Makefile trouble, clarification needed

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?

enter image description here

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

Hey, the image is not displayed anymore - could you please maybe upload it or smth so that others could see it too?? — pseudonym_127, Jun 28 '13 at 12:42

score 1 · Accepted Answer · edited May 23 '17 at 10:30

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".

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 $@.

edited May 23 '17 at 10:30

Community

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answered Aug 08 '12 at 03:22

Jonathon Reinhart

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It is currently trying to `g++ -pedantic -Wall -c src/a.cpp -o obj//src/a.o`, where `obj//src` does not exist. – James Raitsev Aug 08 '12 at 03:40
You need to change SOURCES to not have the path in front. Maybe cd first in your shell command. – Jonathon Reinhart Aug 08 '12 at 03:46
Try `SOURCES = $(shell cd src && echo *.cpp)` and replace your usage of `$(SOURCES)` with `src/$(SOURCES)`. – Jonathon Reinhart Aug 08 '12 at 03:59
Same deal, `src` appears out of somewhere, updated scripts on top – James Raitsev Aug 08 '12 at 04:01

score 0 · Answer 2 · answered Aug 08 '12 at 14:03

0

All is ok when used like this. A small modification from what Jonathon suggested

enter image description here

answered Aug 08 '12 at 14:03

James Raitsev

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All is *not* okay. You have no dependencies listed for $(OBJECTS), so they will never get re-built. – Jonathon Reinhart Aug 08 '12 at 15:43

Makefile trouble, clarification needed

2 Answers2