From -4723604438259478647 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,2ec33dfd7f6145e8 X-Google-Attributes: gidf78e5,public X-Google-Thread: fc772,f8b38cec4251c9a8 X-Google-Attributes: gidfc772,public From: Stephen.Clamage@Eng.Sun.COM (Steve Clamage) Subject: Re: main()??? Date: 1997/04/02 Message-ID: <199704012254.OAA14410@taumet.eng.sun.com>#1/1 X-Deja-AN: 230182384 References: X-Original-Date: Tue, 1 Apr 1997 14:54:40 -0800 Organization: - X-Auth: PGPMoose V1.1 PGP comp.std.c++ Newsgroups: comp.std.c++,comp.lang.c++.moderated Originator: austern@isolde.mti.sgi.com In article 054215@cs.mu.oz.au, fjh@mundook.cs.mu.OZ.AU (Fergus Henderson) writes: >Stephen.Clamage@Eng.Sun.COM (Steve Clamage) writes: > >>Here is the relevent part of the draft standard (3.6.1 "Main function"): >> >>"The function main shall not be called from within a program. The linkage >>(3.5) of main is implementation-defined. A program that takes the address >>of main, or declares it inline or static is ill-formed." >> >>The "shall not" and "ill-formed" phrases means a diagnostic message is >>required for any violation. (A compiler is allowed to accept the code >>anyway, but normally you get an error message and no runnable program.) >>A C++ compiler that accepts a call to main without complaint is not >>conforming. > >The "ill-formed" phrase does mean that a diagnostic message is >required for any violation, but the "shall not" phrase can mean >either that a diagnostic is required, or that violation results >in undefined behaviour, depending on exactly how the requirement >is stated. ... > >With regard to the case in question, the requirement that Steve Clamage >quoted, "the function main shall not be called from within a program" >seems to me to be a requirement on the execution of a program, not on >its form, and so no diagnostic is required. (In contrast, if there >requirement were "a program shall not contain a call to the function >main", then it would be a requirement on the form, and so a diagnostic >would be required -- but that is not the case.) > >>Calling main or taking its address was even disallowed by the ARM. > >Yes, but the ARM just says that "the function main may not be called >from within a program", ... The draft standard started out as the ARM with the commentary omitted (literally: the troff source of the ARM was used for the original draft). Wording of sections was modified as deficiencies were discovered. This is a phrase that has survived unchanged so far. It should have always been understood that in C++ it is an error requiring a diagnostic to attempt to call main or take its address. I guess no one noticed before that the words of the draft when taken literally do not say that. (For example, the popular Plum Hall C++ Validation Suite has always had a test for calling or taking the address of main in its "should not compile" section.) I've submitted a request to clarify the wording in the draft. --- Steve Clamage, stephen.clamage@eng.sun.com --- [ comp.std.c++ is moderated. To submit articles: Try just posting with your newsreader. If that fails, use mailto:std-c++@ncar.ucar.edu comp.std.c++ FAQ: http://reality.sgi.com/austern/std-c++/faq.html Moderation policy: http://reality.sgi.com/austern/std-c++/policy.html Comments? mailto:std-c++-request@ncar.ucar.edu ]