Question

I have third party library which calls an macro for logging. Inside that macro they are using fprintf for logging.
I am thinking about modifying the code to define a custom callback for logging, but I am not sure what will be best way.

Solution I want is:

• User can define a callback for logging.
• If callback is not define use fprint.

So I am looking for some type of static function with default definition which I can override if I want.

What will be the best way of doing this ?
As we can’t overload static function so everyone needs to define their definition of the logging function.

Answer 1

Something like this:

typedef void (*logfuncp)(...);

logfuncp callbackfuncp = NULL;

void logfunction(...)
{
   if (callbackfuncp) 
       callbackfuncp(...);
   else
       fprintf(logfile, ...);
}


void setcustomlogfunction(logfuncp newcallback)
{
    callbackfuncp = newcallback;
}

should work. The ... represent your logging arguments, which of course could be var-args using that real ... C syntax, but doesn’t have to be. All depends on what your logging is.