From: Paolo Bonzini <bonzini@gnu.org>
Date: Mon, 31 Oct 2016 17:08:07 +0000 (+0100)
Subject: autoconf: prefer an unrolled loop for trivial AC_CHECK_HEADERS
X-Git-Tag: v2.69b~54
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0e2eecedb12dd472c9a008748be6edd6ea68fa0e;p=thirdparty%2Fautoconf.git

autoconf: prefer an unrolled loop for trivial AC_CHECK_HEADERS

An unrolled loop avoids the cost of spawning sed in AS_TR_SH and
AS_TR_CPP.  Prefer it if there is nothing in the second and third
argument of AC_CHECK_HEADERS and the first argument is a literal.

* lib/autoconf/headers.m4 (AC_CHECK_HEADERS): Unroll loop if safe.
(_AC_CHECK_HEADERS): Move basic implementation here.
(AC_CHECK_INCLUDES_DEFAULT): Remove unnecessary arguments after the first.

Signed-off-by: Paolo Bonzini <bonzini@gnu.org>
Message-Id: <1477933688-4884-3-git-send-email-bonzini@gnu.org>
[eblake: perform AC_CHECK_HEADERS_ONCE changes separately, use
dnl to reduce generated blank lines]
Signed-off-by: Eric Blake <eblake@redhat.com>

Signed-off-by: Eric Blake <eblake@redhat.com>
---

diff --git a/lib/autoconf/headers.m4 b/lib/autoconf/headers.m4
index 5f4ab4a8..8e2dbb02 100644
--- a/lib/autoconf/headers.m4
+++ b/lib/autoconf/headers.m4
@@ -185,12 +185,17 @@ m4_define([AH_CHECK_HEADERS],
 # header.  Either ACTION may include `break' to stop the search.
 AC_DEFUN([AC_CHECK_HEADERS],
 [m4_map_args_w([$1], [_AH_CHECK_HEADER(], [)])]dnl
-[AS_FOR([AC_header], [ac_header], [$1],
-[AC_CHECK_HEADER(AC_header,
-		 [AC_DEFINE_UNQUOTED(AS_TR_CPP([HAVE_]AC_header)) $2],
-		 [$3], [$4])dnl])
+[m4_if([$2$3]AS_LITERAL_IF([$1], [[yes]], [[no]]), [yes],
+       [m4_map_args_w([$1], [_$0(], [, [], [], [$4])])],
+       [AS_FOR([AC_header], [ac_header], [$1], [_$0(AC_header, [$2], [$3], [$4])])])dnl
 ])# AC_CHECK_HEADERS
 
+m4_define([_AC_CHECK_HEADERS],
+[AC_CHECK_HEADER([$1],
+		 [AC_DEFINE_UNQUOTED(AS_TR_CPP([HAVE_]$1)) $2],
+		 [$3], [$4])dnl
+])
+
 
 # _AC_CHECK_HEADER_ONCE(HEADER-FILE)
 # ----------------------------------
@@ -285,8 +290,7 @@ ac_includes_default="\
 #endif"
 ])]dnl
 [_AC_CHECK_HEADERS_ONCE(
-  [sys/types.h sys/stat.h strings.h inttypes.h stdint.h unistd.h],
-  [], [], [$ac_includes_default])]dnl
+  [sys/types.h sys/stat.h strings.h inttypes.h stdint.h unistd.h])]dnl
 dnl For backward compatibility, provide unconditional AC_DEFINEs of
 dnl HAVE_STDLIB_H, HAVE_STRING_H, and STDC_HEADERS.
 [AC_DEFINE([HAVE_STDLIB_H], [1],