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Re: how to compile a .m

From: David Chisnall
Subject: Re: how to compile a .m
Date: Wed, 14 Oct 2009 13:33:30 +0100

Just add it to the GNUmakefile, so this line

test_OBJC_FILES = hello.m

becomes something like

test_OBJC_FILES = hello.m main.m

You don't need to specify headers in the GNUmakefile unless you are building a framework, or some other target where the headers need to be installed.


On 14 Oct 2009, at 13:28, Jean-Loïc Mauduy wrote:

Thank you everyone for your answers.
The GNUmakefile worked well!
Now I have another .m, that I used in a main.m, described by a .h. How do I include this new information in the makefile?

Thank you for your help!


2009/10/14 David Chisnall <address@hidden>
A couple of other people have already mentioned GNUstep Make. For short programs, gnustep-config is also an option. You can compile a simple Objective-C program like this:

gcc `gnustep-config --objc-flags --base-libs` hello.m

This will generate an a.out file linked against GNUstep Base (Foundation). Substitute --gui-libs if you want to link AppKit (but, generally, if you are linking against AppKit you will want to make a bundle and then it's much easier to use GNUstep Make). For both, you will need to source the GNUstep.sh file first, I believe (I'm not 100% sure if gnustep-config needs this).

On 14 Oct 2009, at 00:30, Jean-Loïc Mauduy wrote:

#import <stdio.h>

This is wrong. A few Objective-C tutorials make this mistake, and tell you to just use #import instead of #include in Objective-C programs, but this is terrible advice. #include is a trivial preprocessor directive that just inserts the contents of the specified file at this point. #import is a bit more clever, and ensures that the file is only ever inserted once.

Objective-C headers are, generally, designed to be used with #import. A lot of C (and C++) headers, however, are not. They will protect themselves from multiple inclusion with macros and may be designed to work differently if included more than once in a compilation unit. If you get into the habit of using #import with C headers, then you are going to end up with something breaking eventually, and you are going to be very confused about why. Only use #import with Objective-C headers; stick with #include for C headers. This also provides a clue to people reading your code about what kind of header you are including.


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