[PATCH] upgrade for Basic auth helpers config.test scripts

On 29/04/2013 1:07 p.m., Amos Jeffries wrote:
> One of the outstanding issues in ./configure has been the dependence
> on standalone bash scripts for detecting whether a helper is able to
> build or not.
> The problem is that they are standalone so we cannot re-use test
> results already existing in configure.ac in the scripts and vice-versa.
> We also encounter some errors (as seen in the bugs about SASL
> location) as a side effect of different tests being run.
>
> To resolve this I propose changing the config.test files into small M4
> scriptlets which can be included directly into configure at bootstrap
> time.
>
> Pros:
> * we gain a huge amount of information from existing configure.ac tests
> * we gain ability to run autoconf checks in the test scriptlets
> * we can push test results back to the main configure.ac cache from
> the scriptlets for faster overall process

The attached patch implements the above. I managed to avoid the expected
problem.

The nature of m4 macros however has added two smaller ones in its place.
Both well-known issues with m4_include() expansion:
  * the macro is expanded in-place without scoping separation.
  So any brokenness in the child scripts will be a little harder to
identify and may result in breakage of modues other than the one whose
child script was the cause.

  * the macro takes literal arguments without variable expansion.
  So a "full" path relative to the main configure.ac script is required
in every include. Meaning the modules.m4 file cannot simply sub-include
using the $helper script variable, but must be a full expansion of the
modules set.

I believe these are well outweighted by the Pros above however. Already
this patch is catching fails-to-build error in PAM, SASL, and LDAP far
better on several systems just by way of the macro usage in the
required.m4 files.

Amos