CODEWITHSUNDEEP
objective-ccfunctioninlinemessage-passing
ma11hew28
ma11hew28

Reputation: 126327

Will C functions with Objective-C be inlined?

  1. Will the typical compiler inline a C function that makes one or more Objective-C method calls? E.g.:

    NSUInteger AACStringGetLength(NSString *string)
{
    return [string length];
}

  2. Bonus points for a thorough proof with explanation.

  3. What other things besides recursion might prevent the compiler from inlining a C function?

Upvotes: 0

Views: 86

Answers (1)

Greg Parker
Greg Parker

Reputation: 8012

AACStringGetLength() can be inlined into its callers assuming the other requirements of inlining are satisfied. There's nothing about calls to Objective-C methods that prevents inlining of C functions.

Of course Objective-C methods cannot be inlined themselves, because the compiler cannot know that there is no unusual dynamic dispatch going on.

Things that can prevent inlining include:

  • the caller and callee are in different translation units (i.e. different source code files), unless you are using link-time optimization of some sort
  • the caller's code might end up "too big" after inlining according to the compiler's inlining heuristics
  • the callee performs control flow that is too complicated for the compiler's inlining machinery to handle so it gives up

Upvotes: 2

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