Link with GNUstep on Ubuntu 14.04, 64 bit

Question

I am attempting to compile a simple application that references GNUstep classes, with GNUstep on my Ubuntu 14.04, 64 bit, machine:

#import <Foundation/Foundation.h>
#import <Cocoa/Cocoa.h>

int main(int argc, char **argv)
{
    NSString *bestType = [[NSPasteboard generalPasteboard]
                          availableTypeFromArray: nil];
    NSLog(@"best type: %@", bestType);
    return 0;
}

Here are my compile and link flags (some of which may be overkill):

CFLAGS=`gnustep-config --objc-flags` -std=gnu99
LDFLAGS=`gnustep-config --base-libs` -lgnustep-base -lobjc -lm -lglut -lGLU -lGL

Before compilation I ran the script:

/usr/share/GNUstep/Makefiles/GNUstep.sh

And here is the output from 'make -n'

gcc main.m `gnustep-config --objc-flags` -std=gnu99 -L. `gnustep-config --base-libs` -lgnustep-base -lobjc -lm -lglut -lGLU -lGL -o tester

But when linking, Cocoa classes seem to not be pulled in, and I get an undefined reference error:

/tmp/ccnyXBoH.o:(.data.rel+0x8): undefined reference to `__objc_class_name_NSPasteboard'

If I remove all references to Cocoa classes in main.m, the app compiles without error.

Answer 1

The reason why you can't find the class definition for NSPasteboard is because it's in the gnustep-config --gui-libs options - i.e. the symbol is in the gui library of GNUStep, not in the base library of GNUStep. The solution is to change the LDFLAGS line to:

LDFLAGS=`gnustep-config --gui-libs` -lglut -lGLU -lGL

You shouldn't need to double-specify -lgnustep-base -lobjc -lm - they're part of both --base-libs and --gui-libs.