Question

I’m having an annoying problem with my iPhone app. Whenever I set the optimization level to something other than ‘None’, I get computation errors. This only happens in when building for the iPhone SDK (the iPhone Simulator is always fine).

I wouldn’t mind disabling optimizations in release mode, but the application is a tiny bit too slow when I do that.

The application is complex, so it is hard to locate the part that is too aggressively optimized.

I think that the problem is on the GCC side since it seems to have problem optimizing the code for the ARM architecture.

Is there a way to only disable optimizations only for certain part of the code? How would you deal with that kind of issue?

Answer 1

Yes, that’s entirely possible. GCC has an attribute for that:

/* disable optimization for this function */ void my_function(void) __attribute__((optimize(0)));  void my_function(void) {     /* ... */ } 

Sets the optimization level for that function to -O0. You can enable/disable specific optimizations:

/* disable optimization for this function */ void my_function(void) __attribute__((optimize('no-inline-functions')));  void my_function(void) {     /* ... */ }