问题描述
C ++ 11
我想让一个向量 std :: thread s。以下三点的结合说明我可以。
I am trying to make a vector of std::threads. The combination of the following three points says I can.
1。）根据，
线程' s默认构造函数创建一个不代表线程的
1.) According to http://en.cppreference.com/w/cpp/thread/thread/thread, thread’s default constructor creates a
2。）根据，线程的 operator = / p>
2.) According to http://en.cppreference.com/w/cpp/thread/thread/operator%3D, thread’s operator=
3。）根据
，将
只传递一个大小类型变量到一个向量构造函数将构造
3.) According to http://en.cppreference.com/w/cpp/container/vector/vector, passing only a size type variable to a vector constructor will construct
所以，我这样做：
#include <iostream>
#include <thread>
#include <vector>
void foo()
{
std::cout << "Hello\n";
return;
}
int main()
{
std::vector<std::thread> vecThread(1);
vecThread.at(0) = std::thread(foo);
vecThread.at(0).join();
return 0;
}
这在VC11和，如下所示：
This runs as expected in VC11 and g++ 4.8.0 (online compiler here) as seen in the following:
控制台输出：
Hello
然后我在clang 3.2中通过在同一个网页上切换编译器菜单进行了尝试：
stderr:
pure virtual method called
terminate called without an active exception
当代表线程的线程对象在 join（）之前超出范围 ed或 detach（） ed，程序将被强制终止。我有 join（） ed vecThread.at（0），所以唯一留下的问题是临时线程
When a thread object—that represents a thread—goes out of scope before being join()ed or detach()ed, the program will be forced to terminate. I have join()ed vecThread.at(0), so the only thing left in question is the temporary thread
std :: thread（foo）;
vecThread.at（0）= std :: thread（foo）;
分配。
但是，根据Web引用，线程只能通过移动线程右值引用来分配。我不能想到任何方式到 join（）或 detach（）一个临时线程对象。
However, according to the web reference, threads can only be assigned by moving a thread rvalue reference. I cannot think of any way to join() or detach() a temporary thread object.
所以如果clang的输出是正确的，那么线程的用法是 operator = ？
So if clang’s output is correct, then what is the use of thread’s operator=? Or is this a clang compiler bug?
在g ++ 4.8.0中，更改行
In g++ 4.8.0, changing the line
vecThread.at（0）= std :: thread（foo）
到
vecThread.at（0）= std :: thread {foo}
大括号）仍然给出预期的 Hello 输出。
(replacing parentheses with braces) still gives the expected Hello output.
但是，将行更改为 vecThread.at（0）= {foo} 让它抱怨：
However, changing the line to vecThread.at(0) = {foo} makes it complain:
g ++ 4.8.0对大括号的投诉
不知道它是什么意思。
在clang中进行同样的更改会更加高级：
Making the same change in clang gives the even more advanced:
clang 3.2对大括号的投诉：
clang 3.2's complaint on braces:
error: no viable overloaded '='
vecThread.at(0) = {foo};
...
note: candidate function not viable: cannot convert initializer list
argument to 'const std::thread'
thread& operator=(const thread&) = delete;
...
note: candidate function not viable: cannot convert initializer list
argument to 'std::thread'
thread& operator=(thread&& __t) noexcept
我不知道这是什么意思。
and I don’t know what that means either.
我无法使用VC11来证实上述
I cannot use VC11 to corroborate the above
vecThread.at（0） = {foo}
问题，因为VC11在2012年11月的CTP编译器不支持标准库上的统一初始化语法。 / p>
problems because VC11, as of the November 2012 CTP compiler, does not support uniform initialization syntax on the Standard Library.
推荐答案
您的第一个例子是正确的。抛出异常是一个已知的，当您使用clang与libstdc ++。要解决它，你必须安装libc ++（llvm版本的c ++库）。请参阅下面的使用libc ++编译的示例
Your first example is correct. Throwing an exception is a known bug, when you using clang with libstdc++. To solve it, you have to install libc++(llvm version of c++ library). See an example of compiling with libc++ below
#include <thread>
int main()
{
std::thread t([] () {});
t.join();
return 0;
}
$ clang ++ -std = c ++ 11 - stdlib = libc ++ main.cpp -o main -lc ++ -lsupc ++ -lpthread
PS请参见，为什么是 -lsupc ++ 。
P.S. See here, why is the flag -lsupc++ required too.
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