Why is there no gcc/g++ warning for unused temporaries?

Question

Consider the following code :

void ListenerImpl::attach(boost::shared_ptr subscriber)
{
    boost::unique_lock(mtx);
          


        

Answer 1

hmm.. I am not sure but can't this be protected against with normal c++ also?

class Mutex;
class Lock {
    Lock(Mutex *mutex);
};

int main() {
    Lock /* lock */ (&mtx);
    return 0;
}

I get this compiler warning when compiling with DJGPP:

C:\df>gxx -c a.cpp
a.cpp: In function 'int main()':
a.cpp:8:30: error: 'mtx' declared as reference but not initialized

It compiles fine if I uncomment "lock" and add a mutex variable.

So if your "mtx" variable is a pointer. What happens if you change it and pass it as "&mtx" instead.