Re: gcc 4.3: when will it become standard compiler?

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...

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>

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 :)