require: autoconf >= 2.65; related simplifications

The new support for Objective C++ (to be added in Automake 1.12.1) can be
simplified if we assume Autoconf version 2.65 or later (2.65 being the
version that introduced support for Objective C++).  Since such an Autoconf
version is two and half years old now (and will likely be almost three
years old when Automake 1.13 gets released), requiring it is acceptable.
This will also simplify testing and maintenance of Automake, because we'll
need to test with fewer Autoconf version, and possibly rely on new Autoconf
features.

* NEWS (Version requirements): Automake 1.13 will require Autoconf
2.65 or later.
* configure.ac ($required_autoconf_version): Bump to 2.65.
* m4/init.m4 (AM_INIT_AUTOMAKE): Require Autoconf >= 2.65.
Assume AC_PROG_OBJCXX is unconditionally defined.
* m4/depout.m4: Adjust a comment about a nugget of defensive programming.
* t/ext.sh: Assume that AC_PROG_OBJCXX is unconditionally defined,
and that we are using Autoconf >= 2.65.  Related simplifications.
* t/objc-megademo.sh: Likewise.
* t/objcxx-basic.sh: Likewise.
* t/objcxx-deps.sh: Likewise.
* t/objcxx-flags.sh: Likewise.
* t/objcxx-minidemo.sh: Likewise.
* t/nodep2.sh: Likewise.
* t/backcompat3.sh: Assume AC_INIT accepts an URL argument.
* t/depend5.sh: Adjust a comment.
* syntax-checks.mk (sc_test_names): Delete this check as now useless:
autoconf >= 2.65 (>= 2.63, actually) can handle arguments to AC_INIT
that contain or are m4 builtins or predefined macros.
(m4_builtin): Delete this now-useless variable as well, was used only
by the check above.
(syntax_check_rules): Update.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>

2 files changed, 6 insertions, 9 deletions

diff --git a/m4/depout.m4 b/m4/depout.m4
index 749e592df..ecf62688d 100644
--- a/m4/depout.m4
+++ b/m4/depout.m4
@@ -6,13 +6,13 @@
 # gives unlimited permission to copy and/or distribute it,
 # with or without modifications, as long as this notice is preserved.
 
-# serial 6
+# serial 7
 
 # _AM_OUTPUT_DEPENDENCY_COMMANDS
 # ------------------------------
 AC_DEFUN([_AM_OUTPUT_DEPENDENCY_COMMANDS],
 [{
-  # Autoconf 2.62 quotes --file arguments for eval, but not when files
+  # Older Autoconf quotes --file arguments for eval, but not when files
   # are listed without --file.  Let's play safe and only enable the eval
   # if we detect the quoting.
   case $CONFIG_FILES in
diff --git a/m4/init.m4 b/m4/init.m4
index 9db4eea0c..91a0620d9 100644
--- a/m4/init.m4
+++ b/m4/init.m4
@@ -6,7 +6,7 @@
 # gives unlimited permission to copy and/or distribute it,
 # with or without modifications, as long as this notice is preserved.
 
-# serial 19
+# serial 20
 
 # This macro actually does too much.  Some checks are only needed if
 # your package does certain things.  But this isn't really a big deal.
@@ -23,7 +23,7 @@
 # arguments mandatory, and then we can depend on a new Autoconf
 # release and drop the old call support.
 AC_DEFUN([AM_INIT_AUTOMAKE],
-[AC_PREREQ([2.62])dnl
+[AC_PREREQ([2.65])dnl
 dnl Autoconf wants to disallow AM_ names.  We explicitly allow
 dnl the ones we care about.
 m4_pattern_allow([^AM_[A-Z]+FLAGS$])dnl
@@ -100,13 +100,10 @@ AC_PROVIDE_IFELSE([AC_PROG_OBJC],
 		  [_AM_DEPENDENCIES([OBJC])],
 		  [define([AC_PROG_OBJC],
 			  defn([AC_PROG_OBJC])[_AM_DEPENDENCIES([OBJC])])])dnl
-dnl Support for Objective C++ was only introduced in Autoconf 2.65,
-dnl but we still cater to Autoconf 2.62.
-m4_ifdef([AC_PROG_OBJCXX],
-[AC_PROVIDE_IFELSE([AC_PROG_OBJCXX],
+AC_PROVIDE_IFELSE([AC_PROG_OBJCXX],
 		  [_AM_DEPENDENCIES([OBJCXX])],
 		  [define([AC_PROG_OBJCXX],
-			  defn([AC_PROG_OBJCXX])[_AM_DEPENDENCIES([OBJCXX])])])])dnl
+			  defn([AC_PROG_OBJCXX])[_AM_DEPENDENCIES([OBJCXX])])])dnl
 ])
 AC_REQUIRE([AM_SILENT_RULES])dnl
 dnl The 'parallel-tests' driver may need to know about EXEEXT, so add the