Re: link-warning usage improvements

[Eric Blake]

Bruno Haible <bruno <at> clisp.org> writes:

> > gl_CHECK_NEXT_HEADERS invokes AC_CHECK_HEADERS under the hood.
> 
> Well, it does, but it's not documented. It's an abstraction violation to
> exploit this knowledge (even though we do in some places).
> 
> > That means several other .m4 file can probably be simplified:
> 
> Reducing two invocations of AC_CHECK_HEADERS_ONCE to a single one will
> IMO not bring large benefits.

Then how about a patch in the converse direction, that ensures 
AC_CHECK_HEADERS_ONCE is called prior to any use of ac_cv_header_xxx_h, rather 
than the few modules that currently exploit gl_CHECK_NEXT_HEADERS.  The beauty 
of AC_CHECK_HEADERS_ONCE is that it doesn't add much to the configure file (an 
extra newline or two) on the second invocation, and the impact to m4 processing 
time is not that noticeable.  So, that would mean sys_select_h.m4, and maybe a 
few others.

-- 
Eric Blake