Created attachment 17294 [details] [review]
fontconfig-2.6.0-parallel.patch

We've receive a bug report about build failure of fontconfig during parallel build:

https://bugs.gentoo.org/show_bug.cgi?id=225079

To explain the problem let me first show you fc-case/Makefile.am sniplet:

TARG=fccase.h

noinst_PROGRAMS=fc-case

fc_case_SRCS= \
        fc-case.c \
        fccaseint.h \
        fccaseread.c

$(TARG): $(STMPL) fc-case$(EXEEXT) $(SCASEFOLDING)
        rm -f $(TARG)
        ./fc-case$(EXEEXT) $(SCASEFOLDING) < $(STMPL) > $(TARG)

ALIAS_FILES = fcalias.h fcaliastail.h

BUILT_SOURCES = $(ALIAS_FILES) $(TARG)

$(ALIAS_FILES):
        touch $(ALIAS_FILES)


In some cases (when touch works slower then other things) rebuilt of fccase.h
($(TARG) in BUILT_SOURCES) starts rebuild of fc-case earlier then touch
finishes and thus the error. This bug is reproducible with make -j N where N
>= 3 (as fccase.h is third in BUILT_SOURCES). To reproduce it even better just
add 'sleep 2' before touch $(ALIAS_FILES) and call make -j3 in fc-case
directory. Suggested patch to fix the issue is in attachment.