Testcases for a C interpreter
===

I would like to test a little ANSI C interpreter.
My tool interprets my C program. It doesn't produce machine code; and I can't access the heap/stack after execution!
I was thinking of validating return values / outputs against GCC or something like this.

I was searching for something that fits for me, but i hardly found anything FREE or open source.

Does anybody have an idea/suggestion how to test my interpreter?
Can anybody recommend something like a test suite; or a package of test cases?