Getting make to create object files in a specific directory

Question

GNU Make 3.82 gcc 4.7.2 c89 

I have the following make file:

INC_PATH=-I/home/dev_tools/apr/include/apr-1 LIB_PATH=-L/home/dev_tools/apr/lib LIBS=-lapr-1 -laprutil-1 RUNTIME_PATH=-Wl,-rpath,/home/dev_tools/apr/lib CC=gcc CFLAGS=-Wall -Wextra -g -m32 -O2 -D_DEBUG -D_THREAD_SAFE -D_REENTRANT -D_LARGEFILE64_SOURCE $(INC_PATH) SOURCES=$(wildcard src/*.c) OBJECTS=$(patsubst %.c, %.o, $(SOURCES))  EXECUTABLE=bin/to  all:    build $(EXECUTABLE)  $(EXECUTABLE):  $(OBJECTS)     $(CC) $(CFLAGS) -o $@ $(RUNTIME_PATH) $(OBJECTS) $(LIB_PATH) $(LIBS)  $(OBJECTS): $(SOURCES)     $(CC) $(CFLAGS) -c $(SOURCES) $(LIB_PATH) $(LIBS)  build:     @mkdir -p bin  clean:     rm -rf $(EXECUTABLE) $(OBJECTS) bin     find . -name "*~" -exec rm {} \;     find . -name "*.o" -exec rm {} \; 

My directory structure is like this project/src project/bin. My Makefile is in the project (root) folder, and all my *.h and *.c are in the src directory. Currently I have only one source file called timeout.c

I get this error:

gcc: error: src/timeout.o: No such file or directory 

I have used this to get all the source files:

SOURCES=$(wildcard src/*.c) 

And the object files:

OBJECTS=$(patsubst %.c, %.o, $(SOURCES)) 

However, the make seems to create the object file in the project root folder where the Makefile is. Should it not put it in the src directory?

Answer 1

You have two problems in this rule (well, three):

$(OBJECTS): $(SOURCES)     $(CC) $(CFLAGS) -c $(SOURCES) $(LIB_PATH) $(LIBS) 

You haven't noticed yet, but the rule makes each object dependent on all sources, and tries to build that way. Not a problem as long as you have only one source. Easy to fix with a static pattern rule and an automatic variable:

$(OBJECTS): src/%.o : src/%.c     $(CC) $(CFLAGS) -c $< $(LIB_PATH) $(LIBS) 

Also, the command ("$(CC)...") doesn't specify an output file name, so gcc will infer it from the source file name; if you give it src/timeout.c, it will produce timeout.o (in the working directory, project/). So you should specify the desired path to the output file. Easy to do with another automatic variable:

$(OBJECTS): src/%.o : src/%.c     $(CC) $(CFLAGS) -c $< $(LIB_PATH) $(LIBS) -o $@