parse-datetime: Avoid warnings from bison versions >= 3.3.

Reported by Bernhard Voelker <mail@bernhard-voelker.de>.

* modules/parse-datetime (Makefile.am): Don't pass option '-y' to bison.

ChangeLog

@@ -1,3 +1,9 @@
+2019-07-19  Bruno Haible  <bruno@clisp.org>
+
+	parse-datetime: Avoid warnings from bison versions >= 3.3.
+	Reported by Bernhard Voelker <mail@bernhard-voelker.de>.
+	* modules/parse-datetime (Makefile.am): Don't pass option '-y' to bison.
+
 2019-07-19  Bruno Haible  <bruno@clisp.org>
 
 	parse-datetime: Require Bison 2.4 or newer.

modules/parse-datetime

@@ -30,22 +30,26 @@ configure.ac:
 gl_PARSE_DATETIME
 
 Makefile.am:
-# This rule overrides the Automake generated .y.c rule, to ensure that the
-# parse-datetime.c file gets generated in the source directory, not in the
-# build directory.
+# The Automake generated .y.c rule is broken: When executed in a VPATH build,
+#   - The .c file gets generated in the build directory. But since it requires
+#     special tools to rebuild it, we need to distribute it in the tarballs,
+#     and by the GNU Coding Standards
+#     <https://www.gnu.org/prep/standards/html_node/Makefile-Basics.html>
+#     the file should be generated in the source directory.
+#   - The #line numbers in the .c file refer to a nonexistent file once it
+#     has been moved from the build directory to the source directory. This
+#     leads to error if 'lcov' is used later.
+# Additionally, here we assume GNU Bison and therefore don't need the ylwrap
+# script.
+# Therefore we override this rule.
 parse-datetime.c: parse-datetime.y
-	$(AM_V_GEN)$(SHELL) $(YLWRAP) $(srcdir)/parse-datetime.y \
-	                              y.tab.c parse-datetime.c \
-	                              y.tab.h parse-datetime.h \
-	                              y.output parse-datetime.output \
-	                              -- $(PARSE_DATETIME_BISON) -y -d $(YFLAGS) $(AM_YFLAGS) && \
-	sed -e 's|".*/parse-datetime.y"|"parse-datetime.y"|' \
-	 < parse-datetime.c > parse-datetime.c-t && \
-	rm -f parse-datetime.c && \
-	mv parse-datetime.c-t $(srcdir)/parse-datetime.c
+	$(AM_V_YACC)$(PARSE_DATETIME_BISON) -d $(YFLAGS) $(AM_YFLAGS) $(srcdir)/parse-datetime.y \
+	&& sed -e 's|".*/parse-datetime.y"|"parse-datetime.y"|' < parse-datetime.tab.c > parse-datetime.c-t \
+	&& rm -f parse-datetime.tab.c parse-datetime.tab.h \
+	&& mv parse-datetime.c-t $(srcdir)/parse-datetime.c
 lib_SOURCES += parse-datetime.y
 BUILT_SOURCES += parse-datetime.c
-MOSTLYCLEANFILES += parse-datetime.c-t
+MOSTLYCLEANFILES += parse-datetime.tab.c parse-datetime.tab.h parse-datetime.c-t
 MAINTAINERCLEANFILES += parse-datetime.c
 EXTRA_DIST += parse-datetime.c