Re: RFE: configure -> dependency list on exit.

[Paul Eggert]

Hugh Sasse Staff Elec Eng <address@hidden> writes:

>    * some macro such as  AC_NEEDS(Tthis, That) expresses the idea
>      that This feature is KNOWN to depend on the existence of That
>      feature.

This is a bit vague.  Can you give some specific examples of
invocations of this macro?  For example, you might give some specific
invocations of AC_NEEDS that are suitable for Autoconf itself.
Also, I'd like to know exactly where these invocations of AC_NEEDS
would go, and why.

>    * where such dependency is not declared, it is not assumed.to be
>      true or false.  In essence, do as is done now to avoid breakage.

But AC_NEEDS specifies only true relationships.  How does one specify
false relationships?  One would need some way to do that, if the
default is that the relationship is not known.

>    * the dependency tree thereby constructed (using topological sort)
>      be used to prune searches for further features
>      AND be used to search branches which can still be
>      explored.

Can you give a specific example of this, based on the example AC_NEEDS
invocation examples suggested above?

>    * the information collected on a pass through all practical
>      branches (pruned by known dependency information) be presented
>      *at the end of configure's output*, in a manner which is
>      informative as possible.  This is in order to suggest a
>      "shopping list" to process before retrying the build.

Can you show what this new output would look like, assuming the
examples I asked for above?

>    * A macro be provided to declare such useful information for a test
>      that fails -- off the top of my head:
>      AC_NEEDS_FAILURE(This, Message)
>      or some such.

Again, this is a bit vague.  I would like to see a couple of specific
examples of invocations of this macro, and where they would go in the
Autoconf source code, and how the user would cause that message to
appear, and what the whole output from "configure" would look like
when that message appears, compared to what the output would look like
if AC_NEEDS_FAILURE wasn't invoked.