Re: max-specpdl-size errors.

[ I'm _NOT_ subscribed, please observe MFT ] I know that c.e.x would be a better forum for this, but my INN has gone belly up. :-( The error: "Variable binding depth exceeds max-specpdl-size" is giving me grief with one of my projects. What does it mean? What causes it? How can I debug it? What on earth is "specpdl" an abbreviation of? It certainly isn't a word in any language I know.

max-specpdl-size is the maximum size of the special variable bindings stack (stack is called "push-down list" in MIT-speak, hence "pdl"). In human language, it means that when you do this: (let ((case-fold-search nil)) ... some code ...) there is a stack to which the previous value of case-fold-search is pushed. When the `let' form is finished, the previous value of case-fold-search is restored by popping the old value from the specpdl stack. max-specpdl-size exceeded can mean either that the nesting of `let' and `unwind-protect' forms has genuinely exceeded the limit, or (more usual) that an infinite recursion has occurred. The current default for max-specpdl-size is 3000, which is pretty hard to exceed without an infinite recursion. Although, with the complex new applications such as the Semantic Bovinator, anything is possible.