CODEWITHSUNDEEP
cgccmakefile
Alexandru Barbarosie
Alexandru Barbarosie

Reputation: 2992

"No rule to make target" althoug the rule exists

I have an issue with my makefile which says No rule to make target /obj/%.o, needed by /bin/exec. Stop. But from what I understand I have it:

# define the C compiler to use
CC = gcc

# define any compile-time flags
# add -DDEBUG for debug mode
CFLAGS = -Wall 

# define any directories containing header files
INCLUDES = -I/includes

# define src folder
SRC_FOLDER = /src

# define src files
SRC = $(wildcard $(SRC_FOLDER)/%.cpp)

# define object folder
OBJ_FOLDER = /obj

# define obj files
OBJ = $(patsubst %.cpp, %.o, $(SRC))

# define binary path
BIN_FOLFER = /bin

# define the executable file 
MAIN = $(BIN_FOLFER)/exec

# compile object files
$(OBJ_FOLDER)/%.o: $(SRC_FOLDER)/%.cpp
    $(CC) $(CFLAGS) $< -o $@

# build
$(MAIN): $(OBJ_FOLDER)/%.o
    $(CC) $(CFLAGS) $^ -o $@

# cleaning 
.PHONY: clean

clean:
    rm -f $(OBJ_FOLDER)/%.o

I am sorry for any possible major errors in the makefile, this is my first makefile. What am I doing wrong?

Upvotes: 0

Views: 1516

Answers (2)

Jan Hudec
Jan Hudec

Reputation: 76236

$(MAIN): $(OBJ_FOLDER)/%.o

requests %.o exactly. The % does not act as pattern here, because it does not appear on both sides of the rule. You need to use the $(OBJ) variable there. But it first need to be fixed, because you are only replacing the extension, but you need to replace the directory too.

  1. Finish the $(OBJ) variable (as Lutin already said) (ok, but I modified it a bit; I presume you only want the direct descendants of the directory):

    SRC = $(wildcard $(SRC_FOLDER)/*.cpp)
OBJ = $(patsubst $(SRC_FOLDER)/%.cpp, $(OBJ_FOLDER)/%.o, $(SRC))

  2. Fix the rule to actually use the $(OBJ) variable:

    $(MAIN): $(OBJ)

  3. Oh, and you most probably don't want SRC_FOLDER, OBJ_FOLDER and BIN_FOLDER to start with / as that puts them in the filesystem root it's not where your project lives. And with the patterns above they should not end with slash either.

Upvotes: 4

Lutin
Lutin

Reputation: 3

It works with that: 

SRC = $(wildcard $(SRC_FOLDER)*/*.cpp $(SRC_FOLDER)*.cpp)
OBJ = $(patsubst $(SRC_FOLDER)%.cpp, $(OBJ_FOLDER)%.o, $(SRC))

Upvotes: 0

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