Objective c undefined reference to objc class

[Celtrix]

i get an undefined reference to _objc_class_name_greeter error when I compile
When I remove the line
Greeter * Hi=[[greeter alloc] init];
it compiles and all but one option works any idea what's wrong with that line
Also the error is at .data+0xa4 and correction it actually happens during linking ?
Take note that I wrote this on my iPod touch and auto correct is on all the time

[Celtrix]

I have solved the general problem but not my specific problem I'm compiling on Linux so I have to invoke a few extra gcc options
Ex
gcc -o main main.m -lobjc -i /usr/include -L(I'll post this in a little while) -lgnu-base
Ill finish the whole thing in a sec