Makefile.in: fix occasional parallel build failures around bison rule (#1167)

trofi · web-flow · commit 46cfbf313d81 · 2024-11-04T13:26:05.000+01:00
Without the change `make -j16 --shuffle` occasinally fails to build as: $ make -j16 --shuffle ... bison -y -d -o util/configparser.c ./util/configparser.y ... /libtool --tag=CC --mode=compile gcc -I. -I...-openssl-3.3.2-dev/include -I...-libevent-2.1.12-dev/include -I...-expat-2.6.3-dev/include -DSRCDIR=. -g -O2 -flto -fPIE -pthread -o configparser.lo -c util/configparser.c ... util/configparser.c:755:3: error: expected ',' or '}' at end of input 755 | YYSYMBOL_server_low_rtt = 626, /* server_low_rtt */ | ^ The build failure happens due to this `Makefile.in` rule: util/configparser.c util/configparser.h: $(srcdir)/util/configparser.y @-if test ! -d util; then $(INSTALL) -d util; fi $(YACC) -d -o util/configparser.c $(srcdir)/util/configparser.y For GNU make that means that each of the targets will attempt the rule execution when the file is missing: one for .c file and another for .h file: https://www.gnu.org/software/make/manual/html_node/Multiple-Targets.html The workaround is to only run $(YACC) for .c target and use .c as a pre-requisite for an .h file. Before the change the build fails about every 10-th run. After the change no build failures after 100 successful builds.
diff --git a/Makefile.in b/Makefile.in
@@ -509,10 +509,15 @@ util/configlexer.c:  $(srcdir)/util/configlexer.lex util/configparser.h
 	fi
 	@if test ! -f $@; then echo "No $@ : need flex and bison to compile from source repository"; exit 1; fi
 
-util/configparser.c util/configparser.h:  $(srcdir)/util/configparser.y
+# Builds both util/configparser.c and util/configparser.h.
+# To avoid double-building we split one target out.
+util/configparser.c:  $(srcdir)/util/configparser.y
 	@-if test ! -d util; then $(INSTALL) -d util; fi
 	$(YACC) -d -o util/configparser.c $(srcdir)/util/configparser.y
 
+util/configparser.h: util/configparser.c
+	touch $@
+
 clean:
 	rm -f *.o *.d *.lo *~ tags
 	rm -f unbound$(EXEEXT) unbound-checkconf$(EXEEXT) unbound-host$(EXEEXT) unbound-control$(EXEEXT) unbound-anchor$(EXEEXT) unbound-control-setup libunbound.la unbound.h
