I have the following source files:
% ls
data_lexicon.c data_lexicon.h lex.l makefile
And the following makefile:
% cat makefile
CC = cc
CFLAGS = -Wall -std=c89
LDFLAGS = -ll
OBJFILES = lex.o data_lexicon.o
TARGET = lexical_analyzer_1
all: $(TARGET) lex.c
lex.c: lex.l data_lexicon.h
lex -olex.c lex.l
$(TARGET): $(OBJFILES)
$(CC) $(CFLAGS) -o $(TARGET) $(OBJFILES) $(LDFLAGS)
clean:
rm -f $(OBJFILES) lex.c $(TARGET)
If I do make all I get:
% ls
data_lexicon.c data_lexicon.o lex.l
lexical_analyzer_1 data_lexicon.h lex.c
lex.o makefile
So far so good.
However, I would like to move the source files (data_lexicon.c, data_lexicon.h, lex.l) to a folder src and generate the intermediate files (data_lexicon.o lex.c, lex.o) into a obj folder.
I create both folders but I do not understand how the makefile file shall be configured.
I am using FreeBSD make, so the more portable the solution given the better.
However, I would like to move the source files (data_lexicon.c,
data_lexicon.h, lex.l) to a folder src and generate the intermediate
files (data_lexicon.o lex.c, lex.o) into a obj folder.
It never ceases to amaze me how people insist on making extra work for themselves. You can certainly do what you describe, but it will require writing explicit rules for the object files.
First of all, however, you need to understand that make itself doesn't really know anything about directories. (Traditional make doesn't, anyway. GNU make and perhaps others know a little about them.) That is, it doesn't have any sense of varying directories against which it resolves file names. Rather, every target name is resolved against make's working directory. If you want to refer to something in a subdirectory, then you must say so. To begin with:
OBJFILES = obj/lex.o obj/data_lexicon.o
Similar goes for target and prerequisite names in rules:
obj/lex.c: src/lex.l src/data_lexicon.h
lex -o$# src/lex.l
That's also one reason to favor make's automatic variables, such as the $# in the above rule representing the name of the target being built.
Your makefile presently relies on make's built-in rule for building object files from corresponding C source files, but "corresponding" means target and prerequisite names are identical, including any path components, except for the suffixes (.c vs .o). You will no longer have that correspondence for data_lexicon.o, so you will need to write an explicit rule for it building it. This part is left as an exercise.
Related
I'm struggling with the correct syntax of a makefile.
This is my folder structure:
project
│ Makefile
│ HERE SHOULD BE THE OUT FILE AFTER make command
│
└───include
│ header.h
│
│
└───src
function1.c
function2.c
How must the makefile look to ensure correct results?
This is my current makefile:
SOURCES = src/function.c src/function.c src/function.c
OBJECTS = $(SOURCES:.c=.o)
CC = cc
RM = rm -f
CFLAGS = -Wall -Wextra -Werror
NAME = output.a
all: $(NAME)
$(NAME):
$(CC) $(CFLAGS) -c $(SOURCES)
ar rcs $(NAME) $(OBJECTS)
clean:
$(RM) $(OBJECTS)
fclean: clean
$(RM) $(NAME)
re: fclean $(NAME)
my current output if i run make all:
cc -Wall -Wextra -Werror -c src/function1.c src/function2.c
ar rcs output.a src/function1.o src/function2.o src/function1.o
ar: src/function1.o: No such file or directory
make: *** [Makefile:15: output.a] Error 1
if i run make flcean the output looks the following:
rm -f src/function1.o src/function2.o
rm -f output.a
So it doesn´t remove anything because the .o files are stored in the root, not the /src subdirectory
I'm struggling with the correct syntax of a makefile.
Your makefile syntax is fine. In fact, your makefile is syntactically valid and reasonably well structured. It looks a lot better than many of the ones we see around here.
