From -6007606807559807356 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,e94695845965b249 X-Google-Attributes: gidf78e5,public X-Google-ArrivalTime: 1992-12-10 11:03:51 PST Path: sparky!uunet!mdcbbs!swordfish!alanb Newsgroups: comp.std.c++ Subject: Re: Zero-length structures and pointer comparisons Message-ID: From: alanb@sdl.mdcbbs.com (Alan Braggins) Date: 10 Dec 92 16:12:17 GMT References: <1992Dec07.222242.18703@microsoft.com> <1992Dec8.103218.27689@lth.se><9234423.15066@mulga.cs.mu.OZ.AU> <1992Dec10.121200.18889@ucc.su.OZ.AU> Organization: Shape Data (Division of EDS), Cambridge UK Nntp-Posting-Host: 134.244.153.110 In-reply-to: maxtal@extro.ucc.su.OZ.AU's message of Thu, 10 Dec 1992 12:12:00 GMT Lines: 35 >>>>> On Thu, 10 Dec 1992 12:12:00 GMT, maxtal@extro.ucc.su.OZ.AU (John MAX Skaller) said: > This seems like an excellent suggestion. It suffers only > in those cases where we must ask whether it makes sense to > compare two pointers at all. For example a char* and a function > pointer. Might not these accidentally have the same address? > Similarly suppose we allowed nested functions, then > pointers to them would need a pointer to a stack frame as well > as the function address (or instead of?). They would be totally > different types of objects really. My understanding of the ANSI-C standard (prompted by some complaints from lint) is that functions aren't objects, and that casting a function pointer to void* is implementation dependent, so so is comparing them with ptrcmp(void*, void*). If imposing a total ordering over both objects and functions is really desirable and possible, it could be a seperate function. I think the function should become part of the standard C library, and should have a name from ISO section 7.13 Future library directions. "mem" seems the most appropriate prefix, but stdlib.h seems more appropriate than strings.h, which means it should "begin with str and a lowercase letter (followed by any combination...". If possible, it should be implemented in such a way that it is no slower than using "<" on pointers where that is a total ordering. What's the current state of the library functions may be macros/ inline functions/inline functions with external linkage discussion? -- Alan Braggins, alanb@sdl.mdcbbs.com, abraggins@cix.compulink.co.uk Shape Data - A division of EDS-Scicon Limited. Cambridge, UK +44-223-316673 "Any technology distinguishable from magic is insufficiently advanced." "My employer does not necessarily share my views - but I'm working on it."