objective-c compilation error

Question

I'm using Fedora(laughlin). I've done lots of programming in c, and java on this distro. So i decided to try out some Objective-C programming in linux. I searched lots of pages over the internet and finally found one.

http://www.techotopia.com/index.php/Building_and_Installing_GNUstep_on_Linux

I went as per the instructions given on this page to install GNUstep.

Everything went well in the installation. But after writing a small piece of code and compiling it using the command:

gcc gnustep-config --objc-flags` -L/usr/GNUstep/System/Library/Libraries -lgnustep-base hello.m -o hello

It gave me the following error:

/usr/bin/ld: /usr/GNUstep/System/Library/Libraries/libgnustep-base.so: undefined reference to symbol 'objc_msg_lookup' /usr/bin/ld: note: 'objc_msg_lookup' is defined in DSO /usr/lib/libobjc.so.2 so try adding it to the linker command line /usr/lib/libobjc.so.2: could not read symbols: Invalid operation collect2: ld returned 1 exit status

I'm new to Objective-C. I have no idea where the linker command exists. I tried adding the /usr/lib to the env. variable. But it didn't work out. I also tried to find out solutions on their forum(if they had one!!). But they have none.

Can anyone please help me with this?

Thanks in advance!!

Answer 1

It's complaining that you're referencing code that you aren't linking to your application. Helpfully, it's telling you what's missing and where it is. Try adding -lobjc to the flags.