Re: [Boost-users] mutexes : Is this thread-safe ?

From: Emre Birol (ebirol_at_[hidden])
Date: 2006-02-17 12:38:36

Dhanvi Kapila wrote:
> Hi :
>  I have this piece of code for mutex operations.  is this code 
> thread-safe ? I plan to use this code in threads...
> ------------------------------------
> class BoostMutexLock
> {
>    public :
>         void lock() {
>                lk = new boost::mutex::scoped_lock(global_mutex);
>        }
>         void unlock() {
>               delete lk;
>         }
>   BoostMutexLock() : lk( 0 ) { }
>   ~BoostMutexLock() { }
> 
> private:
>       boost::mutex global_mutex;
>       boost::mutex::scoped_lock* lk;
> };
> ------------------------------------------------------
> I appreciate all the help.. How do I know to check for thread-safety in 
> a code ? Are there any documents?  I have checked online and have some 
> links, but havent found documents which provide examples and explain.. 
> such a document would be really useful.
> 
> Thanks...
> Dhanvi

This code is against to RAII (Resource Allocation Is Initialization) 
idiom.

Would be better if you use it that way:

try {
        boost::mutex::scoped_lock(global_mutex);
        ...
        <your code here>
}
catch {
        
}

if you don't need to use try-catch then just add a scope:

{
        boost::mutex::scoped_lock(global_mutex);
        ...
        <your code here>

}

It's guarantied that mutex will be released when execution leaves the scope.