I know there are ways to remove duplicates $(CC) $(CFLAGS) $# $^ in Makefile. Can you tell me how to make the Makefile below more concise?
CC=gcc
CFLAGS=-pthread -g -o
all: p1 p2
p1: p1.c
$(CC) $(CFLAGS) $# $^
p2: p2.c
$(CC) $(CFLAGS) $# $^
To make your Makefile more concise, you can write it as follows.
CC=gcc
CFLAGS=-pthread -g -o
all: p1 p2
%: %.c
$(CC) $(CFLAGS) $# $^
Then you can add as many p's as you want on the all: line. As long as you provide pN.c, make will compile them into the corresponding pN.
Yes, you can combine commands "by prerequisite". For example:
CC=gcc
CFLAGS=-O3
INCLS=-I$(BASEDIR)/include
LIBS=$(BASEDIR)/lib/thread.a
OBJS = dotprod_mutex.o dotprod_serial.o
EXEC = dotprod
$(EXEC): $(OBJS)
$(CC) -o $(EXEC) $(OBJS) $(LIBS)
$(OBJS): dotprod.h
$(CC) $(CFLAGS) $(INCLS) -c $*.c
or somesuch -- you'll need to go through the details and make sure those libraries and so on actually make sense.
Note that the phrase $(OBJS): dotprod.h means that $(OBJS): depends on the presence of dotprod.h.
You will want to read the manual to get all the gory details, in particular:
Letting Make deduce commands
Combine by prerequisite
As for tools to automate this stuff, you want automake and autoconf: http://sourceware.org/autobook/
Related
I have multiple programs which share the same structure of compilation.
test_variance : test_variance.o
$(CPP) -o test_variance.exe $(CFLAGS) test_variance.o $(LIBDIR) $(LIBS)
test_variance_incremental: test_variance_incremental.o
$(CPP) -o test_variance_incremental.exe $(CFLAGS) test_variance_incremental.o $(LIBDIR) $(LIBS)
test_hyper: test_hyper.o
$(CPP) -o test_hyper.exe $(CFLAGS) test_hyper.o $(LIBDIR) $(LIBS)
test_hyper.o: test_hyper.cpp
$(CPP) $(CFLAGS) $(INCLUDES) -c test_hyper.cpp
test_variance_incremental.o: test_variance_incremental.cpp
$(CPP) $(CFLAGS) $(INCLUDES) -c test_variance_incremental.cpp
test_variance.o : test_variance.cpp
$(CPP) $(CFLAGS) $(INCLUDES) -c test_variance.cpp
So for compling .o, I can use the pattern
%.o: %.cpp
$(CPP) $(CFLAGS) $(INCLUDES) -c $<
I wonder if there is a general pattern for compling the executive. I've tried
TARGETS = test_variance test_variance_incremental test_hyper
$(TARGETS): $#.o
$(CPP) -o $#.exe $^ $(CFLAGS) $(LIBDIR) $(LIBS)
But Make tells me there is no input files and I think my usage of $# is wrong. Any advice?
You should use CC and CFLAGS for compiling C code, and CXX and CXXFLAGS for compiling C++ code. CPP (in make) is used for running the C preprocessor (only). The standard variable to hold libraries is LDLIBS.
If you use these variables then you don't even need to define your own rules at all: there are built-in rules in make that already know how to compile and link C++ programs. All you need is this:
TARGETS = test_variance test_variance_incremental test_hyper
all: $(TARGETS)
Anyway, if you want to write it explicitly you can write:
TARGETS = test_variance test_variance_incremental test_hyper
all: $(TARGETS)
% : %.o
$(CXX) -o $# $^ $(CXXFLAGS) $(LDFLAGS) $(LDLIBS)
(you should definitely not name the target test_variance, but then have your link line build test_variance.exe: the target name and the file that the recipe builds must always be the same).
