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Add nodiscard attribute #31

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Dec 14, 2021
Merged

Add nodiscard attribute #31

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2 changes: 1 addition & 1 deletion CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,7 @@ if(CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_SOURCE_DIR)
if(MSVC)
add_compile_options(/permissive- /W4)
else()
add_compile_options(-Wall -Wextra -Wpedantic)
add_compile_options(-Wall -Wextra -Wpedantic -Wno-c++17-extensions)
endif()

find_package(Threads REQUIRED)
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24 changes: 17 additions & 7 deletions include/rigtorp/SPSCQueue.h
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Expand Up @@ -30,6 +30,15 @@ SOFTWARE.
#include <stdexcept>
#include <type_traits> // std::enable_if, std::is_*_constructible

#ifdef __has_cpp_attribute
#if __has_cpp_attribute(nodiscard)
#define RIGTORP_NODISCARD [[nodiscard]]
#endif
#endif
#ifndef RIGTORP_NODISCARD
#define RIGTORP_NODISCARD
#endif

namespace rigtorp {

template <typename T, typename Allocator = std::allocator<T>> class SPSCQueue {
Expand Down Expand Up @@ -110,7 +119,7 @@ template <typename T, typename Allocator = std::allocator<T>> class SPSCQueue {
}

template <typename... Args>
bool try_emplace(Args &&...args) noexcept(
RIGTORP_NODISCARD bool try_emplace(Args &&...args) noexcept(
std::is_nothrow_constructible<T, Args &&...>::value) {
static_assert(std::is_constructible<T, Args &&...>::value,
"T must be constructible with Args&&...");
Expand Down Expand Up @@ -142,7 +151,7 @@ template <typename T, typename Allocator = std::allocator<T>> class SPSCQueue {
emplace(std::forward<P>(v));
}

bool
RIGTORP_NODISCARD bool
try_push(const T &v) noexcept(std::is_nothrow_copy_constructible<T>::value) {
static_assert(std::is_copy_constructible<T>::value,
"T must be copy constructible");
Expand All @@ -151,11 +160,12 @@ template <typename T, typename Allocator = std::allocator<T>> class SPSCQueue {

template <typename P, typename = typename std::enable_if<
std::is_constructible<T, P &&>::value>::type>
bool try_push(P &&v) noexcept(std::is_nothrow_constructible<T, P &&>::value) {
RIGTORP_NODISCARD bool
try_push(P &&v) noexcept(std::is_nothrow_constructible<T, P &&>::value) {
return try_emplace(std::forward<P>(v));
}

T *front() noexcept {
RIGTORP_NODISCARD T *front() noexcept {
auto const readIdx = readIdx_.load(std::memory_order_relaxed);
if (readIdx == writeIdxCache_) {
writeIdxCache_ = writeIdx_.load(std::memory_order_acquire);
Expand All @@ -179,7 +189,7 @@ template <typename T, typename Allocator = std::allocator<T>> class SPSCQueue {
readIdx_.store(nextReadIdx, std::memory_order_release);
}

size_t size() const noexcept {
RIGTORP_NODISCARD size_t size() const noexcept {
std::ptrdiff_t diff = writeIdx_.load(std::memory_order_acquire) -
readIdx_.load(std::memory_order_acquire);
if (diff < 0) {
Expand All @@ -188,12 +198,12 @@ template <typename T, typename Allocator = std::allocator<T>> class SPSCQueue {
return static_cast<size_t>(diff);
}

bool empty() const noexcept {
RIGTORP_NODISCARD bool empty() const noexcept {
return writeIdx_.load(std::memory_order_acquire) ==
readIdx_.load(std::memory_order_acquire);
}

size_t capacity() const noexcept { return capacity_ - 1; }
RIGTORP_NODISCARD size_t capacity() const noexcept { return capacity_ - 1; }

private:
#ifdef __cpp_lib_hardware_interference_size
Expand Down
16 changes: 8 additions & 8 deletions src/SPSCQueueTest.cpp
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Expand Up @@ -104,16 +104,16 @@ int main(int argc, char *argv[]) {
// lvalue
Test v;
q.emplace(v);
q.try_emplace(v);
(void)q.try_emplace(v);
q.push(v);
q.try_push(v);
(void)q.try_push(v);
static_assert(noexcept(q.emplace(v)) == false, "");
static_assert(noexcept(q.try_emplace(v)) == false, "");
static_assert(noexcept(q.push(v)) == false, "");
static_assert(noexcept(q.try_push(v)) == false, "");
// xvalue
q.push(Test());
q.try_push(Test());
(void)q.try_push(Test());
static_assert(noexcept(q.push(Test())) == false, "");
static_assert(noexcept(q.try_push(Test())) == false, "");
}
Expand All @@ -129,16 +129,16 @@ int main(int argc, char *argv[]) {
// lvalue
Test v;
q.emplace(v);
q.try_emplace(v);
(void)q.try_emplace(v);
q.push(v);
q.try_push(v);
(void)q.try_push(v);
static_assert(noexcept(q.emplace(v)) == true, "");
static_assert(noexcept(q.try_emplace(v)) == true, "");
static_assert(noexcept(q.push(v)) == true, "");
static_assert(noexcept(q.try_push(v)) == true, "");
// xvalue
q.push(Test());
q.try_push(Test());
(void)q.try_push(Test());
static_assert(noexcept(q.push(Test())) == true, "");
static_assert(noexcept(q.try_push(Test())) == true, "");
}
Expand All @@ -154,9 +154,9 @@ int main(int argc, char *argv[]) {
// q.try_push(v);
// xvalue
q.emplace(std::unique_ptr<int>(new int(1)));
q.try_emplace(std::unique_ptr<int>(new int(1)));
(void)q.try_emplace(std::unique_ptr<int>(new int(1)));
q.push(std::unique_ptr<int>(new int(1)));
q.try_push(std::unique_ptr<int>(new int(1)));
(void)q.try_push(std::unique_ptr<int>(new int(1)));
auto v = std::unique_ptr<int>(new int(1));
static_assert(noexcept(q.emplace(std::move(v))) == true, "");
static_assert(noexcept(q.try_emplace(std::move(v))) == true, "");
Expand Down