Re: [PATCH 1/3] AC_CHECK_HEADER/AC_CHECK_HEADERS: complete transition to compile tests.

[Eric Blake]

On 03/16/2013 10:37 AM, Zack Weinberg wrote:
> * lib/autoconf/headers.m4 (AC_CHECK_HEADER): Use _AC_CHECK_HEADER_COMPILE
>   by default.  Continue to use _AC_CHECK_HEADER_PREPROC if fourth arg is '-'.
>   (_AC_CHECK_HEADER_PREPROC): Issue a deprecation warning.
>   (_AC_CHECK_HEADER_MONGREL, _AC_CHECK_HEADER_MONGREL_BODY): Remove.
> 
> * tests/local.at (AT_CHECK_M4): Support 'stderr' as fourth argument.
> * tests/c.at, tests/semantics.at: Update uses of AC_CHECK_HEADER(S).
> * doc/autoconf.texi, NEWS: Document change.
> 
> Signed-off-by: Zack Weinberg <address@hidden>
> ---

>  # The m4_indir allows for fewer expansions of address@hidden
>  AC_DEFUN([AC_CHECK_HEADER],
>  [m4_indir(m4_case([$4],
> -               [],  [[_AC_CHECK_HEADER_MONGREL]],
>                 [-], [[_AC_CHECK_HEADER_PREPROC]],
>                      [[_AC_CHECK_HEADER_COMPILE]]), $@)

Micro-optimization: when we had a ternary condition, m4_case was indeed
fastest, but now that we have a binary condition, write this:

[m4_indir(m4_if([$4], [-], [[_AC_CHECK_HEADER_PREPROC]],
                [[_AC_CHECK_HEADER_COMIPLE]]), $@)

> +++ b/tests/local.at
> @@ -113,13 +113,14 @@ m4_define([AT_CHECK_M4],
>  [AT_CHECK([$1], [$2], [$3],
>            m4_case([$4], [], [], [ignore], [ignore], [stderr]))
>  m4_case([$4], [], [], [ignore], [],
> -[AT_CHECK([[sed 's/^[^:]*m4[-.ex0-9]*: *\([^:]*:\) *\([0-9][0-9]*: 
> \)/m4:\1\2/
> +[AT_CHECK([[mv stderr stderr-raw &&
> +   sed 's/^[^:]*m4[-.ex0-9]*: *\([^:]*:\) *\([0-9][0-9]*: \)/m4:\1\2/
>       s/^\([^:]*:\) *\([0-9][0-9]*:\)[^:]*m4[-.ex0-9]*: /m4:\1\2 /
>       s/: C\(annot open \)\([^`:]*\):/: c\1`\2'\'':/
>       s/: include:\( cannot open\)/:\1/
>       s/^autom4te: [^ ]*m4[.ex]* /autom4te: m4 /
>       s/ (E[A-Z]*)$//
> -    ' stderr >&2]], [0], [], [$4])])
> +    ' stderr-raw >&2]], [0], [], [$4])])

This might be worth splitting into a separate patch, as it's a useful
cleanup whether or not you change AC_CHECK_HEADER.

Looks good with those changes.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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