Re: Speedup in the working state

[Ralf Wildenhues]

* Full Decent wrote on Tue, Oct 04, 2005 at 05:14:21AM CEST:
> I spend a good part of my life watching lines like this fly by:
> 
> checking for stdlib.h... yes
*snip*
> I would like to propose a possible optimization to make the most
> common "everything's OK" case move a lot faster. The most basic way is
> by grouping as many possible simple checks into one program and
> compiling and running that program. Then compare this program's output
> to the expected output and if that fails, resort to the existing
> method.

Valid optimization.  Might result in a larger configure script even,
though.  (And requires changes to Autoconf .. not that this would be
a strong argument against it ;)

> Since autoconf is more complicated, checking whether certain things
> exist while producing non-fatal results if they aren't, there's
> another possibility. Cache all the autoconf findings on the first run.
> Each time autoconf is run, confirm that settings haven't changed, by
> compiling a simple program and running and comparing output.

Yes, and somebody else has thought of something very similar before.  :)
Check out the documentation chapters
  info Autoconf "Caching Results"
  info Autoconf "Site Defaults"

and then you may start putting
  ac_cv_header_stdlib_h=yes
  ...

into an appropriate config.site file, or running `configure -C' by
default.

Cheers,
Ralf