«

Hi,

I have often wondered if casting the return value of malloc() (or
friends) actually helps anything, recent threads here suggest that it
does not .. so I hope to find out.

For instance :

char *tmp = NULL;

tmp = (char *) malloc(1024);

Is there any pointing in casting the return value of malloc? I see
many people do that, but not test the result such as :

if (tmp == (char *) NULL)
.. some code about malloc() failing ...

Is there any point in casting it?

Cheers,
--Tim

Tinkertim wrote:
> Hi,
>
> I have often wondered if casting the return value of malloc() (or
> friends) actually helps anything, recent threads here suggest that it
> does not .. so I hope to find out.
>
> For instance :
>
> char *tmp = NULL;
>
> tmp = (char *) malloc(1024);
>
> Is there any pointing in casting the return value of malloc?

None what so ever.

--
Ian Collins.

In article <7ce1a426-30ed-47ee-bd72->,
Tinkertim <> wrote:
>Hi,
>
>I have often wondered if casting the return value of malloc() (or
>friends) actually helps anything, recent threads here suggest that it
>does not .. so I hope to find out.

Good to see we're back on familiar ground.

On 2 Oct, 10:22, Tinkertim <tinker...@gmail.com> wrote:
> Hi,
>
> I have often wondered if casting the return value of malloc() (or
> friends) actually helps anything, recent threads here suggest that it
> does not .. so I hope to find out.
>
> For instance :
>
> char *tmp = NULL;
>
> tmp = (char *) malloc(1024);
>
> Is there any pointing in casting the return value of malloc? I see
> many people do that, but not test the result such as :
>
> if (tmp == (char *) NULL)
> * *.. some code about malloc() failing ...
>
> Is there any point in casting it?

This is a FAQ
FAQ 7.7b "What's wrong with casting malloc's return value?"

the FAQ lives at http://c-faq.com

C++ requires a cast on the return of malloc(). But malloc()
is unusual in C++ code (an implementation of C++ might need it).
Some people write code that is required to compile under both C and
C++ (eg. library writers). They also might want to cast the return
value of malloc().


--
Nick Keighley

"Those are my principles. If you don't like them, I have others."
- Groucho Marx

On 2 Oct, 10:59, Nick Keighley <nick_keighley_nos...@hotmail.com>
wrote:
> On 2 Oct, 10:22, Tinkertim <tinker...@gmail.com> wrote:
>
>
>
> > Hi,
>
> > I have often wondered if casting the return value of malloc() (or
> > friends) actually helps anything, recent threads here suggest that it
> > does not .. so I hope to find out.
>
> > For instance :
>
> > char *tmp = NULL;
>
> > tmp = (char *) malloc(1024);
>
> > Is there any pointing in casting the return value of malloc? I see
> > many people do that, but not test the result such as :
>
> > if (tmp == (char *) NULL)
> > .. some code about malloc() failing ...
>
> > Is there any point in casting it?
>
> This is a FAQ
> FAQ 7.7b "What's wrong with casting malloc's return value?"
>
> the FAQ lives athttp://c-faq.com
>
> C++ requires a cast on the return of malloc(). But malloc()
> is unusual in C++ code (an implementation of C++ might need it).
> Some people write code that is required to compile under both C and
> C++ (eg. library writers). They also might want to cast the return
> value of malloc().
>

As far as I understood it (which might be somewhat wrong) actually
casting the return value is unwanted. Am I wrong that without
including stdlib.h the return value is int (or int * cant remember
which exactly) from malloc and so not casting the return value will
provide a warning/error during compilation if you have missed this
header? Whereas casting the value will hide this problem and result in
strange behaviour

