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Makefile
Quick reference https://www.gnu.org/software/make/manual/html_node/Quick-Reference.html
one shell
.ONESHELL: foo : bar/lose cd $(<D) gobble $(<F) > ../$@
disable built-in rules
# Disable built-in rules and variables MAKEFLAGS += --no-builtin-rules MAKEFLAGS += --no-builtin-variables
VPATH
https://www.gnu.org/software/make/manual/html_node/General-Search.html
VPATH tells makefile where to search for prerequisities:
VPATH = .:$(OBJDIR):$(LIBDIR)
order only prereq
Special pipe “|” character is used. If any $(objects) has to be build, then obj has to be build first. But if obj is out of date or missing, this doesn't force $(objects) to built.
$(objects): | obj obj: @mkdir -p $@''
targets : normal-prerequisites | order-only-prerequisites
https://www.gnu.org/software/make/manual/html_node/Prerequisite-Types.html
double colon rules
https://www.chemie.fu-berlin.de/chemnet/use/info/make/make_4.html#SEC40
It can be useful, when target needs to be updated and command to update target depends on which prerequisite file caused the update.
all::
Another scenario is to find source .c file in different dirs
build/%.o:: test/%.c $(COMPILE) $(CFLAGS) $< -o $@ build/%.o:: src/%.c $(COMPILE) $(CFLAGS) $< -o $@ build/%.o:: lib/src/%.c lib/src/%.h $(COMPILE) $(CFLAGS) $< -o $@
- The same target can appear in more than one rule
- each rule is executed if target is older than any prerequisite of that rule
- if no prereq, command is always executed
- Order of execution is not guaranteed
Parallel make
Disabling parallel
For whole file:
.NOTPARALLEL:
For single target:
.NOTPARALLEL: %.a .NOTPARALLEL: foo.c bar.c