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I have a makefile that is trying to do the following: identify all files under the current directory (all sub-directories included) with .c and .s extensions, for each one compile a non-linked object file and put it into a directory. All C files end up in objects/c, all assembly files end up in objects/ass.
The makefile always works as expected on the first execution (all commands are called in the right order) and no errors are produced.
However if I call make again, half of the time i get "nothing to be done for 'all'.". Which is what you would expect, since no files have been modified. But the other half of the time, make is selecting a random assembly file and compiling that file. That is to say,if I keep doing "make" I sometimes compile file1.s sometimes file2.s. and it keeps randomly swapping between the assembly files add infinitum (it never reaches a "nothing to be done") state.
How is make exhibitting non deterministic behaviour?
This is the smallest makefile I could make that reproduces the error:
SRC_C = $(wildcard *.c) $(wildcard **/*.c)
SRC_ASS = $(wildcard *.s) $(wildcard **/*.s)
OBJECTS_C = $(addprefix $(OBJECT_DIR)c/, $(notdir $(SRC_C:.c=.o)))
OBJECTS_ASS = $(addprefix $(OBJECT_DIR)ass/, $(notdir $(SRC_ASS:.s=.o)))
OBJECTS = $(OBJECTS_C) $(OBJECTS_ASS)
OBJECT_DIR = objects/
all: $(OBJECTS)
%/:
mkdir $#
$(OBJECTS_C): $(OBJECT_DIR) $(OBJECT_DIR)c/
arm-none-eabi-gcc -O0 -march=armv8-a $(wildcard */$(#F:.o=.c)) -nostartfiles -c -o $#
$(OBJECTS_ASS): $(OBJECT_DIR) $(OBJECT_DIR)ass/
arm-none-eabi-as -march=armv8-a $(wildcard */$(#F:.o=.s)) -c -o $#
.PHONY: clean
clean:
rm -rf $(OBJECT_DIR)
You have many errors here.
The biggest is a conceptual one: By flattening all your object files into one directory, there's no way to express proper dependencies using pattern rules, so your object files do not really depend on their respective source files. I'd say: just don't do that! Having object directories is fine, but they should mirror the directory structure of the source tree.
Further errors:
directly depending on directories. This will not work as expected, directories should always be order-only dependencies, as already stated in the comments
Make doesn't support recursive wildcards -- if you really need that, you could write your own function or, assuming you're always building on *nix, just call find instead
Pattern rules for creating directories are not the best idea either -- I'd suggest to collect all needed directories in a variable and loop over that.
Stylistic improvements:
Assign variables that don't need deferred evaluation with :=
Assign variables influencing the build process with ?=, so the user can override them at the command line
Use "standard" variables like CC, AS, CROSS_COMPILE
declare all phony targets in .PHONY.
Your Makefile with these changes applied would look like this:
OBJECT_DIR ?= objects
C_OBJECT_DIR ?= $(OBJECT_DIR)/c
AS_OBJECT_DIR ?= $(OBJECT_DIR)/ass
SRC_C:= $(shell find -name \*.c)
SRC_ASS:= $(shell find -name \*.s)
OBJECTS_C:= $(addprefix $(C_OBJECT_DIR)/, $(SRC_C:.c=.o))
OBJECTS_ASS:= $(addprefix $(AS_OBJECT_DIR)/, $(SRC_ASS:.s=.o))
OBJECTS:= $(OBJECTS_C) $(OBJECTS_ASS)
OUTDIRS:= $(sort $(dir $(OBJECTS)))
CROSS_COMPILE ?= arm-none-eabi-
CC ?= gcc
AS ?= as
CFLAGS ?= -O0 -march=armv8-a -nostartfiles
ASFLAGS ?= -march=armv8-a
all: $(OBJECTS)
$(OUTDIRS):
$(foreach _dir,$#,mkdir -p $(_dir);)
$(C_OBJECT_DIR)/%.o: %.c | $(OUTDIRS)
$(CROSS_COMPILE)$(CC) -c -o $# $(CFLAGS) $<
$(AS_OBJECT_DIR)/%.o: %.s | $(OUTDIRS)
$(CROSS_COMPILE)$(AS) -c -o $# $(ASFLAGS) $<
clean:
rm -rf $(OBJECT_DIR)
.PHONY: all clean
Note there is one important thing missing: automatic dependencies. With this Makefile, each object file depends on its respective source file, but completely misses any headers included. For anything other than a simple toy, you should add that, google for "gnu make gcc automatic dependencies" or something similar (not the scope of this question).
This question is different from the one at makefiles - compile all c files at once in the sense that I have one extra requirement: I want to redirect all the object files in a separate directory.
Here is the setup:
I have multiple sources in a directory say src/mylib.
I want the objects files to end up in build/mylib.
Please note also that under mylib there are subdirectories.
The first attempt was as follows:
sources = $(shell find src/ -name ".c")
objects_dirs = $(subst src/, build/, $(dir $(sources)) # This variable is used by the build rule to create directories for objects files prior to compilation
objects = $(subst src/, build/, $(patsubst %.c, %.o, $(sources))) # This variable has the paths to the objects files that will be generated in the build directory
# This is where things aren't working as expected
$(objects): build $(sources)
$(cc) $(cflags) -o $# $(word 2, $^))
build:
$(foreach dir, $(objects_dirs), $(shell mkdir -p $(dir)))
For the makefile above, only one object file was being generated. I guessed this might have something to do with GCC only being able to generate one object file at a time. Regardless of that, checking the values of $# and $(word 2, $^) in the $(objects) target shows that only one file is being considered even though I have multiple files.
So I changed my makefile to the following:
sources = $(shell find src/ -name ".c")
objects = $(subst src/, build/, $(patsubst %.c, %.o, $(sources))) # This variable has the paths to the objects files that will be generated in the build directory
# This works as expected but it appears to me like make is generating all the objects files even though source files did not change. This can be seen by checking the timestamps on new object files after running make again.
