Path: csiph.com!optima2.xanadu-bbs.net!xanadu-bbs.net!feeder.erje.net!1.eu.feeder.erje.net!eternal-september.org!feeder.eternal-september.org!mx02.eternal-september.org!.POSTED!not-for-mail From: Keith Thompson Newsgroups: comp.lang.c Subject: Re: More physical source files Date: Sat, 04 Jul 2015 12:36:44 -0700 Organization: None to speak of Lines: 46 Message-ID: References: <36e79c40-a86d-416d-b290-b2de49560c61@googlegroups.com> <7cf2be57-a46a-454a-a6cb-0c81d77ed7fb@googlegroups.com> <56d054c6-5316-46eb-b7b4-686bd405149d@googlegroups.com> <39cf9193-5d10-4db9-b766-9452d7c1b0bf@googlegroups.com> <71c62ee8-0007-446b-9004-c6def341205a@googlegroups.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Injection-Info: mx02.eternal-september.org; posting-host="945944de09706c9b4e29b53c9d2efdc2"; logging-data="12184"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1/IcZRB+8AWn8vJJWe5acme" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.1 (gnu/linux) Cancel-Lock: sha1:3Z9lNmNZl0UUdOKMngyN+OkN1RM= sha1:hdbAcCnfOmuWoACTz0BSG2W7u5U= Xref: csiph.com comp.lang.c:64674 David Kleinecke writes: > On Friday, July 3, 2015 at 10:05:21 AM UTC-7, Keith Thompson wrote: >> David Kleinecke writes: >> >> > I hadn't noticed this before. Appendix G.1 of the C90 standard lists >> > 22 unspecified features. Appendix J.1 of N1570 has many more. One item >> > is "floating type representation". Doesn't that mean that a strictly >> > conforming program cannot use floating types? >> > >> > If so the floating types are essentially excluded from strict >> > conformity. I haven't thought this through - what exactly does >> > "not produce output dependent on any unspecified ... behavior" >> > mean? >> >> The representation of floating-point objects is a separate issue from >> the behavior of floating-point operations. >> >> A program that outputs the raw representation of a floating-point object >> cannot be strictly conforming. A program that uses floating-point can >> be strictly conforming, as long as its output doesn't depend on any >> unspecified behavior. > > If the representation of floating point is unspecified how can the > size be known? It is easy to write code to give different answers for > different values of sizeof (float). Of course it is. You can write a program that uses floating-point whose output depends on unspecified, undefined, or implementation-defined behavior. Such a program is not strictly conforming. You can write a program that uses floating-point whose output *doesn't* depend on unspecified, undefined, or implementation-defined behavior. Such a program may be strictly conforming. > Am I, perhaps confusing "implementatio-defined" with "unspecified"? > What exactly is the difference. The terms are defined in section 3 of the standard. -- Keith Thompson (The_Other_Keith) kst-u@mib.org Working, but not speaking, for JetHead Development, Inc. "We must do something. This is something. Therefore, we must do this." -- Antony Jay and Jonathan Lynn, "Yes Minister"