE_INTEGER
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uint32_t rotate_right(uint32_t val, uint32_t count) {
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const uint32_t mask = 31;
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count &= mask;
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return (val >> count) | (val << (-count & mask));
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}
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#if defined(_MSC_VER)
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#pragma warning(pop)
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#endif
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}
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SimplePcg32::SimplePcg32(result_type seed_) {
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seed(seed_);
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}
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void SimplePcg32::seed(result_type seed_) {
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m_state = 0;
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(*this)();
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m_state += seed_;
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(*this)();
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}
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void SimplePcg32::discard(uint64_t skip) {
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// We could implement this to run in O(log n) steps, but this
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// should suffice for our use case.
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for (uint64_t s = 0; s < skip; ++s) {
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static_cast<void>((*this)());
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}
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}
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CATCH2_CLANG_NO_SANITIZE_INTEGER
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SimplePcg32::result_type SimplePcg32::operator()() {
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// prepare the output value
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const uint32_t xorshifted = static_cast<uint32_t>(((m_state >> 18u) ^ m_state) >> 27u);
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const auto output = rotate_right(xorshifted, static_cast<uint32_t>(m_state >> 59u));
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// advance state
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m_state = m_state * 6364136223846793005ULL + s_inc;
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return output;
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}
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bool operator==(SimplePcg32 const& lhs, SimplePcg32 const& rhs) {
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return lhs.m_state == rhs.m_state;
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}
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bool operator!=(SimplePcg32 const& lhs, SimplePcg32 const& rhs) {
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return lhs.m_state != rhs.m_state;
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}
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}
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