$(objects): build $(sources)
$(foreach source, $(sources), $(shell $(cc) $(cflags) -o $(subst src/,build/, $(patsubst %.o,%.c,$(source))) $(source)))
build:
$(foreach dir, $(objects_dirs), $(shell mkdir -p $(dir)))
The second makefile works as expected but objects files are being rebuilt again which defeats another purpose of using make: only recompile those source files that changed from the last compilation.
Hence my question: how does one generate all object files in a separate directory at once (by this I mean perform the compilation of all sources files in one rule) while making sure that if a source file didn't change the associated object file should not be regenerated.
I am not after speeding up compilation. What I seek is one rule that will generate all objects files such that only updated source files should be recompiled.
The last makefile does the job but there is a recompiling of all source files which defeats another purpose of using make: only changed source files should be recompiled.
EDIT
After reading comments, it appears I have not phrased my question properly. As the details of what I have are already present, I leave the question as it is with additional details below.
The second makefile in the source code above does work. But it does only half the job. The build directory effectively mirrors the src directory.
So if I have say a file as src/mylib/point/point.c, I get build/mylib/point/point.o generated. This is the first part.
The second part is that if point.c does not changes, point.o in the build/mylib/point/ directory must not be regenerated. But after checking timestamps on the object file, I can tell that a new object file replaced the old one after running make again. This is not good because for large projects, compilation time remains O(n) with n being the number of source files to compile.
So this question is about how to preserve the second makefile without make regenerating object files.
From what I can gather from comments, I am asking too much from make. But if anyone knows how to make this happen, I leave the question open.
Makefile:
all:
clean:
src_root := src
src_subdirs := foo foo/bar foo/bar/buz
build_root := build
o_suffix := .o
# Build list of sources. Iterate every subfolder from $(src_subdirs) list
# and fetch all existing files with suffixes matching the list.
source_suffixes := .c .cpp .cxx
sources := $(foreach d,$(addprefix $(src_root)/,$(src_subdirs)),$(wildcard $(addprefix $d/*,$(source_suffixes))))
# If src_subdirs make variable is unset, use 'find' command to build list of sources.
# Note that we use the same list of suffixes but tweak them for use with 'find'
ifeq ($(src_subdirs),)
sources := $(shell find $(src_root) -type f $(foreach s,$(source_suffixes),$(if $(findstring $s,$(firstword $(source_suffixes))),,-o) -name '*$s'))
endif
$(info sources=$(sources))
# Build source -> object file mapping.
# We want map $(src_root) -> $(build_root) and copy directory structure
# of source tree but populated with object files.
objects := $(addsuffix $(o_suffix),$(basename $(patsubst $(src_root)%,$(build_root)%,$(sources))))
$(info objects=$(objects))
# Generate rules for every .o file to depend exactly on corresponding source file.
$(foreach s,$(sources),$(foreach o,$(filter %$(basename $(notdir $s)).o,$(objects)),$(info New rule: $o: $s)$(eval $o: $s)))
# This is how we compile sources:
# First check if directory for the target file exists.
# If it doesn't run 'mkdir' command.
$(objects): ; $(if $(wildcard $(#D)),,mkdir -p $(#D) &&) g++ -c $< -o $#
# Compile all sources.
all: $(objects)
clean: ; rm -rf $(build_root)
.PHONY: clean all
Environment:
$ find
.
./src
./src/foo
./src/foo/bar
./src/foo/bar/bar.cxx
./src/foo/bar/buz
./src/foo/bar/buz/buz.c
./src/foo/bar/foo.c
./src/foo/foo.cpp
Run makefile:
$ make -f /cygdrive/c/stackoverflow/Makefile.sample -j
sources=src/foo/bar/bar.cxx src/foo/bar/buz/buz.c src/foo/bar/foo.c src/foo/foo.cpp
objects=build/foo/bar/bar.o build/foo/bar/buz/buz.o build/foo/bar/foo.o build/foo/foo.o
New rule: build/foo/bar/bar.o: src/foo/bar/bar.cxx
New rule: build/foo/bar/buz/buz.o: src/foo/bar/buz/buz.c
New rule: build/foo/bar/foo.o: src/foo/bar/foo.c
New rule: build/foo/foo.o: src/foo/bar/foo.c
New rule: build/foo/bar/foo.o: src/foo/foo.cpp
New rule: build/foo/foo.o: src/foo/foo.cpp
mkdir -p build/foo/bar && g++ -c src/foo/bar/bar.cxx -o build/foo/bar/bar.o
mkdir -p build/foo/bar/buz && g++ -c src/foo/bar/buz/buz.c -o build/foo/bar/buz/buz.o
mkdir -p build/foo/bar && g++ -c src/foo/bar/foo.c -o build/foo/bar/foo.o
mkdir -p build/foo && g++ -c src/foo/bar/foo.c -o build/foo/foo.o
Environment again:
$ find
.
./build
./build/foo
./build/foo/bar
./build/foo/bar/bar.o
./build/foo/bar/buz
./build/foo/bar/buz/buz.o
./build/foo/bar/foo.o
./build/foo/foo.o
./src
./src/foo
./src/foo/bar
./src/foo/bar/bar.cxx
./src/foo/bar/buz
./src/foo/bar/buz/buz.c
./src/foo/bar/foo.c
./src/foo/foo.cpp
Try running this Makefile with 'src_subdirs=' to exercise another approach to locate sources. Output should be the same.
