I've got a make file that generates multiple targets. Something like:
target-a: target-a.src target-include.src
#$(BUILD_TOOL) -f $< -o $#
target-b: target-b.src target-include.src
#$(BUILD_TOOL) -f $< -o $#
target-c: target-c.src target-include.src
#$(BUILD_TOOL) -f $< -o $#
The actual build process (abbreviated as $(BUILD_TOOL) above) is a multiple line thing involving compilers, scripts and various whatnot, but suffice to say, the build process acts on the first target dependency ($<) and produces the output target ($#).
This is quite unwieldly. Would what I've got below be considered a safe way to replace the above (using a pattern rule that doesn't have a suffix)?
all: target-a target-b target-c
% : %.src target-include.src
#$(BUILD_TOOL) -f $< -o $#
The make tool is GNU, and I'm content to use it's powerful extensions.
If target is a literal string, renierpost's solution is very good. If it isn't (or even if it is) this will work:
TARGETS := target-a target-b target-c
all: $(TARGETS)
$(TARGETS): % : %.src target-include.src
#$(BUILD_TOOL) -f $< -o $#
Note that this rule will not build targets you did not intend, not even target-include.
It depends on the rest of your Makefile, but in principle this should work,
if all files are in one directory.
It's better practice to use extensions on your targets.
Is target a literal string? In that case, you can be more specific
(and speed up rule application a tiny little bit, but it's fast already) by using
all: target-a target-b target-c
target-% : target-%.src target-include.src
#$(BUILD_TOOL) -f $< -o $#
GNU make's advanced syntax will come into play if you want to automatically deduce the names of target-a target-b target-c from the target-*.src filenames on the filesystem or something similar.
Related
With explicit targets I can combine several rules like
foo.o bar.o: $(SOURCES)
cc $< -o $#
This is equivalent of
foo.o: $(SOURCES)
cc $< -o $#
bar.o: $(SOURCES)
cc $< -o $#
But I want to use pattern rules.
I have several troff documents (man, README) and I want to generate .html and .ascii files.
Naive approach is
GROFF := groff
DOCS := man README
DOC_FILES = $(foreach doc,$(DOCS),$(doc).html $(doc).ascii)
CALL_GROFF = $(GROFF) -T$(subst $*.,,$#) -mman $< > $#
%.html %.ascii: %.doc
$(CALL_GROFF)
.DEFAULT: all
all: $(DOC_FILES)
.PHONY: clean
clean:
rm $(DOC_FILES)
But it doesn't work, because make believes that all files are created with one command (much like & in modern make: https://www.gnu.org/software/make/manual/html_node/Multiple-Targets.html)
Obviously I can do
GROFF := groff
DOCS := man README
DOC_FILES = $(foreach doc,$(DOCS),$(doc).html $(doc).ascii)
CALL_GROFF = $(GROFF) -T$(subst $*.,,$#) -mman $< > $#
%.ascii: %.doc
$(CALL_GROFF)
%.html: %.doc
$(CALL_GROFF)
.DEFAULT: all
all: $(DOC_FILES)
.PHONY: clean
clean:
rm $(DOC_FILES)
But it is a kind of copy-paste.
Could it be solved with GNU make?
This is exactly how this works; it's a long-standing feature. From the documentation:
Pattern rules may have more than one target; however, every target must contain a % character. Pattern rules are always treated as grouped targets (see Multiple Targets in a Rule) regardless of whether they use the : or &: separator.
As example states, it was meant to deal with programs that generate more than one output in one invocation, like bison. You can either update your recipe to generate both files in one shot, or keep the rules separated as you do now.
I have a series of directories organized like this:
foo/
foo.file1 foo.file2
bar/
bar.file1 bar.file2
baz/
baz.file1 baz.file2
Right now I'm processing these files using a script that does all the checking for file existence etc but I thought that perhaps I could use a Makefile for it (since said script is very fragile), to avoid reprocessing files that did not change.
The problem is that each directory is independent, and I'd need to do, for example:
foo.file1.processed: foo.file1
run_random_program foo.file1 -o foo.file1.processed
for each of the 71 directories that are in total in that path. This looks like being extremely tedious and I wonder if there's something that would prevent me from writing all of this by hand.
Is such a thing possible?
EDIT: Some examples that show what I have in mind, had I a single Makefile for each directory:
file1.cds.callable: file1.callable
long_script_name -i $< -o $#
file1.rds: file1.cds.callable
another_long_script_name $< additional_file_in_folder $#
file1.csv: file1.rds
yet_another_script $< $#
Seems like pattern rules are exactly what you need:
# These are the original source files (based on the example)
CALLABLE := $(wildcard */*.callable)
# These are the final targets
TARGETS := $(CALLABLE:%.callable=%.csv)
all: $(TARGETS)
%.csv : %.rds
yet_another_script $< $#
%.rds: %.cds.callable
another_long_script_name $< additional_file_in_folder $#
%.cds.callable: %.callable
long_script_name -i $< -o $#
This is my first Makefile, and I am can't figure out some of the syntax used. The questions are marked below.
$(BUILD_DIR)/%.o: %.c $(BUILD_DIR)
$(CC) -c $(CFLAGS) -Wa,-a,-ad,-alms=$(BUILD_DIR)/$(notdir $(<:.c=.lst)) $< -o $#
What is the usage of "$(BUILD_DIR)" in the dependency?
What is the meaning of "$(BUILD_DIR)/$(notdir $(<:.c=.lst)) $< -o $#" in the role?
