Casting the return value of malloc() ?

**Richard Bos** · Oct 6 '08, 07:45 AM

Re: Casting the return value of malloc() ?

Keith Thompson <kst-u@mib.orgwrote:

Old Wolf <oldwolf@inspir e.net.nzwrites:

On Oct 3, 10:27 pm, Nick Keighley <nick_keighley_ nos...@hotmail. com>

Yes C and C++ are different. But you can write a programs
using a LARGE subset of C that will compile with C and C++.

True, but in the general case they'll be both bad C and worse C++.
_Correct_, yes, but horrible style.

The question is, why would you want to do this?

You can write programs that compile in both C
and Fortran. But again, why would you?

Here's the reasons I can think of:
1) For curiosity's sake
2) You are an idiot

What's your reason?

>
As we've mentioned several times in this thread, P.J. Plauger seems to
have sound business reasons for doing this.

He does, but so far, he's the only one who has managed to convince me
that _in his specific case_, the advantages outweigh the downsides. In
every other case I've seen, the claim that "but I might want to compile
my C code as C++" is very simply put aside with the argument that you
just should not do that, as there are mechanisms in C++ to make such
half-hearted practices superfluous.

Richard

**Keith Thompson** · Oct 6 '08, 07:55 AM

Re: Casting the return value of malloc() ?

rlb@hoekstra-uitgeverij.nl (Richard Bos) writes:

Keith Thompson <kst-u@mib.orgwrote:

>Old Wolf <oldwolf@inspir e.net.nzwrites:

On Oct 3, 10:27 pm, Nick Keighley <nick_keighley_ nos...@hotmail. com>
>Yes C and C++ are different. But you can write a programs
>using a LARGE subset of C that will compile with C and C++.

>
True, but in the general case they'll be both bad C and worse C++.
_Correct_, yes, but horrible style.

As far as I know, the only thing you need to do that I'd consider poor
C style is casting the result of malloc -- and more generally, not
taking advantage of C's implicit conversions for void*.

I'm sure a lot of programmers trying to write code that's compatible
with both C and C++ will write stylistically bad code -- but then a
lot of programmers manage to do that trying to write plain C.

[...]

>As we've mentioned several times in this thread, P.J. Plauger seems to
>have sound business reasons for doing this.

>
He does, but so far, he's the only one who has managed to convince me
that _in his specific case_, the advantages outweigh the downsides. In
every other case I've seen, the claim that "but I might want to compile
my C code as C++" is very simply put aside with the argument that you
just should not do that, as there are mechanisms in C++ to make such
half-hearted practices superfluous.

Agreed. *Most* programmers don't need to write code that compiles as
both C and C++ (and far too many think they do). But to suggest that
*everyone* who does so is stupid, or has stupid customers, is absurd.

--
Keith Thompson (The_Other_Keit h) kst-u@mib.org <http://www.ghoti.net/~kst>
Nokia
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"

**RocTheEngy** · Oct 6 '08, 09:35 PM

Re: Casting the return value of malloc() ?

Not that I can think of. Testing the return value, on the other hand, is
crucial.
>
I suggest you find someone who advocates the cast, and ask them why. Most
likely, they won't know. In the event that you find someone who does know
why they're casting, why not present this group with the reason he or she
gives you, and ask us what we think of it?
>
--
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

The professor at my college where I learned C (he was newly hired at
the time; almost 20 years ago) was the first person to teach C at
the university. Previous programming classes were purely pascal.

He was therefore, by defacto standard, the "guru" and not to be
questioned... (at least not by us undergrads).

He was _adamant_ that the malloc() family *required* casts. To this
day,
the only answer I recall him giving is "...to give the compiler a
warm,
fuzzy feeling". To inquire further left one with the feeling that
your next test grade may suffer if you pressed him. Looking back, I
suspect the intimidation was to avoid embarrasment.

The system, as best I recall, was some type of VAX. It ran a flavor
of Unix, and we compiled our code with "cc" (not gcc). I used that
programming convention for years on many platforms until I read the
CLC FAQ.

To this day, many of us would like to know WHY we were
required to cast for malloc's. I wish I could remember more details.
For all I now, he may have had a reason. Beats me.

**Richard Heathfield** · Oct 6 '08, 09:35 PM

Re: Casting the return value of malloc() ?

RocTheEngy said:

>

>Not that I can think of. Testing the return value, on the other hand, is
>crucial.
>>
>I suggest you find someone who advocates the cast, and ask them why.
>Most likely, they won't know. In the event that you find someone who
>does know why they're casting, why not present this group with the
>reason he or she gives you, and ask us what we think of it?
>>

The professor at my college where I learned C (he was newly hired at
the time; almost 20 years ago) was the first person to teach C at
the university. Previous programming classes were purely pascal.
>
He was therefore, by defacto standard, the "guru" and not to be
questioned... (at least not by us undergrads).
>
He was _adamant_ that the malloc() family *required* casts.

