[PATCH 07/12] use a shell function for AC_CHECK_HEADER

[Paolo Bonzini]

Let's go again.  I retimed the effect of upgrading from 2.61 to after
the whole series of patches, and I get a 45-55% reduction in autoconf
execution time (approx. 20% are already there in 2.63) and 30-35%
reduction in configure script size.  In other words, with the latest
patches the complexity of m4sh processing is lowered, and the speedup
is more consistent with the decrease in output size.

These six patches include all the tricks learnt from patches 1-6,
including splitting the function body outside the main macro, and
passing the cache variable name to the macro itself.

Paolo

2008-10-27  Paolo Bonzini  <address@hidden>

        * lib/autoconf/headers.m4 (_AC_CHECK_HEADER_OLD,
        _AC_CHECK_HEADER_NEW): Use a shell function.
---
 lib/autoconf/headers.m4 |   59 +++++++++++++++++++++++++++++++++++-----------
 1 files changed, 45 insertions(+), 14 deletions(-)

diff --git a/lib/autoconf/headers.m4 b/lib/autoconf/headers.m4
index 4c588ca..81a9d06 100644
--- a/lib/autoconf/headers.m4
+++ b/lib/autoconf/headers.m4
@@ -153,7 +153,7 @@ esac
 m4_define([_AC_CHECK_HEADER_MONGREL],
 [AC_REQUIRE_SHELL_FN([ac_func_]_AC_LANG_ABBREV[_check_header_mongrel],
   [AS_FUNCTION_DESCRIBE([ac_func_]_AC_LANG_ABBREV[_check_header_mongrel],
-    [LINENO FUNC VAR INCLUDES],
+    [LINENO HEADER VAR INCLUDES],
     [Tests whether HEADER exists, giving a warning if it cannot be compiled
      using the include files in INCLUDES and setting the cache variable VAR
      accordingly.])],
@@ -165,33 +165,65 @@ AS_VAR_IF([ac_Header], [yes], [$2], [$3])
 AS_VAR_POPDEF([ac_Header])])# _AC_CHECK_HEADER_MONGREL
 
 
+# _AC_CHECK_HEADER_NEW_BODY
+# -------------------------
+# Shell function body for _AC_CHECK_HEADER_NEW
+m4_define([_AC_CHECK_HEADER_NEW_BODY],
+[  AS_LINENO_PUSH([$[]1])
+  AC_CACHE_CHECK([for $[]2], [$[]3],
+                [AC_COMPILE_IFELSE([AC_LANG_SOURCE([$[]4
address@hidden:@include <$[]2>])],
+                                   [AS_VAR_SET([$[]3], [yes])],
+                                   [AS_VAR_SET([$[]3], [no])])])
+  AS_LINENO_POP
+])# _AC_CHECK_HEADER_NEW_BODY
+
 # _AC_CHECK_HEADER_NEW(HEADER-FILE,
 #                     [ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND],
 #                     [INCLUDES = DEFAULT-INCLUDES])
 # --------------------------------------------------------------
 # Check the compiler accepts HEADER-FILE.  The INCLUDES are defaulted.
 m4_define([_AC_CHECK_HEADER_NEW],
-[AS_VAR_PUSHDEF([ac_Header], [ac_cv_header_$1])dnl
-AC_CACHE_CHECK([for $1], [ac_Header],
-              [AC_COMPILE_IFELSE([AC_LANG_SOURCE([AC_INCLUDES_DEFAULT([$4])
address@hidden:@include <$1>])],
-                                 [AS_VAR_SET([ac_Header], [yes])],
-                                 [AS_VAR_SET([ac_Header], [no])])])
+[AC_REQUIRE_SHELL_FN([ac_func_]_AC_LANG_ABBREV[_check_header_new],
+  [AS_FUNCTION_DESCRIBE([ac_func_]_AC_LANG_ABBREV[_check_header_new],
+    [LINENO HEADER VAR INCLUDES],
+    [Tests whether HEADER exists and can be compiled using the include files
+     in INCLUDES, setting the cache variable VAR accordingly.])],
+  [$0_BODY])]dnl
+[AS_VAR_PUSHDEF([ac_Header], [ac_cv_header_$1])]dnl
+[ac_func_[]_AC_LANG_ABBREV[]_check_header_new ]dnl
+["$LINENO" "$1" "ac_Header" "AS_ESCAPE([AC_INCLUDES_DEFAULT([$4], [""])])"
 AS_VAR_IF([ac_Header], [yes], [$2], [$3])
 AS_VAR_POPDEF([ac_Header])dnl
 ])# _AC_CHECK_HEADER_NEW
+
+
+# _AC_CHECK_HEADER_OLD_BODY
+# -------------------------
+# Shell function body for _AC_CHECK_HEADER_OLD.
+m4_define([_AC_CHECK_HEADER_OLD_BODY],
+[  AS_LINENO_PUSH([$[]1])
+  AC_CACHE_CHECK([for $[]2], [$[]3],
+  [AC_PREPROC_IFELSE([AC_LANG_SOURCE(address@hidden:@include <$[]2>])],
+                    [AS_VAR_SET([$[]3], [yes])],
+                    [AS_VAR_SET([$[]3], [no])])])
+  AS_LINENO_POP
+])# _AC_CHECK_HEADER_OLD_BODY
+
 
 
 # _AC_CHECK_HEADER_OLD(HEADER-FILE,
 #                     [ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND])
 # --------------------------------------------------------------
 # Check the preprocessor accepts HEADER-FILE.
-m4_define([_AC_CHECK_HEADER_OLD],
+AC_DEFUN([_AC_CHECK_HEADER_OLD],
+[AC_REQUIRE_SHELL_FN([ac_func_]_AC_LANG_ABBREV[_check_header_old],
+  [AS_FUNCTION_DESCRIBE([ac_func_]_AC_LANG_ABBREV[_check_header_old],
+    [LINENO HEADER VAR],
+    [Tests whether HEADER is present, setting the cache variable VAR 
accordingly.])],
+  [$0_BODY])]dnl
 [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 
<$1>])],
-                                        [AS_VAR_SET([ac_Header], [yes])],
-                                        [AS_VAR_SET([ac_Header], [no])])])
+ac_func_[]_AC_LANG_ABBREV[]_check_header_old "$LINENO" "$1" "ac_Header"
 AS_VAR_IF([ac_Header], [yes], [$2], [$3])
 AS_VAR_POPDEF([ac_Header])dnl
 ])# _AC_CHECK_HEADER_OLD
-- 
1.5.5