Makefile: rebuild target if its source changes - makefile

I've got this Makefile in a PHP project (this is trimmed down from the full Makefile). How can I change this so automake detects that public/assets/styles/main.scss has changed & re-run sass?
all: public/assets/styles/styles.css
public/assets/styles/styles.css:
sass public/assets/styles/main.scss > public/assets/styles/styles.css

Simply make the .scss file a prerequisite of your .css target. As a bonus, avoid repetition of your base path and use automatic variables to make the recipe less redundant:
STYLEDIR := public/assets/styles
all: $(STYLEDIR)/styles.css
$(STYLEDIR)/styles.css: $(STYLEDIR)/main.scss
sass $< > $#

Related

makefile ignore removed file names

A directory with css files in it and for each file in the directory I want a separate minified .min.css file in the same directory.
So for example my.css get minified into my.min.css in the same directory.
First I tried
css/*.css:
uglifycss $# > $(subst .css,.min.css,$#)
make -B yeaaa victorie its working :D
But after doing make -B again I get a new separate file each time resulting in my.min.css my.min.min.css my.min.min.min.css
Then I tried
.PHONY: clean
css/*.css: clean
uglifycss $# > $(subst .css,.min.css,$#)
clean:
-rm css/*.min.css
DOH! after clean it is still remembering the files it deleted in the first place resulting again in a my.min.min.min.css file
How can I tell make to stop doing my.min.min.min.css?
(make: GNU Make 3.81 OSX)
First get a list of all files with the suffix .css:
ALL := $(wildcard *.css)
then remove files that have the suffix .me.css:
NEW := $(filter-out %.me.css,$(ALL))
and add the suffix to remaining files:
ME := $(patsubst %.css,%.me.css,$(NEW))
Then you add those files as prerequisites to the default target, and add you own recipe that builds those files, in this case a simple echo:
%.me.css:
echo 123 > $#
default: $(ME)
Compared to your approach, this has the benefit that you don't have to use the flag -B, as only the files that need to be built are built. Therefore invoking make is done by simply caling make without any targets or flags (assuming the makefile is named makefile or Makefile):
make

Percentage used in the Makefile rule that aims at renaming all .c files

I think percentage in Makefile means wildcard. As a try, I test a contrive Makefile that aims at changing any .c file to 'hi'. This is my Makefile rule:
%.c:
mv $# hi
I save the file above to 'Makefile', and then type in the terminal
touch hello.c
make
The terminal says
make: `hello.c' is up to date.
which is certainly not what I wanted. Two naive questions:
a) Why does makefile determine that 'hello.c' is actually "up to date"?
b) How can we enforce the rule to be applied anyway?
You have not defined any dependencies in your rule. The hello.c already exists and none of the dependencies have newer timestamp than hello.c.
There are rules with no dependencies like clean. In this case the file clean does not exist and make tries to create it by executing the rule's set of commands. However, as mentioned in GNU make documentation this will not work in the case where clean file is created. The solution on this is to define clean as "Phony Target".
Additionally the output of the command is file hi and not %.c
The Makefile should look like:
%.hi : %.c
mv $< $#

Directory independent target in Makefile

I'm trying to make a rule that will generate files regarding their names but regardless of the directory.
I'm starting from this makefile (see a previous question of mine):
TARGETS:=$(patsubst %_tpl,%,$(wildcard *_tpl))
.PHONY: all
all: $(TARGETS)
.SECONDEXPANSION:
$(TARGETS): %: $$(wildcard %*_tpl)
./generate $#_tpl > $#
With this, I can do, for instance, make foo.xml. It looks if a set of foo.xml*_tpl files are there, consider them as prerequisites and call the generate script to generate the target.
What I would like to do is, for example, make ../ressources/foo.xml and have make use the rule to create foo.xml but creating it in the ../ressources/ directory, without having to explicitely specify this directory in the makefile.
What I have tried for the moment is adding this to the Makefile:
../ressources/%: $(notdir %)
mv $< $#
Which works, but I would like to avoid creating the file in the current directory before moving it to the destination folder. I would also like not having to specify the possible destination folders in the makefile (but this is less important).
But first of all, does this make any sense? Or is what I want to do just conceptually wrong?
EDIT: Some precisions regarding the _tpl files and the generate script to avoid confusions:
Each target has a main template ($#_tpl) that includes others ($#-part1_tpl, $#-part2_tpl...) and the generate script only takes the main template as argument. The templates are written with Jinja2 (the subparts included with the {% include %} jinja directive).
If you always want the targets in another directory, just say so.
TARGETS:=$(patsubst %_tpl,../resources/%,$(wildcard *_tpl))
.PHONY: all
all: $(TARGETS)
.SECONDEXPANSION:
$(TARGETS): ../resources/%: $$(wildcard %*_tpl)
./generate $#_tpl > $#
I'm not sure if you should have generate $^ >$# instead; superficially, this would make more sense.
If there are multiple *_tpl files for each target (i.e. there are more tpl files than xml files), the TARGETS definition isn't really correct; but we don't have enough information to actually fix it.
On the other hand, if the target directory can change a lot, the sane way forward might be to cd into the target directory and use make -f ../path/to/Makefile -- just make sure your VPATH is set up so that the source files can be found.

