Improve perl style in ecpg's parser-construction scripts.

parse.pl and check_rules.pl used "no warnings 'uninitialized'",
which doesn't seem like it measures up to current project standards.
Removing that shows that it was hiding various places that accessed
off the end of an array, which are easily protected by minor logic
adjustments.  There's no change in the script results.

While here, improve the Makefile rule that invokes these scripts.
It neglected to depend on check_rules.pl, so that editing that file
didn't result in re-running the check; and it ran check_rules.pl
after building preproc.y, so that if check_rules.pl did fail the
next "make" attempt would just bypass it.  check_rules.pl failures
are sufficiently un-heard-of that I don't feel a need to back-patch
this.

Discussion: https://postgr.es/m/838180.1658181982@sss.pgh.pa.us

src/interfaces/ecpg/preproc/Makefile

@@ -64,9 +64,9 @@ preproc.h: preproc.c
 
 preproc.c: BISONFLAGS += -d
 
-preproc.y: ../../../backend/parser/gram.y parse.pl ecpg.addons ecpg.header ecpg.tokens ecpg.trailer ecpg.type
-	$(PERL) $(srcdir)/parse.pl --srcdir $(srcdir) --parser $< --output $@
+preproc.y: ../../../backend/parser/gram.y parse.pl check_rules.pl ecpg.addons ecpg.header ecpg.tokens ecpg.trailer ecpg.type
 	$(PERL) $(srcdir)/check_rules.pl --srcdir $(srcdir) --parser $<
+	$(PERL) $(srcdir)/parse.pl --srcdir $(srcdir) --parser $< --output $@
 
 # generate keyword headers
 c_kwlist_d.h: c_kwlist.h $(GEN_KEYWORDLIST_DEPS)

src/interfaces/ecpg/preproc/check_rules.pl

@@ -18,7 +18,6 @@
 
 use strict;
 use warnings;
-no warnings 'uninitialized';
 use Getopt::Long;
 
 my $srcdir  = '.';
@@ -142,7 +141,8 @@ while (<$parser_fh>)
 			$in_rule = 0 if $arr[$fieldIndexer] eq ';';
 		}
 		elsif (($arr[$fieldIndexer] =~ '[A-Za-z0-9]+:')
-			|| $arr[ $fieldIndexer + 1 ] eq ':')
+			   || (   $fieldIndexer + 1 < $n
+					  && $arr[ $fieldIndexer + 1 ] eq ':'))
 		{
 			die "unterminated rule at grammar line $.\n"
 			  if $in_rule;

src/interfaces/ecpg/preproc/parse.pl

@@ -14,7 +14,6 @@
 
 use strict;
 use warnings;
-no warnings 'uninitialized';
 use Getopt::Long;
 
 my $srcdir  = '.';
@@ -40,7 +39,8 @@ my $tokenmode             = 0;
 
 my (%buff, $infield, $comment, %tokens, %addons);
 my ($stmt_mode, @fields);
-my ($line,      $non_term_id);
+my $line = '';
+my $non_term_id;
 
 
 # some token have to be replaced by other symbols
@@ -195,6 +195,16 @@ sub main
 		# Now split the line into individual fields
 		my @arr = split(' ');
 
+		if (!@arr)
+		{
+			# empty line: in tokenmode 1, emit an empty line, else ignore
+			if ($tokenmode == 1)
+			{
+				add_to_buffer('orig_tokens', '');
+			}
+			next line;
+		}
+
 		if ($arr[0] eq '%token' && $tokenmode == 0)
 		{
 			$tokenmode = 1;
@@ -341,7 +351,8 @@ sub main
 
 			# Are we looking at a declaration of a non-terminal ?
 			if (($arr[$fieldIndexer] =~ /[A-Za-z0-9]+:/)
-				|| $arr[ $fieldIndexer + 1 ] eq ':')
+				|| (   $fieldIndexer + 1 < scalar(@arr)
+					&& $arr[ $fieldIndexer + 1 ] eq ':'))
 			{
 				$non_term_id = $arr[$fieldIndexer];
 				$non_term_id =~ tr/://d;
@@ -409,11 +420,13 @@ sub main
 			if (   $copymode
 				&& !$prec
 				&& !$comment
+				&& $fieldIndexer < scalar(@arr)
 				&& length($arr[$fieldIndexer])
 				&& $infield)
 			{
 				if ($arr[$fieldIndexer] ne 'Op'
-					&& (   $tokens{ $arr[$fieldIndexer] } > 0
+					&& ((   defined $tokens{ $arr[$fieldIndexer] }
+							&& $tokens{ $arr[$fieldIndexer] } > 0)
 						|| $arr[$fieldIndexer] =~ /'.+'/)
 					|| $stmt_mode == 1)
 				{
@@ -472,11 +485,12 @@ sub include_addon
 	my $rec = $addons{$block};
 	return 0 unless $rec;
 
-	if ($rec->{type} eq 'rule')
+	my $rectype = (defined $rec->{type}) ? $rec->{type} : '';
+	if ($rectype eq 'rule')
 	{
 		dump_fields($stmt_mode, $fields, ' { ');
 	}
-	elsif ($rec->{type} eq 'addon')
+	elsif ($rectype eq 'addon')
 	{
 		add_to_buffer('rules', ' { ');
 	}
@@ -487,7 +501,7 @@ sub include_addon
 
 	push(@{ $buff{$buffer} }, @{ $rec->{lines} });
 
-	if ($rec->{type} eq 'addon')
+	if ($rectype eq 'addon')
 	{
 		dump_fields($stmt_mode, $fields, '');
 	}