I have the following Makefile:
VERSION = 0.1.1
CC = g++
CFLAGS = -Wall -g -DVERSION=\"$(VERSION)\"
LDFLAGS = -lm
DEPFILE = .dep
SOURCES := ${wildcard *.cpp}
HEADERS := ${wildcard *.h}
OBJECTS := ${SOURCES:.cpp=.o}
BINARY = main.exe
.PHONY: all dep clean
all: $(BINARY)
$(BINARY): $(DEPFILE) $(OBJECTS)
$(CC) $(CFLAGS) -o $(BINARY) $(OBJECTS) $(LDFLAGS)
%.o: %.cpp
$(CC) $(CFLAGS) -c $<
dep: $(DEPFILE)
$(DEPFILE): $(SOURCES) $(HEADERS)
$(CC) -MM $(SOURCES) > $(DEPFILE)
-include $(DEPFILE)
clean:
rm -vf $(BINARY) $(OBJECTS) $(DEPFILE)
When I run make dep I get
g++ -MM Monomial.cpp main.cpp Variable.cpp > .dep
make: Nothing to be done for 'dep'.
It seems as if dep is called twice. Why is that?
I am using GNU Make 4.2.1 under Cygwin.
Also it would be great if you could give me some best practises for this Makefile if you spot some bad design patterns (other than the double call of dep).
Your makefile contains an include directive:
-include $(DEPFILE)
So when Make starts, before it even considers the target(s) you've asked it to build, it tries to rebuild the file that is to be included in the makefile. Once it's done rebuilding .dep, it gets to work on the file you asked for... which is .dep.
You probably don't have to explicitly make dep, ever.
And you can simplify a couple of your rules in light of this fact, and the useful nature of automatic variables:
$(BINARY): $(OBJECTS)
$(CC) $(CFLAGS) -o $# $^ $(LDFLAGS)
$(DEPFILE): $(SOURCES) $(HEADERS)
$(CC) -MM $(SOURCES) > $#
I'm trying to understand deeply how makefiles work.
For example, I've the following one:
CC = gcc
CFLAGS = -I.
DEPS = int_array.h
OBJS = int_array.o test_int_array.o
%.o: %.c $(DEPS)
$(CC) -c -o $# $< $(CFLAGS)
test_int_array: $(OBJS)
$(CC) -o $# $^ $(CFLAGS)
clean:
rm -rf *.o test_int_array *.dSYM
The part that I really don't understand fully is :
...
%.o: %.c $(DEPS)
$(CC) -c -o $# $< $(CFLAGS)
test_int_array: $(OBJS)
$(CC) -o $# $^ $(CFLAGS)
...
I know that the option -c basically indicates just to run the preprocessor, compiling and assembling steps (i.e. without producing executables, I guess).
-o means to write the output to the specified file. Which file in this case?
I understood that $# (and $^ for right) is apparently referring to a "left" side, but which one? Is it referring, in the first case, to the left side of :, that is %.o?
What does $< mean?
Could you please explain step by step how the make tool would interpret those two statements?
I think I understood this part more or less:
...
test_int_array: $(OBJS)
$(CC) -o $# $^ $(CFLAGS)
...
which should mean produce an executable called "test_int_array" (which basically is indicated by these options -o $# from the $(OBJS) files on the right (stated using the option $^).
Is $(CFLAGS) needed in both cases? Does the order matter?
In the example:
test_int_array: $(OBJS)
$(CC) -o $# $^ $(CFLAGS)
$# is the filename of the target for this rule: test_int_array.
$^ is the names of all prerequisites.
This would be whatever is contained in OBJS, so: int_array.o test_int_array.o
In the example:
%.o: %.c $(DEPS)
$(CC) -c -o $# $< $(CFLAGS)
$< is the name of the first prerequisite: %.c
$# is the filename of the target for this rule: %.o
$(CFLAGS) is not needed for linking, since it only includes the flag -I. Also the CFLAGS indicates that the flags are used for compiling only, hence C FLAGS.
