Question

The following is the Makefile i use. All is well, except for .o should be created in obj/ directory and it’s not.

What am i doing wrong please?

After making sure that

• src directory contains a.cpp
• target directory exists and is empty
• obj directory exists and is empty

When make is ran, i see

g++ -pedantic -Wall -c src/a.cpp  -o /Users/me/Dropbox/dev/c++/hott/obj/src/a.o

when it should be

g++ -pedantic -Wall -c src/a.cpp  -o /Users/me/Dropbox/dev/c++/hott/obj/a.o

What am i doing wrong please?

UPDATE: Nothing seems to change when hardcoding path and not relying on pwd resolution

Answer 1

If you use -o you have to specify the filename, not just the output path. Try:

$(CC) $(FLAGS) $(SOURCES) $(OBJ)/$@

This question may help, too:

• What do the makefile symbols $@ and $< mean?

Also, you may want to call FLAGS something like CFLAGS, meaning “the flags for compilation”.

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Edit

Note that you are not using make efficiently, because you are always recompiling all your .o files from your .cpp files. You should instead use a Pattern Rule, so that Make can have rules to only build what is necessary. (ie. “To build any .o file from a .cpp file, do this: ___”) 

%.o : %.c
    $(CC) -c $(CFLAGS) $(CPPFLAGS) $< -o $@

You could edit this to include $(OBJ) before the $@.