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NNTP-Posting-Date: Wed, 27 Jul 2011 01:24:59 -0500
From: Gareth Owen <gwowen@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: is there anything unstandard in the c part here
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Date: Wed, 27 Jul 2011 07:24:59 +0100
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Xref: x330-a1.tempe.blueboxinc.net comp.lang.c:8764

James Kuyper <jameskuyper@verizon.net> writes:

> What are the drawbacks? I'm not familiar with any.

Lets look at the code (roughly) as given

char *pa;
/* yadda yadda yadda */
.
.
.
pa = (char*) malloc(50);
.
.
.
/* code that presumably assumes 50 elements in pa[] */


Now the advice given was "if you change the type of *pa, the cast is
wrong".  So lets do that...

With the cast
-----------------------------------------------------------------------------
int *pa;
/* yadda yadda yadda */
.
.
.
pa = (char*) malloc(50);
.
.
.
/* code that presumably assumes 50 elements in pa[] */
result: compiler error.
-----------------------------------------------------------------------------


Take the cast away 
-----------------------------------------------------------------------------
int *pa;
/* yadda yadda yadda */
.
.
.
pa = malloc(50);
.
.
.
/* code that presumably assumes 50 elements in pa[] */
result: undefined behaviour unless sizeof(int) == 1

The *failure* to cast malloc() has hidden a bug in *exactly* the case for
which casting malloc() was held up as being wrong.
-----------------------------------------------------------------------------

Personally, when I accidentally write buggy code, I want a compiler
error rather undefined behaviour. YMMV.

Yes, I know all about the pa = malloc(50 * sizeof(*pa)) idiom, thanks,
and I know that there *are* drawbacks to casting malloc. But my
underlying point is correct - casting malloc() is a *style* issue, and
only idiots argue that their style is correct and anything else is
wrong.