[RFC] Make getenv O(1)

[Alexander Monakov]

On Mon, 21 Oct 2013, Ondřej Bílka wrote:

> On Mon, Oct 21, 2013 at 08:55:37PM +0400, Alexander Monakov wrote:
> > On Mon, 21 Oct 2013, Ondřej Bílka wrote:
> > > Why, following does not need synchronization.
> > > 
> > > #define GETENV(x) ({ \
> > >   static char *__ret = NULL; \
> > >   if (__builtin_constant_p (x) && !__cached) \
> > >     __ret = getenv (x) + 1; \
> > >   __builtin_constant_p (x) ? __ret - 1: getenv (x);})
> > 
> > This wouldn't compile as __cached is not defined (and I'll admit I don't see
> > what approach you're trying to convey).
> > 
> s/__cached/__ret/ 

Ah, my bad.  While this would be ok in practice, I think incrementing a
pointer containing a NULL value invokes undefined behavior, doesn't it?

Alexander