Build backend/parser/scan.l and interfaces/ecpg/preproc/pgc.l standalone.

Back-patch commit 72b1e3a21 into the pre-9.6 branches.

As noted in the original commit, this has some extra benefits: we can
narrow the scope of the -Wno-error flag that's forced on scan.c.  Also,
since these grammar and lexer files are so large, splitting them into
separate build targets should have some advantages in build speed,
particularly in parallel or ccache'd builds.

However, the real reason for doing this now is that it avoids symbol-
redefinition warnings (or worse) with the latest version of flex.
It's not unreasonable that people would want to compile our old branches
with recent tools.  Per report from Дилян Палаузов.

Discussion: https://postgr.es/m/d845c1af-e18d-6651-178f-9f08cdf37e10@aegee.org

src/backend/parser/Makefile

@@ -12,7 +12,7 @@ include $(top_builddir)/src/Makefile.global
 
 override CPPFLAGS := -I. -I$(srcdir) $(CPPFLAGS)
 
-OBJS= analyze.o gram.o keywords.o kwlookup.o parser.o \
+OBJS= analyze.o gram.o scan.o keywords.o kwlookup.o parser.o \
       parse_agg.o parse_clause.o parse_coerce.o parse_collate.o parse_cte.o \
       parse_expr.o parse_func.o parse_node.o parse_oper.o parse_param.o \
       parse_relation.o parse_target.o parse_type.o parse_utilcmd.o scansup.o
@@ -20,12 +20,9 @@ OBJS= analyze.o gram.o keywords.o kwlookup.o parser.o \
 include $(top_srcdir)/src/backend/common.mk
 
 
-# scan is compiled as part of gram
-gram.o: scan.c
-
 # Latest flex causes warnings in this file.
 ifeq ($(GCC),yes)
-gram.o: CFLAGS += -Wno-error
+scan.o: CFLAGS += -Wno-error
 endif
 
 
@@ -47,7 +44,7 @@ scan.c: FLEX_NO_BACKUP=yes
 
 
 # Force these dependencies to be known even without dependency info built:
-gram.o keywords.o parser.o: gram.h
+gram.o scan.o keywords.o parser.o: gram.h
 
 
 # gram.c, gram.h, and scan.c are in the distribution tarball, so they

src/backend/parser/gram.y

@@ -13978,13 +13978,3 @@ parser_init(base_yy_extra_type *yyext)
 {
 	yyext->parsetree = NIL;		/* in case grammar forgets to set it */
 }
-
-/*
- * Must undefine this stuff before including scan.c, since it has different
- * definitions for these macros.
- */
-#undef yyerror
-#undef yylval
-#undef yylloc
-
-#include "scan.c"

src/backend/parser/scan.l

@@ -1,4 +1,4 @@
-%{
+%top{
 /*-------------------------------------------------------------------------
  *
  * scan.l
@@ -6,7 +6,7 @@
  *
  * NOTE NOTE NOTE:
  *
- * The rules in this file must be kept in sync with psql's lexer!!!
+ * The rules in this file must be kept in sync with psql's psqlscan.l!
  *
  * The rules are designed so that the scanner never has to backtrack,
  * in the sense that there is always a rule that can match the input
@@ -34,12 +34,13 @@
 #include <ctype.h>
 #include <unistd.h>
 
+#include "parser/gramparse.h"
 #include "parser/parser.h"				/* only needed for GUC variables */
-#include "parser/scanner.h"
 #include "parser/scansup.h"
 #include "mb/pg_wchar.h"
+}
 
-
+%{
 /* Avoid exit() on fatal scanner errors (a bit ugly -- see yy_fatal_error) */
 #undef fprintf
 #define fprintf(file, fmt, msg)  fprintf_to_ereport(fmt, msg)

src/interfaces/ecpg/preproc/Makefile

@@ -26,7 +26,7 @@ override CPPFLAGS := -I../include -I$(top_srcdir)/src/interfaces/ecpg/include \
 
 override CFLAGS += $(PTHREAD_CFLAGS) -DECPG_COMPILE
 
-OBJS=	preproc.o type.o ecpg.o output.o parser.o \
+OBJS=	preproc.o pgc.o type.o ecpg.o output.o parser.o \
 	keywords.o c_keywords.o ecpg_keywords.o kwlookup.o ../ecpglib/typename.o descriptor.o variable.o \
 	$(WIN32RES)
 
@@ -44,9 +44,6 @@ ecpg: $(OBJS) | submake-libpgport
 ../ecpglib/typename.o: ../ecpglib/typename.c
 	$(MAKE) -C $(dir $@) $(notdir $@)
 
-# pgc is compiled as part of preproc
-preproc.o: pgc.c
-
 preproc.h: preproc.c ;
 preproc.c: BISONFLAGS += -d
 
@@ -54,7 +51,7 @@ preproc.y: ../../../backend/parser/gram.y parse.pl ecpg.addons ecpg.header ecpg.
 	$(PERL) $(srcdir)/parse.pl $(srcdir) < $< > $@
 	$(PERL) $(srcdir)/check_rules.pl $(srcdir) $<
 
-ecpg_keywords.o c_keywords.o keywords.o preproc.o parser.o: preproc.h
+ecpg_keywords.o c_keywords.o keywords.o preproc.o pgc.o parser.o: preproc.h
 
 kwlookup.c: % : $(top_srcdir)/src/backend/parser/%
 	rm -f $@ && $(LN_S) $< .

src/interfaces/ecpg/preproc/ecpg.trailer

@@ -1917,11 +1917,3 @@ void parser_init(void)
 {
  /* This function is empty. It only exists for compatibility with the backend parser right now. */
 }
-
-/*
- * Must undefine base_yylex before including pgc.c, since we want it
- * to create the function base_yylex not filtered_base_yylex.
- */
-#undef base_yylex
-
-#include "pgc.c"

src/interfaces/ecpg/preproc/pgc.l

@@ -1,4 +1,4 @@
-%{
+%top{
 /*-------------------------------------------------------------------------
  *
  * pgc.l
@@ -23,7 +23,19 @@
 #include <limits.h>
 
 #include "extern.h"
+#include "preproc.h"
 
+/*
+ * Change symbol names as expected by preproc.y.  It'd be better to do this
+ * with %option prefix="base_yy", but that affects some other names that
+ * various files expect *not* to be prefixed with "base_".  Cleaning it up
+ * is not worth the trouble right now.
+ */
+#define yylex           base_yylex
+#define yylval          base_yylval
+}
+
+%{
 extern YYSTYPE yylval;
 
 static int		xcdepth = 0;	/* depth of nesting in slash-star comments */