printf() checking for custom functions

[Randall Hopper <viznut@xxxxxxxxxxx>]

-Wformat causes printf() args to be checked based on the format:

   int printf(const char *format, ...);

How do ask gcc to apply this same checking to user-defined functions?

   int myDebug(const char *format, ...);

Apps often implement their own version of printf() for debugs, warnings,
etc. with output switchable between console, log files, both, etc.  It
would be very useful to have gcc perform similar sanity checks for their
arg lists.

Thanks,

Randall