• State Not Answered
  • Locked Locked
  • Replies 3 replies
  • Subscribers 21 subscribers
  • Views 1452 views
  • Users 0 members are here
2025 survey

We are running a survey to help us improve the experience for all of our members. If you see the survey appear, please take the time to tell us about your experience if you can.

Options
Related
How was your experience today?
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Add DISABLEWARNING support to C51?

Bob Shaver

The new BL51 option to disable specific warning messages is very nice! I would also like to have this capability in the C51 compiler (finer-grained control than WARNINGLEVEL). Specifically, there are times when I want to disable warning C280 (unreferenced local variable) when I know that I will not reference a parameter to the subroutine, and then re-enable that warning for subsequent functions in that module. For example:

#pragma DISABLEWARNING(280)
void funct1( char p1, char p2 )
{
// this function does not need p1
do something with p2, ignore p1
}
#pragma ENABLEWARNING(280)
void funct2( char p1, char p2 )
{
//this function SHOULD use both params
// so I want the warning if I mess up
}

  • 0

    I second that!

    Or maybe something like

    #pragma unused p1
    This is a particularly common problem when writing state machines using function pointers, as all the functions must have the same set of parameters - whether they need them or not.
    I have yet to come across a compiler which handles this well. :-(

    Keil makes the problem worse as it gives the same message, "unreferenced local variable," for both parameters and real local variables! :-(

    You could try something like:
    void funct1( char p1, char p2 )
{
   p1 = p1; // dummy - does nothing, stops warning.
   do something with p2...
}
    I think C51 is smart enough to avoid generating any code for the p1=p1, but it might depend on the optimisation level? (note that some compilers will give a warning such as "code with possibly no effect" in this case).

    BTW: Note the use of &ltpre&gt and &lt/pre&gt tags for code extracts - see the Tips for Posting Messages in the sidebar to the left.

  • 0 in reply to Andrew Neil

    When you don't use a parameter, I confirm that instruction "p1=p1;" don't gererate any code if parameter p1 is a register. But if a parameter p1 is in memory, you must use instruction "if(p1);" for do not generate any code and suppress warning.

  • 0 in reply to Andrew Neil

    When you don't use a parameter, I confirm that instruction "p1=p1;" don't gererate any code if parameter p1 is a register. But if a parameter p1 is in memory, you must use instruction "if(p1);" for do not generate any code and suppress warning.