[KJ] is there a short form for "memset(blah, 0, len)"?

[KJ] is there a short form for "memset(blah, 0, len)"?

[Robert P. J. Day]

  i doubt anything will ever come of this but, given the number of
calls to "memset(addr, 0, len)", did anyone ever consider defining a
macro short form, say:

  clearmem(addr, len)
  zeromem(addr, len)

or something like that?  just curious.

rday

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Re: [KJ] is there a short form for "memset(blah, 0, len)"?

[Bernd Petrovitsch]

On Sat, 2007-02-10 at 11:14 -0500, Robert P. J. Day wrote:
>   i doubt anything will ever come of this but, given the number of
> calls to "memset(addr, 0, len)", did anyone ever consider defining a
> macro short form, say:
> 
>   clearmem(addr, len)
>   zeromem(addr, len)

*BSD had "bzero()".

> or something like that?  just curious.

Did you ever read the man page of "bzero()"?

	Bernd
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Re: [KJ] is there a short form for "memset(blah, 0, len)"?

[Robert P. J. Day]

On Sat, 10 Feb 2007, Bernd Petrovitsch wrote:

> On Sat, 2007-02-10 at 11:14 -0500, Robert P. J. Day wrote:
> >   i doubt anything will ever come of this but, given the number of
> > calls to "memset(addr, 0, len)", did anyone ever consider defining a
> > macro short form, say:
> >
> >   clearmem(addr, len)
> >   zeromem(addr, len)
>
> *BSD had "bzero()".
>
> > or something like that?  just curious.
>
> Did you ever read the man page of "bzero()"?

sure, but that's a *userspace* routine.  AFAIK, there is no such
routine in the linux kernel.  is there a reason there isn't?  wouldn't
it be kind of useful?

rday
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====================================
Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry
Waterloo, Ontario, CANADA

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Re: [KJ] is there a short form for "memset(blah, 0, len)"?

[Bernd Petrovitsch]

On Sat, 2007-02-10 at 13:25 -0500, Robert P. J. Day wrote:
> On Sat, 10 Feb 2007, Bernd Petrovitsch wrote:
> 
> > On Sat, 2007-02-10 at 11:14 -0500, Robert P. J. Day wrote:
> > >   i doubt anything will ever come of this but, given the number of
> > > calls to "memset(addr, 0, len)", did anyone ever consider defining a
> > > macro short form, say:
> > >
> > >   clearmem(addr, len)
> > >   zeromem(addr, len)
> >
> > *BSD had "bzero()".
> >
> > > or something like that?  just curious.
> >
> > Did you ever read the man page of "bzero()"?
> 
> sure, but that's a *userspace* routine.  AFAIK, there is no such

Yes, of course. I mentioned it because there is/was already a function
with the above semantics and signature. So why invent another name?

> routine in the linux kernel.  is there a reason there isn't?  wouldn't

No, because bzero() is - according to the man page - deprecated.

> it be kind of useful?

I don't think so. But who knows what maintainers and others higher in
the food chain think .....

	Bernd
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Re: [KJ] is there a short form for "memset(blah, 0, len)"?

[Richard Knutsson]

Robert P. J. Day wrote:
> On Sat, 10 Feb 2007, Bernd Petrovitsch wrote:
>
>   
>> On Sat, 2007-02-10 at 11:14 -0500, Robert P. J. Day wrote:
>>     
>>>   i doubt anything will ever come of this but, given the number of
>>> calls to "memset(addr, 0, len)", did anyone ever consider defining a
>>> macro short form, say:
>>>
>>>   clearmem(addr, len)
>>>   zeromem(addr, len)
>>>       
>> *BSD had "bzero()".
>>
>>     
>>> or something like that?  just curious.
>>>       
>> Did you ever read the man page of "bzero()"?
>>     
>
> sure, but that's a *userspace* routine.  AFAIK, there is no such
> routine in the linux kernel.  is there a reason there isn't?  wouldn't
> it be kind of useful?
>   
> grep -Enr "define +.*memset *\(.*0" *
arch/alpha/boot/misc.c:25:#define memzero(s,n)  memset ((s),0,(n))
arch/cris/arch-v10/boot/compressed/misc.c:38:#define memzero(s, n)     memset ((s), 0, (n))
arch/cris/arch-v32/boot/compressed/misc.c:40:#define memzero(s, n)     memset ((s), 0, (n))
arch/i386/boot/compressed/misc.c:110:#define memzero(s, n)     memset ((s), 0, (n))
arch/m32r/boot/compressed/misc.c:26:#define memzero(s, n)     memset ((s), 0, (n))
arch/sh/boot/compressed/misc.c:30:#define memzero(s, n)     memset ((s), 0, (n))
arch/sh64/boot/compressed/misc.c:28:#define memzero(s, n)     memset ((s), 0, (n))
...

So it seems memzero() is a candidate, don't you think?

Richard Knutsson


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Re: [KJ] is there a short form for "memset(blah, 0, len)"?