In a Makefile, each rule follows this format:
resulting_file : source_files
steps to get resulting_file from source_files
What is called respectively lefthand and righthand in a rule is the resulting_file and the source_files.
%.ext : %.ext2
is a pattern rule. It allows your Makefile to automatically create any .ext file it needs if it can find a file at the same path with .ext2.
%.c : %.o
is a pattern rule to obtain your .o files (int_array.o test_int_array.o) from their equivalent .c files (int_array.c test_int_array.c)
This is invoked when you specify that $(OBJS) is needed to build the test_int_array file.
Pattern rules automatically use certain variables, such as $(CFLAGS) so you do not need to manually add it in that rule. You can find a full list of implicitly used variables in pattern rules here: https://ftp.gnu.org/old-gnu/Manuals/make-3.79.1/html_chapter/make_10.html#SEC96
You can find out about $#, $< and $^ and similar here: https://ftp.gnu.org/old-gnu/Manuals/make-3.79.1/html_chapter/make_10.html#SEC101
$#: the entire lefthand
$<: the first file in the righthand
$^: the entire righthand list of files, space separated.
I have simple makefile:
CC=gcc
CFLAGS=-I.
DEPS = hellomake.h
%.o: %.c $(DEPS)
$(CC) -c -o $# $< $(CFLAGS)
hellomake: hellomake.o hellofunc.o
gcc -o hellomake hellomake.o hellofunc.o -I.
According to makefile description "first rule in makefile is default goal". According to my understanding the first rule is:
%.o: %.c $(DEPS)
$(CC) -c -o $# $< $(CFLAGS)
But I suppose this is not "default goal" since goal is to create hellomake executable? Where is my mistake?
According to the gnu make manual, By default, make starts with the first target (not targets whose names start with ‘.’).
%.o : ... does not count as an actual target, but rather is a pattern, which is resolved to actual goals when needed.
I am having trouble with my makefile, i have been reading somme tutoriels on how to make a more re-usable makefile but i am facing this error, and i have been searching for a while now, especially on the GNU make manual and here.
Here is my makefile :
SRC_DIR=./src
BUILD_DIR=./build
OBJS= $(BUILD_DIR)/main.o $(BUILD_DIR)/hamming.o
$(BUILD_DIR)/%.o: $(SRC_DIR)/%.c $(SRC_DIR)/%.h
$(CC) -c $< $(CFLAGS) -o $#
$(BUILD_DIR)/main: $(OBJS)
$(CC) -o $# $^ $(CFLAGS)
I am having the error :
make: No rule to make target build/main.o', needed bybuild/main'. Stop.
It seems to me that the objects in the variable OBJS are not associated with the %.o pattern rule, but i don't know why.
In my working directory there is : my makefile and the two directories 'src' and 'build'.
Thank you.
I'll go out on a limb and guess that there is no src/main.h. If that's the case, you could fix things this way:
$(BUILD_DIR)/hamming.o: $(BUILD_DIR)/%.o : $(SRC_DIR)/%.h
$(BUILD_DIR)/%.o: $(SRC_DIR)/%.c
$(CC) -c $< $(CFLAGS) -o $#
EDIT:
Now I'm puzzled. Please try this (it is crude, but if it works we can refine it):
SRC_DIR=./src
BUILD_DIR=./build
OBJS= $(BUILD_DIR)/main.o $(BUILD_DIR)/hamming.o
$(BUILD_DIR)/%.o: $(SRC_DIR)/%.c $(SRC_DIR)/%.h
$(CC) -c $< $(CFLAGS) -o $#
$(BUILD_DIR)/main.o: $(SRC_DIR)/main.c
$(CC) -c $< $(CFLAGS) -o $#
$(BUILD_DIR)/main: $(OBJS)
$(CC) -o $# $^ $(CFLAGS)
Here is a little documentation I put together for NMake a while back I hope it helps. Are you sure there are only tabs before the commands. You can't have spaces that is the number one error I have seen in the past.