Problems building a generic Makefile with dependency tracking-CodePudding

I have the following project structure: a folder called "src" with all the .cpp, a folder called "include" with the .h, a folder called "build" for the .o (object files), another folder called "dep" for the .d files (dependencies) and finally another folder called "bin" for the executables.

Given that, I have done this makefile to carry out the build process

OPTIONS := -O2 -Wall

EXE_NAME = example.exe

BIN_PATH     = bin/
BUILD_PATH   = build/
DEP_PATH     = dep/
INCLUDE_PATH = include/
SRC_PATH     = src/

################################################################################

# get project files
ALL_CPP := $(shell find $(SRC_PATH) -type f -name "*.cpp")
ALL_H := $(shell find $(INCLUDE_PATH) -type f -name "*.h")
ALL_O := $(subst $(SRC_PATH),$(BUILD_PATH),$(subst .cpp,.o,$(ALL_CPP)))
ALL_D := $(subst $(SRC_PATH),$(DEP_PATH),$(subst .cpp,.d,$(ALL_CPP)))


all: $(BIN_PATH)$(EXE_NAME)

#linking
$(BIN_PATH)$(EXE_NAME): $(ALL_O)
    g   $(OPTIONS) -o $@ $(ALL_O)

# generic build rule
$(BUILD_PATH)%.o: $(SRC_PATH)%.cpp
    g   $(OPTIONS) -c $< -o $(BUILD_PATH)$@ -I$(INCLUDE_PATH) -MMD -MF $(DEP_PATH)$(@:.o=.d)


.PHONY: clean

clean:
    rm $(ALL_D) $(ALL_O) $(BIN_PATH)$(EXE_NAME)

-include $(ALL_D)

But whenever I try to execute it, this error pops out:

make: *** No rule to make target 'build/file.o', needed by 'bin/example.exe'.  Stop.

Which does not make sense, as there is a rule for building targets that end in ".o".

What might be going on here?

CodePudding user response：

First, you should avoid using subst since it substitutes every instance of one set of text with another. Safer is to use patsubst:

ALL_O := $(patsubst $(SRC_PATH)%.cpp,$(BUILD_PATH)%.o,$(ALL_CPP))
ALL_D := $(patsubst $(SRC_PATH)%.cpp,$(DEP_PATH)%.d,$(ALL_CPP))

Second, your command line is wrong: $@ already contains the path so you don't want to use $(BUILD_DIR)$@. You want just $@ by itself. You'll have a similar problem for .d.

But I don't see any way to get the error you show (no rule to make target 'build/file.o') given the makefile you provide. Either there's something different about your makefile than what you have here or something mysterious is happening.

You can add the -d option to make to get some debug info.

CodePudding user response：

Thanks to all who replied. As many of you suggested, the error I provided does not appear in the makefile version I posted, and that is because I did some code cleaning before posting which ironically end up solving the error (I had no idea the changes I made would be important). More precisely, I am sure the problem was with the line

$(BUILD_PATH)%.o: $(SRC_PATH)%.cpp

Which in the original makefile was

$(BUILD_PATH)%.o: %.cpp

I have also tried without the $(BUILD_PATH), which gave no luck, that's why I thought that line was not important.

I did some of the changes you suggested and the final working version of the Makefile is as follows

OPTIONS := -O2 -Wall -Wno-sign-compare -Wno-unused-parameter

EXE_NAME = example

BIN_PATH     = bin/
BUILD_PATH   = build/
DEP_PATH     = dep/
INCLUDE_PATH = include/
SRC_PATH     = src/

################################################################################

# get project files
ALL_CPP := $(shell find $(SRC_PATH) -type f -name "*.cpp")
ALL_H := $(shell find $(INCLUDE_PATH) -type f -name "*.h")
ALL_O := $(subst $(SRC_PATH),$(BUILD_PATH),$(subst .cpp,.o,$(ALL_CPP)))
ALL_D := $(subst $(SRC_PATH),$(DEP_PATH),$(subst .cpp,.d,$(ALL_CPP)))


all: $(BIN_PATH)$(EXE_NAME)

#linking
$(BIN_PATH)$(EXE_NAME): $(ALL_O)
    @echo ' -> linking'
    @g   $(OPTIONS) -o $@ $(ALL_O)
    @echo Finished!

# generic build rule
$(BUILD_PATH)%.o: $(SRC_PATH)%.cpp
    @echo ' -> building:' $<
    @g   $(OPTIONS) -c $< -o $@ -I$(INCLUDE_PATH) -MMD -MF  $(subst $(BUILD_PATH),$(DEP_PATH),$(@:.o=.d))


.PHONY: clean

clean:
    @echo Removed files: $(ALL_D) $(ALL_O) $(BIN_PATH)$(EXE_NAME)
    @rm $(ALL_D) $(ALL_O) $(BIN_PATH)$(EXE_NAME)

-include $(ALL_D)