How to turn on optimization in C source code?

Question

Is it possible to write C code so that when it is compiled with

gcc -o foo foo.c

it in fact compiles foo.c with -O2?

I am using gcc 4.4.6.

Answer 1

最近的gcc知道#pragma GCC optimize pragma（ http://gcc.gnu.org/onlinedocs/gcc/Function-Specific-Option-Pragmas.html ）