From -9115718722167032048 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,ea96cc047f6a22cc X-Google-Attributes: gidf78e5,public X-Google-ArrivalTime: 2001-08-10 15:12:01 PST Path: archiver1.google.com!newsfeed.google.com!newsfeed.stanford.edu!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!colt.net!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: Fri, 10 Aug 2001 22:11:18 GMT Organization: Comeau Computing; http://www.comeaucomputing.com Approved: Fergus Henderson , moderator of comp.std.c++ Message-ID: <9l1los$281$1@panix3.panix.com> References: <090820010209154805%BobbySchmidt@mac.com> Reply-To: comeau@comeaucomputing.com X-Trace: mail2news.demon.co.uk 997481484 mail2news:10452 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: 70 Xref: archiver1.google.com comp.std.c++:6934 In article , Hans Aberg wrote: >In article <090820010209154805%BobbySchmidt@mac.com>, Bobby Schmidt > wrote: >... > extern "C" A f(B x) { > // C++ definition > } >Here, A and B must be C types, but the body of the function is defined >using C++ objects. Must be C types? No, extern "C" does not mean the compiler needs to enter a C mode or anything. It is normal C++ code. >>So I'm appealing for wisdom here: what *exactly* is the Committee's >>intent for `extern "C"`? > >So the first intent I think is merely that the C++ compiler produces to >the linker functions that can be linked together with other C functions. >If the extern "C" functions are called in C++ code, the compiler should >know how to link them with C++ code. Your first sentence is only an intent (since Standard C++ doesn't control Standard C). But your second sentence is a requirement (at least upon a sole C++ implementation). >> And what of that intent is guaranteed by the >>standard vs. simply tolerated? > >Now, there is another snag, namely that C++ objects may depend on >initialization/termination. Then I think the note in verse 3.6.1:1 about >"freestanding environments" applies, which says it is implementation >defined. Clearly, if "main" is in C, the C compiler must know how to make >the initialization and termination of the C++ global objects for the >program to work. The same applies to DLL's. It must know as a practical consideration, otherwise, right, what you're trying to do won't work, but neither standard requires it to work. >So for this to work in practise, the C compiler must be tuned together >with the C++ compiler, Right. >but it is not required by the C++ standard Or the C standard :) >I think that early C/C++ compilers may not have allowed it, but more recent >compilers do. Some did, some didn't, some do, some don't. :) > (My compiler, which is not the latest model, does not accept >C linkage definitions with C++ in the body, but I think that GCC might.) If I understand you correctly, I've never heard that before. Can you give an example of what you mean? -- 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 ]