makefile conditionals

Note: using MinGW's make (should be GNU make)
i have a couple of -include statements in my makefile to import dependencies which were generated using g++ -MM. However I would like to only do this when necessary. I have several different build targets and I don't want all of their respective dependency files to be included since this takes a while (suppose I'm running make clean: no need to include them in this case)
Here's the format of my makefile.
DEPS_debug = $(patsubst %.cpp,build_debug/%.d,$(SRC))
OBJ_debug = $(patsubst %.cpp,build_debug/%.o,$(SRC))
all: program_debug
-include $(DEPS_debug) #make: include: Command not found
program_debug: $(OBJ_debug)
$(CC) $(CFLAGS) $(OBJ_debug) -o $#
If you really don't want to include those files needlessly, you have a couple of options:
You can put in a conditional as Diego Sevilla suggests (but I would recommend using MAKECMDGOALS so that you can write a more flexible version, specific to targets, e.g. you'll include foo.d if and only if you're making foo.o).
You can use make recursively (heresy!), invoking $(MAKE) for each target object, using a makefile that includes that target's dependencies.
But actually including the file takes negligible time, it's the rebuilding of the file (automatic for any included file that's out of date) that takes time.
If needless rebuilding is what you want to avoid, you can use a very clever trick. When must foo.d be rebuilt? Only when something about foo has changed. But in that case foo.o must also be rebuilt. So don't have a seperate rule for foo.d, just rebuild it as a side effect of making foo.o. That way you can include all dependency files and not waste time rebuilding them if they aren't needed.
EDIT:
I'm astounded that merely including these files can add 2-3 seconds to make clean. My last paragraph is off the mark, so let me expand on the first two options.
If all is the only target for which these files should be included, and you make all from the command line (and not e.g. make all tests tarball install kitchenSink), then this will do it:
ifeq ($(MAKECMDGOALS),all)
-include $(DEPS_debug)
endif
Note that this will not include foo.d if you make foo.o. You can write a more sophisticated conditional, something like
$(foreach targ,$(MAKECMDGOALS),$(eval $(call include_deps $(targ)))...
but that's pretty advanced, so let's get a simple version working first.
If you'd rather avoid the conditional and use recursive Make, the simplest way is to split the makefile in two:
makefile:
all:
$(MAKE) -f makefile.all
clean:
rm whatever
...other rules
makefile.all:
DEPS_debug = $(patsubst %.cpp,build_debug/%.d,$(SRC))
OBJ_debug = $(patsubst %.cpp,build_debug/%.o,$(SRC))
-include $(DEPS_debug)
all: program_debug
program_debug: $(OBJ_debug)
$(CC) $(CFLAGS) $(OBJ_debug) -o $#
Indenting a line by a TAB makes make think it's a command to be passed to the shell (as you found out). It doesn't work that way.
The - in front of include suppresses errors that might result from DEPS_debug not existing (e.g. when running clean or release without having had a dependency-file-generating call first). Since DEPS_debug is not a dependency of those rules (clean / release), your dependency files do not get generated when you call them, and everything is fine. I don't really see the problem you're having - you don't have to make the include conditional.
Perhaps you'd like to change your approach, though. Instead of having a seperate *.d target, with a seperate -M preprocessor pass, you might want to try something like -MMD -MP which generates the dependency files inline during code generation, in your standard *.c -> *.o pass.
(I know this sounds completely wrong at first, but when you think about it, it makes sense. Makefile logic is a bit backwards that way, unless you're familiar with functional programming.)
includes are independent of the rules, as they are makefile indications, not compilation indications. You can, however, use makefile conditionals based on special makefile variables such as MAKECMDGOALS, that is set to the default goal:
ifeq ($(MAKECMDGOALS),all)
-include whatever
endif
This is included when no default goal is specified. You can change the condition to specify the exact goal you want to check to include other sub-makefiles.

making all rules depend on the Makefile itself

When I change a Makefile, its rules may have changed, so they should be reevaluated, but make doesn't seem to think so.
Is there any way to say, in a Makefile, that all of its targets, no matter which, depend on the Makefile itself?
(Regardless of its name.)
I'm using GNU make.
This looks like one more simple, useful, logical thing that Make should be able to do, but isn't.
Here is a workaround. If the clean rule is set up correctly, Make can execute it whenever the makefile has been altered, using an empty dummy file as a marker.
-include dummy
dummy: Makefile
#touch $#
#$(MAKE) -s clean
This will work for most targets, that is targets that are actual files and that are removed by clean, and any targets that depend on them. Side-effect targets and some PHONY targets will slip through the net.
Since GNU make version 4.3 it is now possible with the use of those two special variable:
.EXTRA_PREREQS
To add new prerequisite to every target
MAKEFILE_LIST
To get the path of the make file
To have every target depend on the current make file:
Put near the top of the file (before any include since it would affect the MAKEFILE_LIST) the following line:
.EXTRA_PREREQS:= $(abspath $(lastword $(MAKEFILE_LIST)))
To have every target depend on the current make file and also the make files which were included
Put the following line at the end of your file:
.EXTRA_PREREQS+=$(foreach mk, ${MAKEFILE_LIST},$(abspath ${mk}))
The only answer I know to this is to add makefile explicitly to the dependencies. For example,
%.o: %.c makefile
$(CC) $(CFLAGS) -c $<

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