So, you've removed half the code (probably including the code that has the actual problem) and the error message, and you want us to solve the problem?

As has been pointed out, there is nothing intrinsically wrong with curr->nd->element, so something else must be wrong.

What error is it showing? Are you getting a compile-time error or a runtime error?

It's not a good idea to #include C files in C files. Rename stack_check.c to stack_check.h and make sure it only has header stuff in it. Better still, merge everything into one C file, solve the problems, then you can split it back out again as necessary.