220 40467 article Path: news.gmane.org!.POSTED!not-for-mail From: David Brown Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Optional fixed point arithmetic was standardised into C in 2008. Why doesn't C++ adopt it? 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Original-Received: from list by blaine.gmane.org with local (Exim 4.84_2) (envelope-from ) id 1gA9ZD-00020e-UA for std-proposals@isocpp.org; Wed, 10 Oct 2018 10:10:03 +0200 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 44 Original-X-Complaints-To: usenet@blaine.gmane.org In-Reply-To: X-Original-Sender: david@westcontrol.com X-Original-Authentication-Results: mx.google.com; spf=neutral (google.com: 195.159.176.226 is neither permitted nor denied by best guess record for domain of gclcip-std-proposals@m.gmane.org) smtp.mailfrom=gclcip-std-proposals@m.gmane.org Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Spam-Checked-In-Group: std-proposals@isocpp.org X-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:40467 Archived-At: On 08/10/18 20:25, Niall Douglas wrote: > So, learned something new from WG14 today, namely that C standardised > optional fixed point arithmetic back in 2004, with a second edition in > 2008. I didn't know that before. Here is a pre-publication draft of the > standard *ISO/IEC TR 18037:2008*: > > http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1169.pdf > > Why doesn't WG21 simply adopt this instead of the (library) fixed point > arithmetic proposals currently before it? > Well, almost no C compilers support that standard - because almost no one wants to use it. The TR has 3 key areas that are supposed to improve C programming in the embedded world. It covers fixed-point arithmetic in a way no one wants (especially not embedded programmers), named address spaces that are underpowered, and hardware I/O that is not needed, not useful, and contrary to the way every embedded compiler and programmer handles it. The TR for "C Extensions to support embedded processors" is a huge disappointment, a result of a /total/ failure to look at the realities of the industry in terms of what embedded toolchains provide and what embedded programmers want, combined with an absurd time schedule. While the group behind this spend many years slowly writing the document in a couple of versions, everyone in the embedded development industry got on with their jobs. So by the time it was published, it would have been irrelevant even if it had been useful. I only know of one compiler that has some implementation of this TR's fixed point types - that is gcc, which implements it on some targets. I have tried it, and the code generated is hopeless despite the target processor having support for some fixed point formats. It is basically a matter of a gcc developer in the past having implemented the front-end parts and very basic code generation, presumably with the intention that others would pick up the ball and turn it into more optimal code now that the process had been started. However, it has seen no interest (AFAIK) from either compiler developers or users. I haven't heard anything about a C++ standard library for fixed-point arithmetic, but it would be very difficult to produce something worse than this C "extension" TR that has been rightly ignored. -- You received this message because you are subscribed to the Google Groups "ISO C++ Standard - Future Proposals" group. To unsubscribe from this group and stop receiving emails from it, send an email to std-proposals+unsubscribe@isocpp.org. To post to this group, send email to std-proposals@isocpp.org. To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/ppkc4l%246u0%241%40blaine.gmane.org. .