我想通过从C 11包装std :: thread类来使用我自己的Thread实现，所以我将能够处理我想要的异常 .
这是我的包装类：
#include <Types.hpp>
#include <thread>
#include <exception>
#include <functional>
class Thread
{
private:
std::exception_ptr exceptionPtr;
std::thread thread;
public:
using Id = std::thread::id;
using NativeHandleType = std::thread::native_handle_type;
Thread() noexcept = default;
Thread(Thread &&t) noexcept :
exceptionPtr(std::move(t.exceptionPtr)),
thread(std::move(t.thread))
{
}
Thread &operator =(Thread &&t) noexcept
{
exceptionPtr = std::move(t.exceptionPtr);
thread = std::move(t.thread);
return *this;
}
template<typename Callable, typename... Args>
Thread(Callable &&f, Args &&... args) :
exceptionPtr(nullptr),
thread([&](Callable &&f, Args &&... args)
{
try
{
std::once_flag flag;
std::call_once(flag, f, args...);
}
catch (...)
{
exceptionPtr = std::current_exception();
}
}, f, args...)
{
if (exceptionPtr != nullptr)
{
std::rethrow_exception(exceptionPtr);
}
}
bool joinable() const noexcept
{
return thread.joinable();
}
void join()
{
thread.join();
}
void detach()
{
thread.detach();
}
Id getId() const noexcept
{
return thread.get_id();
}
NativeHandleType nativeHandle()
{
return thread.native_handle();
}
static uint32_t hardwareConcurrency() noexcept
{
return std::thread::hardware_concurrency();
}
static void wait(Time t)
{
std::this_thread::sleep_for(t);
}
};
如果没有参数，它的效果非常好：
Thread([&]() { /* do something */ }).detach();
...但是如果我尝试传递可变参数：
Thread(&GUI::refreshTask, this, refreshDelay).detach();
...我在编译时遇到错误：
buildroot-2014.02 / output / host / usr / i586-buildroot-linux-uclibc / include / c /4.8.2/functional：实例化'struct std :: _ Bind_simple）（std :: chrono :: duration>）; Args = {CRH :: GUI const，std :: chrono :: duration>＆}] :: __ lambda1（void（CRH :: GUI ::）（std :: chrono :: duration>），CRH :: GUI，std :: chrono :: duration>）>'：buildroot-2014.02 / output / host / usr / i586-buildroot-linux-uclibc / include / c /4.8.2/thread:137:47：从'std :: thread中需要:: thread（Callable &&， Args && ...）[with _Callable = CRH :: Thread :: Thread（Callable &&，Args && ...）[with Callable = void（CRH :: GUI ::）（std :: chrono ::持续时间>）; Args = {CRH :: GUI const，std :: chrono :: duration>＆}] :: __ lambda1; _Args = {void（CRH :: GUI ::＆）（std :: chrono :: duration>），CRH :: GUI const＆，std :: chrono :: duration>＆}]'/ home / cyril / Documents / crh -2016 / src / robot2 /../core / Thread.hpp：72：30：'CRH :: Thread :: Thread（Callable &&，Args && ...）[需要Callable = void（CRH :: GUI ::） ）（std :: chrono :: duration>）; Args = {CRH :: GUI const，std :: chrono :: duration>＆}]'src / core / GUI.cpp:90:57：从这里需要buildroot-2014.02 / output / host / usr / i586-buildroot- linux-uclibc / include / c /4.8.2/functional:1697:61：错误：'class std :: result_of）中没有名为'type'的类型（std :: chrono :: duration>）; Args = {CRH :: GUI const，std :: chrono :: duration>＆}] :: __ lambda1（void（CRH :: GUI ::）（std :: chrono :: duration>），CRH :: GUI，std :: chrono :: duration>）>'typedef typename result_of <_Callable（_Args ...）> :: type result_type; ^ buildroot-2014.02 / output / host / usr / i586-buildroot-linux-uclibc / include / c /4.8.2/functional:1727:9：错误：'class std :: result_of中没有名为'type'的类型）（ std :: chrono :: duration>）; Args = {CRH :: GUI const，std :: chrono :: duration>＆}] :: __ lambda1（void（CRH :: GUI ::）（std :: chrono :: duration>），CRH :: GUI，std :: chrono :: duration>）>'_M_invoke（_Index_tuple <_Indices ...>）
它可能会更清楚......但对海湾合作委员会来说要求太高了 .
知道如何解决这个问题吗？
Solution
#include <Types.hpp>
#include <thread>
#include <exception>
#include <functional>
class Thread
{
private:
std::exception_ptr exceptionPtr;
std::thread thread;
public:
using Id = std::thread::id;
using NativeHandleType = std::thread::native_handle_type;
Thread() noexcept = default;
Thread(Thread &&t) noexcept :
exceptionPtr(std::move(t.exceptionPtr)),
thread(std::move(t.thread))
{
}
Thread &operator =(Thread &&t) noexcept
{
exceptionPtr = std::move(t.exceptionPtr);
thread = std::move(t.thread);
return *this;
}
template<typename Callable, typename... Args>
Thread(Callable &&f, Args &&... args) :
exceptionPtr(nullptr),
thread([&](typename std::decay<Callable>::type &&f, typename std::decay<Args>::type &&... args)
{
try
{
std::bind(f, args...)();
}
catch (...)
{
exceptionPtr = std::current_exception();
}
}, std::forward<Callable>(f), std::forward<Args>(args)...)
{
}
bool joinable() const noexcept
{
return thread.joinable();
}
void join()
{
thread.join();
if (exceptionPtr != nullptr)
{
std::rethrow_exception(exceptionPtr);
}
}
void detach()
{
thread.detach();
}
Id getId() const noexcept
{
return thread.get_id();
}
NativeHandleType nativeHandle()
{
return thread.native_handle();
}
static uint32_t hardwareConcurrency() noexcept
{
return std::thread::hardware_concurrency();
}
static void wait(Time t)
{
std::this_thread::sleep_for(t);
}
};
1 回答
Callable和Args是转发引用，因此模板参数推导可以使它们成为左值引用或普通类型，具体取决于参数表达式的值类别 .这意味着当您在lambda声明中重用推导出的类型时：
引用折叠发挥作用，对于左值参数
refreshDelay，Args成为左值引用 .但是，
std::thread存储它接收的参数的衰减副本，然后它从内部存储移动到实际处理程序，将存储的对象转换为xvalues . 这就是错误告诉您的内容：处理程序无法使用线程尝试传入的参数进行调用 .相反，您可以按如下方式实现它：