Rectifying autogenerated dependencies (from gcc) in make

Question

I have the following makefile (fragment)

SRC_DIR     = src
OBJ_DIR     = obj
DEP_DIR     = dep
BIN_DIR     = .
SRC_FILES  := $(wildcard $(SRC_DIR)/*.cpp)
OBJ_FILES  := $(patsubst $(SRC_DIR)/%.cpp,$(OBJ_DIR)/%.o,$(SRC_FILES))
DEP_FILES  := $(patsubst $(SRC_DIR)/%.cpp,$(DEP_DIR)/%.d,$(SRC_FILES))

# Development build directive
dev: $(DEP_FILES) $(OBJ_FILES)
  $(CPPC) $(LIBS) $(FLAGS_DEV) $(OBJ_FILES) -o $(BIN_DIR)/$(PROJECT)

# Object file directives
$(OBJ_DIR)/%.o: $(SRC_DIR)/%.cpp $(DEP_DIR)/%.d
  $(CPPC) -c $(FLAGS_DEV) $< -o $@

# Dependency directives
$(DEP_DIR)/%.d: $(SRC_DIR)/%.cpp
  $(CPPC) -MM -MD $< -o $@

include $(DEP_FILES)

When I run make dev I see the following

makefile:59: dep/area.d: No such file or directory
makefile:59: dep/avatar.d: No such file or directory
makefile:59: dep/board.d: No such file or directory
makefile:59: dep/socket.d: No such file or directory
g++ -MM -MD src/socket.cpp -o dep/socket.d
g++ -MM -MD src/board.cpp -o dep/board.d
g++ -MM -MD src/avatar.cpp -o dep/avatar.d
g++ -MM -MD src/area.cpp -o dep/area.d
g++ -c -ggdb3 -ansi -Wall -Werror -pedantic-errors src/area.cpp -o obj/area.o
g++ -c -ggdb3 -ansi -Wall -Werror -pedantic-errors src/avatar.cpp -o obj/avatar.o
g++ -c -ggdb3 -ansi -Wall -Werror -pedantic-errors src/board.cpp -o obj/board.o
g++ -c -ggdb3 -ansi -Wall -Werror -pedantic-errors src/socket.cpp -o obj/socket.o
g++ -ggdb3 -ansi -Wall -Werror -pedantic-errors obj/area.o obj/avatar.o obj/board.o obj/socket.o  -o ./game

When changing src/socket.h (a file upon which the others all depend) and running make, I expected it would rebuild the entire project, but it only emits one action

g++ -ggdb3 -ansi -Wall -Werror -pedantic-errors obj/area.o obj/avatar.o obj/board.o obj/socket.o  -o ./game

I believe I'm generating the automatic dependencies correctly - so I get the sense I'm simply not using them properly. Where have I gone wrong? I know the makefile:59:... errors are a clue, but I've never worked with auto generated dependencies before.

Thanks in advance; Cheers!

Answer 1

Unfortunately, your *.d files aren't getting their full dependencies; they depend on all of the header files, too. One way to fix this would be to add an extra line to the %.d directive:

# Dependency directives
$(DEP_DIR)/%.d: $(SRC_DIR)/%.cpp
  $(CPPC) -MM -MD $< -o $@
  sed -i 'p;s|$(OBJ_DIR)/\(.*\)\.o:|$(DEP_DIR)/\1.d:|' $@

If the -i scares you, you could try sponge (in the moreutils package on my distribution).