Installing Objective-C Compiler

Setup the Compiler

Objective-C is a strict superset of C; the additional functionality is obtained by linking to the Objective-C library when building using the standard GNU GCC Compiler. This makes setting up a new compiler very simple, as we can make a copy of the standard compiler and change the linker settings.

Caution: Make sure your GNU GCC Compiler is properly setup before attempting to setup for Objective-C

1) Go to Settings->Compiler and debugger...

2) Select GNU GCC Compiler and make a copy it; name it whatever you like, but "GNU GCC Obj-C Compiler" would be the most descriptive.

3) Under Linker Settings, add -lobjc to Other linker options; you don't need to explicitly add the libobjc.a library, as the flag tells gcc to include it for us.

Shared Library Trouble

In the past, there has been some trouble with the -lobjc flag trying to link to libobjc-2.dll, which had been a nonfunctional shared library for some time. It was recently repaired according to several newsgroup listings, but it is still suggested you remove it from your MinGW or GCC library search path and only leave the static library. This will not affect the license of your program.

Adding Filetype Support

1) Go to Settings->Environment...

2) Select Files extension handling and add *.m

3) Go to Project->Project tree->Edit file types & categories...

4) Under Sources, add *.m to the list of filetypes.

Proper Syntax Highlighting

1) Go to Settings->Editor...

2) Select Syntax highlighting and go to Filemasks.... Add *.m to the list of filetypes.

3) Go to Keywords... (next to Filemasks...) and create a new set (up arrow). Add this to the Keywords: box:

Keywords

@interface @implementation @end id BOOL YES NO

Optional Changes

1) Go to Settings->Compiler and dubugger...

2) Under Other Settings, change Compiler logging to Full command line. If ObjC still refuses to build properly for you, you can use this to compare the command line arguments C::B uses against the commands you would use if you were building the program manually on the command line.

3) Under Other Settings, go to Advanced Options. For Link object files to executable and Link object files to console executable, move -o $exe_output to the end of the macros. For reasons beyond my understanding, GCC will sometimes (albeit rarely) complain during complex builds if this isn't the last argument on the line.

Important Notes

1) By default, C::B will select CPP as the default compiler variable for a new source file, and the file will not be compiled or linked to a target. Whenever you add or create a new ObjC source (*.m) in your project, you must right-click on it and go to Properties.... Under advanced, change the compiler variable to CC. Under Build, select both Compile file and Link file. Before you close the dialog, go to General and uncheck File is read-only. This will automatically get selected when you change the other options and if you close the dialog before you uncheck it, you'll have to go back and change it, then close and reopen the file in the viewer before you can edit it.

2) When you add a header file (*.h), you'll also need to open up its properties window and change the compiler variable to CC. You don't need to do anything else to it.

Test Build

Here's a bare-bones project you can throw together to test if your C::B settings will compile ObjC correctly. You can't actually test with just strict C, since any problems with the Objective-C compiler will only manifest when using ObjC functionality.

main.m

#import <stdlib.h>
#import "TestObject.h"

int main(int argc, char** argv)
{
	TestObject *aTestObject = [[TestObject alloc] init];
	printf("Initial Value: %d\n", [aTestObject value]);
	printf("+45 Value: %d\n", [aTestObject add: 45]);
	printf("-63 Value: %d\n", [aTestObject subtract: 63]);

	[aTestObject add: 103];
	printf("+103 Value: %d\n", [aTestObject value]);

	return (EXIT_SUCCESS);
}

TestObject.h

#import <objc/Object.h>

@interface TestObject : Object
{
	int internalInt;
}

- (int)add:(int)anInt;
- (int)subtract:(int)anInt;
- (int)value;

@end

TestObject.m

#import "TestObject.h"

@implementation TestObject

- (id)init
{
	if ((self = [super init]))
	{
		internalInt = 0;
	}

	return self;
}

- (int)add:(int)anInt
{
	internalInt += anInt;
	return internalInt;
}

- (int)subtract:(int)anInt
{
	internalInt -= anInt;
	return internalInt;
}

- (int)value
{
	return internalInt;
}

@end

Objective-C Library Licensing

Unlike other libraries included with GCC, the Objective-C library may be statically linked into a project without extending the GNU GPL to that project. Although the library is covered under the GNU GPL itself, it has a special exemption in its license because it is a necessary library to compile a language.

License Exemption

/* As a special exception, if you link this library with files compiled with
GCC to produce an executable, this does not cause the resulting executable
to be covered by the GNU General Public License. This exception does not
however invalidate any other reasons why the executable file might be
covered by the GNU General Public License */