Fix the makefiles to fail cleanly if Perl is needed but not present. This

used to work as intended, but got broken some time ago (a quoted empty string
is not an empty string), and got broken some more by the changes to generate
ecpg's preproc.y automatically.  Given all the unprotected uses of $(PERL)
elsewhere, it seems best to make use of the $(missing) script rather than
trying to ensure each such use is protected individually.  Also fix various
bits of documentation that omitted to mention Perl as a requirement for
building from a CVS pull.  Per a complaint from Robert Haas.

README.CVS

@@ -8,7 +8,7 @@ If you are using CVS, you can view the most recent install instructions at:
 and the current release notes at:
 	http://developer.postgresql.org/docs/postgres/release.html
 
-Users compiling from CVS will also need compatible versions of Bison and
-Flex, as discussed in the install documentation.  Bison and Flex are not
+Users compiling from CVS will also need compatible versions of Bison, Flex,
+and Perl, as discussed in the install documentation.  These programs are not
 needed when using a tarball, since the files they are needed to build are
-already present in the tarball.
+already present in the tarball.  (On Windows, however, you need Perl anyway.)

config/missing

 #! /bin/sh
 
-# $PostgreSQL: pgsql/config/missing,v 1.4 2006/03/11 04:38:28 momjian Exp $
+# $PostgreSQL: pgsql/config/missing,v 1.5 2009/06/23 03:46:00 tgl Exp $
 
 # This is *not* the GNU `missing' script, although it is similar in
 # concept. You can call it from the makefiles to get consistent
@@ -17,7 +17,7 @@ case $1 in
 WARNING: \`$1' is missing on your system. You should only need it
 if you changed the file \`$input'; these changes will not take effect.
 You can get $1 from a GNU mirror site.
-***"
+***" >&2
             echo "touch $output"
             touch "$output"
             exit 0
@@ -28,8 +28,27 @@ ERROR: \`$1' is missing on your system. It is needed to create the
 file \`$output'. You can either get $1 from a GNU mirror site
 or download an official distribution of PostgreSQL, which contains
 pre-packaged $1 output.
-***"
+***" >&2
             exit 1
         fi
         ;;
+
+    perl)
+        # `missing perl'
+        echo "\
+***
+ERROR: Perl is missing on your system. It is needed unless you are building
+from an unmodified official distribution of PostgreSQL.
+***" >&2
+        exit 1
+        ;;
+
+    *)
+        # `missing something-or-other'
+        echo "\
+***
+ERROR: \`$1' is missing on your system.
+***" >&2
+        exit 1
+        ;;
 esac

doc/src/sgml/cvs.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/cvs.sgml,v 1.50 2008/04/21 11:06:13 mha Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/cvs.sgml,v 1.51 2009/06/23 03:46:00 tgl Exp $ -->
 
 <appendix id="cvs">
  <appendixinfo>
@@ -171,6 +171,7 @@ cvs update
    pull requires reasonably up-to-date versions of <application>bison</>
    and <application>flex</>, which are not needed to build from a distribution
    tarball because the files made with them are pre-built in a tarball.
+   You will need Perl as well.
    Otherwise the tool requirements are the same as building from source.
   </para>
  </sect1>

doc/src/sgml/installation.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/installation.sgml,v 1.324 2009/06/17 21:58:49 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/installation.sgml,v 1.325 2009/06/23 03:46:00 tgl Exp $ -->
 
 <chapter id="installation">
  <title><![%standalone-include[<productname>PostgreSQL</>]]>
@@ -294,13 +294,25 @@ su - postgres
       </indexterm>
 
       GNU <application>Flex</> and <application>Bison</>
-      are needed to build a CVS checkout or if you changed the actual
+      are needed to build from a CVS checkout, or if you changed the actual
       scanner and parser definition files. If you need them, be sure
       to get <application>Flex</> 2.5.4 or later and
       <application>Bison</> 1.875 or later. Other <application>lex</>
       and <application>yacc</> programs cannot be used.
      </para>
     </listitem>
+    <listitem>
+     <para>
+      <indexterm>
+       <primary>perl</primary>
+      </indexterm>
+
+      <application>Perl</> is also needed to build from a CVS checkout,
+      or if you changed the input files for any of the build steps that
+      use Perl scripts.  If building on Windows you will need
+      <application>Perl</> in any case.
+     </para>
+    </listitem>
    </itemizedlist>
   </para>
 

src/Makefile.global.in

 # -*-makefile-*-
-# $PostgreSQL: pgsql/src/Makefile.global.in,v 1.253 2009/02/19 10:32:30 petere Exp $
+# $PostgreSQL: pgsql/src/Makefile.global.in,v 1.254 2009/06/23 03:46:00 tgl Exp $
 
 #------------------------------------------------------------------------------
 # All PostgreSQL makefiles include this file and use the variables it sets,
@@ -248,8 +248,12 @@ X = @EXEEXT@
 
 # Perl 
 
-# quoted for pathname with spaces
-PERL			= "@PERL@"
+ifneq (@PERL@,)
+    # quoted to protect pathname with spaces
+    PERL		= "@PERL@"
+else
+    PERL		= $(missing) perl
+endif
 perl_archlibexp		= @perl_archlibexp@
 perl_privlibexp		= @perl_privlibexp@
 perl_useshrplib		= @perl_useshrplib@

src/bin/psql/Makefile

@@ -5,7 +5,7 @@
 # Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
 # Portions Copyright (c) 1994, Regents of the University of California
 #
-# $PostgreSQL: pgsql/src/bin/psql/Makefile,v 1.62 2009/03/07 00:13:58 alvherre Exp $
+# $PostgreSQL: pgsql/src/bin/psql/Makefile,v 1.63 2009/06/23 03:46:00 tgl Exp $
 #
 #-------------------------------------------------------------------------
 
@@ -40,13 +40,8 @@ dumputils.c keywords.c: % : $(top_srcdir)/src/bin/pg_dump/%
 kwlookup.c: % : $(top_srcdir)/src/backend/parser/%
 	rm -f $@ && $(LN_S) $< .
 
-ifdef PERL
 $(srcdir)/sql_help.h: create_help.pl $(wildcard $(REFDOCDIR)/*.sgml)
 	$(PERL) $< $(REFDOCDIR) $@
-else
-$(srcdir)/sql_help.h:
-	@echo "*** Perl is needed to build psql help."
-endif
 
 $(srcdir)/psqlscan.c: psqlscan.l
 ifdef FLEX