I guess what you're actually struggling with is that it doesn't work, even after you fix the weird disagreement between the source file list in the makefile itself and the actual source files on disk. But "doesn't work" is a pretty vague, though lamentably common, description. You would get better help, faster, by saying something along the lines of "the .o files are created in the top-level directory instead of in the src/ directory." (Which is exactly what I expect to happen, and as a result, the ar command will fail, and the clean target will not clean the .o files.)
You need to understand that make itself doesn't know much about building software. What it knows is how to match rules to patterns so as to execute associated recipes of shell commands. The particular kinds of patterns it matches and the built-in rules that come with it are oriented toward building software, but you can't expect it to go very far with anticipating what you mean. It, like any other computer program, will happily do what you say, instead, when that differs. In this case, it just runs the cc command with the arguments you specify, and cc will choose under those circumstances to put the .o files in the working directory.
From a stylistic and best-practices standpoint, it's best to write rules that build only their target file, unlike your rule for $(NAME) that attempts to build not just $(NAME) but also all the component object files. The object files would be better built according to their own rule or rules. Making the object files prerequisites of the rule for $(NAME) will ensure that they get built when needed. That will also allow for them to not be built when that is not needed. That variation on your rule would look like this:
$(NAME): $(OBJECTS)
ar rcs $# $^
Note also that in the recipe, I have substituted automatic variable $# for a repetition of the rule target name. That's good form, but not obligatory. I have also substituted automatic variable $^ for a repetition of the prerequisite list. That's less clear-cut, in part because $^ is specific to GNU make, but if you're ok with that dependency then it's a great way to avoid repeating yourself.
Now, about building the object files: you could write a pattern rule (GNU make only) or a suffix rule that builds an object file from a corresponding C source file, or you could even write a separate rule for each object file. But you don't actually need to do that. make comes with a built in rule that will serve your needs in that area just fine, so your best bet may be to not attempt to provide your own rule for that at all. That is: modifying the rule for $(NAME) as suggested above should be sufficient for successful building, supposing, again, that the contents of your SOURCES variable accurately reflect the source files you want to build.
I have a makefile that looks like this
CC=gcc
CFLAGS=-pedantic -ansi -Wall -O2
TARGET=assembler
SUBDIRS = utils preprocessor parser symbols
.PHONY: clean all subdirs $(SUBDIRS)
subdirs: $(SUBDIRS)
$(SUBDIRS):
$(MAKE) -C $#
all: subdirs
clean:
for dir in $(SUBDIRS); do \
$(MAKE) -C $$dir clean; \
done
And I want to add
$(TARGET): subdirs $(TARGET).c
$(CC) $(CFLAGS) $(TARGET).c -o $#
But then I get linking error because the objects files from the subdirs aren't found. Is there a way to pass all object files under the project root directory?
Is there a way to pass all object files under the project root directory?
Usage of the word "pass" suggests that you have altogether the wrong mental model of makefiles and make operation. Makefiles are specifications, not scripts, and the rules within are not functions and do not operate like functions. Among other things, the targets and prerequisites of explicit rules are determined when the makefile is parsed, not dynamically at the time of (consideration of) rule execution.
It follows that what you propose to do is altogether unworkable, because you cannot rely on any of the object files -- they being built files -- to exist when make starts. You have a chicken and egg problem.
I fully agree with #Andreas that using globbing and similar dynamic target or prerequisite detection in a makefile is bad.* Targets and prerequisites that are named at all should be named explicitly (not to preclude assigning them to a variable or using substitution references or similar). But if you nevertheless do use globbing or another form of dynamic detection to locate files, then you should be locating files distributed with the project, not built ones.
If you want to maintain the modularity of your recursive make build system (which is not by any means a clear win), then one reasonable alternative would be for the make in each subdirectory to build a static archive named after the directory name. The top-level makefile then does not need to know any of the details of the subdirectory makes; it just includes the static library resulting from each one in the link.
*There are multiple reasons for this, but they are tangential to the question at hand.
My project includes .c and .s (asm) files. I compile both types with 'gcc' and put output .o files to separate directory './bin'. To do that I'm using single makefile rule like this
bin/%.o: %.[cs]
$(CC) $(CFLAGS) -o $# -c $<
(As far as I understand, using square brackets wildcard in such context is a little bit unconventional, but it's working and it looks neat, so...)
