From 324021309977899504 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,ea96cc047f6a22cc X-Google-Attributes: gidf78e5,public X-Google-ArrivalTime: 2001-08-13 11:35:01 PST Path: archiver1.google.com!newsfeed.google.com!sn-xit-02!supernews.com!newsfeed.direct.ca!look.ca!dispose.news.demon.net!news.demon.co.uk!demon!mail2news.demon.co.uk!not-for-mail From: comeau@panix.com (Greg Comeau) Newsgroups: comp.std.c++ Subject: Re: extern "C" -- what is the intent? Date: Mon, 13 Aug 2001 18:32:40 GMT Organization: Comeau Computing; http://www.comeaucomputing.com Approved: Fergus Henderson , moderator of comp.std.c++ Message-ID: <9l8qvc$7ig$1@panix3.panix.com> References: <090820010209154805%BobbySchmidt@mac.com> <9l62tf$c2g$1@panix3.panix.com> Reply-To: comeau@comeaucomputing.com X-Trace: mail2news.demon.co.uk 997727658 mail2news:6796 mail2news mail2news.demon.co.uk X-Complaints-To: abuse@demon.net X-Mail2News-Path: news.demon.net!mulga.cs.mu.oz.au X-Authentication-Warning: mulga.cs.mu.OZ.AU: fjh set sender to devnull@stump.algebra.com using -f X-Robomod: STUMP, ichudov@algebra.com (Igor Chudov) Lines: 82 Xref: archiver1.google.com comp.std.c++:6965 In article , Hans Aberg wrote: >In article <9l62tf$c2g$1@panix3.panix.com>, comeau@comeaucomputing.com wrote: >>IMO, it gets fuzzy, but the thing is that the liberty for >>it to "do the right thing" does exist. I'm not sure what you >>mean by "special Pascal compiler" since usually so-called >>"LanguageX calling convention" is a slippery beast in itself, >>and so one usually is talking about calling conventions >>for a specific release of a specific compiler (though clearly >>some convention are popular). > >I am disregarding the fact that the compilers always must somehow be tuned >together. Ok (it seem you want to go somewhere with this). >Then there is the question how much the linker should check for the >accuracy of the linking. In the example I gave, I figure that as Pascal >does not have name overloading, perhaps the linker would just be handed >down a function name, assuming that the binary argument is correct. Then >there would be no problems with > extern "Pascal" void f(unsigned char*); >as the argument is untyped by the time the linker sees the function a >Pascal type. If I understand what you've said, yes, I think that's possible. >In article , Francis Glassborow > wrote: >>... the C++ compiler has no idea >>what will link to C. That is an issue for the programmer, knowing what >>the compilers require. There is no reason that even this will link to C >>object code: >> >>extern "C" int foo(int, int); > >It seems me that the standard is flawed, as what is called "linkage to the >language X" does not mean that one can actually link to code written in >the language X. There are two ways around this: One is to change the name >to say "pseudo-linkage", so that it becomes explicitly clear that it is >merely a way for the C++ compiler can attach language labels onto the code >so that the linker might use it for linking. There probably is a terminology issue here, but I don't think that means (or at least has to mean) it is flawed. Either way the semantics (or lack thereof) need to be described. Anyway, I agree, there often seem to be confusion in the part of the standard. >Another way would be to strengthen the requirement so that linkage to the >language X actually means that one can link code to that language (even >though, clearly, it still depends on the two compiler being tuned >together). Then > extern "C" short foo(int); >is not legal unless one has specified conversion operators > extern "C++" int -> extern "C" int > extern "C" short -> extern "C++" short > >The spin off if forcing such conversion operators to be explicit in the >language is that the types of the different languages need not be tuned >together: In the example, it does not matter anymore that the integral >types of the two different languages are the same. One could also go a >step further, and use it to tune together different compilers of the same >language, that is, if it is somehow possible to indicate in the "extern" >declaration the name of the compiler. A problem that I have with this is that to link to Language X can't actually mean to link to Language X because often Language X doesn't describe what linking to it actually means. So it would seem wrong for Standard C++ to do so. I mean, how could it? (I think you may actually say so above, but I didn't get it.) -- Greg Comeau Countdown to "export": December 1, 2001 Comeau C/C++ ONLINE ==> http://www.comeaucomputing.com/tryitout Tasty C99/C++ Combo: Dinkumware libs + Comeau Compilers == WOW!!! --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.research.att.com/~austern/csc/faq.html ]