I finally had some time to experiment with this, so here is what I came up with:
BUILD_DIR = build
SRC_DIR = src
SOURCES = $(shell find $(SRC_DIR)/ -name "*.c")
TARGET = program
OBJECTS = $(SOURCES:$(SRC_DIR)/%.c=$(BUILD_DIR)/%.o)
default: $(TARGET)
.SECONDEXPANSION:
$(OBJECTS) : $$(patsubst $(BUILD_DIR)/%.o,$(SRC_DIR)/%.c,$$#)
mkdir -p $(#D)
$(CC) -c -o $# $(CFLAGS) $<
$(TARGET): $(OBJECTS)
$(CC) -o $# $(CFLAGS) $^
.PHONY: default
Points of interest:
I had to change the sources find pattern from ".c" to "*.c", I'm not sure if it depends on the exact shell used, but if you want to stay portable, be sure to use a widely accepted pattern.
The .SECONDEXPANSION: is needed to enable the $$ rules for GNU Make. It is needed to allow target based substitution rules in the prerequisites for the $(OBJECTS).
The prerequisite $$(patsubst $(BUILD_DIR)/%.o,$(SRC_DIR)/%.c,$$#) is saying, that the current target depends on a specific source file with the same folder structure and name.
The command mkdir -p $(#D) is ensuring, that the path of the current target is created if it's missing.
If all you want is a single rule to handle all object files, without necessarily needing to "compile all at once" then you could have something like this:
BUILD_DIR = build
SOURCES = ...
TARGET = ...
OBJECTS = $(SOURCES:%.c=$(BUILD_DIR)/%.o)
default: target
target: $(TARGET)
$(TARGET): $(OBJECTS)
$(LD) -o $# $(LDFLAGS) $^ $(LIBS)
$(BUILD_DIR)/%.o: %.c
$(CC) -c -o $# $< $(CFLAGS)
$(BUILD_DIR):
-mkdir $#
[Note: This is written from memory and without testing.]
After reading the GNU make manual again, here is a solution that solves the second problem.
The first attempt was the correct path. And the second attempt has the $(sources) in the prerequisites but does not use it in the commands and this is silly.
So the working makefile follows. It puts object files in a separate directory and it only compiles files that have changed.
sources = $(shell find src/ -name ".c")
$objects_dirs = $(subst src/, build/, $(dir $(sources)) # This variable is used by the build rule to create directories for objects files prior to compilation
objects = $(subst src/, build/, $(patsubst %.c, %.o, $(sources))) # This variable has the paths to the objects files that will be generated in the build directory
# This should now work as expected: object files go into their designated directories under "build/" and only updated files will be recompiled.
$(objects): build $(sources)
# After running say "make clean", make will figure out the need to run the first prerequisite.
# If we are doing a clean build, the number of prerequisites will equal the number of new prerequisites.
ifeq ($(words $?), $(words $^))
# Note the use of "$?" instead of "$^". $? is used since it holds prerequisites that are newer than the target while $^ will holds all prerequisites whether they are new or not.
$(foreach source, $(wordlist 2, $(words $?), $?), $(shell $(cc) $(cflags) -o $(subst src/,build, $(patsubst %.c,%.o, $(source))) $(source)))
else
# If we have a few new targets, no need to exclude "build" from prerequisites because the first prerequisite will be a file that changed.
$(foreach source, $?, $(shell $(cc) $(cflags) -o $(subst src/,build, $(patsubst %.c,%.o, $(source))) $(source)))
endif
.PHONY: build
build:
$(foreach dir, $(objects_dirs), $(shell mkdir -p $(dir)))
.PHONY: clean
clean:
#rm -rf build/
The makefile is heavily commented with changes that made it work. The most important changes were:
Use of $(foreach) to compile each file individually as required by GCC
Use of $? to work only with prerequisites that are newer than the target
Use of conditional to detected whether the first prerequisite has changed depending on circumstances. If we have a clean build (running make for the first time or after running make clean), the number of updated prerequisites will be the same as the number of newer prerequisites compared to the target. In other words $(words $?) == $(words $^) will be true. So we use this fact to exclude the firs prerequisite listed (build in our case) from the list of files to pass to GCC.
Also, when building the executable from the objects files, make sure to use $^ and not $? when selecting prerequisites else you will end up with only newer files in the executable and it will not run.
target = bin/mylib.a
.PHONY: all
all: $(target)
$(target): $(objects)
ar -cvq $# $^ # Notice that we're not using $? else only updated object files will end up in the archive.
I would like to build a C-project for my microcontroller with the GNU make tool. I would like to do it in a clean way, such that my source code is not cluttered with object files and other stuff after the build. So imagine that I have a project folder, called "myProject" with two folders in it:
- myProject
|
|---+ source
|
'---+ build
The build folder only contains a makefile. The figure below shows what should happen when I run the GNU make tool:
So GNU make should create an object file for each .c source file it can find in the source folder. The object files should be structured in a directory tree that is similar to the structure in the source folder.
GNU make should also make a .d dependency file (in fact, a dependency file is some sort of makefile itself) for each .c source file. The dependency file is described in the GNU make manual chapter 4.14 "Generating Prerequisites Automatically":
For each source file name.c there is a makefile name.d which lists
what files the object file name.o depends on.
From the following Stackoverflow question About the GNU make dependency files *.d, I learned that adding the options -MMD and -MP to the CFLAGS of the GNU gcc compiler can help to automate that.
So now comes the question. Has anyone a sample makefile that performs such out-of-source build? Or some good advices on how to get started?
I'm pretty sure that most people who have written such a makefile, are Linux-people. But the microcontroller project should build also on a Windows machine. Anyway, even if your makefile is Linux-only, it provides a good starting point ;-)
PS: I would like to avoid extra tools like CMake, Autotools, or anything that has to do with an IDE. Just pure GNU make.
I would be very grateful :-)
Updating the dependency files
Please have a look at this question: What is the exact chain of events when GNU make updates the .d files?
