The cdecl calling convention: 1. arguments are passed on the stack, right to left. 2. int values and pointer values are returned in %eax. 3. floats are returned in %st(0). 4. when calling a function, %st(0) ~ %st(7) are all free. 5. functions are free to use %eax, %ecx, %edx, because caller needs to save them. 6. stack must be aligned to 4 bytes (before gcc 4.5, for gcc 4.5+, aligned to 16 bytes).
