Path: utzoo!attcan!uunet!usenix!jsq From: jsh@usenix.org (Jeffrey S. Haemer) Newsgroups: comp.std.unix Subject: Standards Update, X3J16: C++ Message-ID: <571@usenix.ORG> Date: 3 Oct 90 14:58:36 GMT Sender: jsq@usenix.ORG Reply-To: std-unix@uunet.uu.net Organization: USENIX Standards Watchdog Committee Lines: 322 Approved: jsq@usenix.org (Moderator, John Quarterman) X-Submissions: std-unix@uunet.uu.net Submitted-by: jsh@usenix.org (Jeffrey S. Haemer) An Update on UNIX1-Related Standards Activities October 3, 1990 USENIX Standards Watchdog Committee Jeffrey S. Haemer , Report Editor X3J16: C++ Mike Vilot reports on the July meeting in Seattle, Washington: Standard C++? The C++ programming language has been gaining popularity at a remarkable rate (an informal estimate is that the C++ population doubles every nine months). One reaction to the growing popularity has been a call to stabilize the language's definition, and achieve some consistency across implementations. C++ is popular enough that larger corporations are considering adopting it as an officially endorsed development language -- but some cannot make such a move unless the language is defined by a standard. For these and other reasons, the ANSI secretariat agreed to establish the X3J16 committee to formulate a standard for C++. Dmitry Lenkov, of HP, made the official proposal, and serves as chairman of the committee. To date, X3J16 has met three times: an organizational meeting last December, the first technical meeting in March to get organized, and a meeting in July to really get started. The December meeting, in Washington D.C., was purely administrative: over 50 attendees received lectures and tons of paper on X3 rules and procedures. The highlight of the day was an invited presentation by Bjarne Stroustrup on ``the spirit of C++.'' The transcript is available as committee document X3J16/90-0022 or from Greg Comeau at Comeau Computing, 91-34 120th Street, Richmond Hill, NY 11418, (718) 849-2355. March meeting AT&T hosted the meeting in New Jersey. Most of the week was spent on administrative matters, while the group got organized and accustomed to The Bureaucratic Way. Since most of the members are engineers, the highlight of the week was the evening technical sessions on implementing exception handling for C++. (The week was sort of a __________ 1. UNIXTM is a Registered Trademark of UNIX System Laboratories in the United States and other countries. October 3, 1990 Standards Update X3J16: C++ - 2 - mini-Usenix conference, as most members had gone without a substantial C++ gathering since the October '88, Denver conference.) The week's major activities were discussing and preparing a goals document, describing the committee's activities and priorities. Goals Here is a brief outline of the goals document, which is available as X3J16/90-0023: 1. Base documents: C++ Reference Manual, ANSI C (ANS X3.159-1989), ISO C when available. 2. Standardize syntax and semantics of the language as a token sequence without the presence of preprocessing directives. 3. Define and standardize a minimum set of C++ libraries, their contents, and interfaces. 4. Standardize elements of a C++ environment. 5. Consider proposed major changes: parameterized types and exceptions. 6. Ensure that the standard is suitable for the international community. 7. Ensure a very high level of compatibility with ANSI C. 8. Establish coordinating liaisons with X3J11 (ANSI C) and Numerical C Extensions Group. 9. Produce two deliverables: draft proposed standard and rationale. 10. Priorities: - clear & unambiguous - C++ reference manual - other base documents - consistency - user/implementer experience - portability, efficiency, expressiveness - ease of implementation (including translation to C) October 3, 1990 Standards Update X3J16: C++ - 3 - There was some confusion over the multiple base documents. Most members had seen the AT&TT C++ version 2.0 reference manual, but in preparation for standardization, the language and its reference manual had suffered a number of subsequent, small changes. AT&T made the 2.1 reference manual available to X3J16; it was essentially the text of the book The Annotated C++ Reference Manual by Margaret Ellis and Bjarne Stroustrup published by Addison-Wesley (minus the annotations). My naive suggestion to remove the ANSI C standard as a base document in favor of a single base provoked the most intense and emotional discussion of the week. At stake was compatibility between C++ and C. While most members of X3J16 feel that the existence of a separate committee implies the standardization of a new language, some former members of X3J11, which just finished the C standard, want to eliminate any and all incompatibilities with C. (There was even a threat to sabotage the C++ standard in balloting if they are not removed.) This issue is obviously important and has two sides. Make your preferences known to the committee. For detailed reference material, both ``C++: As Close as Possible to C -- But No Closer,'' (Bjarne Stroustrup and Andy Koenig, The C++ Report, 1(7), 1989) and Chapter 18 of The Annotated C++ Reference Manual document and explain differences and incompatibilities between the languages as they stand today. Focusing on a language without preprocessing directives continues the de-emphasis of the C preprocessor. This is particularly favored by C++ vendors looking into more powerful development environments. [Editor: Admittedly, improper preprocessor use can sink us in deep and dirty bath water, but let's make sure to save the baby. When writing portable C, I personally find #ifdefs extremely valuable; I suspect they will remain valuable in C++, and I would hate to see the working group neglect this valuable porting tool.] The libraries effort includes asking what to do about the ANSI-C library, and investigating what can be standardized in a more C++-like approach. The environment work addresses the linking and executing of C++ code with non-C++ code (i.e., linkage and program execution models), rather than development environment tools. There are thousands of