Here's the Makefile I've added to the documentation (currently in review so I'll post it here) :
# Set project directory one level above the Makefile directory. $(CURDIR) is a GNU make variable containing the path to the current working directory
PROJDIR := $(realpath $(CURDIR)/..)
SOURCEDIR := $(PROJDIR)/Sources
BUILDDIR := $(PROJDIR)/Build
# Name of the final executable
TARGET = myApp.exe
# Decide whether the commands will be shown or not
VERBOSE = TRUE
# Create the list of directories
DIRS = Folder0 Folder1 Folder2
SOURCEDIRS = $(foreach dir, $(DIRS), $(addprefix $(SOURCEDIR)/, $(dir)))
TARGETDIRS = $(foreach dir, $(DIRS), $(addprefix $(BUILDDIR)/, $(dir)))
# Generate the GCC includes parameters by adding -I before each source folder
INCLUDES = $(foreach dir, $(SOURCEDIRS), $(addprefix -I, $(dir)))
# Add this list to VPATH, the place make will look for the source files
VPATH = $(SOURCEDIRS)
# Create a list of *.c sources in DIRS
SOURCES = $(foreach dir,$(SOURCEDIRS),$(wildcard $(dir)/*.c))
# Define objects for all sources
OBJS := $(subst $(SOURCEDIR),$(BUILDDIR),$(SOURCES:.c=.o))
# Define dependencies files for all objects
DEPS = $(OBJS:.o=.d)
# Name the compiler
CC = gcc
# OS specific part
ifeq ($(OS),Windows_NT)
RM = del /F /Q
RMDIR = -RMDIR /S /Q
MKDIR = -mkdir
ERRIGNORE = 2>NUL || true
SEP=\\
else
RM = rm -rf
RMDIR = rm -rf
MKDIR = mkdir -p
ERRIGNORE = 2>/dev/null
SEP=/
endif
# Remove space after separator
PSEP = $(strip $(SEP))
# Hide or not the calls depending of VERBOSE
ifeq ($(VERBOSE),TRUE)
HIDE =
else
HIDE = #
endif
# Define the function that will generate each rule
define generateRules
$(1)/%.o: %.c
#echo Building $$#
$(HIDE)$(CC) -c $$(INCLUDES) -o $$(subst /,$$(PSEP),$$#) $$(subst /,$$(PSEP),$$<) -MMD
endef
# Indicate to make which targets are not files
.PHONY: all clean directories
all: directories $(TARGET)
$(TARGET): $(OBJS)
$(HIDE)echo Linking $#
$(HIDE)$(CC) $(OBJS) -o $(TARGET)
# Include dependencies
-include $(DEPS)
# Generate rules
$(foreach targetdir, $(TARGETDIRS), $(eval $(call generateRules, $(targetdir))))
directories:
$(HIDE)$(MKDIR) $(subst /,$(PSEP),$(TARGETDIRS)) $(ERRIGNORE)
# Remove all objects, dependencies and executable files generated during the build
clean:
$(HIDE)$(RMDIR) $(subst /,$(PSEP),$(TARGETDIRS)) $(ERRIGNORE)
$(HIDE)$(RM) $(TARGET) $(ERRIGNORE)
#echo Cleaning done !
Main features
Automatic detection of C sources in specified folders
Multiple source folders
Multiple corresponding target folders for object and dependency files
Automatic rule generation for each target folder
Creation of target folders when they don't exist
Dependency management with gcc : Build only what is necessary
Works on Unix and DOS systems
Written for GNU Make
How to use this Makefile
To adapt this Makefile to your project you have to :
Change the TARGET variable to match your target name
Change the name of the Sources and Build folders in SOURCEDIR and BUILDDIR
Change the verbosity level of the Makefile in the Makefile itself or in make call (make all VERBOSE=FALSE)
Change the name of the folders in DIRS to match your sources and build folders
If required, change the compiler and the flags
In this Makefile Folder0, Folder1 and Folder2 are the equivalent to your FolderA, FolderB and FolderC.
Note that I have not had the opportunity to test it on a Unix system at the moment but it works correctly on Windows.
Explanation of a few tricky parts :
Ignoring Windows mkdir errors
ERRIGNORE = 2>NUL || true
This has two effects :
The first one, 2>NUL is to redirect the error output to NUL, so as it does not comes in the console.
The second one, || true prevents the command from rising the error level. This is Windows stuff unrelated with the Makefile, it's here because Windows' mkdir command rises the error level if we try to create an already-existing folder, whereas we don't really care, if it does exist that's fine. The common solution is to use the if not exist structure, but that's not UNIX-compatible so even if it's tricky, I consider my solution more clear.
Creation of OBJS containing all object files with their correct path
OBJS := $(subst $(SOURCEDIR),$(BUILDDIR),$(SOURCES:.c=.o))
Here we want OBJS to contain all the object files with their paths, and we already have SOURCES which contains all the source files with their paths.
$(SOURCES:.c=.o) changes *.c in *.o for all sources, but the path is still the one of the sources.
$(subst $(SOURCEDIR),$(BUILDDIR), ...) will simply subtract the whole source path with the build path, so we finally have a variable that contains the .o files with their paths.
Dealing with Windows and Unix-style path separators
SEP=\\
SEP = /
PSEP = $(strip $(SEP))
This only exist to allow the Makefile to work on Unix and Windows, since Windows uses backslashes in path whereas everyone else uses slashes.
SEP=\\ Here the double backslash is used to escape the backslash character, which make usually treats as an "ignore newline character" to allow writing on multiple lines.
PSEP = $(strip $(SEP)) This will remove the space char of the SEP variable, which has been added automatically.
