在带有std = c99的gcc中强制内联函数

Question

I am writing a pure c code (for fast performance) and I am hoping that gcc can at least expand all the functions that I declared as "static inline" (because I am using std=c99, the semantics of inline has changed and static inline is what preferred), some of those functions include matrix manipulation, heap up/down sift, etc. usually fairly small operations that occurs many time. Is there a way to achieve this by specifying any options of GCC? I have already enabled -o3, and somewhere I came across saying that by -o3 and "static inline" function declaring, all function calls will be expanded. Is that true? How can I verify that? Thanks!

Answer 1

You might try __attribute__((always_inline)) , but in general, normal inline should be enough, unless you go for -Os . If a function is not inlined, gcc might have good reasons not to.

A better way would be to use profiling and link time optimization (LTO). In general, hand-optimizing code should be the last ressort.

Of course you can verify if a function has been inlined: just look at the generated code.