Build all Flex files standalone

The proposed Meson build system will need a way to ignore certain
generated files in order to coexist with the autoconf build system,
and C files generated by Flex which are #include'd into .y files make
this more difficult. In similar vein to 72b1e3a21, arrange for all Flex
C files to compile to their own .o targets.

Reviewed by Andres Freund

Discussion: https://www.postgresql.org/message-id/20220810171935.7k5zgnjwqzalzmtm%40awork3.anarazel.de
Discussion: https://www.postgresql.org/message-id/CAFBsxsF8Gc2StS3haXofshHCzqNMRXiSxvQEYGwnFsTmsdwNeg@mail.gmail.com

4 files changed, 22 insertions, 19 deletions

diff --git a/src/bin/pgbench/.gitignore b/src/bin/pgbench/.gitignore
index 983a3cd7a6..07492a993c 100644
--- a/src/bin/pgbench/.gitignore
+++ b/src/bin/pgbench/.gitignore
@@ -1,3 +1,4 @@
+/exprparse.h
 /exprparse.c
 /exprscan.c
 /pgbench
diff --git a/src/bin/pgbench/Makefile b/src/bin/pgbench/Makefile
index f402fe7b91..6647c9fe97 100644
--- a/src/bin/pgbench/Makefile
+++ b/src/bin/pgbench/Makefile
@@ -10,6 +10,7 @@ include $(top_builddir)/src/Makefile.global
 OBJS = \
 	$(WIN32RES) \
 	exprparse.o \
+	exprscan.o \
 	pgbench.o
 
 override CPPFLAGS := -I. -I$(srcdir) -I$(libpq_srcdir) $(CPPFLAGS)
@@ -26,8 +27,14 @@ all: pgbench
 pgbench: $(OBJS) | submake-libpq submake-libpgport submake-libpgfeutils
 	$(CC) $(CFLAGS) $^ $(LDFLAGS) $(LDFLAGS_EX) $(LIBS) -o $@$(X)
 
-# exprscan is compiled as part of exprparse
-exprparse.o: exprscan.c
+# See notes in src/backend/parser/Makefile about the following two rules
+exprparse.h: exprparse.c
+	touch $@
+
+exprparse.c: BISONFLAGS += -d
+
+# Force these dependencies to be known even without dependency info built:
+exprparse.o exprscan.o: exprparse.h
 
 distprep: exprparse.c exprscan.c
 
@@ -45,7 +52,7 @@ clean distclean:
 	rm -rf tmp_check
 
 maintainer-clean: distclean
-	rm -f exprparse.c exprscan.c
+	rm -f exprparse.h exprparse.c exprscan.c
 
 check:
 	$(prove_check)
diff --git a/src/bin/pgbench/exprparse.y b/src/bin/pgbench/exprparse.y
index b5592d4b97..ade2ecdaab 100644
--- a/src/bin/pgbench/exprparse.y
+++ b/src/bin/pgbench/exprparse.y
@@ -526,18 +526,3 @@ make_case(yyscan_t yyscanner, PgBenchExprList *when_then_list, PgBenchExpr *else
 					 find_func(yyscanner, "!case_end"),
 					 make_elist(else_part, when_then_list));
 }
-
-/*
- * exprscan.l is compiled as part of exprparse.y.  Currently, this is
- * unavoidable because exprparse does not create a .h file to export
- * its token symbols.  If these files ever grow large enough to be
- * worth compiling separately, that could be fixed; but for now it
- * seems like useless complication.
- */
-
-/* First, get rid of "#define yyscan_t" from pgbench.h */
-#undef yyscan_t
-/* ... and the yylval macro, which flex will have its own definition for */
-#undef yylval
-
-#include "exprscan.c"
diff --git a/src/bin/pgbench/exprscan.l b/src/bin/pgbench/exprscan.l
index 4f63818606..fe8e32838a 100644
--- a/src/bin/pgbench/exprscan.l
+++ b/src/bin/pgbench/exprscan.l
@@ -1,4 +1,4 @@
-%{
+%top{
 /*-------------------------------------------------------------------------
  *
  * exprscan.l
@@ -22,9 +22,19 @@
  *
  *-------------------------------------------------------------------------
  */
+#include "postgres_fe.h"
 
+/*
+ * NB: include exprparse.h only AFTER including pgbench.h, because pgbench.h
+ * contains definitions needed for YYSTYPE. Likewise, pgbench.h must come after
+ * psqlscan_int.h for yyscan_t.
+ */
 #include "fe_utils/psqlscan_int.h"
+#include "pgbench.h"
+#include "exprparse.h"
+}
 
+%{
 /* context information for reporting errors in expressions */
 static const char *expr_source = NULL;
 static int	expr_lineno = 0;