Re: Which casting conversion to use for void*?

From:
Noah Roberts <dont@email.me>
Newsgroups:
comp.lang.c++
Date:
Mon, 09 May 2011 09:21:37 -0700
Message-ID:
<4dc8147b$0$2413$cc2e38e6@news.uslec.net>
On 5/8/2011 11:31 PM, Qi wrote:

On 2011-5-9 6:44, Nephi Immortal wrote:

Which should I use correct casting conversion after I create void
variables?

For example:

void *memory = malloc( 0x1000 );

char *pString = static_cast< char*>( memory );

or

char *pString = reinterpret_cast< char*>( memory );

After I deallocate the memory, I will convert from char* back to
void* prior free( void* ) function.


*static_cast* until compiler complains. Then use reinterpret_cast.
static_cast is type safe cast, reinterpret_cast not.


I can't say I recommend this procedure. It can easily lead people to
cast when they don't have to. For example, I found code like this in a
project I worked on:

// whatnot.h

struct A
struct B

struct whatnot
{
   A* a;
   void fun(B* b) { a = (B*)b; }
};

// B.h

#include "A.h"

struct B : A {....};

Of course, it's quite silly to do an upcast like this. It's even worse
to do a C-style cast. What's even worse than that about it is that this
particular cast will be a reinterpret_cast.

The reason of course that it was done is almost certainly that the
compiler complained about unrelated types and recommended a reinterpret
or C-style cast (the MS compiler does this). A more appropriate
solution of course is to include the appropriate headers and/or move the
body of f() into a cpp file.

So, it's not really a well recommended practice in my opinion to plug in
reinterpret_cast when the compiler starts to bitch. This cast should
really be reserved for very special cases and, in fact, with almost all
modern C++ it's completely unnecessary.

--
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