C programming tricks

While programming optimization that makes ones' code completely unreadable is often a bad thing, there are places for it, like that one inner loop of your code that takes up 98% of the program's running time.

What are you tricks for improving performance in C, other than the obvious inline assembly or the like?

>>170
What, you save about 3 bytes in memory? Big deal. Unless you're programming an embedded system in which every byte is precious, you'd better stick with the more widely-used and more readable "malloc(sizeof(struct s))".