[Robert P. J. Day]

On Sat, 10 Feb 2007, Bernd Petrovitsch wrote:

> On Sat, 2007-02-10 at 13:25 -0500, Robert P. J. Day wrote:
> > On Sat, 10 Feb 2007, Bernd Petrovitsch wrote:
> >
> > > On Sat, 2007-02-10 at 11:14 -0500, Robert P. J. Day wrote:
> > > >   i doubt anything will ever come of this but, given the number of
> > > > calls to "memset(addr, 0, len)", did anyone ever consider defining a
> > > > macro short form, say:
> > > >
> > > >   clearmem(addr, len)
> > > >   zeromem(addr, len)
> > >
> > > *BSD had "bzero()".
> > >
> > > > or something like that?  just curious.
> > >
> > > Did you ever read the man page of "bzero()"?
> >
> > sure, but that's a *userspace* routine.  AFAIK, there is no such
>
> Yes, of course. I mentioned it because there is/was already a function
> with the above semantics and signature. So why invent another name?

oh, sorry, i misunderstood.  i thought you were saying that there
already *was* a bzero() in kernel space.  my mistake.

> > routine in the linux kernel.  is there a reason there isn't?
> > wouldn't
>
> No, because bzero() is - according to the man page - deprecated.

ah, yes, i just checked up on that.  this wasn't a big deal, it just
struck me that there are a *ton* of calls to memset() to do nothing
more than zero a chunk of memory, and it would seem simpler to define
a macro as a wrapper.  but i'm not going to make a big deal out of it.

rday

p.s.  in general, whenever i see the same construct being used more
than a dozen times, i start thinking of a way to make it shorter.

-- 
====================================
Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry
Waterloo, Ontario, CANADA

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Re: [KJ] is there a short form for "memset(blah, 0, len)"?

[Robert P. J. Day]

On Sat, 10 Feb 2007, Richard Knutsson wrote:

> Robert P. J. Day wrote:
> > On Sat, 10 Feb 2007, Bernd Petrovitsch wrote:
> >
> >
> > > On Sat, 2007-02-10 at 11:14 -0500, Robert P. J. Day wrote:
> > >
> > > >   i doubt anything will ever come of this but, given the number of
> > > > calls to "memset(addr, 0, len)", did anyone ever consider defining a
> > > > macro short form, say:
> > > >
> > > >   clearmem(addr, len)
> > > >   zeromem(addr, len)
> > > >
> > > *BSD had "bzero()".
> > >
> > >
> > > > or something like that?  just curious.
> > > >
> > > Did you ever read the man page of "bzero()"?
> > >
> >
> > sure, but that's a *userspace* routine.  AFAIK, there is no such
> > routine in the linux kernel.  is there a reason there isn't?  wouldn't
> > it be kind of useful?
> >   grep -Enr "define +.*memset *\(.*0" *
> arch/alpha/boot/misc.c:25:#define memzero(s,n)  memset ((s),0,(n))
> arch/cris/arch-v10/boot/compressed/misc.c:38:#define memzero(s, n)     memset
> ((s), 0, (n))
> arch/cris/arch-v32/boot/compressed/misc.c:40:#define memzero(s, n)     memset
> ((s), 0, (n))
> arch/i386/boot/compressed/misc.c:110:#define memzero(s, n)     memset ((s), 0,
> (n))
> arch/m32r/boot/compressed/misc.c:26:#define memzero(s, n)     memset ((s), 0,
> (n))
> arch/sh/boot/compressed/misc.c:30:#define memzero(s, n)     memset ((s), 0,
> (n))
> arch/sh64/boot/compressed/misc.c:28:#define memzero(s, n)     memset ((s), 0,
> (n))
> ...
>
> So it seems memzero() is a candidate, don't you think?

it would seem so, but you should really have let that list go on a bit
longer.  all of the above examples are in *userspace*, so adding that
definition to a kernel header file wouldn't help, right?  if you let
that command run a bit longer, then you find a few kernel space
examples (some of them *very* badly named):

...
drivers/block/floppy.c:317:#define CLEARSTRUCT(x) memset((x), 0, sizeof(*(x)))
drivers/video/sun3fb.c:67:#define mymemset(x,y) memset(x,0,y)
...

  in any event, i think defining memzero() that way is the obvious
enhancement.  is there any obvious reason this can't be done?

rday

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====================================
Robert P. J. Day
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Re: [KJ] is there a short form for "memset(blah, 0, len)"?

[Robert P. J. Day]

  as a short followup, if you see how many memset() calls are used to
just clear memory:

  $ grep -Er "memset ?\(.*,0 ?,.*\)" * | less

you can see that adding a memzero() call would definitely be useful.
in addition, there are another ton of calls of the form:

  memset(&fpr_final,0, sizeof(fpr_final));

perhaps another simple macro wrapper of the form

  #define structzero(s) memset(&s, 0, sizeof(s))

thoughts?

rday

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====================================
Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry
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