Automatic generation of rules for each target folder
define generateRules
$(1)/%.o: %.c
#echo Building $$#
$(HIDE)$(CC) -c $$(INCLUDES) -o $$(subst /,$$(PSEP),$$#) $$(subst /,$$(PSEP),$$<) -MMD
endef
That's maybe the trick that is the most related with your usecase. It's a rule template that can be generated with $(eval $(call generateRules, param)) where param is what you can find in the template as $(1).
This will basically fill the Makefile with rules like this for each target folder :
path/to/target/%.o: %.c
#echo Building $#
$(HIDE)$(CC) -c $(INCLUDES) -o $(subst /,$(PSEP),$#) $(subst /,$(PSEP),$<) -MMD
This fairly minimal makefile should do the trick:
VPATH = ../source
OBJS = FolderA/fileA1.o FolderA/fileA2.o FolderB/fileB1.o
CPPFLAGS = -MMD -MP
all: init myProgram
myProgram: $(OBJS)
$(CC) $(LDFLAGS) -o $# $(OBJS) $(LDLIBS)
.PHONY: all init
init:
mkdir -p FolderA
mkdir -p FolderB
-include $(OBJS:%.o=%.d)
The main tricky part is ensuring that FolderA and FolderB exist in the build directory bfore trying to run the compiler that will write into them. The above code will work sequential for builds, but might fail with -j2 the first time it is run, as the compiler in one thread might try to open an output file before the other thread creates the directory. Its also somewhat unclean. Usually with GNU tools you have a configure script that will create those directories (and the makefile) for you before you even try to run make. autoconf and automake can build that for you.
An alternate way that should work for parallel builds would be to redefine the standard rule for compiling C files:
VPATH = ../source
OBJS = FolderA/fileA1.o FolderA/fileA2.o FolderB/fileB1.o
CPPFLAGS = -MMD -MP
myProgram: $(OBJS)
$(CC) $(LDFLAGS) -o $# $(OBJS) $(LDLIBS)
%.o: %.c
mkdir -p $(dir $#)
$(CC) $(CFLAGS) $(CPPFLAGS) -c -o $# $<
-include $(OBJS:%.o=%.d)
Which has the disadvantage that you'll also need to redefine the builtin rules for any other kind of sourcefile you want to compile
Here's a basic one I use all the time, it's pretty much a skeleton as it is but works perfectly fine for simple projects. For more complex projects it certainly needs to be adapted, but I always use this one as a starting point.
APP=app
SRC_DIR=src
INC_DIR=inc
OBJ_DIR=obj
BIN_DIR=bin
CC=gcc
LD=gcc
CFLAGS=-O2 -c -Wall -pedantic -ansi
LFLGAS=
DFLAGS=-g3 -O0 -DDEBUG
INCFLAGS=-I$(INC_DIR)
SOURCES=$(wildcard $(SRC_DIR)/*.c)
HEADERS=$(wildcard $(INC_DIR)/*.h)
OBJECTS=$(SOURCES:$(SRC_DIR)/%.c=$(OBJ_DIR)/%.o)
DEPENDS=$(OBJ_DIR)/.depends
.PHONY: all
all: $(BIN_DIR)/$(APP)
.PHONY: debug
debug: CFLAGS+=$(DFLAGS)
debug: all
$(BIN_DIR)/$(APP): $(OBJECTS) | $(BIN_DIR)
$(LD) $(LFLGAS) -o $# $^
$(OBJ_DIR)/%.o: | $(OBJ_DIR)
$(CC) $(CFLAGS) $(INCFLAGS) -o $# $<
$(DEPENDS): $(SOURCES) | $(OBJ_DIR)
$(CC) $(INCFLAGS) -MM $(SOURCES) | sed -e 's!^!$(OBJ_DIR)/!' >$#
ifneq ($(MAKECMDGOALS),clean)
-include $(DEPENDS)
endif
$(BIN_DIR):
mkdir -p $#
$(OBJ_DIR):
mkdir -p $#
.PHONY: clean
clean:
rm -rf $(BIN_DIR) $(OBJ_DIR)
I would avoid manipulating Makefile directly, and use CMake instead.
Just describe your source files in CMakeLists.txt, as below:
Create file MyProject/source/CMakeLists.txt containing;
project(myProject)
add_executable(myExec FolderA/fileA1.c FolderA/fileA2.c FolderB/fileB1.c)
Under MyProject/build, run
cmake ../source/
You'll get a Makefile now. To build, under the same build/ directory,
make
You may also want to switch to a lightning fast build tool, ninja, simply by adding a switch as following.
cmake -GNinja ..
ninja
I'm not sure what I'm doing wrong here. I'm trying to get make to figure out what dependencies my project has for, not only source files, but non-system included header files. I've many resources from this very site related to this subject.
Such as: Makefile header dependencies and Makefile, header dependencies
However, when I do
touch MyHeader.h
as a test to see if this works, my make process fails to rebuild the source files that include this header. So, here's what I have in my makefile (of relevance that is)
CPP=g++
CPPFLAGS=-Iadditional/includes -MMD
CXXFLAGS=-std=c++0x -c
# not every source file in this directory needs to be included in this build
# this is because of shared code with Windows
SOURCESFILTER = File1.cpp File2.cpp
OBJ_DIR=obj
SOURCES = $(filter-out $(SOURCEFILTER),$(wildcard *.cpp))
OBJECTS = $(addprefix $(OBJ_DIR)/,$(SOURCES:.cpp=.o))
DEPENDENCIES = $(OBJECTS:.o=.d)
.PHONY: archive
archive : $(OBJECTS)
ar mylib.a obj/*.o
-include $(DEPENDENCIES)
$(OBJ_DIR)/%.o: $(SOURCES) $(DEPENDENCIES)
$(CPP) $(CPPFLAGS) $(CXXFLAGS) $< -o $#
I've verified that the above process does indeed generate the expected *.d files. I assume that I'm including them correctly. However, as mentioned, as a test I do:
touch MyHeader.h
which is in the same directory as the sources, and rerun the make, none of the source files which include this header are remade. What am I missing?