20 years ago, he was *right*.

The language changed... 19 years ago.

--
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

**RocTheEngy** · Oct 6 '08, 09:35 PM

Re: Casting the return value of malloc() ?

On Oct 6, 4:35 pm, Richard Heathfield <r...@see.sig.i nvalidwrote:

RocTheEngy said:
>
>
>
>
>
>
>

Not that I can think of. Testing the return value, on the other hand, is
crucial.

>

I suggest you find someone who advocates the cast, and ask them why.
Most likely, they won't know. In the event that you find someone who
does know why they're casting, why not present this group with the
reason he or she gives you, and ask us what we think of it?

>

The professor at my college where I learned C (he was newly hired at
the time; almost 20 years ago) was the first person to teach C at
the university. Previous programming classes were purely pascal.

>

He was therefore, by defacto standard, the "guru" and not to be
questioned... (at least not by us undergrads).

>

He was _adamant_ that the malloc() family *required* casts.

>
20 years ago, he was *right*.
>
The language changed... 19 years ago.
>
--
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- Hide quoted text -
>
- Show quoted text -

I said _almost_ 20 years ago. :) It was 1991...

But to understand your statement; there was a time when this
convention was correct?
(i.e. required)

**Ian Collins** · Oct 6 '08, 09:45 PM

Re: Casting the return value of malloc() ?

RocTheEngy wrote:

>
I said _almost_ 20 years ago. :) It was 1991...
>
But to understand your statement; there was a time when this
convention was correct?
(i.e. required)
>

Before C was standardised, void wasn't part of the language and malloc
returned char*

--
Ian Collins.

**Peter Nilsson** · Oct 6 '08, 10:05 PM

Re: Casting the return value of malloc() ?

Flash Gordon <s...@spam.caus eway.comwrote:

Nick Keighley wrote, On 03/10/08 09:27:

An example of someone who writes code that compiles
with both C and C++ is P.J.Plauger.

Let's not forget Ritchie and Kernighan.

Is he an imbecile or an idiot?

>
I *think* he was calling the customers dumbos, not the
authors of the library.

Plauger shares the view of his customers. So any criticism
of his customers must be applied to Plauger himself, if
consistency is to hold.

Here's what he had to say in 2004...

"What I find interesting about this debate is the two
positions being espoused:

1) Omitting casts on malloc calls is acceptable, but
not necessarily virtuous.

2) Putting casts on malloc calls is stupid.

Those of us in the first camp are going to keep using
casts, and we're going to keep respecting those who
don't. It would be nice if we were granted a bit of
respect in turn, but what the hell. A closed mind
avoids the risk of having to change."

--
Peter

**Flash Gordon** · Oct 8 '08, 01:05 AM

Re: Casting the return value of malloc() ?

Peter Nilsson wrote, On 06/10/08 23:03:

Flash Gordon <s...@spam.caus eway.comwrote:

>Nick Keighley wrote, On 03/10/08 09:27:

>>An example of someone who writes code that compiles
>>with both C and C++ is P.J.Plauger.

>
Let's not forget Ritchie and Kernighan.

That was because there were no compilers conforming to ANSI C at the
time so they had to use a C++ compiler to get access to certain features.

>>Is he an imbecile or an idiot?

>I *think* he was calling the customers dumbos, not the
>authors of the library.

>
Plauger shares the view of his customers. So any criticism
of his customers must be applied to Plauger himself, if
consistency is to hold.

I thought that his view was that it was the right thing for him to do it
because that was his customers' requirement.

Here's what he had to say in 2004...
>
"What I find interesting about this debate is the two
positions being espoused:
>
1) Omitting casts on malloc calls is acceptable, but
not necessarily virtuous.
>
2) Putting casts on malloc calls is stupid.

He missed a view some espouse...

3) Putting casts on malloc is virtuous

Those of us in the first camp are going to keep using
casts, and we're going to keep respecting those who
don't. It would be nice if we were granted a bit of
respect in turn, but what the hell. A closed mind
avoids the risk of having to change."

Well, at least some of the people who in general strongly disagree with
putting the casts in have accepted that sometimes there is a good
reason. So not everyone who is against casting has a completely closed
mind :-)
--
Flash Gordon
If spamming me sent it to smap@spam.cause way.com
If emailing me use my reply-to address
See the comp.lang.c Wiki hosted by me at http://clc-wiki.net/

**Ian Collins** · Oct 8 '08, 01:15 AM

Re: Casting the return value of malloc() ?

