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Suppress "unused variable" warnings with older versions of flex.
Versions of flex before 2.5.36 might generate code that results in an "unused variable" warning, when using %option reentrant. Historically we've worked around that by specifying -Wno-error, but that's an unsatisfying solution. The official "fix" for this was just to insert a dummy reference to the variable, so write a small perl script that edits the generated C code similarly. The MSVC side of this is untested, but the buildfarm should soon reveal if I broke that. Discussion: https://postgr.es/m/25456.1487437842@sss.pgh.pa.us
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6 files changed

+82
-23
lines changed

6 files changed

+82
-23
lines changed

‎src/Makefile.global.in

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Original file line numberDiff line numberDiff line change
@@ -627,6 +627,7 @@ TAS = @TAS@
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ifdef FLEX
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$(FLEX) $(if $(FLEX_NO_BACKUP),-b) $(FLEXFLAGS) -o'$@' $<
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@$(if $(FLEX_NO_BACKUP),if [ `wc -l <lex.backup` -eq 1 ]; then rm lex.backup; else echo "Scanner requires backup; see lex.backup." 1>&2; exit 1; fi)
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$(if $(FLEX_FIX_WARNING),$(PERL) $(top_srcdir)/src/tools/fix-flex-warning.pl '$@')
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else
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@$(missing) flex $< '$@'
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endif

‎src/backend/parser/Makefile

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@@ -20,12 +20,6 @@ OBJS= analyze.o gram.o scan.o parser.o \
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include $(top_srcdir)/src/backend/common.mk
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# Latest flex causes warnings in this file.
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ifeq ($(GCC),yes)
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scan.o: CFLAGS += -Wno-error
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endif
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# There is no correct way to write a rule that generates two files.
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# Rules with two targets don't have that meaning, they are merely
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# shorthand for two otherwise separate rules. To be safe for parallel
@@ -41,6 +35,7 @@ gram.c: BISON_CHECK_CMD = $(PERL) $(srcdir)/check_keywords.pl $< $(top_srcdir)/s
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scan.c: FLEXFLAGS = -CF -p -p
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scan.c: FLEX_NO_BACKUP=yes
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scan.c: FLEX_FIX_WARNING=yes
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# Force these dependencies to be known even without dependency info built:

‎src/bin/psql/Makefile

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@@ -41,11 +41,7 @@ sql_help.h: create_help.pl $(wildcard $(REFDOCDIR)/*.sgml)
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psqlscanslash.c: FLEXFLAGS = -Cfe -p -p
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psqlscanslash.c: FLEX_NO_BACKUP=yes
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# Latest flex causes warnings in this file.
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ifeq ($(GCC),yes)
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psqlscanslash.o: CFLAGS += -Wno-error
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endif
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psqlscanslash.c: FLEX_FIX_WARNING=yes
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distprep: sql_help.h psqlscanslash.c
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‎src/fe_utils/Makefile

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@@ -29,11 +29,7 @@ libpgfeutils.a: $(OBJS)
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psqlscan.c: FLEXFLAGS = -Cfe -p -p
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psqlscan.c: FLEX_NO_BACKUP=yes
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# Latest flex causes warnings in this file.
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ifeq ($(GCC),yes)
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psqlscan.o: CFLAGS += -Wno-error
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endif
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psqlscan.c: FLEX_FIX_WARNING=yes
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distprep: psqlscan.c
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‎src/tools/fix-flex-warning.pl

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@@ -0,0 +1,65 @@
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#!/usr/bin/perl -w
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#----------------------------------------------------------------------
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#
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# fix-flex-warning.pl
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#
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# flex versions before 2.5.36, with certain option combinations, produce
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# code that causes an "unused variable" warning. That's annoying, so
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# let's suppress it by inserting a dummy reference to the variable.
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# (That's exactly what 2.5.36 and later do ...)
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#
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# Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
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# Portions Copyright (c) 1994, Regents of the University of California
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#
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# src/tools/fix-flex-warning.pl
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#
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#----------------------------------------------------------------------
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use strict;
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use warnings;
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# Get command line argument.
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usage() if $#ARGV != 0;
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my $filename = shift;
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# Suck in the whole file.
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local $/ = undef;
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my $cfile;
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open($cfile, $filename) || die "opening $filename for reading: $!";
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my $ccode = <$cfile>;
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close($cfile);
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# No need to do anything if it's not flex 2.5.x for x < 36.
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exit 0 if $ccode !~ m/^#define YY_FLEX_MAJOR_VERSION 2$/m;
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exit 0 if $ccode !~ m/^#define YY_FLEX_MINOR_VERSION 5$/m;
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exit 0 if $ccode !~ m/^#define YY_FLEX_SUBMINOR_VERSION (\d+)$/m;
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exit 0 if $1 >= 36;
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# Apply the desired patch.
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$ccode =~ s|(struct yyguts_t \* yyg = \(struct yyguts_t\*\)yyscanner; /\* This var may be unused depending upon options. \*/
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.*?)
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return yy_is_jam \? 0 : yy_current_state;
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|$1
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(void) yyg;
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return yy_is_jam ? 0 : yy_current_state;
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|s;
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# Write the modified file back out.
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open($cfile, ">$filename") || die "opening $filename for writing: $!";
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print $cfile $ccode;
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close($cfile);
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exit 0;
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sub usage
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{
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die <<EOM;
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Usage: fix-flex-warning.pl c-file-name
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fix-flex-warning.pl modifies a flex output file to suppress
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an unused-variable warning that occurs with older flex versions.
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Report bugs to <pgsql-bugs\@postgresql.org>.
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EOM
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}

‎src/tools/msvc/pgflex.pl

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@@ -51,23 +51,29 @@
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system("flex $flexflags -o$output $input");
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if ($? == 0)
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{
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# For non-reentrant scanners we need to fix up the yywrap macro definition
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# to keep the MS compiler happy.
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# For reentrant scanners (like the core scanner) we do not
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# need to (and must not) change the yywrap definition.
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# Check for "%option reentrant" in .l file.
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my $lfile;
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open($lfile, $input) || die "opening $input for reading: $!";
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my $lcode = <$lfile>;
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close($lfile);
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if ($lcode !~ /\%option\sreentrant/)
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if ($lcode =~ /\%option\sreentrant/)
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{
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# Reentrant scanners usually need a fix to prevent
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# "unused variable" warnings with older flex versions.
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system("perl src\\tools\\fix-flex-warning.pl $output");
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}
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else
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{
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# For non-reentrant scanners we need to fix up the yywrap
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# macro definition to keep the MS compiler happy.
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# For reentrant scanners (like the core scanner) we do not
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# need to (and must not) change the yywrap definition.
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my $cfile;
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open($cfile, $output) || die "opening $output for reading: $!";
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my $ccode = <$cfile>;
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close($cfile);
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$ccode =~ s/yywrap\(n\)/yywrap()/;
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open($cfile, ">$output") || die "opening $output for reading: $!";
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open($cfile, ">$output") || die "opening $output for writing: $!";
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print $cfile $ccode;
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close($cfile);
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}

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