Flexible arrays - v confused

[websnarf@gmail.com]

Re: Flexible arrays - v confused

Keith Thompson wrote:[color=blue]
> websnarf@gmail. com writes:[color=green]
> > Chris Torek wrote:[color=darkred]
> >> #include <stdlib.h>
> >> struct vector {
> >> size_t n; /* number of values in the vector */
> >> double val[1]; /* actually size n */
> >> };
> >>
> >> struct vector *vec_new(size_t n) {
> >> struct vector *p;
> >>
> >> /* need n-1 here because the array has an "extra" element */
> >> p = malloc(sizeof *p + (n ? n - 1 : 0) * sizeof p->val[0]);[/color]
> >
> > I do this as follows:
> >
> > p = (struct vector *) malloc (offsetof (struct vector, val) +
> > n * sizeof (p->val[0]));
> >
> > Which means I need a #include <stddef.h>[/color]
>
> Why do you uselessly cast the result of malloc()?[/color]

Because I like to use automatic error detection tools when I program,
and that includes using a C++ compiler (which has stricter type
checking). It means I have to conceed to things like the above in
order to gain the benefit of stronger type checking elsewhere in my
programs.

So if you take the opposite point of view, would it be fair to say that
you avoid things like Lint and ignore warning messages coming from your
compiler? Or are you saying that anything superfluous, like comments
and whitespace, should be eradicated from code?

--
Paul Hsieh

http://www.pobox.com/~qed/

http://bstring.sf.net/

[Keith Thompson]

Re: Flexible arrays - v confused

websnarf@gmail. com writes:[color=blue]
> Keith Thompson wrote:[/color]
[...][color=blue][color=green]
>> Why do you uselessly cast the result of malloc()?[/color]
>
> Because I like to use automatic error detection tools when I program,
> and that includes using a C++ compiler (which has stricter type
> checking). It means I have to conceed to things like the above in
> order to gain the benefit of stronger type checking elsewhere in my
> programs.
>
> So if you take the opposite point of view, would it be fair to say that
> you avoid things like Lint and ignore warning messages coming from your
> compiler? Or are you saying that anything superfluous, like comments
> and whitespace, should be eradicated from code?[/color]

Yes, absolutely, because you're always right and anyone who disagrees
with you must be a complete idiot. Thank you for bringing this to my
attention.

--
Keith Thompson (The_Other_Keit h) kst-u@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

[websnarf@gmail.com]

Re: Flexible arrays - v confused

Keith Thompson wrote:[color=blue]
> websnarf@gmail. com writes:[color=green]
> > Keith Thompson wrote:[/color]
> [...][color=green][color=darkred]
> >> Why do you uselessly cast the result of malloc()?[/color]
> >
> > Because I like to use automatic error detection tools when I program,
> > and that includes using a C++ compiler (which has stricter type
> > checking). It means I have to conceed to things like the above in
> > order to gain the benefit of stronger type checking elsewhere in my
> > programs.
> >
> > So if you take the opposite point of view, would it be fair to say that
> > you avoid things like Lint and ignore warning messages coming from your
> > compiler? Or are you saying that anything superfluous, like comments
> > and whitespace, should be eradicated from code?[/color]
>
> Yes, absolutely, because you're always right and anyone who disagrees
> with you must be a complete idiot. Thank you for bringing this to my
> attention.[/color]

You intentionally instigated this. You used the language "uselessly"
and your canned argument against this cast is well known to me, and you
know that. So you respond with this question with the intention of
laying this pathetic trap. But, if you've ever bothered to read my
posts, you've known my counter argument before this post.

My reducto ad absurdum in the second paragraph is meant to address the
position "if you take the opposite point of view". If you understood
what I was saying rather than taking an antagonistic-only stance you
would have realized that what I was saying is that the problem is that
you have not clarified the basis for your point of view, and unless its
insane the ball is in your court to explain why you want to remove this
"useless" cast.

--
Paul Hsieh

http://www.pobox.com/~qed/

http://bstring.sf.net/

[Richard Bos]

Re: Flexible arrays - v confused

websnarf@gmail. com wrote:
[color=blue]
> Keith Thompson wrote:[color=green]
> > websnarf@gmail. com writes:[color=darkred]
> > > p = (struct vector *) malloc (offsetof (struct vector, val) +
> > > n * sizeof (p->val[0]));
> > >
> > > Which means I need a #include <stddef.h>[/color]
> >
> > Why do you uselessly cast the result of malloc()?[/color]
>
> Because I like to use automatic error detection tools when I program,
> and that includes using a C++ compiler (which has stricter type
> checking). It means I have to conceed to things like the above in
> order to gain the benefit of stronger type checking elsewhere in my
> programs.[/color]

So in order to gain a few dubious warnings which quite possibly won't
even apply to the language you're writing in, you prevent your real
compiler from spotting what would be a read and potentially dangerous
mistake?

Sheer brilliance.

Richard

[websnarf@gmail.com]

Re: Flexible arrays - v confused

Richard Bos wrote:[color=blue]
> websnarf@gmail. com wrote:[color=green]
> > Keith Thompson wrote:[color=darkred]
> > > websnarf@gmail. com writes:
> > > > p = (struct vector *) malloc (offsetof (struct vector, val) +
> > > > n * sizeof (p->val[0]));
> > > >
> > > > Which means I need a #include <stddef.h>
> > >
> > > Why do you uselessly cast the result of malloc()?[/color]
> >
> > Because I like to use automatic error detection tools when I program,
> > and that includes using a C++ compiler (which has stricter type
> > checking). It means I have to conceed to things like the above in
> > order to gain the benefit of stronger type checking elsewhere in my
> > programs.[/color]
>
> So in order to gain a few dubious warnings which quite possibly won't
> even apply to the language you're writing in, you prevent your real
> compiler from spotting what would be a read and potentially dangerous
> mistake?[/color]

C++ compilers also enforce prototype predeclarations (so would C99
compilers if they existed). So exactly which dangerous mistake do you
think I am going to miss?

--
Paul Hsieh

http://www.pobox.com/~qed/

http://bstring.sf.net/

[Dave Thompson]

Re: Flexible arrays - v confused

On 17 Feb 2006 11:02:13 -0800, websnarf@gmail. com wrote:
[color=blue]
> Richard Bos wrote:[/color]
(casting return of malloc)[color=blue]
> C++ compilers also enforce prototype predeclarations (so would C99
> compilers if they existed). So exactly which dangerous mistake do you
> think I am going to miss?[/color]

C++ does require prototypes (though not using that term).

C99 requires _declarations_ but not necessarily prototypes. That is
enough for the return type, as here, but not arguments.

- David.Thompson1 at worldnet.att.ne t