Af001 wrote:
Why can't I catch this exception in boost::thread?
#include
#include <iostream>
#include <exception>
void helloworld()
{
std::cout << "Hello World!" << std::endl;
throw(std::string("err"));
}
int main()
{
try
{
boost::thread thrd(&helloworld);
thrd.join();
}
catch(...)
{
std::cout<<"err";
}
}
This is a limitation of exceptions in a multi-threaded environment.
Exceptions must be caught in the same thread from which they are thrown.
In your program, you created a new thread for helloworld(). Therefore,
any exceptions thrown by helloworld will cause a runtime error, unless
helloworld itself catches them. You should be able to work around this
my storing the exception in a global variable or something. Perhaps:
#include
#include <iostream>
#include <exception>
volatile bool threaderror = false;
std::string error;
void helloworld()
{
try
{
std::cout << "Hello World!" << std::endl;
throw(std::string("err"));
}
catch (std::string &err)
{
threaderror = true;
error = err;
}
}
int main()
{
try
{
boost::thread thrd(&helloworld);
thrd.join();
if (threaderror)
{
throw error;
}
}
catch(...)
{
std::cout<<"err";
}
}
Notice how, in this version, helloworld() catches the exception itself
and stores it in a global variable. Main() then checks the variable and
throws a copy of the original exception.
Does anyone have any ideas for a cleaner version of this? It looks like
boost.thread allows a functor for the initial function, so maybe you
could convert helloworld() to a functor and declare those global
variables I added as member variables, along with a member function to
rethrow any exceptions caught.
Perhaps someone could create a generic version of this? It could maybe
take a MPL list of exception types that it should marshall across
threads. Is there a way to catch *any* exception in the thread and
store it for a later rethrow?
