SPDX-FileCopyrightText: 2011 Antoine Pitrou <solipsis@pitrou.net>

SPDX-License-Identifier: PSF-2.0

Don't run pgen twice when using make -j
Don't ignore pgen error (on "make Parser/pgen.stamp")

diff --git a/Makefile.pre.in b/Makefile.pre.in
index 25a82aff01..03f85fd04b 100644
--- Makefile.pre.in
+++ Makefile.pre.in
@@ -471,10 +471,12 @@ Modules/getpath.o: $(srcdir)/Modules/getpath.c Makefile
 Modules/python.o: $(srcdir)/Modules/python.c
 	$(MAINCC) -c $(PY_CFLAGS) -o $@ $(srcdir)/Modules/python.c
 
-
-$(GRAMMAR_H) $(GRAMMAR_C): $(PGEN) $(GRAMMAR_INPUT)
+# Use a stamp file to prevent make -j invoking pgen twice
+$(GRAMMAR_H) $(GRAMMAR_C): Parser/pgen.stamp
+Parser/pgen.stamp: $(PGEN) $(GRAMMAR_INPUT)
 		-@ mkdir Include
-		-$(PGEN) $(GRAMMAR_INPUT) $(GRAMMAR_H) $(GRAMMAR_C)
+		$(PGEN) $(GRAMMAR_INPUT) $(GRAMMAR_H) $(GRAMMAR_C)
+		-touch Parser/pgen.stamp
 
 $(PGEN):	$(PGENOBJS)
 		$(CC) $(OPT) $(LDFLAGS) $(PGENOBJS) $(LIBS) -o $(PGEN)
@@ -1030,7 +1032,7 @@ clean: pycremoval
 
 clobber: clean
 	-rm -f $(BUILDPYTHON) $(PGEN) $(LIBRARY) $(LDLIBRARY) $(DLLLIBRARY) \
-		tags TAGS \
+		tags TAGS Parser/pgen.stamp \
 		config.cache config.log pyconfig.h Modules/config.c
 	-rm -rf build platform
 	-rm -rf $(PYTHONFRAMEWORKDIR)