[Swan-dev] pointer initialization and fcfcde7422a4805a56a3a4a175271c56fbbbab12

[Lennart Sorensen]

On Sat, Jun 25, 2016 at 10:24:15PM -0400, D. Hugh Redelmeier wrote:
> This commit is technically wrong.  I admit that the problem will not show 
> up on most machines.
> 
> The C standard does not require that the binary representation of a NULL 
> pointer be 0.  Initializing a struct by zeroing bytes does not guarantee 
> that pointer fields are initialized to NULL.

C11 does require that in fact.

It states (in section 6.3.2.3.3):
An integer constant expression with the value 0, or such an expression
cast to type void *, is called a null pointer constant.  If a null
pointer constant is converted to a pointer type, the resulting pointer,
called a null pointer, is guaranteed to compare unequal to a pointer to
any object or function.

And I have never heard of an implementation that didn't do that.
Doing otherwise made things like "if (!pointer) ..." too damn hard to
get right.

-- 
Len Sorensen