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

3 files changed, 15 insertions, 14 deletions

diff --git a/src/interfaces/ecpg/preproc/Makefile b/src/interfaces/ecpg/preproc/Makefile
index 1ecc4053dae..00f14c69c5b 100644
--- a/src/interfaces/ecpg/preproc/Makefile
+++ b/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) $< .
diff --git a/src/interfaces/ecpg/preproc/ecpg.trailer b/src/interfaces/ecpg/preproc/ecpg.trailer
index 16359a309b7..de0df7440f0 100644
--- a/src/interfaces/ecpg/preproc/ecpg.trailer
+++ b/src/interfaces/ecpg/preproc/ecpg.trailer
@@ -1916,11 +1916,3 @@ 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"
diff --git a/src/interfaces/ecpg/preproc/pgc.l b/src/interfaces/ecpg/preproc/pgc.l
index 0453409d373..e9a7859cc0f 100644
--- a/src/interfaces/ecpg/preproc/pgc.l
+++ b/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 */