Rename configure.in to configure.ac

The new name has been preferred by Autoconf for a long time.  Future
versions of Autoconf will warn about the old name.

Discussion: https://www.postgresql.org/message-id/flat/e796c185-5ece-8569-248f-dd3799701be1%402ndquadrant.com

config/general.m4

@@ -8,7 +8,7 @@
 # argument (other than "yes/no"), etc.
 #
 # The point of this implementation is to reduce code size and
-# redundancy in configure.in and to improve robustness and consistency
+# redundancy in configure.ac and to improve robustness and consistency
 # in the option evaluation code.
 
 

configure.ac

@@ -1,5 +1,5 @@
 dnl Process this file with autoconf to produce a configure script.
-dnl configure.in
+dnl configure.ac
 dnl
 dnl Developers, please strive to achieve this order:
 dnl
@@ -21,7 +21,7 @@ AC_INIT([PostgreSQL], [14devel], [pgsql-bugs@lists.postgresql.org], [], [https:/
 
 m4_if(m4_defn([m4_PACKAGE_VERSION]), [2.69], [], [m4_fatal([Autoconf version 2.69 is required.
 Untested combinations of 'autoconf' and PostgreSQL versions are not
-recommended.  You can remove the check from 'configure.in' but it is then
+recommended.  You can remove the check from 'configure.ac' but it is then
 your responsibility whether the result works or not.])])
 AC_COPYRIGHT([Copyright (c) 1996-2020, PostgreSQL Global Development Group])
 AC_CONFIG_SRCDIR([src/backend/access/common/heaptuple.c])

src/backend/catalog/Makefile

@@ -103,10 +103,10 @@ generated-header-symlinks: $(top_builddir)/src/include/catalog/header-stamp
 # won't update them if they didn't change (to avoid unnecessary recompiles).
 # Technically, this should depend on Makefile.global which supplies
 # $(MAJORVERSION); but then genbki.pl would need to be re-run after every
-# configure run, even in distribution tarballs.  So depending on configure.in
+# configure run, even in distribution tarballs.  So depending on configure.ac
 # instead is cheating a bit, but it will achieve the goal of updating the
 # version number when it changes.
-bki-stamp: genbki.pl Catalog.pm $(POSTGRES_BKI_SRCS) $(POSTGRES_BKI_DATA) $(top_srcdir)/configure.in
+bki-stamp: genbki.pl Catalog.pm $(POSTGRES_BKI_SRCS) $(POSTGRES_BKI_DATA) $(top_srcdir)/configure.ac
 	$(PERL) $< --include-path=$(top_srcdir)/src/include/ \
 		--set-version=$(MAJORVERSION) $(POSTGRES_BKI_SRCS)
 	touch $@

src/include/pg_config.h.in

@@ -1,4 +1,4 @@
-/* src/include/pg_config.h.in.  Generated from configure.in by autoheader.  */
+/* src/include/pg_config.h.in.  Generated from configure.ac by autoheader.  */
 
 /* Define to the type of arg 1 of 'accept' */
 #undef ACCEPT_TYPE_ARG1

src/tools/msvc/Solution.pm

@@ -155,9 +155,9 @@ sub GenerateFiles
 	my $ac_define_openssl_api_compat_found = 0;
 	my $openssl_api_compat;
 
-	# Parse configure.in to get version numbers
-	open(my $c, '<', "configure.in")
-	  || confess("Could not open configure.in for reading\n");
+	# Parse configure.ac to get version numbers
+	open(my $c, '<', "configure.ac")
+	  || confess("Could not open configure.ac for reading\n");
 	while (<$c>)
 	{
 		if (/^AC_INIT\(\[([^\]]+)\], \[([^\]]+)\], \[([^\]]+)\], \[([^\]]*)\], \[([^\]]+)\]/
@@ -185,7 +185,7 @@ sub GenerateFiles
 		}
 	}
 	close($c);
-	confess "Unable to parse configure.in for all variables!"
+	confess "Unable to parse configure.ac for all variables!"
 	  unless $ac_init_found && $ac_define_openssl_api_compat_found;
 
 	if (IsNewer("src/include/pg_config_os.h", "src/include/port/win32.h"))
@@ -834,7 +834,7 @@ EOF
 
 # Read lines from input file and substitute symbols using the same
 # logic that config.status uses.  There should be one call of this for
-# each AC_CONFIG_HEADERS call in configure.in.
+# each AC_CONFIG_HEADERS call in configure.ac.
 #
 # If the "required" argument is true, we also keep track which of our
 # defines have been found and error out if any are left unused at the

src/tools/version_stamp.pl

@@ -9,10 +9,10 @@
 #################################################################
 
 #
-# This script updates the version stamp in configure.in, and also in assorted
+# This script updates the version stamp in configure.ac, and also in assorted
 # other files wherein it's not convenient to obtain the version number from
 # configure's output.  Note that you still have to run autoconf afterward
-# to regenerate configure from the updated configure.in.
+# to regenerate configure from the updated configure.ac.
 #
 # Usage: cd to top of source tree and issue
 #	src/tools/version_stamp.pl MINORVERSION
@@ -74,7 +74,7 @@ else
 # (this also ensures we're in the right directory)
 
 my $aconfver = "";
-open(my $fh, '<', "configure.in") || die "could not read configure.in: $!\n";
+open(my $fh, '<', "configure.ac") || die "could not read configure.ac: $!\n";
 while (<$fh>)
 {
 	if (m/^m4_if\(m4_defn\(\[m4_PACKAGE_VERSION\]\), \[(.*)\], \[\], \[m4_fatal/
@@ -86,13 +86,13 @@ while (<$fh>)
 }
 close($fh);
 $aconfver ne ""
-  || die "could not find autoconf version number in configure.in\n";
+  || die "could not find autoconf version number in configure.ac\n";
 
-# Update configure.in and other files that contain version numbers
+# Update configure.ac and other files that contain version numbers
 
 my $fixedfiles = "";
 
-sed_file("configure.in",
+sed_file("configure.ac",
 	"-e 's/AC_INIT(\\[PostgreSQL\\], \\[[0-9a-z.]*\\]/AC_INIT([PostgreSQL], [$fullversion]/'"
 );