Question

I’m new to makefiles, so I apologize in advance if this is a silly question. Also I removed most variables from my makefile because they weren’t working properly (gnu make tells me that $(myvar) should be completely replaces by the value of myvar, however the output of make was showing me that this was not happening), so I apologize for the ugliness and the more than 80 character lines.

acolibobj = acoLibInit acoGlobalDefs
acolibinterface: $(acolibobj).o
acoLibInit.o:
    gcc -fPIC -g -c -Wall -I/usr/include/dc1394 -o acoLibinit.o acoCommands/acoLibInterface/acoLibInit.c
acoGlobalDefs.o:
    gcc -fPIC -g -c -Wall -I/usr/include/dc1394 -o acoGlobalDefs.o acoCommands/acoLibInterface/acoGlobalDefs.c

When I run this makefile I get:

gcc -fPIC -g -c -Wall -I/usr/include/dc1394 -o acoLibinit.o acoCommands/acoLibInterface/acoLibInit.c
cc   acoLibInit.o   -o acoLibInit
gcc: acoLibInit.o: No such file or directory
gcc: no input files
make: *** [acoLibInit] Error 1

So far as I can tell, what’s happening is that make is trying to compile AND link, even though I explicitly added the -c flag. When I run “gcc -fPIC -g -c…” myself (from bash), I do not get any problems at all. Why does make go on to try “cc acoLibInit.o -o acolibInit”?

Answer 1

make is trying to build acoLibInit. It probably has built-in rule that specifies "whatever" can be produced by linking "whatever.o", which is why you get that cc line.

This line:

acolibinterface: $(acolibobj).o

expands to:

acolibinterface: acoLibInit acoGlobalDefs.o

(note the absence of .o on the first dependency). This is why it’s trying to link acoLibInit.

Try this:

acolibinterface: $(addsuffix .o,$(acolibobj))

if you want only the .o files as dependencies for that target.