Flash Gordon wrote:

Peter Nilsson wrote, On 06/10/08 23:03:

>Flash Gordon <s...@spam.caus eway.comwrote:

>>Nick Keighley wrote, On 03/10/08 09:27:
>>>An example of someone who writes code that compiles
>>>with both C and C++ is P.J.Plauger.

>Let's not forget Ritchie and Kernighan.

>
That was because there were no compilers conforming to ANSI C at the
time so they had to use a C++ compiler to get access to certain features.
>

Like void!

I don't think the original K&R even mentions malloc. They do briefly
describe calloc, which is shown as returning char* so a cast is required.

--
Ian Collins.

**Peter Nilsson** · Oct 8 '08, 05:35 AM

Re: Casting the return value of malloc() ?

Flash Gordon <s...@spam.caus eway.comwrote:

Peter Nilsson wrote, On 06/10/08 23:03:

Flash Gordon <s...@spam.caus eway.comwrote:

Nick Keighley wrote, On 03/10/08 09:27:
>An example of someone who writes code that compiles
>with both C and C++ is P.J.Plauger.

Let's not forget Ritchie and Kernighan.

>
That was because there were no compilers conforming to
ANSI C at the time so they had to use a C++ compiler to
get access to certain features.

<http://groups.google.com/group/comp....ea4a63a610cac?
dmode=source>

>Is he an imbecile or an idiot?
I *think* he was calling the customers dumbos, not the
authors of the library.

Plauger shares the view of his customers. So any criticism
of his customers must be applied to Plauger himself, if
consistency is to hold.

>
I thought that his view was that it was the right thing for
him to do it because that was his customers' requirement.

<http://groups.google.com/group/comp....11d85b17ce318?
dmode=source>

<snip>

--
Peter

**Nick Keighley** · Oct 8 '08, 07:55 AM

Re: Casting the return value of malloc() ?

On 8 Oct, 02:14, Ian Collins <ian-n...@hotmail.co mwrote:

I don't think the original K&R even mentions malloc.

pp 143 and 167

--
Nick Keighley

**Ian Collins** · Oct 8 '08, 08:15 AM

Re: Casting the return value of malloc() ?

Nick Keighley wrote:

On 8 Oct, 02:14, Ian Collins <ian-n...@hotmail.co mwrote:
>

>I don't think the original K&R even mentions malloc.

>
pp 143 and 167
>

Not in my 1979 printing. You are thinking of K&R2.

--
Ian Collins.

**Nick Keighley** · Oct 8 '08, 08:15 AM

Re: Casting the return value of malloc() ?

On 4 Oct, 18:40, Old Wolf <oldw...@inspir e.net.nzwrote:

On Oct 3, 10:27 pm,Nick Keighley<nick_k eighley_nos...@ hotmail.com>
wrote:
>

Yes C and C++ are different. But you can write a programs
using a LARGE subset of C that will compile with C and C++.
I know it is unfashionable to say this in clc.
But it is none the less true.

>
The question is, why would you want to do this?
>
You can write programs that compile in both C
and Fortran.

that's just dumb. Try thinking instead of just repeating dogma.
Fortran doesn't look anything like C. Well written C compiles
with C++. That is a fact.

But again, why would you?
>
Here's the reasons I can think of:
1) For curiosity's sake
2) You are an idiot

whatever.

--
Nick Keighley

**Ian Collins** · Oct 8 '08, 08:15 AM

Re: Casting the return value of malloc() ?

Nick Keighley wrote:

On 4 Oct, 18:40, Old Wolf <oldw...@inspir e.net.nzwrote:

>On Oct 3, 10:27 pm,Nick Keighley<nick_k eighley_nos...@ hotmail.com>
>wrote:
>>

>>Yes C and C++ are different. But you can write a programs
>>using a LARGE subset of C that will compile with C and C++.
>>I know it is unfashionable to say this in clc.
>>But it is none the less true.

>The question is, why would you want to do this?
>>
>You can write programs that compile in both C
>and Fortran.

>
that's just dumb. Try thinking instead of just repeating dogma.
Fortran doesn't look anything like C. Well written C compiles
with C++. That is a fact.
>

No it is not. The common subset of C and C++ compiles as C and C++.
There are a number of C constructs that are not valid C++.

--
Ian Collins.

**Nick Keighley** · Oct 8 '08, 08:25 AM

Re: Casting the return value of malloc() ?

On 8 Oct, 09:09, Ian Collins <ian-n...@hotmail.co mwrote:

Nick Keighley wrote:

On 8 Oct, 02:14, Ian Collins <ian-n...@hotmail.co mwrote:

>

I don't think the original K&R even mentions malloc.

>

pp 143 and 167

>
Not in my 1979 printing. You are thinking of K&R2.

ah! missed the word "original"! And I don't have
K&R1 at my elbow

--
nick keighley

Casting the return value of malloc() ?

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