malloc and calloc

[Rahul Gandhi]

Which one is more fast?
malloc followed by memset
or
calloc

[Mark McIntyre]

On Mon, 02 Feb 2004 11:03:23 -0700, in comp.lang.c , Alan Balmer
<al******@att.n et> wrote:

On Mon, 2 Feb 2004 22:04:31 +1100, "Peter Nilsson" <ai***@acay.com .au>
wrote:

Red functions tend to go faster. But you'll have to do some profiling to
determine the appropriate chromodynamic hue of each function.

But the blue ones are more critical, because they're coming toward
you.

/really/ REALLY fast.....

--
Mark McIntyre
CLC FAQ <http://www.eskimo.com/~scs/C-faq/top.html>
CLC readme: <http://www.angelfire.c om/ms3/bchambless0/welcome_to_clc. html>
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[Christian Bau]

In article <bv**********@n ewsg3.svr.pol.c o.uk>,
"Malcolm" <ma*****@55bank .freeserve.co.u k> wrote:

"Dan Pop" <Da*****@cern.c h> wrote in message

However, this should NOT be the criterion for choosing one or
another.
If your application needs zeroed memory, call calloc, otherwise call
malloc.

I would suggest malloc() followed by memset() for all occasions.
calloc() is a trap for the unwary, since floating point types and pointers
have all bits zero for 0.0 and NULL on almost all platforms, but this isn't
guaranteed.

Excuse me, but malloc () + memset () has exactly the same problem!

[Keith Thompson]

Christian Bau <ch***********@ cbau.freeserve. co.uk> writes:

In article <bv**********@n ewsg3.svr.pol.c o.uk>,
"Malcolm" <ma*****@55bank .freeserve.co.u k> wrote:

"Dan Pop" <Da*****@cern.c h> wrote in message

However, this should NOT be the criterion for choosing one or
another.
If your application needs zeroed memory, call calloc, otherwise call
malloc.

I would suggest malloc() followed by memset() for all occasions.
calloc() is a trap for the unwary, since floating point types and pointers
have all bits zero for 0.0 and NULL on almost all platforms, but this isn't
guaranteed.

Excuse me, but malloc () + memset () has exactly the same problem!

I *think* Malcom's point is that memset() makes it more explicit that
the memory is being set to all-bits-zero, whereas calloc(), being more
implicit might lead the unwary to assume that floating-point values
are set to 0.0 and pointers to NULL.

I'm not convinced, either that Malcolm is right or that I'm correctly
guessing what he meant.

--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://www.sdsc.edu/~kst>
Schroedinger does Shakespeare: "To be *and* not to be"

[Christian Bau]

In article <ln************ @nuthaus.mib.or g>,
Keith Thompson <ks***@mib.or g> wrote:

Christian Bau <ch***********@ cbau.freeserve. co.uk> writes:

In article <bv**********@n ewsg3.svr.pol.c o.uk>,
"Malcolm" <ma*****@55bank .freeserve.co.u k> wrote:

"Dan Pop" <Da*****@cern.c h> wrote in message
> However, this should NOT be the criterion for choosing one or
> another.
> If your application needs zeroed memory, call calloc, otherwise call
> malloc.
>
I would suggest malloc() followed by memset() for all occasions.
calloc() is a trap for the unwary, since floating point types and
pointers
have all bits zero for 0.0 and NULL on almost all platforms, but this
isn't
guaranteed.

Excuse me, but malloc () + memset () has exactly the same problem!

I *think* Malcom's point is that memset() makes it more explicit that
the memory is being set to all-bits-zero, whereas calloc(), being more
implicit might lead the unwary to assume that floating-point values
are set to 0.0 and pointers to NULL.

I'm not convinced, either that Malcolm is right or that I'm correctly
guessing what he meant.

Languages like Pascal did a certain amount of extra work for built-in
functions like "writeln". The C language could in principle do something
similar for calloc: Instead of calloc (nmemb, size) there could be an
alternative calloc (nmemb, type) which would allocate an array of
(nmemb) elements of the given type, each initialised like static
variables would be initialised. For example, calloc (100, double) could
with a little bit of support in the compiler allocate an array of 100
doubles, each set to 0.0.

[Dan Pop]

In <ln************ @nuthaus.mib.or g> Keith Thompson <ks***@mib.or g> writes:

I *think* Malcom's point is that memset() makes it more explicit that
the memory is being set to all-bits-zero, whereas calloc(), being more
implicit might lead the unwary to assume that floating-point values
are set to 0.0 and pointers to NULL.

Even the unwary could ask himself: how could calloc guess which bytes
are going to be used for storing floating-point values and/or pointers,
from the available information: N objects of M bytes each?

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Da*****@ifh.de