Snow Leopard breaks GCC?

GCC is not broken, it is just that the newer (default) version 4.2 of GCC is more sophisticated in giving you warnings (they are not errors) about what might be wrong with your code...

Now I'm more into C++, and don't know my way around ObjC very much, but shouldn't you derive from NSObject, rather than Object?

The error message sounds as if you changed the include, but didn't change Object to NSObject in the declaration of class Fraction.

It isn't "free", it is "release". If you are doing Cocoa code, you should probably start with the Xcode Cocoa template. That will give you all the shared libraries you need.

tkambler wrote:
I am reading "Programming in Objective C" by Stephen Kochan:
The book states that the examples apply to OS X. I guess that's not true?

I can't comment on that. You can compile that code on OS X, if you have all the correct command line parameters. But no one does objective-c outside of Xcode, from the command line.

You just need to link against the Foundation framework.


colin@weasel:/tmp> cat fraction.m
#import <stdio.h>
#import <Foundation/NSObject.h>

@interface Fraction: NSObject
{
int numerator;
int denominator;
}

-(void) print;
-(void) setNumerator: (int) n;
-(void) setDenominator: (int) d;
-(int) numerator;
-(int) denominator;

@end

@implementation Fraction;

-(void) print
{
printf ("%i,%i", numerator, denominator);
}

-(void) setNumerator: (int) n {
numerator = n;
}

-(void) setDenominator: (int) d {
denominator = d;
}

-(int) numerator {
return numerator;
}

-(int) denominator {
return denominator;
}

@end

int main (int argc, char *argv[])
{
Fraction *myFraction;
myFraction = [Fraction alloc];
myFraction = [myFraction init];

// Set fraction to 1/3

[myFraction setNumerator: 1];
[myFraction setDenominator: 3];

// Display the fraction

printf ("The value of the fraction is %i/%i\n", [myFraction numerator], [myFraction denominator]);

[myFraction free];

return 0;
}

colin@weasel:/tmp> gcc fraction.m -framework Foundation
fraction.m: In function ‘main’:
fraction.m:58: warning: ‘Fraction’ may not respond to ‘-free’
fraction.m:58: warning: (Messages without a matching method signature
fraction.m:58: warning: will be assumed to return ‘id’ and accept
fraction.m:58: warning: ‘...’ as arguments.)

colin@weasel:/tmp> ./a.out
The value of the fraction is 1/3
2009-09-03 08:07:02.800 a.out[693:903] * __NSAutoreleaseNoPool(): Object 0x10010c6e0 of class NSCFString autoreleased with no pool in place - just leaking
2009-09-03 08:07:02.808 a.out[693:903] -[Fraction free]: unrecognized selector sent to instance 0x10010c5c0
2009-09-03 08:07:02.808 a.out[693:903] * __NSAutoreleaseNoPool(): Object 0x100110040 of class NSCFString autoreleased with no pool in place - just leaking
2009-09-03 08:07:02.809 a.out[693:903] * __NSAutoreleaseNoPool(): Object 0x1001101b0 of class NSException autoreleased with no pool in place - just leaking
2009-09-03 08:07:02.809 a.out[693:903] * __NSAutoreleaseNoPool(): Object 0x100110a70 of class _NSCallStackArray autoreleased with no pool in place - just leaking
2009-09-03 08:07:02.810 a.out[693:903] * __NSAutoreleaseNoPool(): Object 0x100110ad0 of class _NSCallStackArray autoreleased with no pool in place - just leaking
2009-09-03 08:07:02.810 a.out[693:903] * __NSAutoreleaseNoPool(): Object 0x100110d90 of class NSCFString autoreleased with no pool in place - just leaking
2009-09-03 08:07:02.887 a.out[693:903] * __NSAutoreleaseNoPool(): Object 0x100111ae0 of class NSCFString autoreleased with no pool in place - just leaking
2009-09-03 08:07:02.888 a.out[693:903] * __NSAutoreleaseNoPool(): Object 0x100110bd0 of class NSConcreteMutableData autoreleased with no pool in place - just leaking
2009-09-03 08:07:02.889 a.out[693:903] * Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[Fraction free]: unrecognized selector sent to instance 0x10010c5c0'
* Call stack at first throw:
(
0 CoreFoundation 0x00007fff861025a4 __exceptionPreprocess + 180
1 libobjc.A.dylib 0x00007fff85fa5313 objc exceptionthrow + 45
2 CoreFoundation 0x00007fff8615b2a0 +[NSObject(NSObject) doesNotRecognizeSelector:] + 0
3 CoreFoundation 0x00007fff860d530f __forwarding__ + 751
4 CoreFoundation 0x00007fff860d1458 CF_forwarding_prep0 + 232
5 a.out 0x0000000100000d72 main + 187
6 a.out 0x0000000100000bc8 start + 52
7 ??? 0x0000000000000001 0x0 + 1
)
terminate called after throwing an instance of 'NSException'
Abort trap
colin@weasel:/tmp>

Even though my other post (more or less) shows how to compile ObjC from the command line, I agree that (in particular a beginner) should use XCode with its templates, and follow the introductory tutorials that are part of Apple's developer documentation, before trying to fiddle around with low-level details of the build process...

... and then, you can look at Xcode's build logs and see exactly the parameters you need to pass on the command line.

Guys, I'm new to Objective-C too and encountered the same error on Snow Leopard. The problem only occurs when the Active Architecture in XCode is set to x86_64. If you flip this over to i386 the example code compiles fine.

I recognize the example code referenced. It's from the same Programming in Objective C book that I'm reading which apparently dates back to the pre-xcode days at Apple (circa. 2002/2003).

Neil

iNeil wrote:
Guys, I'm new to Objective-C too and encountered the same error on Snow Leopard.

I doubt it since the original error was user error.

I recognize the example code referenced. It's from the same Programming in Objective C book that I'm reading which apparently dates back to the pre-xcode days at Apple (circa. 2002/2003).

There are no pre-xcode days. There used to be ProjectBuilder, but that was just an old name for Xcode. The code in question was never correct, not even on day 1. Maybe it worked 6 or 7 years ago, but it doesn't now and no one should be using it as a reference.

just use the flag --arch i386

10.6.x is shipped with 64bit defaults. for some reason that i don't know the Object.h header file seems to dislike the 64bit mode.

$gcc -arch i386 -o fraction fraction.m -lobjc

works like a charm.

happy coding

--
costantino