I am using the C++ 11 std::thread library. Is it valid to join a thread in a destructor while an exception is thrown? The code I have is:
#include <thread>
#include <stdio.h>
#include <exception>
#include <unistd.h>
class the_thread {
private:
std::thread t;
bool abort;
public:
the_thread();
~the_thread();
void run();
};
the_thread::the_thread()
{
abort = false;
t = std::thread(&the_thread::run, this);
#if 0
printf("before detach ...\n");
t.detach();
printf("after detach ...\n");
#endif
}
the_thread::~the_thread()
{
abort = true;
printf("destruct thread container\n");
if (t.joinable()) {
printf("into join\n");
t.join();
printf("out of join\n");
}
}
void the_thread::run()
{
int i;
i=0;
while (!abort) {
printf("hallo %d\n", i);
i++;
std::this_thread::sleep_for(std::chrono::milliseconds(3000));
}
}
int run_thread_and_throw_exception(void)
{
the_thread t;
sleep(5);
throw std::runtime_error("some expected exception");
}
int main(int argc, char ** argv)
{
try {
run_thread_and_throw_exception();
} catch (const std::runtime_error &e) {
printf("exception %s caught\n", e.what());
}
return 0;
}
When compiling and running with
gcc --version
gcc (Ubuntu 5.4.0-6ubuntu1~16.04.10) 5.4.0 20160609
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
on my Ubuntu 16.04 development machine, this code behaves as expected:
bash$ ./thread_test
hallo 0
hallo 1
destruct thread container
into join
out of join
exception some expected exception caught
bash$
However when compiling with
arm-linux-gnueabi-g++ -Wall -g -O2 -std=c++11 -c -o main.o main.cpp
arm-linux-gnueabi-g++ -Wall -g -O2 -std=c++11 main.o -o thread_test -lpthread -static
(we need the -static because there is no C++ 11 library on the target) and running it on the target, strange things happen:
bash-on-target# ./thread_test
hallo 0
hallo 1
destruct thread container
into join
terminate called after throwing an instance of 'std::system_error'
what(): Unknown error 1082172112
Aborted
So it seems that the join in the destructor fails for some reason. Furthermore when trying to detach the thread, the detach fails rightaway:
bash-on-target# ./thread_test
before detach ...
terminate called without an active exception
hallo 0
hallo 0
Aborted
So to repeat my question: is joining threads (and possibly sleeping) while an exception is thrown valid in C++11? Is it possible that there is a bug in the C++ 11 library for ARM that comes with Ubuntu 16.04?
The ARM toolchain is:
bash$ arm-linux-gnueabi-g++ --version
arm-linux-gnueabi-g++ (Ubuntu/Linaro 5.4.0-6ubuntu1~16.04.9) 5.4.0 20160609
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
Thanks and best wishes, Johannes
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