std :: async在clang 3.0 + libc ++不工作？ [英] std::async in clang 3.0 + libc++ doesn't work?

问题描述

我刚刚在我的ubuntu 10.04上编译和安装了clang + llvm 3.0，还从svn编译并安装了libc ++。由于libc ++中的状态显示线程支持已完成，我想尝试std :: async。于是我按照

由安东尼·威廉姆斯给出的例子

的 http://www.justsoftwaresolutions.co.uk/threading/multithreading-in-c++0x-part-8-futures-and-promises.html

只需进行细微的修改即可编译：

  #include< future> 
 #include< iostream> 
 
 int calculate_the_answer_to_LtUaE（）
 {
 return 42; 
} 
 
 void do_stuff（）
 {
 std :: cout< 做东西< std :: endl; 
} 
 
 int main（）
 {
 std :: future< int> the_answer = std :: async（calculate_the_answer_to_LtUaE）; 
 do_stuff（）; 
 std :: cout<<生活，宇宙和一切的答案是
<< the_answer.get（）<< std :: endl; 
} 
  

我用

编译

clang ++ --std = c ++ 0x -stdlib = libc ++ -lpthread async.cpp

但是，它运行并总是用核心转储完成： p>

做东西
生命，宇宙和一切的答案是Aborted（core dumped）

检查核心转储，它显示堆栈这样（我不会得到一个提示）

 
＃0 0x00007fd0a1a7ba75在raise从/lib/libc.so.6 
＃2时在0x00007fd0a22a735b的std :: exception_ptr ::〜exception_ptr（此=）/lib/libc.so.6 
＃1 0x00007fd0a1a7f5c0在中止（） ../src/exception.cpp:130 
＃3 0x0000000000404178在无效的std :: __ 1 :: __ assoc_state :: SET_VALUE（INT &&）（）
＃4 0x00000000004051ae在_ZNSt3__119__async_assoc_stateIiNS_12__async_funcIPFivEJEEEE9__executeEv（）
＃ 5 0x0000000000404e00从/lib/libc.so.6 
从/lib/libpthread.so.0 
＃_ZNSt3__114__thread_proxyINS_5tupleIJMNS_19__async_assoc_stateIiNS_12__async_funcIPFivEJEEEEEFvvEPS7_EEEEEPvSC_（）
＃6 0x00007fd0a250f9ca在start_thread（）7 0x00007fd0a1b2e70d在克隆（） ＃8 0x0000000000000000 in ?? （）
 
 
 
 
任何人都知道为什么？
解决方案
 
我在OS X Lion上运行你的例子，使用：
  clang ++ -std = c ++ 0x -stdlib = libc ++ async.cpp 
  
程序输出：
 
 $ b b 
 做东西
生命，宇宙和一切的答案是42 
  
根据moshbear的建议检查libc ++的源代码我看到：
  exception_ptr ::〜 exception_ptr（）_NOEXCEPT 
 {
 #if HAVE_DEPENDENT_EH_ABI 
 __cxa_decrement_exception_refcount（__ ptr_）; 
 #else 
 #warning exception_ptr尚未实现
 :: abort（）; 
 #endif // __APPLE__ 
} 
  
 c $ c>〜exception_ptr（）尚未移植到ubuntu 10.04。这是在便携式C ++中不能实现的低级设施。正在 libc ++ abi 上继续开发此级别的无GPL实现。我可以向你保证的libc ++ ABI还没有准备好，此时黄金时间
 
 
 
有也一直在这样低级别的库一个独立的努力，时间：< a href =https://github.com/pathscale/libcxxrt =nofollow> https://github.com/pathscale/libcxxrt 。我不知道这个库的状态，也不知道它是否已被移植到ubuntu。
 
I just compiled and installed clang+llvm 3.0 on my ubuntu 10.04, and also libc++ from svn. As the status in libc++ shows thread support is complete, I wanted to try std::async. So I follow the example given by Anthony Williams in 

http://www.justsoftwaresolutions.co.uk/threading/multithreading-in-c++0x-part-8-futures-and-promises.html

And just make minor change to make it compile:
#include <future>
#include <iostream>

int calculate_the_answer_to_LtUaE()
{
  return 42;
}

void do_stuff()
{
  std::cout << "doing stuff" << std::endl;
}

int main()
{
  std::future<int> the_answer=std::async(calculate_the_answer_to_LtUaE);
  do_stuff();
  std::cout<<"The answer to life, the universe and everything is "
    <<the_answer.get()<<std::endl;
}
And I compile with 

clang++ --std=c++0x -stdlib=libc++ -lpthread async.cpp

However, it runs and always finish with a core dump:

doing stuff 
The answer to life, the universe and everything is Aborted (core dumped)

I check the core dump and it shows stack like this (which I don't quite get a hint)
#0  0x00007fd0a1a7ba75 in raise () from /lib/libc.so.6
#1  0x00007fd0a1a7f5c0 in abort () from /lib/libc.so.6
#2  0x00007fd0a22a735b in std::exception_ptr::~exception_ptr (this=) at ../src/exception.cpp:130
#3  0x0000000000404178 in void std::__1::__assoc_state::set_value(int&&) ()
#4  0x00000000004051ae in _ZNSt3__119__async_assoc_stateIiNS_12__async_funcIPFivEJEEEE9__executeEv ()
#5  0x0000000000404e00 in _ZNSt3__114__thread_proxyINS_5tupleIJMNS_19__async_assoc_stateIiNS_12__async_funcIPFivEJEEEEEFvvEPS7_EEEEEPvSC_ ()
#6  0x00007fd0a250f9ca in start_thread () from /lib/libpthread.so.0
#7  0x00007fd0a1b2e70d in clone () from /lib/libc.so.6
#8  0x0000000000000000 in ?? ()
Anybody has an idea why?
解决方案
I ran your example on OS X Lion, using:
clang++ -std=c++0x -stdlib=libc++ async.cpp
And the program output:
doing stuff
The answer to life, the universe and everything is 42
Inspecting the source of libc++ as suggested by moshbear's comment I see:
exception_ptr::~exception_ptr() _NOEXCEPT
{
#if HAVE_DEPENDENT_EH_ABI
    __cxa_decrement_exception_refcount(__ptr_);
#else
    #warning exception_ptr not yet implemented
    ::abort();
#endif  // __APPLE__
}
It appears to me that ~exception_ptr() has not been ported to ubuntu 10.04.  This is a low-level facility not implementable in portable C++.  Work on creating a GPL-free implementation of this level is ongoing at libc++abi.  I can assure you that libc++abi is not ready for prime time at this time.

There has also been an independent effort at this low-level library at:  https://github.com/pathscale/libcxxrt .  I do not know the status of this library nor whether it has been ported to ubuntu.

                        
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