Re: [PATCH] opensm: fixing compilation issues in some header files

[Yevgeny Kliteynik <kliteyn-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org>]

On 02-Jun-10 4:03 AM, Sasha Khapyorsky wrote:
> On 00:18 Wed 02 Jun     , Yevgeny Kliteynik wrote:
>>>
>>> AFAIR (anytype *) to (void *) casting is not needed (doing implicitly)
>>> in C and this is already part of some basic standards.
>>
>> True, but the problem is not (anytype *) to (void *) casting.
>> It's the other way around: (void *) to (anytype *) casting.
>
> It is the same meaning. Otherwise it would be useless.

No, it's not.
Casting TO void* is not dangerous - void* is just a "place holder".
Casting FROM void* is more dangerous - it means your program would
actually be using this pointer's content.

Right now gcc allows you to do implicit casting in both ways, g++ doesn't.

Try compiling this code:

#include <stdlib.h>
int main()
{
         void * v = NULL;
         int * t = NULL;
         v = t;
         t = v;
         return 0;
}

try.cc:7: error: invalid conversion from 'void*' to 'int*'

Here are more details:

   http://www2.research.att.com/~bs/bs_faq2.html#void-ptr


-- Yevgeny
  
> Sasha
>

--
To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html