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Re: static functions are your friends (Was GPIO revisited)

On Mon, Aug 10, 2009 at 11:40:16AM +0200, Marc Balmer wrote:
> >[...]
> >That's why we have macros like __predict_true() instead of directly
> >using the relevant GCC features.  They can become NOPs with a compiler
> >that doesn't provide the feature.  One here which gives "static  
> >__noinline"
> >with GCC and "" with pcc would be shorter then typing out the whole
> >GCC syntax and certainly look cleaner!
> Hmm, do we have example code somewehre in the tree?

Yes, in sys/sys/cdefs.h. Look at __predict_true/__predict_false
for example, or __RENAME

> >As to inline or not with debug or diagnostic -- my personal taste is  
> >that
> >if you really want to never have inlining in driver code that you
> >personally maintain, fine.  But I think that in most parts of the  
> >kernel
> >tree, we should not disable optimization unless DEBUG or DIAGNOSTIC.
> >
> >As I think others have (obliquely) pointed out, addr2line or gdb can
> >get you better traceback information than ddb, given a core dump or
> >just the raw addresses from ddb's traceback.  In the face of  
> >aggressive
> >inlining by the compiler, there's really nothing that can get it  
> >entirely
> >right -- but with a full symbol table, gdb/addr2line can do a _little_
> >better than ddb can.
> Thanks for the feedback.  Actually I just saw that /usr/include/sys/ 
> cdefs has the following in it:
> #ifndef __GNUC__
> #define __const                         /* delete pseudo-ANSI C  
> keywords */
> #define __inline
> #define __signed
> #define __volatile
> #endif  /* !__GNUC__ */
> So I assume that as long as I include this file, the use of __inline  
> should be save, right?

__inline is safe; but I'm not sure if we prefer to use __inline or inline
these days. It seems new code uses inline and not __inline.

For your purpose I think you want a __noinline and noinline, which would
need to be added.

Manuel Bouyer <>
     NetBSD: 26 ans d'experience feront toujours la difference

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