On Mon, 18 Sep 2000, Chris Wedgwood wrote:
> On Sun, Sep 17, 2000 at 10:37:51AM -0700, Linus Torvalds wrote:
>
> - "extern inline" -> "static inline". It doesn't matter right now,
> but it's proactive for future gcc versions.
>
> can someone please explain the difference?
Let's assume that gcc decides that it won't inline a function, because
it's too "big", according to some gcc definition of "big".
With "extern inline", the function will not exist AT ALL, and you'll end
up getting a link-time error complaining about the lack of that function.
With "static inline", gcc will emit the function as a separate function
for that compilation block if it didn't get inlined.
Both are valid things. You use "extern inline" when you have a "backing
store" for the funcion (ie you do have the non-inlined version in a
library somewhere). You use "static inline" when you don't.
For the kernel, we very seldom have the non-inlined versions in any
library, so for the kernel "extern inline" is almost always the wrong
thing.
Note that with most versions of gcc this is all a complete non-issue, as
most versions of gcc will _always_ inline a function that the user has
asked to be inlined. So the issue seldom actually comes up.
Linus
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