Execution direction of && Condition [duplicate]

Question

Possible Duplicate:
Logical comparisons: Is left-to-right evaluation guaranteed?

I have been taught that for every C function arguments, Rightmost argument will be executed/processed first and it progresses towards left. Right part will be executed first and it progresses towards left.

Is this applicable to conditions like && and || ??

If I am writing a C++ Code, I check for NULL condtion first and then in next if I perform my action. for e.g.

 if( CommDevice != NULL)
   {
      if(CommDevice->isOpen == TRUE)
         { 
                //Do Something
         }

   }

Can I convert this in if((CommDevice != NULL) && (CommDevice->isOpen == TRUE) )

That "Code executes from Right to Left" fear is stopping me coz what if CommDevice is NULL and I am trying to access a member of NULL. It will generate exception.

Answer 1

I have been taught that every C function takes argument from right to left. Right part will be executed first and it progresses towards left.

This is 100% not true. The order of argument evaluation is unspecified!

The order of && and || is defined because it forms a sequence point. First the left is evaluated, and if not short-circuiting then the right is evaluated.

if((CommDevice != NULL) && (CommDevice->isOpen == TRUE) )

This is correct.