How to get left or right node in tsearch node

Question

I used the example (exactly that example) given here: https://man7.org/linux/man-pages/man3/tsearch.3.html

But I could not use LEFT macro or struct node_t struct. I just want to move left or right node by myself because I need to check the tree created by tsearch if it is full tree, or balanced or ccomplete etc.

While using LEFT, I am getting implicit declaration error, with struct node_t I am getting dereferencing pointer to incomplete type.

How can I move to left or right child by myself? Is there any way to check the tree created by tsearch is balanced or not (e.g.)

Thanks

I checked search.c source code, found some macros but cannot use them because of compiling errors