Nick

--------
Mesham Parallel Programming Language
www.mesham.net

On 2 Oct, 13:12, Richard Heathfield <r...@see.sig.invalid> wrote:
> polas said:
>
> <snip>
>
> > As far as I understood it (which might be somewhat wrong) actually
> > casting the return value is unwanted.
>
> If you mean "unnecessary", you're right.
>
> > Am I wrong that without
> > including stdlib.h the return value is int (or int * cant remember
> > which exactly) from malloc
>
> In C90, whenever the compiler encounters any call to any function for which
> it has not yet seen a declaration, it is required to assume that the
> function returns int, even if We Know Different. (And indeed even if the
> compiler knows different, which it is allowed to but not required to.)
>
> Since you're assigning the value returned by malloc to a pointer object,
> omitting the header therefore gives a type mismatch between int and
> pointer, which the compiler is obliged to diagnose - UNLESS you foolishly
> cast the diagnosis away.
>
> If pointers are returned in a different way to ints, or if pointers are
> longer than ints, or have completely different representations, this can
> cause a very real problem.
>
> > and so not casting the return value will
> > provide a warning/error during compilation if you have missed this
> > header? Whereas casting the value will hide this problem and result in
> > strange behaviour
>
> Yes, that's almost right - casting the value will hide the problem and
> *may* result in strange behaviour. Or it may not. Until your boss is
> watching...
>
> --
> Richard Heathfield <http://www.cpax.org.uk>
> Email: -http://www. +rjh@
> Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
> "Usenet is a strange place" - dmr 29 July 1999

Right, thanks for the help clearing that one up for me

Nick
-----
Mesham Parallel Programming Language
www.mesham.net

On 2 Oct, 12:42, polas <n...@helpforce.com> wrote:
> On 2 Oct, 10:59, Nick Keighley <nick_keighley_nos...@hotmail.com>
> wrote:
> > On 2 Oct, 10:22, Tinkertim <tinker...@gmail.com> wrote:

> > > I have often wondered if casting the return value of malloc() (or
> > > friends) actually helps anything, recent threads here suggest that it
> > > does not .. so I hope to find out.
>
> > > For instance :
>
> > > char *tmp = NULL;
>
> > > tmp = (char *) malloc(1024);
>
> > > Is there any pointing in casting the return value of malloc? I see
> > > many people do that, but not test the result such as :
>
> > > if (tmp == (char *) NULL)
> > > .. some code about malloc() failing ...
>
> > > Is there any point in casting it?
>
> > This is a FAQ
> > FAQ 7.7b "What's wrong with casting malloc's return value?"
>
> > the FAQ lives athttp://c-faq.com
>
> > C++ requires a cast on the return of malloc(). But malloc()
> > is unusual in C++ code (an implementation of C++ might need it).
> > Some people write code that is required to compile under both C and
> > C++ (eg. library writers). They also might want to cast the return
> > value of malloc().

and note the "C++" in my answer. C and C++ are different langauges
and the rules are slightly different. The C++ rules may in some
slightly obscure cases lead to C being written to C++ rules.

> As far as I understood it (which might be somewhat wrong) actually
> casting the return value is unwanted. Am I wrong that without
> including stdlib.h the return value is int (or int * cant remember
> which exactly)

int

> from malloc and so not casting the return value will
> provide a warning/error during compilation if you have missed this
> header? Whereas casting the value will hide this problem and result in
> strange behaviour

yes

--
Nick Keighley

Nick Keighley wrote:
>
.... snip ...
>
> C++ requires a cast on the return of malloc(). But malloc() is
> unusual in C++ code (an implementation of C++ might need it).
> Some people write code that is required to compile under both C
> and C++ (eg. library writers). They also might want to cast the
> return value of malloc().

Not library writers. That would be an excellent way of installing
library bugs. However some people want to sell their software,
written in C source, to imbeciles who will simply compile it and
then use it. They want this to work even though the idiots are
using a C++ compiler. After all, why have a support call? Without
it the dumbos are happy, and the selling firm makes more money.

--
[mail]: Chuck F (cbfalconer at maineline dot net)
[page]: <http://cbfalconer.home.att.net>
Try the download section.

Tinkertim <tinker...@gmail.com> wrote:
> I have often wondered if casting the return value
> of malloc() (or friends) actually helps anything,
> ...

You should first define what you mean by 'help', then
ask the more basic question of whether casts help
anything period.

--
Peter

In article <8be39e8f-ccd3-4a22-9c6b->,
Nick Keighley <> wrote some good stuff,
leading up to:
....
>An example of someone who writes code that compiles with both
>C and C++ is P.J.Plauger. Is he an imbecile or an idiot?
>
>you are on the verge of a plonk

I'm not sure who is the better archetype of the senile old fool: CBF or
McBush.