Modernizing the handling of headers (was: autoconf 2.5, 2.13, and Vim)

[Akim Demaille]

Well, for a start I'm applying this part of my patch.  I don't think
we need to debate about it, it is straight forward.

Index: ChangeLog
from  Akim Demaille  <address@hidden>

        * acheaders.m4 (AC_CHECK_HEADER, AC_CHECK_HEADERS): Support $4 =
        INCLUDES.

Index: NEWS
===================================================================
RCS file: /cvs/autoconf/NEWS,v
retrieving revision 1.152
diff -u -u -r1.152 NEWS
--- NEWS 2001/06/12 14:46:13 1.152
+++ NEWS 2001/06/13 07:37:59
@@ -8,6 +8,10 @@
 - configure accepts --prefix='' again.
 - AC_CHECK_LIB works properly when its first argument is not a
   literal.
+
+** Generic macros
+- AC_CHECK_HEADER and AC_CHECK_HEADERS support a fourth argument to
+  specify pre-includes.
 
 * Major changes in Autoconf 2.50
 
Index: acheaders.m4
===================================================================
RCS file: /cvs/autoconf/acheaders.m4,v
retrieving revision 1.9
diff -u -u -r1.9 acheaders.m4
--- acheaders.m4 2001/06/12 14:46:13 1.9
+++ acheaders.m4 2001/06/13 07:37:59
@@ -60,12 +60,15 @@
 ## 1. Generic tests for headers.  ##
 ## ------------------------------ ##
 
-# AC_CHECK_HEADER(HEADER-FILE, [ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND])
-# ----------------------------------------------------------------------
+# AC_CHECK_HEADER(HEADER-FILE,
+#                 [ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND],
+#                 [INCLUDES])
+# ---------------------------------------------------------
 AC_DEFUN([AC_CHECK_HEADER],
 [AS_VAR_PUSHDEF([ac_Header], [ac_cv_header_$1])dnl
 AC_CACHE_CHECK([for $1], ac_Header,
-               [AC_PREPROC_IFELSE([AC_LANG_SOURCE(address@hidden:@include 
<$1>])],
+               [AC_PREPROC_IFELSE([AC_LANG_SOURCE([m4_n([$4])dnl
address@hidden:@include <$1>])],
                                   [AS_VAR_SET(ac_Header, yes)],
                                   [AS_VAR_SET(ac_Header, no)])])
 AS_IF([test AS_VAR_GET(ac_Header) = yes], [$2], [$3])[]dnl
@@ -83,6 +86,7 @@
 
 # AC_CHECK_HEADERS(HEADER-FILE...
 #                  [ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND])
+#                 [INCLUDES])
 # ----------------------------------------------------------
 AC_DEFUN([AC_CHECK_HEADERS],
 [AH_CHECK_HEADERS([$1])dnl
@@ -90,7 +94,8 @@
 do
 AC_CHECK_HEADER($ac_header,
                 [AC_DEFINE_UNQUOTED(AS_TR_CPP(HAVE_$ac_header)) $2],
-                [$3])dnl
+                [$3],
+                [$4])dnl
 done
 ])
 
Index: doc/autoconf.texi
===================================================================
RCS file: /cvs/autoconf/doc/autoconf.texi,v
retrieving revision 1.463
diff -u -u -r1.463 autoconf.texi
--- doc/autoconf.texi 2001/06/12 14:46:13 1.463
+++ doc/autoconf.texi 2001/06/13 07:38:03
@@ -3860,15 +3860,20 @@
 as well as find out whether it is present, you have to write your own
 test for it (@pxref{Writing Tests}).
 
address@hidden AC_CHECK_HEADER (@var{header-file}, @ovar{action-if-found}, 
@ovar{action-if-not-found})
address@hidden AC_CHECK_HEADER (@var{header-file}, @ovar{action-if-found}, 
@ovar{action-if-not-found}, @ovar{includes})
 @maindex CHECK_HEADER
 If the system header file @var{header-file} exists, execute shell commands
 @var{action-if-found}, otherwise execute @var{action-if-not-found}.  If
 you just want to define a symbol if the header file is available,
 consider using @code{AC_CHECK_HEADERS} instead.
+
+This macro actually checks whether @var{header-file} can be included
+without error.  If @var{includes} is specified, they are included before
address@hidden  Note that the @var{includes} are @emph{not}
+defaulted.  They might be in future releases.
 @end defmac
 
address@hidden AC_CHECK_HEADERS (@address@hidden, @ovar{action-if-found}, 
@ovar{action-if-not-found})
address@hidden AC_CHECK_HEADERS (@address@hidden, @ovar{action-if-found}, 
@ovar{action-if-not-found}, @ovar{includes})
 @maindex CHECK_HEADERS
 @cvindex address@hidden
 For each given system header file @var{header-file} in the
@@ -3878,6 +3883,11 @@
 files is found.  You can give it a value of @samp{break} to break out of
 the loop on the first match.  If @var{action-if-not-found} is given, it
 is executed when one of the header files is not found.
+
+This macro actually checks whether @var{header-file} can be included
+without error.  If @var{includes} is specified, they are included before
address@hidden  Note that the @var{includes} are @emph{not}
+defaulted.  They might be in future releases.
 @end defmac
 
 @node Declarations, Structures, Header Files, Existing Tests