suggested ``improvements'' proposed as extensions to C++, but there is consensus on two named in the goals document: parameterized types and exception handling. Their proposals are detailed, and both have been implemented (in some form) in a few C++ implementations. The emphasis on international concerns reflects the lessons learned from the difficulties of C standardization. X3J16 has some fences to October 3, 1990 Standards Update X3J16: C++ - 4 - mend, particularly in the international community. Rather than waiting until the last minute to spring a standard on the ISO, the C++ committee is involving itself with the international community right from the start. July meeting Microsoft hosted the second, Seattle meeting. Sub-groups focused on the key topics listed in the goals statement began work at the March meeting, and reported their progress in Seattle. International Concerns Steve Carter, of Bellcore, presented the major International Concerns (particularly character sets and formal specification) and asked the other groups to work on these issues. He also suggested various sites overseas where future X3J16 meetings could help cooperation with international standardization efforts. Editorial Jonathan Shopirio, of AT&T, presented the Editorial group's proposal for organizing and formatting the standard. Jon is also working on an abstract machine model, and a way to define the semantics in the standard precisely and consistently. Formal Syntax James Roskind, an independent consultant, presented the work of the Formal Syntax group. He has developed (and published on the net) a yacc-able grammar for C++, and is concerned about ambiguities in the the language. Most of the discussion was spent trying to discover whether C++ can (or should) be made LALR(1). Core Language Andy Koenig, of AT&T, presented the Core Language group's work. Initially, they identified and classified difficulties in the working document. Environment John Vasta, of HP, presented the work of the Environment group. A key issue addressed by this group is the interaction of C++ with other programming languages. Among the important topics are linkage of C++ and non-C++ translation units, especially the construction and destruction of static C++ objects. Libraries I presented the Library group's work. There were many suggestions, from both inside and outside of the committee. (Interested outside suggesters were James Coggins, Keith Gorlen, and Doug Lea, who have each developed large C++ libraries.) A few people noted similarity with topics covered by other standards October 3, 1990 Standards Update X3J16: C++ - 5 - (notably POSIX). Initially, the library group will focus on a few commonly-used components. Parameterized types and exception handling will significantly effect the way we design libraries in C++. Language Extensions Bjarne Stroustrup, of AT&T, presented the work of the Extensions group, which was by far the most active. The technical sessions presented experience with implementation and use of the template facility. The most active and emotional debate of the week was on exception handling, discussing the proposal outlined by Andy Koenig and Bjarne Stroustrup in their paper ``Exception Handling for C++'' presented at the Usenix C++ conference in April. Martin O'Riordan, of Microsoft, and Mike Miller, of Glockenspiel, presented arguments in favor of extending the current proposal (which defines termination semantics for exceptions) to include resumption semantics. Andy and Bjarne explained their reasons for not including resumption -- the most important was the complexity and cost of implementation. To their credit, the group worked hard to find a proposal that provided both kinds of exceptions with acceptably small time/space overhead. However, at the end of the week, Bjarne declared the debate deadlocked, and refused to impose his proposal while substantial disagreement remained. This is another topic where you should make your opinions heard. C Compatibility Mike Miller presented the work of the C Compatibility group. Tom Plum, of Plum-Hall, produced a list of every section of the C++ reference manual that was not C. Much of the group's near-term activity will be devoted to explaining the many items on the list. The Seattle meeting produced tangible progress on the language standard. X3J16 voted to accept the proposed document outline and format. They also agreed to incorporate the template proposal (the text from Chapter 14 of The Annotated Reference Manual, minus the annotations -- it was literally a scissors-and-tape job). We hope C++ vendors will regard templates as now officially in the language, and provide users an opportunity to work with this feature. Next events A few substantial issues lie ahead. The next meeting should see some resolution on the exception proposal. We should see some progress on the review of language ambiguities and inconsistencies, and have some idea of how difficult it will be to ANSIfy the document. We should also see some specific proposals on library contents. The most October 3, 1990 Standards Update X3J16: C++ - 6 - substantial will be a simplified version of iostreams by Jerry Schwarz (now at Stardent, formerly at AT&T). Our target date for delivering a draft standard is the end of 1992. X3J16 meets three times per year. The next three meetings (and their hosts) will be: + November 12-26, Cupertino CA (Hewlett Packard) + March 11-15, Nashua NH (Digital) + June 17-21, Lund Sweden (Lund Institute of Technology) Membership on an X3 committee is open to any individual or organization with expertise and material interest in the topic addressed by the committee. The cost for membership is $250. Contact the chair or vice chair for details. Chair: Dmitry Lenkov HP California Language Lab 19447 Pruneridge Avenue MS 47 LE Cupertino, CA 95014 (408)447-5279 FAX (408)447-4924 email dmitry%hpda@hplabs.hp.com Vice Chair: William M. Miller Glockenspiel, Ltd P.O. Box 366 Sudbury, MA 01776-0003 (508)443-5779 email wmmiller@cup.portal.com October 3, 1990 Standards Update X3J16: C++ Volume-Number: Volume 21, Number 174