GCC errors using Pthreads

spaaarky21 · 07-16-2006, 04:55 PM

Hi everyone. I am writing a simple wrapper class for POSIX threads and mutexes but in my mutex class, I get an error saying

Code:

error: expected primary-expression before '{' token
error: expected ';' before '{' token

when trying to initialize the pthread_mutex_t in the mutex class's constructor.

Code:

Mutex::Mutex(void)
{
	mutex = PTHREAD_MUTEX_INITIALIZER;
}

However, that assignment does not cause any trouble when made outside of the Mutex() declaration, like in main() for example. I looked up the declaration of PTHREAD_MUTEX_INITIALIZER and it is #defined as

Code:

{_PTHREAD_MUTEX_SIG_init, {0}}

Could those brackets be causing the trouble when used inside of method declarations? If so, how can it be fixed? Any help would be appreciated.

-Brandon R

tuxdev · 07-16-2006, 08:09 PM

First, doing (void) as a parameter list is bad C++ form. Use just () instead.
Second, always use initializer lists, and this could be the source of the problem.
Third, IMO tabs are evil, since the default is 8 spaces and you can't nest effectively.
If my first suggestion doesn't work, try initializing it with the declaration.

Code:

Mutex::Mutex()
 : mutex(PTHREAD_MUTEX_INITIALIZER)
{
}

spaaarky21 · 07-16-2006, 09:36 PM

I would initialize the pthread_mutex_t as part of the declaration but, since it is a data member of the Mutex class I am writing, it can't be initialized as part of the declaration. I tried initializing the pthread_mutex_t in the initializer list but still get one of the two errors:

Code:

error: expected primary-expression before '{' token

One is better than two but it still needs some work. I still think it has to do with the fact that PTHREAD_MUTEX_INITIALIZER is a preprocessor definition. When processed,

Code:

Mutex::Mutex()
 : mutex(PTHREAD_MUTEX_INITIALIZER)
{
}

would work out to be

Code:

Mutex::Mutex()
 : mutex({_PTHREAD_MUTEX_SIG_init, {0}})
{
}

I'm not familiar with expressions like that. Should that compile? If so, is there any reason why it wouldn't?

As a more immediate solution, I've decided to use pthread_mutexattr_init() instead but I would still be interested in hearing an explanation of PTHREAD_MUTEX_INITIALIZER - how it works and why it doesn't here.