标签:stdthread c c11 pass-by-reference
为什么在创建std :: thread时不能通过引用传递对象?
例如,以下snippit给出了编译错误:
#include <iostream>
#include <thread>
using namespace std;
static void SimpleThread(int& a) // compile error
//static void SimpleThread(int a) // OK
{
cout << __PRETTY_FUNCTION__ << ":" << a << endl;
}
int main()
{
int a = 6;
auto thread1 = std::thread(SimpleThread, a);
thread1.join();
return 0;
}
错误:
In file included from /usr/include/c++/4.8/thread:39:0,
from ./std_thread_refs.cpp:5:
/usr/include/c++/4.8/functional: In instantiation of ‘struct std::_Bind_simple<void (*(int))(int&)>’:
/usr/include/c++/4.8/thread:137:47: required from ‘std::thread::thread(_Callable&&, _Args&& ...) [with _Callable = void (&)(int&); _Args = {int&}]’
./std_thread_refs.cpp:19:47: required from here
/usr/include/c++/4.8/functional:1697:61: error: no type named ‘type’ in ‘class std::result_of<void (*(int))(int&)>’
typedef typename result_of<_Callable(_Args...)>::type result_type;
^
/usr/include/c++/4.8/functional:1727:9: error: no type named ‘type’ in ‘class std::result_of<void (*(int))(int&)>’
_M_invoke(_Index_tuple<_Indices...>)
^
我改变了传递指针,但有更好的解决方法吗?
解决方法:
使用reference_wrapper
by using std::ref
显式初始化线程:
auto thread1 = std::thread(SimpleThread, std::ref(a));
(或者std :: cref而不是std :: ref,视情况而定).来自cppreference on std:thread
的说明:
The arguments to the thread function are moved or copied by value. If a reference argument needs to be passed to the thread function, it has to be wrapped (e.g. with
std::ref
orstd::cref
).
标签:stdthread,c,c11,pass-by-reference 来源: https://codeday.me/bug/20190917/1809260.html
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