[vorbis-dev] Re: [vorbis] Re: Different average bitrates on different machines

[Daniel B. Miller]

well I wouldn't defend it to the death, but it seems clear to me that a
post-increment should be 'post' whatever else goes on in the statement.  I
would be surprised if any compilers compiled this differently.

Not that it wouldn't be nice to have a warning-free codebase -- but that's
more of a platonic ideal than a common reality IMHO.

 ___  Dan Miller
(++,) Founder, CTO, On2.com

On Mon, 10 Dec 2001, Segher Boessenkool wrote:

> [moved to vorbis-dev at xipf from vorbis at xiph]
>
>
> Cameron Simpson wrote:
> >
> > On Mon, Dec 10, 2001 at 03:30:24AM -0500, Monty <xiphmont at xiph.org> wrote:
> > | > BTW, has anyone done a scan of the source with gcc 3.x with the
> > | > -Wsequence-point warning enabled? There's been a fair bit of discussion
> > | > recently about dodgy code doing things like:
> > | >     a[i]=f(i++)
> > | > which gives undefined results. That really could screw up encoding algorithms.
> > | That's not 'dodgy', it's an outright error.  No C programmer should
> > | ever even think of the above code being acceptable.
> >
> > Naturally not, but sometimes they creep in. There was a thread in the
> > Linux-Kernel list about such code just recently. Since gcc-3.x has a
> > sequence point checker for this kind of issue, I'll make a pass over
> > the code with it on just on principle sometime this week (since I have
> > to rebuild oggenc et al to look for a bug anyway).
>
> I normally compile with
>
> -Wall -W -pedantic -std=c9x -Wtraditional -Wpointer-arith -Wconversion
> -Wsign-compare
>
> and boy, libvorbis looks really unclean, then.
>
> -pedantic -std=c9x  makes everything not strictly ANSI C99 a warning
> (we're supposed to be C99).
>
> -Wall  catches common errors.
>
> -W  catches even more errors (it sometimes bitches about perfectly valid
> comstructs, but small code rearrangements will normally fix those
> warnings.
>
> -Wtraditional  warns about stuff that's not the same in ANSI C as it is
> in K&R C;  this helps portability, but it complains about float function
> parameters (these are promoted to double in K&R C).
>
> -Wpointer-arith  should _always_ be enabled, and be an error.  Better yet,
> it should hunt down the programmer who wrote that code and do bad things to
> him.  No further comments.
>
> -Wconversion  is really important.  It warns about dangerous type conversions
> (dangerous in the sense that the compiler might not be doing what the programmer
> thinks the compiler whould do).  This catches oodles of signed <-> unsigned
> mismatches, for example.
>
> Especially this last warning option generates a lot of warnings on the
> Vorbis code.
> Fixing this is not completely trivial, though.  Quite a number of
> objects which
> really should have unsigned type, have signed type in libvorbis, because negative
> values are used for signalling special conditions.  I think this is a
> bad thing.
>
> Having objects of "natural" unsigned type (sizes, array offsets, most
> loop counters,
> are a few examples) actually _be_ unsigned type, enables the compiler to
> do a much
> better job of optimizing.  And it catches actual bugs, and it catches a
> lot of
> wacky things which ain't actual bugs, but only not because the actual
> range of the
> possible values is smaller than the type.
>
> Hey, I'm not complaining;  but maybe someone might want to clean up a
> little? :-)
>
> Cheers,
>
> Segher
>
>
> --- >8 ----
> List archives:  http://www.xiph.org/archives/
> Ogg project homepage: http://www.xiph.org/ogg/
> To unsubscribe from this list, send a message to 'vorbis-dev-request at xiph.org'
> containing only the word 'unsubscribe' in the body.  No subject is needed.
> Unsubscribe messages sent to the list will be ignored/filtered.
>

--- >8 ----
List archives:  http://www.xiph.org/archives/
Ogg project homepage: http://www.xiph.org/ogg/
To unsubscribe from this list, send a message to 'vorbis-dev-request at xiph.org'
containing only the word 'unsubscribe' in the body.  No subject is needed.
Unsubscribe messages sent to the list will be ignored/filtered.