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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.