[Development] 0 vs. NULL

[Pocheptsov Timur]

Well, that's a static type system.

I would explain this 'asymmetry' as:

some_pointer_type -> pointer_to_void conversion is safe (given that it's possible at all, since not every pointer type can be implicitly converted to void *).

while hypothetical (non-existent) implicit

pointer_to_void -> some_pointer_type 

IS NOT, and compiler, issuing error messages will help you to avoid some troubles.

________________________________________
From: René J.V. Bertin <rjvbertin at gmail.com>
Sent: Friday, October 09, 2015 5:51 PM
To: Pocheptsov Timur
Cc: development at qt-project.org
Subject: Re: [Development] 0 vs. NULL

On Friday October 09 2015 13:58:37 Pocheptsov Timur wrote:

> if NULL was (void *)0 - you'd have a compilation error in C++, since there is no such implicit conversion.
>
> And yes, void * in C++ can be indeed considered generic, because you can do this:
>
> int * p = ...
> void * pv = p;

Coming from C I have some trouble with that concept of generic pointer. Once you're used that it implies not only "can be assigned to any type of pointer" but also "can be assigned any type of pointer" it's not so easy to remember which of the 2 properties has been dropped. I don't see any evident reason why in the above example it should be possible to assign p to pv without an explicit cast, but not the other way round.

R.