Makefile error message

Question

I'm new to Stack Overflow. I'm currently having a hard time solving a simple problem.

In my shell/ directory, I have:

CVS/
include/
Makefile
obj
src

My problem occurs when trying to direct object files to be built in obj, but when I run make with the following code:

# Beginning of Makefile
OBJS = obj/shutil.o obj/parser.o obj/sshell.o
HEADER_FILES = include/shell.h include/parser.h
EXECUTABLE = simpleshell
CFLAGS = -Wall
CC = gcc
# End of configuration options

#What needs to be built to make all files and dependencies
all: $(EXECUTABLE)

#Create the main executable
$(EXECUTABLE): $(OBJS)
         $(CC) -o $(EXECUTABLE) $(OBJS)

#Recursively build object files
%.o: %.c
        $(CC) $(CFLAGS) -c -o $@ $<

#Define dependencies for objects based on header files
#We are overly conservative here, parser.o should depend on parser.h only
$(OBJS) : $(HEADER_FILES)

clean:
        -rm -f $(EXECUTABLE) obj/*.o
run: $(EXECUTABLE)
        ./$(EXECUTABLE)

tarball:
         -rm -f $(EXECUTABLE) obj/*.o
         (cd .. ; tar czf Kevin_Fairchild_a3.tar.z shell )

# End of Makefile

I get this error:

gcc -o simpleshell obj/shutil.o obj/parser.o obj/sshell.o
gcc: obj/shutil.o: No such file or directory
gcc: obj/parser.o: No such file or directory
gcc: obj/sshell.o: No such file or directory
gcc: no input files
make: *** [simpleshell] Error 1

What simple piece am I missing? I will continue to research and learn more about Makefiles

Answer 1

after adding that simple modification, which I originally attempted before posting here, i.e.

obj/%.o: src/%.c 

I recieved this error, so originally I though it was something else.

gcc -Wall -c -o obj/shutil.o 
src/shutil.c
src/shutil.c:14:19: error: shell.h: No such file or directory
src/shutil.c: In function ‘signal_c_init’:
src/shutil.c:72: error: ‘waitchildren’ undeclared (first use in this function)
src/shutil.c:72: error: (Each undeclared identifier is reported only once
src/shutil.c:72: error: for each function it appears in.)
src/shutil.c: In function ‘checkbackground’:
src/shutil.c:90: warning: implicit declaration of function ‘striptrailingchar’
src/shutil.c: At top level:
src/shutil.c:101: warning: conflicting types for ‘striptrailingchar’
src/shutil.c:90: note: previous implicit declaration of ‘striptrailingchar’ was here
make: *** [obj/shutil.o] Error 1` 

Thanks for the quick reply by the way!

Answer 2

The trouble is that the pattern rule

%.o: %.c
    ...

doesn't actually match what you're trying to do. The source file is actually src/shutil.c, so this rule doesn't fit. All Make sees is this rule:

$(OBJS) : $(HEADER_FILES)

There are no commands, so Make concludes that no action is necessary. It then proceeds with the rule for simpleshell, which fails because the objects aren't there.

Try this:

obj/%.o: src/%.c
    $(CC) $(CFLAGS) -c -o $@ $<

There are more sophisticated variations, once this much is working.