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I am trying to do a project for school in which I have to write a multithreaded program using pthreads. I can't seem to get the basics down on this, though. Here's my problem - basically my program looks like this:
Code:
#include<pthread.h>
int main(void)
{
pthread_mutex_t *test;
pthread_mutex_init(test, NULL);
}
Now, when I compile this using the following command line it runs just fine...
g++ -o test test.cpp
However, if I use this command line to compile, I get a segmentation fault when I run the resulting binary...
g++ -lpthread -o test test.cpp
I have to use the -lpthread option, however, since the project has to be multithreaded. So, what is the deal? This is an extremely simple program and it doesn't run. Is there an option that I need to be adding that I'm not aware of?
Also, I'm not sure if this is helpful or not, but here it is... if I run the same program with an actual instantiation of the pthread_mutex_t object and pass by reference instead of using a pointer, I get no segmentation faults either way. I need to create these mutexes dynamically, though, so I can't do it this way. Thanks in advance for any help.
That's odd ... have you got more than one version
of libpthread installed?
The thing is that the first version must implicitly
find the library, otherwise you'd be getting linker
errors...
Another thing. My understanding is that pthread
is a C-library (not sure whether gcc comes with
c++ wrappers for it, never used it), but you're compiling
that snippet with g++
I have another problem involving pthreads now... I have to be able to create the threads dynamically because the number of client threads varies. Here is a snippet of code that works...
uhh, u need to initialize those pointers with dynamically allocated memory, they point to nothing. or u need to use a plain pthread_t and pass it by reference.
int main(void)
{
pthread_mutex_t *test; <-- BAD!!! You didn't point the pointer to anything, use static object instead (i.e. pthread_mutex_t test
pthread_mutex_init(test, NULL); <-- "&test" for static object, not "test"
}
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