Re: Extracting configuration info from config.status

[Paolo Bonzini]

Brian Dessent wrote:
> Barry Leslie wrote:
> 
>> It would be really useful if there was a configure option that would allow
>> you to point to another location and tell configure to get it's settings
>> from there.
> 
> If you just want to get the content of variables from a foreign build
> dir you can run it's config.status with --file=FILE[:TEMPLATE] or
> --header=FILE[:TEMPLATE] and it will instantiate FILE from TEMPLATE
> performing the normal AC_SUBST style substitutions, even if TEMPLATE is
> something you created and is not part of the foreign tree.

Indeed, I think this is what Barry is looking for.  Something like

AC_CONFIG_COMMANDS([mysql-config.h],
[cat > mysql-config.h.in <<_EOF
/* Totally made up, but you should indeed have #undef
   lines like these.  */
#undef DEBUG_LAYOUT
#undef FOOBAR
#undef USE_64BIT_OFFSETS
_EOF
$with_mysql/config.status --header=mysql-config.h:mysql-config.h.in
rm -f mysql-config.h.in],
[with_mysql="$with_mysql])

> But the quoted text seems to imply you want to do even more than that,
> to actually have access those variables during the execution of the
> configure script.  In that case you'd probably want to try sharing a
> config cache between them.

He can just create the file in the configure script (instead of using
AC_CONFIG_COMMANDS) and add one of these two:

  echo '#include "./mysql-config.h"' >> confdefs.h

  cat mysql-config.h >> confdefs.h

after the invocation of $with_mysql/config.status

Paolo