Re: can someone explain "inline" once and for all?

[Robert P. J. Day]

On Fri, 19 Jan 2007, Adrian Bunk wrote:

> With the current implementation in the kernel (and considering that
> CONFIG_FORCED_INLINING was implemented in a way that it never had
> any effect), __always_inline and inline are currently equivalent.

yes, that option was implemented in a half-assed sort of way.  if you
look at compiler-gcc4.h, at first glance the preprocessing looks like
it's doing the right thing for that config option:

==================================
#include <linux/compiler-gcc.h>

#ifdef CONFIG_FORCED_INLINING
# undef inline
# undef __inline__
# undef __inline
# define inline                 inline          __attribute__((always_inline))
# define __inline__             __inline__      __attribute__((always_inline))
# define __inline               __inline        __attribute__((always_inline))
#endif
==================================

  but it's too late for checking that kernel config option, since
compiler-gcc.h has already been included, which includes:

==================================
#define inline          inline          __attribute__((always_inline))
#define __inline__      __inline__      __attribute__((always_inline))
#define __inline        __inline        __attribute__((always_inline))
==================================

so, as you say, "__always_inline and inline are currently equivalent".
which is sort of confusing and might come as a nasty surprise to some
developers who weren't expecting that.

rday

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