Date: Fri, 09 Jan 2009 16:53:05 +0100 From: Christoph Mallon <christoph.mallon@gmx.de> To: Roman Divacky <rdivacky@freebsd.org> Cc: Andrew Reilly <andrew-freebsd@areilly.bpc-users.org>, freebsd-current@freebsd.org, Ollivier Robert <roberto@keltia.freenix.fr> Subject: Re: gcc 4.3: when will it become standard compiler? Message-ID: <496772E1.2050504@gmx.de> In-Reply-To: <20090109150750.GA50331@freebsd.org> References: <49668763.8020705@mail.zedat.fu-berlin.de> <20090108233311.GA69883@keltia.freenix.fr> <20090109031147.GB44317@duncan.reilly.home> <49672189.5060109@gmx.de> <20090109110508.GA12123@freebsd.org> <496751D1.20605@gmx.de> <20090109134725.GA38233@freebsd.org> <49675F04.20006@gmx.de> <20090109143339.GA45569@freebsd.org> <49676598.7040708@gmx.de> <20090109150750.GA50331@freebsd.org>
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Roman Divacky schrieb: > On Fri, Jan 09, 2009 at 03:56:24PM +0100, Christoph Mallon wrote: >> Roman Divacky schrieb: >>> On Fri, Jan 09, 2009 at 03:28:20PM +0100, Christoph Mallon wrote: >>>> Roman Divacky schrieb: >>>>> On Fri, Jan 09, 2009 at 02:32:01PM +0100, Christoph Mallon wrote: >>>>>> Roman Divacky schrieb: >>>>>>>> I'm not saying it's wrong to look for alternatives, but you cannot >>>>>>>> just change your system compiler like you change underwear. >>>>>>> well... the first step is imho starting to compile world with C99... >>>>>>> that might reveal some bugs, note that as of a few months ago >>>>>>> 8-current compiles cleanly with C99, that does not mean that it's >>>>>>> working when you run those programs correctly :) >>>>>> One step in the right direction is embracing the nice features modern C >>>>>> offers you. For example declaring a variable right were you need it >>>>>> instead of dozens of lines away is one such nice thing which improves >>>>>> readability. Designated initializers improve readability, too. >>>>>> But I'm not exactly sure what you mean by "compile world with C99". C99 >>>>>> is pretty much backwards compatible to C89. >>>>> sorry for the bad wording - I meant to turn C99 compilation on default. >>>>> We compile in gnu89 mode now. >>>> I still have no idea what you mean. Sure, you can specify -std=c99 (or >>>> more likely gnu99), but an int is still an int - what do you expect? In >>>> fact default mode of GCC accepts many C99 constructs like // comments >>>> and mixed declarations and code, which are not valid C89. >>> for example __restricted is C99 thing and there are others, I want this >> __restrict (not __restricted) is a GCC extension. The C99 spelling is >> restrict. GCC also accepts __restrict__. Further, you should be *very* >> careful with the restrict qualifier, because its exact semantic is >> non-trivial (?6.7.3.1, it's one page of standardese speak). >> But I see no problem for existing code in this respect. C99 mostly only >> adds new language constructs. Only very few were removed. E.g. implicit >> int was removed, but GCC still accepts it (and I guess clang too, >> cpareser does). > > my point is that in C89 mode *restrict* (in whatever spelling) got expanded > to nothing. we had a bug (typo in fact) related to *restrict* and we didnt > catch it because of C89 compilation mode... Ah, you mean a simple syntax error like char __restrict* a instead of char* __restrict a. I thought you meant something serious like different behaviour between the standards. Why somebody would #define away __restrict (or #define away any other extension, which GCC accepts anyway) is beyond me. If the source code already contains distinctions between C89 and C99 then, imo, somebody did something wrong. > thats my point (and the *restrict* thing is just an example) > >>> because clang for example defaults to C99 (in fact gnu99 as they support >>> gnu extensions on default). By switching to default compilation in C99 >>> mode we can be sure we stay compatible with clang and others.... >> I'm pretty sure clang also accepts __restrict. >> A compiler, which does not support most GCC extensions (inline assembler >> being the most important) has no chance anyway. > > yes.... the problem is (was?) that clang is C99 on default while gcc is C89 > on default. > >>> for example opensolaris seems to use C99 features which are not enabled >>> in our world because of this (I found same assert() related stuff) etc. >> assert() predates C99. The only C99 specific aspect about assert(), that >> I'm aware of, is, that C99 guarantees that the name of the function is >> printed. > > they had code like > > <pseudocode> > #if C99 > #define __assert(..) something > #else > #define __assert(..) something_else > #endif > </pseudocode> This is probably, as mentioned above, because C89 does not have __func__. > my point is that we might have bugs in the C99 code that other (non-gcc) compilers > expose and it's a good thing to unite on one standard. ie. C99 :) In general I agree: C99 should be used as language standard for compilation. style(9) needs some updates for this, too.
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