Subject: question Sorry for not responding sooner; I was away. And I should have remembered the original question. In practice a (non ANSI) compiler can't be too strict about diagnosing mismatch of actual and formal parameters, or imputed actual parameters, because of routines like printf. Nevertheless, the intent of the "compiler does not compare" clause was more to warn the programmer that consistency was his responsibility than to forbid a compiler from detecting inconsistency. Again pragmatically, I suspect that a compiler should probably be somewhat liberal if it does detect a mismatch-- give warnings rather than fatal errors, for example. In particular, you do want to be able to compile printf together with routines that use it! In addition, there is lots of code floating around that is actually in error, but if compiled straightforwardly and blindly will in fact work. You will need to deal with this somehow. An ANSI compiler is presumably entitled to be more stringent, because there are explicit means of indicating that a function's arguments are variadic. In short, you're welcome to check argument consistency, but be careful that your compiler doesn't cause more trouble than it saves: the purpose is presumably to alert users to problematic programs, not to prevent importation of code that will in fact work, at least on most machines (including the one you are compiling for). Dennis