+
+GEN_SUBST = $(call quiet-command, \
+ sed -e "s!@libexecdir@!$(libexecdir)!g" < $< > $@, \
+ "GEN","$@")
+
+%.json: %.json.in
+ $(call GEN_SUBST)
+
+# Support for building multiple output files by atomically executing
+# a single rule which depends on several input files (so the rule
+# will be executed exactly once, not once per output file, and
+# not multiple times in parallel.) For more explanation see:
+# https://www.cmcrossroads.com/article/atomic-rules-gnu-make
+
+# Given a space-separated list of filenames, create the name of
+# a 'sentinel' file to use to indicate that they have been built.
+# We use fixed text on the end to avoid accidentally triggering
+# automatic pattern rules, and . on the start to make the file
+# not show up in ls output.
+sentinel = .$(subst $(SPACE),_,$(subst /,_,$1)).sentinel.
+
+# Define an atomic rule that builds multiple outputs from multiple inputs.
+# To use:
+# $(call atomic,out1 out2 ...,in1 in2 ...)
+# <TAB>rule to do the operation
+#
+# Make 4.3 will have native support for this, and you would be able
+# to instead write:
+# out1 out2 ... &: in1 in2 ...
+# <TAB>rule to do the operation
+#
+# The way this works is that it creates a make rule
+# "out1 out2 ... : sentinel-file ; @:" which says that the sentinel
+# depends on the dependencies, and the rule to do that is "do nothing".
+# Then we have a rule
+# "sentinel-file : in1 in2 ..."
+# whose commands start with "touch sentinel-file" and then continue
+# with the rule text provided by the user of this 'atomic' function.
+# The foreach... is there to delete the sentinel file if any of the
+# output files don't exist, so that we correctly rebuild in that situation.
+atomic = $(eval $1: $(call sentinel,$1) ; @:) \
+ $(call sentinel,$1) : $2 ; @touch $$@ \
+ $(foreach t,$1,$(if $(wildcard $t),,$(shell rm -f $(call sentinel,$1))))
+
+print-%:
+ @echo '$*=$($*)'