C ++：带有packaged_task的核心转储 [英] C++: Core dump with packaged_task
问题描述
我得到了一个奇怪的核心转储，我从 http： //en.cppreference.com/w/cpp/thread/packaged_task ，
#include< future>
#include< iostream>
#include< cmath>
void task_lambda（）{
std :: packaged_task< int（int，int）> task（[]（int a，int b）{
return std :: pow（a，b）;
}）;
std :: future< int> result = task.get_future（）;
任务（2，9）;
std :: cout<< task_lambda：\ t<< result.get（）<< \\\
;
}
int main（）{
task_lambda（）;
}
我得到了这个
在抛出'std :: system_error'实例后调用terminate
what（）：未知错误-1
[1] 28373 abort（core dumped）。 /a.out
调用堆栈如下所示：
＃0 0x00007ffff71a2428 in __GI_raise（sig = sig @ entry = 6）at ../sysdeps/unix/sysv/linux/raise.c:54
＃ 1中的0x00007ffff71a402a在abort.c中的__GI_abort（）中：89
＃2 0x00007ffff7ae484d在__gnu_cxx :: __ verbose_terminate_handler（）（）from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
＃ 3 0x00007ffff7ae26b6在？ （）from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
＃4 0x00007ffff7ae2701 in std :: terminate（）（）from /usr/lib/x86_64-linux-gnu/libstdc++.so .6
＃5 0x00007ffff7ae2919来自/usr/lib/x86_64-linux-gnu/libstdc++.so.6
＃6的__cxa_throw（）0x00007ffff7b0b7fe来自/ usr的std :: __ throw_system_error（int）（） /lib/x86_64-linux-gnu/libstdc++.so.6
＃7在std :: call_once中的0x0000000000404961< void（std :: __ future_base :: _State_baseV2 :: *）（std :: function< std :: unique_ptr< ; std :: __ future_base :: _ Result_base，std :: __ future_base :: _ Result_base :: _ Deleter>（）> *，bool *），std :: __ future_base :: _State_baseV2 *，std :: function< std :: unique_ptr< std :: __ future_base :: _ Result_base，std :: __ future_base :: _ Result_base :: _ Deleter> （std :: once_flag&; void（std :: _ future_base :: _ state_baseV2 :: *&& amp; ：_Result_base，std :: __ future_base :: _ Result_base :: _ Deleter>（）> *，bool *），std :: __ future_base :: _State_baseV2 *& amp;< std :: function< std :: unique_ptr< std :: __future_base :: _ Result_base，std :: __ future_base :: _ Result_base :: _ Deleter>（）&&& ;,; bool *&&）（__once = ...，__f =< home / / usr / include / c ++ / 5 / mutex：746
＃8 0x0000000000403eb2 in std :: __ future_base :: _ State_baseV2 :: _ M_set_result （std :: function< std :: unique_ptr< std :: _ future_base :: _ Result_base，std :: _ future_base :: _ Result_base :: _ Deleter>（）>，bool）（
this = 0x61ec30，__res = .. （），__ignore_failure = false）在/ usr / include / c ++ / 5 / future：387
＃9 0x0000000000402b76在std :: __ future_base :: _ Task_state< task_lambda（）::< lambda（int，int）> ，std :: allocator< int> ;, int（int，int）> :: _ M_run（< / home / ace / test / a.out中的未知类型，CU 0x0，DIE 0x17680> ;,< /home/ace/test/a.out中的未知类型，CU 0x0，DIE 0x17685>） （this = 0x61ec30，__args＃0 =< / home / ace / test / a.out中的未知类型，CU 0x0，DIE 0x17680> ;,
__args＃1 =< test / a.out，CU 0x0，DIE 0x17685>）在/ usr / include / c ++ / 5 / future：1403
＃10 0x00000000004051c1在std :: packaged_task< int（int，int）> :: operator在/ usr / include / c ++ / 5 / future：1547
＃11 0x0000000000401c7d在task_lambda（）上的（）（）（int，int）（this = 0x7fffffffdca0，__args＃0 = 2，__args＃1 = 9） .cc：12
＃12 0x0000000000401d1b in main（）at aa.cc:19
然后，我在程序中添加了一些示例代码，它变成了
#include< iostream>
#include< cmath>
#include< future>
#include< thread>
int f（int x，int y）{return std :: pow（x，y）; }
void task_thread（）{
std :: packaged_task< int（int，int）>任务（F）;
std :: future< int> result = task.get_future（）;
std :: thread task_td（std :: move（task），2，10）;
task_td.join（）;
std :: cout<< task_thread：\ t<< result.get（）<< \\\
;
}
void task_lambda（）{
std :: packaged_task< int（int，int）> task（[]（int a，int b）{
return std :: pow（a，b）;
}）;
std :: future< int> result = task.get_future（）;
任务（2，9）;
std :: cout<< task_lambda：\ t<< result.get（）<< \\\
;
}
int main（）{
task_lambda（）;
}
错误消失了。我可以通过添加一个函数来纠正程序，即使我从来没有调用它？
gcc版本
gcc版本5.4.0 20160609（Ubuntu 5.4.0-6ubuntu1〜16.04.4）
用命令编译的Promgram：
g ++ -std = c ++ 11 aa.cc -lpthread
在@ fedepad的帮助下，我通过用pthread替换lpthread得到了正确的输出结果。 但我仍然困惑第二个代码是如何通过添加一个虚拟函数来实现的！
我试过你的第一个代码片段使用以下版本的g ++：
g ++（Ubuntu 5.4.0-6ubuntu1〜16.04.4）5.4.0 20160609 p>
并用以下编译
g ++ -o test_threads test_threads.cpp -std = c ++ 11 -pthread
我可以运行程序没有问题，并获得以下输出：
$ ./test_threads
>
task_lambda：512
如果我接着使用 -lpthread
g ++ -o test_threads test_threads.cpp -std = c ++ 11 -lpthread
我得到
$ ./test_threads
终止后调用抛出一个实例o f'std :: system_error'
what（）：未知错误-1
[1] 7890 abort ./test_threads
所以请使用 -pthread 作为标志，而不要使用 -lpthread 。
这个行为在下面也提到 -
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59830
有 -pthread 和 -lpthread 之间的区别。
查看g ++的手册页
-pthread
使用pthreads添加对多线程的支持图书馆。此选项为预处理器和链接器设置标志。
看看两个人都激活了哪些标志可以检查以下内容：
g ++ -dumpspecs | grep pthread
g ++ -dumpspecs | grep lpthread
正如人们可以清楚地看到的那样，有一些预处理器宏在使用时未被激活 -lpthread 。
I got a strange core dump which I copied from a part of code in http://en.cppreference.com/w/cpp/thread/packaged_task,