As with most computer languages the syntax of make cannot be clear if you don't know it. If you are using GNU make the GNU make manual is your friend. In the following explanations I will assume that BUILD_DIR = build and that one of the source files is bar/foo.c.
$(BUILD_DIR) in the list of prerequisites (dependencies) tells make that the build directory (in which object files are supposed to go) must exist before the recipe is executed; logical. There must be another rule somewhere to create the directory if it does not exist yet. Something like:
$(BUILD_DIR):
mkdir -p $#
But unless you forgot to copy an important character, this dependency is terribly sub-optimal. As the last modification time of a directory changes each time its content changes (files or sub-directories added or removed), it will force the re-compilation of all source files every time the directory changes, which is not what you want. A better dependency would be order-only:
$(BUILD_DIR)/%.o: %.c | $(BUILD_DIR)
that tells make to consider only the existence of $(BUILD_DIR), not its last modification time, when deciding to re-build or not.
$(BUILD_DIR)/$(notdir $(<:.c=.lst)) $< -o $# is just a combination of make automatic variables and functions.
$< and $# expand as the first prerequisite (bar/foo.c) and the target (build/bar/foo.o) respectively.
$(<:.c=.lst) replaces .c by .lst in $<: bar/foo.lst.
$(notdir $(<:.c=.lst)) removes the directory part: foo.lst.
All in all, for a bar/foo.c source file, and with BUILD_DIR = build, the pattern rule would be equivalent to:
build/bar/foo.o: bar/foo.c | build
$(CC) -c $(CFLAGS) -Wa,-a,-ad,-alms=build/foo.lst bar/foo.c -o build/bar/foo.o
Note that there are two different situations to consider:
All your source files are in the same directory as the Makefile (no bar/foo.c, just foo.c). Then you can simplify your recipe:
$(CC) -c $(CFLAGS) -Wa,-a,-ad,-alms=$(BUILD_DIR)/$(<:.c=.lst) $< -o $#
because the $(notdir...) is useless.
Your source files can be in sub-directories (bar/foo.c). Then you need the $(notdir...) in your recipe. But be warned that if you have two source files with the same base name (bar/foo.c and baz/foo.c) you will have a name conflict for $(BUILD_DIR)/foo.lst and your Makefile will not work as expected. Moreover, the order-only prerequisite of the rule should be equivalent to build/bar (or build/baz), not just build. And there should be a rule to create it if needed. If it is your case I suggest to change your pattern rule for:
$(BUILD_DIR)/%.o: %.c
mkdir -p $(dir $#)
$(CC) -c $(CFLAGS) -Wa,-a,-ad,-alms=$(BUILD_DIR)/$(notdir $(<:.c=.lst)) $< -o $#
There are other solutions (secondary expansion...) but there are a bit too complicated for this already too long answer.
I have created a Makefile to generate pdf and html for a md file mentioned while invoking make like make a.md should generate a.pdf and a.html, and should not convert other md files present in the directory.
My make file
But I am, getting error Nothing to be done for a.md
Could you please suggest changes?
Because a.md is already in place, make indeed does have nothing further to do. You can either just use for instance a as the specified target (which can depend on pdf and html files as prerequisites). Or pass the desired source through a variable and determine your desired target from that.
One (the latter) option would be this:
EXPORTED= $(SOURCE:%.md=%.html) $(SOURCE:%.md=%.pdf)
%.html : %.md
pandoc -o $# $<
%.pdf : %.md
pandoc -o $# $<
all: $(EXPORTED)
Which you can call with make SOURCE=a.md.
The other option (former):
%.html : %.md
pandoc -o $# $<
%.pdf : %.md
pandoc -o $# $<
.PHONY: $(MAKECMDGOALS)
$(MAKECMDGOALS): $(MAKECMDGOALS:%=%.html) $(MAKECMDGOALS:%=%.pdf)
Allows you to call make a.
But to reiterate. You cannot use (existing) source as a target, because make would (as it did) conclude it's done making that target.
Except (but I personally do not really like this as it is IMO confusing), if you insisted, you could do a variation on the previous take... but work with *.md targets... which you all declare as .PHONY. I.e. not real files and always to be considered/remade:
%.html : %.md
echo pandoc -o $# $<
%.pdf : %.md
echo pandoc -o $# $<
.PHONY: $(MAKECMDGOALS)
$(MAKECMDGOALS): $(MAKECMDGOALS:%.md=%.html) $(MAKECMDGOALS:%.md=%.pdf)
Now you could indeed call make a.md. I'd still prefer one of the two above.
When I compile large programs (like gcc or clang for example) there is a chance that my computer will overheat, and be forced to shut down.
I would like to resume the make process from where I left off. The problem seems to be that there are half completed/written .o files that are floating around that cause the rest of the built to break (this is especially bad when I specify -j 8)
Is there an easy way to get around this problem (whithout doing a make clean or make distclean or the like)?
Using GNU Make 3.81
Along the same lines as Beta's comment, but more reliable and less confusing IMO, would be to change your compile rule so that you compile to a temporary file, then at the end rename it to the real file. So where you might have something like:
%.o : %.c
$(CC) $(CFLAGS) $(CPPFLAGS) -o $# -c $<
instead you would use something like:
%.o : %.c
$(CC) $(CFLAGS) $(CPPFLAGS) -o $#.tmp -c $< \
&& mv -f $#.tmp $#
You may or may not want to add a "rm -f $#" as well.
As to whether you can make this change "programmatically" or not, it all dependes on your makefile and how it's structured. If it's a well-formed makefile then you can just make these changes in a few places in a few implicit rules, as above.