The other day I decided to move some of my .c files to dedicated directory './common', so I added
vpath %.c common
at the beginning of the makefile. And now each time I try to 'make', it stops and throws an error on a file I had moved. For example, for 'common/foo.c' I get
"*** No rule to make target bin/foo.o, needed by..."
as if I haven't specified 'vpath'. But when I modify the rule to compile only .c files
bin/%.o: %.c
... ...
magically it starts to operate properly again and checks './common' for sources.
Looks like 'vpath' mechanism and wildcards can not work together, but I'm still new to 'make' and eager to learn what's the exact reason of such behavior. Any ideas anyone? Thanks in advance.
(Tested with make–3.81 and make–4.1.)
UPD: Having all the files and 'bin' directory reside on the same level like so
|-bin/
|-foo.c
|-bar.s
|-baz.c
|-Makefile
here's MWE
ROOTS = foo.o bar.o
OBJS = baz.o
SS = $(addprefix bin/,$(ROOTS) $(OBJS))
all: ff.out
ff.out: $(SS)
ld -o $# $^
bin/%.o: %.[cs]
gcc -o $# -c $<
Now if I move, say, 'foo.c' to separate directory and specify 'vpath', build stops with "No rule to make target bin/foo.o, needed by ff.out".
I suggest careful reading of How Not to Use VPATH as you seem to be at Step Three of that by having the OBJDIR in some places but not others.
To be explict, using a static pattern rule doesn't get you away from needing either at least one rule per source directory, or at least one make invocation per source directory. So, the simple answer is add a new rule for the new common/ directory that's the same as the other one:
bin/%.o: common/%.[cs]
gcc -o $# -c $<
There are lots of more comprehensive, but complex, answers, see the followon article for some of them.
For simple projects, there is no reason not to just track what directories you have in your main Makefile by adding extra rules. Also, there's a reasonable case for not having that bin/ dir and splitting .o and .out locations. Distributors and others expect to be able to control where files are created running from a seperate directory anyway.
I've thrown up a git repo with branches based on your cut down example that may clarify things.
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.
I have a C project that consists of a fairly large number of source files, and to make some sense of them, I have put them into subdirectories (with subdirectories). The whole project results in only one executable file, however.
In order to build this project, then, I am using recursive Makefiles, where the Makefile in each non-toplevel directory links all the object files produced in that directory into a concatenated lib.o file (using ld -r, that is). I do have a Makefile system that can build this and works rather fine for what it is, but it cannot support parallel make, which I would like to fix.
The problem is that I cannot figure out a proper way to both force make to descend into each directory's subdirectories, but also have the local lib.o target depend on that without being forced to rebuild even when nothing has changed.
This is how it works, somewhat abbreviated (leaving out CFLAGS and whatnot):
default: build
SUBOBJECTS = $(patsubst %,%/lib.o,$(SUBDIRS))
.PHONY: $(SUBDIRS)
$(SUBDIRS):
#$(MAKE) -C $#
build: $(SUBDIRS) lib.o
lib.o: $(OBJECTS) $(SUBOBJECTS)
$(LD) $(LDFLAGS) -r -o $# $^
This is from a Makefile.common which all other Makefiles include. Every other Makefile would also define their own SUBDIRS and OBJECTS. It might look like this, for instance:
SUBDIRS = dir1 dir2
OBJECTS = object1.o object2.o
include ../Makefile.common # Or ../../Makefile.common, &c.
As you can see from this, the main target is really the build target, which depends on the subdirectories and lib.o. If I invoke parallel make on this, it won't know that lib.o cannot be built until make has already run recursively on the subdirectories and will sometimes attempt that, causing errors. However, if I make lib.o depend on the subdirectories, then lib.o will always be unnecessarily rebuilt on each invocation, in each directory.
Is there a way to solve this? I've wrecked my brains on this for quite a while now without being able to find a way out. I'm only using GNU make, so don't worry too much about being POSIX-compatible.