Andy
First, you cannot include prerequisites in a suffix rule. Even if you could, you certainly would not want to include $(SOURCES) or $(DEPENDENCIES), because that would cause every object to rebuild whenever any source or dependency file changed.
Second, you cannot create the target file in a different directory from where make expects it to be. Make will put the place where it wants to find the target in the variable $#, and you must write the output into that location exactly. If you ever see a rule that modifies the target, such as above where you use obj/$#, that won't work.
Most likely GCC is writing the files as obj/foo.d, but your include is trying to include foo.d but that doesn't exist... but since you used -include make doesn't complain.
I recommend you first write the object files into the local directory and get that working with dependencies. Once that works, then read up on how to write targets to a different directory and/or ask again.
ETA:
Try something like this:
CXX := g++
CPPFLAGS := -Iadditional/includes -MMD
CXXFLAGS := -std=c++0x
# not every source file in this directory needs to be included in this build
# this is because of shared code with Windows
SOURCESFILTER := File1.cpp File2.cpp
OBJ_DIR := obj
SOURCES := $(filter-out $(SOURCEFILTER),$(wildcard *.cpp))
OBJECTS := $(addprefix $(OBJ_DIR)/,$(SOURCES:.cpp=.o))
DEPENDENCIES := $(OBJECTS:.o=.d)
.PHONY: archive
archive: mylib.a
mylib.a: $(OBJECTS)
$(AR) $# $^
-include $(DEPENDENCIES)
$(OBJ_DIR)/%.o: %.cpp
$(CXX) $(CPPFLAGS) $(CXXFLAGS) -c -o $# $<
just for quick terminology:
#basic makefile rule
target: dependencies
recipe
The Problem: I want to generate the dependencies automatically.
For example, I am hoping to turn this:
#one of my targets
file.o: file.cpp 1.h 2.h 3.h 4.h 5.h 6.h 7.h 8.h another.h lots.h evenMore.h
$(COMPILE)
Into this:
#one of my targets
file.o: $(GENERATE)
$(COMPILE)
and I'm not too sure if it's possible..
What I do know:
I can use this compiler flag:
g++ -MM file.cpp
and it will return the proper target and dependency.
so from the example, it would return:
file.o: file.cpp 1.h 2.h 3.h 4.h 5.h 6.h 7.h 8.h another.h lots.h evenMore.h
however, 'make' does NOT allow me to explicitly write shell code in the target or dependency section of a rule :(
I know there is a 'make' function called shell
but I can't quite plug this in as dependency and do parsing magic because it relies on the macro $# which represents the target.. or at least I think that’s what the problem is
I've even tried just replacing the "file.cpp" dependency with this makefile function and that won't work either..
#it's suppose to turn the $# (file.o) into file.cpp
THE_CPP := $(addsuffix $(.cpp),$(basename $#))
#one of my targets
file.o: $(THE_CPP) 1.h 2.h 3.h 4.h 5.h 6.h 7.h 8.h another.h lots.h evenMore.h
$(COMPILE)
#this does not work
So all over google, there appear to be two solutions. both of which I don't fully grasp.
From GNU Make Manual
Some Site that says the GNU Make Manual one is out-of-date
So my ultimate question is: Is it possible to do it the way I want to do it,
and if not, can somebody break down the code from one of these sites and explain to me in detail how they work. I'll implement it one of these ways if I have to, but I'm weary to just paste a chunk of code into my makefile before understanding it
Newer versions of GCC have an -MP option which can be used with -MD. I simply added -MP and -MD to the CPPFLAGS variable for my project (I did not write a custom recipe for compiling C++) and added an "-include $(SRC:.cpp=.d)" line.
Using -MD and -MP gives a dependency file which includes both the dependencies (without having to use some weird sed) and dummy targets (so that deleting header files will not cause errors).
To manipulate the filenames when you already know what the dependencies should be, you can use a pattern rule:
file.o: %.o : %.cpp 1.h 2.h 3.h 4.h 5.h 6.h 7.h 8.h another.h lots.h evenMore.h
$(COMPILE)
And you can reuse the rule for other targets:
# Note these two rules without recipes:
file.o: 1.h 2.h 3.h 4.h 5.h 6.h 7.h 8.h another.h lots.h evenMore.h
anotherFile.o: 4.h 9.h yetAnother.h
file.o anotherFile.o: %.o : %.cpp
$(COMPILE)
But if you want Make to figure out the list of dependencies automatically, the best way (that I know of) is Advanced Auto-Dependency Generation. It looks like this:
%.o : %.cc
#g++ -MD -c -o $# $<
#cp $*.d $*.P; \
sed -e 's/#.*//' -e 's/^[^:]*: *//' -e 's/ *\\$$//' \
-e '/^$$/ d' -e 's/$$/ :/' < $*.d >> $*.P; \
rm -f $*.d
-include *.P
Basically, when it builds file.o, it also builds file.d. Then it runs file.d through a bewildering sed command that turns the list of dependencies into a rule with no recipes. The last line is an instruction to include any such rules that exist. The logic here is subtle and ingenious: you don't actually need the dependencies the first time you build foo.o, because Make already knows that foo.o must be built, because it doesn't exist. The next time you run Make, it will use the dependency list it created last time. If you change one of the files so that there is actually a new dependency which is not in the list, Make will still rebuild foo.o because you changed a file which was a dependency. Try it, it really works!
Excellent answers but in my build I put the .obj files in a subdirectory based on build type (ie: debug vs. release). So for example, if I'm building debug, I put all the object files in a build/debug folder. It was a mind-numbing task to try to get the multiline sed command above to use the correct destination folder, but after some experimentation, I stumbled on a solution that works great for my build. Hopefully it'll help someone else as well.
