🚀 go-pugleaf

joe (j.) halpin (jhalpin@bnr.ca) wrote:
> In 3.7.3.2.4 the January working paper says:

> 4 A deallocation function can free the storage referenced by the pointer
>   given  as  its  argument and renders the pointer invalid.  The storage
>   can be made available for further allocation.  An invalid pointer con-
>   tains an unusable value:  it cannot even be used in an expression.

> This sounds as though, in the following:

> char *pc = new char[128];
> delete pc;
> pc = 0;

> it makes the final assignment (an expression) invalid.

It says that the pointer *contains an unuseable value*. Assignment to the 
pointer replaces this with a potentially useable value. It's important 
not to confuse an object with the value it contains.

BTW "delete pc" is required to be "delete[] pc"

> Am I misunderstanding something, or is it illegal to zero out pointers
> after they've been deallocated? I'm assuming that the intent was to
> disallow dereferencing of pointers that have been handed to
> delete. The wording seems to disallow the above as well.

> In fact, it sounds like it also rules out things like 'if(pc == 0)
> ...' after the above fragment.

No; the pointer is perfectly good now that it contains a valid value.

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