Thread: Quick Makefile Question

Sometimes when I run my makefile that consist of the following

[code]
default:
g++ -o prog1 prog1.cpp

clean:
rm -rf *.o
rm -rf core*
[code]

It sometimes says the file is updated, but I've just updated the source and it won't call the default tag for some reason.

I'm suppose to make a makefile that properly makes the program. Calling "make default" should only do the necessary work - it shouldn't recompile anything that doesn't need it. "make clean" should remove any core dump files and the .o and executable files.

Is this correct? I think someone said I had to worry about depencies or something, I guess what I have to do is that if the source is update or executable is, then it shouldn't update or something?

So if prog.o is older than prog.c then it will compile the source with this makefile, else it will skip it ?

Code:

#Makefile
#############

default: clean compile

compile: prog.cpp
            g++ -o prog prog.cpp

clean:
            rm -f *.o prog a.out core*

Originally Posted by cisokay

So if prog.o is older than prog.c then it will compile the source with this makefile, else it will skip it ?

Code:

#Makefile
#############

default: clean compile

compile: prog.cpp
            g++ -o prog prog.cpp

clean:
            rm -f *.o prog a.out core*

A simple make statement is like this:

Code:

target: dependancies
    command

if any of the dependancies is newer than target, command is run. Note that the command must have a tab char before.

Your make will always compile prog. You're stating that compile depends on prog.cpp. When that command is run no file named compile exists, so the command is always run, whenever make is run.
Also you're not stating that prog depends on prog.cpp. re-read my previous post.

and finally since I seriously doubt that there'll ever be any file called compile declare compile like this
.PHONY compile
In other words, compile will always be a word passed through the command line like clean
To sum up we have

Code:

prog: prog.cpp
    g++ prog.cpp -o prog

.PHONY clean compile

compile: prog

clean:
    rm -f *.o prog a.out core*

Thanks, I think I get it now. One question, I get makefile:4: *** missing separator. Stop. error. I'm copying directly from your post.

It isn't liking the
.PHONY clean compile

it happens