Here's a snippet:
# List my sources
CPP_SOURCES := foo.cpp bar.cpp
# If I'm debugging, change my output location
ifeq (1,$(DEBUG))
OBJ_DIR:=./obj/debug
CXXFLAGS+= -g -DDEBUG -O0 -std=c++0x
else
CXXFLAGS+= -s -O2
OBJ_DIR:=./obj/release
endif
# destination path macro we'll use below
df = $(OBJ_DIR)/$(*F)
# create a list of auto dependencies
AUTODEPS:= $(patsubst %.cpp,$(OBJ_DIR)/%.d,$(CPP_SOURCES))
# include by auto dependencies
-include $(AUTODEPS)
.... other rules
# and last but not least my generic compiler rule
$(OBJ_DIR)/%.o: %.cpp
## Build the dependency file
#$(CXX) -MM -MP -MT $(df).o -MT $(df).d $(CXXFLAGS) $< > $(df).d
## Compile the object file
#echo " C++ : " $< " => " $#
#$(CXX) -c $< $(CXXFLAGS) -o $#
Now for the details:
The first execution of CXX in my generic build rule is the interesting one. Note that I'm not using any "sed" commands. Newer versions of gcc do everything I needed (I'm using gcc 4.7.2).
-MM builds the main dependency rule including project headers but not system headers. If I left it like this, my .obj file would NOT have the correct path. So I use the -MT option to specify the "real" path to my .obj destination. (using the "df" macro I created).
I also use a second -MT option to make sure the resulting dependency file (ie: .d file) has the correct path, and that it is included in the target list and therefor has the same dependencies as the source file.
Last but not least is the inclusion of the -MP option. This tell gcc to also make stubbed rules for each header solving the problem that occurs if I delete a header causing make to generate an error.
I suspect that since I'm using gcc for all the dependency generation instead of piping out to sed, my build is faster (although I've yet to prove that since my build is relatively small at this point). If you see ways I can improve upon this, I'm always open to suggestions. Enjoy
For the record, this is how I generate dependencies automatically now:
CPPFLAGS = -std=c++1y -MD -MP
SRC = $(wildcard *.cpp)
all: main
main: $(SRC:%.cpp=%.o)
g++ $(CPPFLAGS) -o $# $^
-include $(SRC:%.cpp=%.d)
The compiler flags -MD and -MP help do the trick.
First, you can have THE_CPP=$(patsubst %.o,%.cpp,$#)
Then you can run make -p to understand the builtin rules of make
A usual way of doing could be to generate the makefile dependencies into *.md files:
%.o: %.c
$(COMPILE.c) $(OUTPUT_OPTION) $< -MMD -MF $(patsubst %.c,%.md,$#)
and later in your Makefile including them with something like
-include $(wildcard *.md)
But you can also consider using other builders like omake and many many others
WOOO! I did manage to get the code in Beta's post to work on a small test project.
I should note, for anyone else who may come across this,
If you're using the bash shell(which I was), you will need to add an escape character in front of the pound sign to escape from making the rest of the expression a comment. (see 4th line of code)
%.o : %.cpp
g++ -c -MD -o $# $<
cp $*.d $*.P; \
sed -e 's/\#.*//' -e 's/^[^:]*: *//' -e 's/ *\\$$//' \
-e '/^$$/ d' -e 's/$$/ :/' < $*.d >> $*.P; \
rm -f $*.d
-include *.P
Now I want to share information that I found in Managing Projects with GNU Make, 3rd Edition. because it's points out some important issues on this matter, and supplies code that I still don't fully grasp yet.
A method appears in the book that is similar to the method found on the Make manual page.
It looks like this:
include $(subst .c,.d,$(SOURCES))
%.d: %.c
$(CC) -M $(CPPFLAGS) $< > $#.$$$$; \
sed 's,\($*\).o[ :]*,\1.o $# : ,g' < $#.$$$$ > $#; \
rm -f $#.$$$$
This is what I believe is happening.
Right away, 'make' wants to include a ".d" file for every source file.
Because no .d files initially exist, the chunk of code is ran again and again in order to create all the missing .d files.
This means make will start over again and again until every .d file is created and included in the makefile.
Each ".d" file is what Beta said: a target with a set of dependencies and NO recipe.
If a header file is ever changed, those rules that are included in, will need the dependencies updated first. This is what throws me off a bit, how is it that the chunk of code is able to be called again? It is used to update .d files, so if a .h file changes how does it get called? Aside from this, I realize that the default rule is used to compile the object. Any clarifications/misconceptions to this explanation are appreciated.
Later in the book it points out problems with this method, and problems that I believe also exist in the Advanced Auto-Dependency Generation implementation.
Problem 1: It's inefficient. 'make' must restart every time it makes a .d file
Problem 2: make generates warning messages for all the missing .d files- Which is mostly just a nuisance and can be hidden by adding a "-" in front of the include statement.
Problem 3: If you delete a src file because it's no longer needed, 'make' will crash the next time you try to compile because some .d file has the missing src as a dependency, and because there is no rule to recreate that src, make will refuse to go any further.
They say a fix to these issues is Tromey's method, but the code looks very different from the code on the website. Perhaps it's just because they used some macros, made it a function call, and wrote it slightly different. I'm still looking into it, but wanted to share some discoveries I've made so far. Hopefully this opens up a little bit more discussion, and gets me closer to the bottom of all this.
A simple and elegant solution, inclusive of a detailed explanation of how it works, is available here.
