"Running non recursive evaluator"

[parisse]

I don't know any portable way to check for stack overflow in C. That's the reason for the max recursive eval parameter. Initially, you got a runtime error if the max number of recursive calls was reached, later I implemented a non-recursive evaluator (with dynamic allocation of the space required to make recursive calls), you don't get an error anymore, but it's slower, therefore the warning remains.
By the way, you should not consider the CAS programming language like a traditional programming language designed by CS people for large projects. Like for many other CAS, it's just a scripting language to make easily small programming extensions (say up to about 1000 lines of code on a PC). Large CAS development should be done in C++ on a PC/Mac with libgiac.