Makefile: rule to put .o in different directory

Question

I've got this directory structure:

./src contains the the .cpp and the .h of all the files I need
./bin should contain the .o temporarily and the .bin permanently. Also, this folder should be deleted when calling make clean.
./ contains the Makefile

This is my current Makefile:

CFLAGS = -Wall -pedantic -g
CC = g++
EXEC = flrfile
SRC_DIR = src
BIN_DIR = bin
OBJ = FixedLengthFieldsRecord.o FixedLengthRecordFile.o main.o

all: flrfile

../$(BIN_DIR)/%.o: $(SRC_DIR)%.cpp $(SRC_DIR)%.h
    $(CC) $(CFLAGS) -c $(SRC_DIR)%.cpp -o $@

$(EXEC): $(OBJ)
    @mkdir -p bin
    $(CC) $(CFLAGS) $(BIN_DIR)/$(OBJ) -o $(BIN_DIR)/$(EXEC)

.PHONY : clean

clean:
    -rm -rf $(BIN_DIR)

When I run make, I get this error:

make: *** No rule to make target `FixedLengthFieldsRecord.o', needed by `flrfile'.  Stop.

Why is this?

PS: Also, how could I make the OBJ = FixedLengthFieldsRecord.o FixedLengthRecordFile.o main.o more generic? I don't want to write all the .o...

http://stackoverflow.com/questions/5178125/gnu-make-how-to-get-object-files-in-separate-subdirectory — gongzhitaao, Apr 03 '13 at 19:23

Akobold · Answer 1 · 2013-04-03T19:42:08.510

3

It's because you don't have a rule for something.o, you have a rule for ../bin/something.o.

If you change your OBJ declaration to

OBJ = ../$(BIN_DIR)/FixedLengthFieldsRecord.o ../$(BIN_DIR)/FixedLengthRecordFile.o ../$(BIN_DIR)/main.o

It should work.

You could get objects from source dir using wildcards

SOURCES := $(wildcard $(SRC_DIR)/*.cpp)
OBJ := $(patsubst $(SRC_DIR)/%,%,$(SOURCES))
OBJ := $(patsubst %.cpp,%.o,$(OBJ))
OBJ := $(addprefix ../$(BIN_DIR)/,$(OBJ))

What this does is that first it get a list of cpp files from $(SRC_DIR), removes the path, then replaces all cpp suffixes for o and lastly add `../$(BIN_DIR)/' in front of each item.

edited Apr 03 '13 at 19:42

answered Apr 03 '13 at 19:20

Akobold

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Also, `$(BIN_DIR)/$(OBJ)` in `$(EXEC): $(OBJ)` should be changed to `$(OBJ)`. – Andrejs Cainikovs Apr 03 '13 at 19:23
@Akobold, I get this: `Makefile:6: *** unterminated call to function `addsuffix': missing `)'. Stop.` – Maria Ines Parnisari Apr 03 '13 at 19:26
@i19: Indeed, I missed a few ')' - just fixed it :) – Akobold Apr 03 '13 at 19:27
@Akobold, now I get a "missing separator" error :( on this line: `@mkdir -p bin` – Maria Ines Parnisari Apr 03 '13 at 19:29
@l19: just edited my answer :) – Akobold Apr 03 '13 at 19:32
@Akobold I still get the same error :S – Maria Ines Parnisari Apr 03 '13 at 19:36
Ok, I solved it... I was using white spaces instead of tabs. – Maria Ines Parnisari Apr 03 '13 at 20:02

Makefile: rule to put .o in different directory

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