#include <future>
#include <iostream>
#include <cmath>
void task_lambda() {
std::packaged_task<int(int,int)> task([](int a, int b) {
return std::pow(a, b);
});
std::future<int> result = task.get_future();
task(2, 9);
std::cout << "task_lambda:\t" << result.get() << '\n';
}
int main() {
task_lambda();
}
I got this
terminate called after throwing an instance of 'std::system_error'
what(): Unknown error -1
[1] 28373 abort (core dumped) ./a.out
The call stack is like below:
#0 0x00007ffff71a2428 in __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:54
#1 0x00007ffff71a402a in __GI_abort () at abort.c:89
#2 0x00007ffff7ae484d in __gnu_cxx::__verbose_terminate_handler() () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#3 0x00007ffff7ae26b6 in ?? () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#4 0x00007ffff7ae2701 in std::terminate() () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#5 0x00007ffff7ae2919 in __cxa_throw () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#6 0x00007ffff7b0b7fe in std::__throw_system_error(int) () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#7 0x0000000000404961 in std::call_once<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::once_flag&, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&) (__once=..., __f=<unknown type in /home/ace/test/a.out, CU 0x0, DIE 0x1246d>)
at /usr/include/c++/5/mutex:746
#8 0x0000000000403eb2 in std::__future_base::_State_baseV2::_M_set_result(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>, bool) (
this=0x61ec30, __res=..., __ignore_failure=false) at /usr/include/c++/5/future:387
#9 0x0000000000402b76 in std::__future_base::_Task_state<task_lambda()::<lambda(int, int)>, std::allocator<int>, int(int, int)>::_M_run(<unknown type in /home/ace/test/a.out, CU 0x0, DIE 0x17680>, <unknown type in /home/ace/test/a.out, CU 0x0, DIE 0x17685>) (this=0x61ec30, __args#0=<unknown type in /home/ace/test/a.out, CU 0x0, DIE 0x17680>,
__args#1=<unknown type in /home/ace/test/a.out, CU 0x0, DIE 0x17685>) at /usr/include/c++/5/future:1403
#10 0x00000000004051c1 in std::packaged_task<int (int, int)>::operator()(int, int) (this=0x7fffffffdca0, __args#0=2, __args#1=9) at /usr/include/c++/5/future:1547
#11 0x0000000000401c7d in task_lambda () at aa.cc:12
#12 0x0000000000401d1b in main () at aa.cc:19
Then I added some sample code into my program, it became
#include <iostream>
#include <cmath>
#include <future>
#include <thread>
int f(int x, int y) { return std::pow(x,y); }
void task_thread() {
std::packaged_task<int(int,int)> task(f);
std::future<int> result = task.get_future();
std::thread task_td(std::move(task), 2, 10);
task_td.join();
std::cout << "task_thread:\t" << result.get() << '\n';
}
void task_lambda() {
std::packaged_task<int(int,int)> task([](int a, int b) {
return std::pow(a, b);
});
std::future<int> result = task.get_future();
task(2, 9);
std::cout << "task_lambda:\t" << result.get() << '\n';
}
int main() {
task_lambda();
}
the error was gone. How can I correct the program by adding a function even though I never call it?
gcc version
gcc version 5.4.0 20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.4)
Promgram compiled with command:
g++ -std=c++11 aa.cc -lpthread
With @fedepad's help, I got correct output by replace lpthread with pthread. But I still confused how second code work by add a dummy function!
I tried your first code snippet using the following version of g++:
g++ (Ubuntu 5.4.0-6ubuntu1~16.04.4) 5.4.0 20160609
and compiled with the following
g++ -o test_threads test_threads.cpp -std=c++11 -pthread
and I can run the program with no problems, and getting the following output:
$ ./test_threads
task_lambda: 512
If I then use the -lpthread as you did with the following
g++ -o test_threads test_threads.cpp -std=c++11 -lpthread
I get
$ ./test_threads terminate called after throwing an instance of 'std::system_error'
what(): Unknown error -1
[1] 7890 abort ./test_threads
So please use -pthread as a flag and not -lpthread.
This behavior is also mentioned in the following
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59830
There's a difference between -pthread and -lpthread.
Looking at the man page for g++
-pthread
Adds support for multithreading with the pthreads library. This option sets flags for both the preprocessor and linker.
To have a look to what flags are activated for both one can check with the following:
g++ -dumpspecs | grep pthread
g++ -dumpspecs | grep lpthread
As one can clearly see, there are some preprocessor macros that are not activated if one is using -lpthread.
这篇关于C ++：带有packaged_task的核心转储的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
