I recently realised that there are very few views of computing and “the right way to do things” which I hold now as unchanged from when I started at University in 1994.
One of them is “Ten years is enough time to pass after a C language standard before you can rely on it. If your system doesn't support the current C standard after ten years, then your system is unsupported by the vendor and other people should be hesitant to support it.”
Back then, ten years was the amount of time that had passed since ANSI C was standardised and so this is why I never bothered with K&R compatibility in my C.
We're now at about twelve years since ANSI ratified C99.
I think that any new code (not for existing projects) I write in C will henceforth use the standards-mandated c99 compiler by default in the Makefile and make free use of new features.
Variable declarations where first used, designated initialisers, stdbool.h, variadic macros …