DEPDIR := .deps
DEPFLAGS = -MT $# -MMD -MP -MF $(DEPDIR)/$*.d
%.o : %.cpp
%.o : %.cpp $(DEPDIR)/%.d | $(DEPDIR)
g++ -c $(DEPFLAGS) $(CFLAGS) $<
$(DEPDIR): ; #mkdir -p $#
DEPFILES := $(SRCS:%.c=$(DEPDIR)/%.d)
$(DEPFILES):
include $(wildcard $(DEPFILES))
I prefer to use $(shell ...) function with find. Here is a sample of one of my Makefiles:
SRCDIR = src
OBJDIR = obj
LIBDIR = lib
DOCDIR = doc
# Get Only the Internal Structure of Directories from SRCDIR
STRUCTURE := $(shell find $(SRCDIR) -type d)
#Filter-out hidden directories
STRUCTURE := $(filter-out $(shell find $(SRCDIR)/.* -type d),$(STRUCTURE))
# Get All Files From STRUCTURE
CODEFILES := $(addsuffix /*,$(STRUCTURE))
CODEFILES := $(wildcard $(CODEFILES))
## Filter Only Specific Files
SRCFILES := $(filter %.c,$(CODEFILES))
HDRFILES := $(filter %.h,$(CODEFILES))
OBJFILES := $(subst $(SRCDIR),$(OBJDIR),$(SRCFILES:%.c=%.o))
DOCFILES := $(addprefix $(DOCDIR)/, \
$(addsuffix .md, \
$(basename $(SRCFILES))))
# Filter Out Function main for Libraries
LIBDEPS := $(filter-out $(OBJDIR)/main.o,$(OBJFILES))
In this approach, I first get all the internal directory structure, with any depth. Then I get all files inside the Structure. At this time, I can use filter, filter-out, addsuffix, etc, to get exactly what I need at each time.
This example covers *.c files, but you can change it to *.cpp as well.
Building on the content of the Auto-Dependency Generation article referenced in comments on a previous post at I've created an annotated makefile project which includes a generic Makefile annotated with comments and implemented for a simple project with 3 .c files and 2 .h files. See full Makefile content below. Simple projects should be able to just customize the TODO section
# See http://make.mad-scientist.net/papers/advanced-auto-dependency-generation/
# for the template used to start this file
# -- TODO: customize the list below for your project ---
# List of source .c files used with the project
SRCS := main.c file1.c file2.c
# The aplication generated
APPNAME = depend-generation-test
# -- End of customization section ---
# Replace .c extension on SRCS to get objfiles using gnu make pattern rules and substitution references.
# See https://www.gnu.org/software/make/manual/html_node/Pattern-Intro.html#Pattern-Intro for pattern rules and
# https://www.gnu.org/software/make/manual/html_node/Substitution-Refs.html#Substitution-Refs for substitution references overview
OBJFILES := $(SRCS:%.c=%.o)
# Build the app you've specified in APPNAME for the "all" or "default" target
all : $(APPNAME)
default : $(APPNAME)
# Remove all build intermediates and output file
clean : ; #rm -rf $(APPNAME) *.o
# Build the application by running the link step with all objfile inputs
$(APPNAME) : $(OBJFILES)
$(CC) $(LDFLAGS) $^ -o $(APPNAME)
# Add all warnings/errors to cflags default. This is not required but is a best practice
CFLAGS += -Wall -Werror
# The below content is from http://make.mad-scientist.net/papers/advanced-auto-dependency-generation/
# with the following changes:
# 1) Added comments
# 2) Removed TARGET_ARCH from COMPILE.c since it's no longer listed in the [default rules](https://www.gnu.org/software/make/manual/html_node/Catalogue-of-Rules.html#Catalogue-of-Rules) and [isn't documented](https://lists.gnu.org/archive/html/help-make/2010-06/msg00005.html)
# Original content below is:
# Copyright © 1997-2019 Paul D. Smith Verbatim copying and distribution is permitted in any medium, provided this notice is preserved.
# The directory (hidden) where dependency files will be stored
DEPDIR := .deps
# Flags passed to gcc to automatically build dependencies when compiling
# See https://www.gnu.org/software/make/manual/html_node/Automatic-Variables.html for detail about variable names
# $# references the target file of the rule and will be "main.o" when compiling "main.c"
# $* references the stem of the rule, and will be "main" when target is "main.o"
DEPFLAGS = -MT $# -MMD -MP -MF $(DEPDIR)/$*.d
# Rules for compiling a C file, including DEPFLAGS along with Implicit GCC variables.
# See https://www.gnu.org/software/make/manual/html_node/Implicit-Variables.html
# and see https://www.gnu.org/software/make/manual/html_node/Catalogue-of-Rules.html#Catalogue-of-Rules
# for the default c rule
COMPILE.c = $(CC) $(DEPFLAGS) $(CFLAGS) $(CPPFLAGS) -c
# Delete the built-in rules for building object files from .c files
%.o : %.c
# Define a rule to build object files based on .c or dependency files by making the associated dependency file
# a prerequisite of the target. Make the DEPDIR an order only prerequisite of the target, so it will be created when needed, meaning
# the targets won't get rebuilt when the timestamp on DEPDIR changes
# See https://www.gnu.org/software/make/manual/html_node/Prerequisite-Types.html for order only prerequesites overview.
%.o : %.c $(DEPDIR)/%.d | $(DEPDIR)
$(COMPILE.c) $(OUTPUT_OPTION) $<
# Create the DEPDIR when it doesn't exist
$(DEPDIR): ; #mkdir -p $#
# Use pattern rules to build a list of DEPFILES
DEPFILES := $(SRCS:%.c=$(DEPDIR)/%.d)
# Mention each of the dependency files as a target, so make won't fail if the file doesn't exist
$(DEPFILES):
# Include all dependency files which exist, to include the relevant targets.
# See https://www.gnu.org/software/make/manual/html_node/Wildcard-Function.html for wildcard function documentation
include $(wildcard $(DEPFILES))