Re: jscript: Do not call memcpy() with a NULL pointer argument

[Andrew Talbot]

On Thu Dec 18 22:41 , 'James Hawkins' <truiken(a)gmail.com> sent:
> I didn't write jscript, so I'm not the expert, but create_string is
> internal, so we should probably crash if str is NULL instead of hiding
> the error.  What is this patch for?
>
> -- 
> James Hawkins

Hi James,

create_string() is called on line 1323 of this file, with str == NULL and
len = 0. This function always allocates memory for at least one one WCHAR,
so I zero-terminated it.

-- 
Andy.

jscript: Do not call memcpy() with a NULL pointer argument

[Jacek Caban]

Andrew Talbot wrote:
> On Thu Dec 18 22:41 , 'James Hawkins' <truiken(a)gmail.com> sent:
> > I didn't write jscript, so I'm not the expert, but create_string is
> > internal, so we should probably crash if str is NULL instead of hiding
> > the error.  What is this patch for?
> >
> > -- 
> > James Hawkins
>
> Hi James,
>
> create_string() is called on line 1323 of this file, with str == NULL and
> len = 0. This function always allocates memory for at least one one WCHAR,
> so I zero-terminated it.

The string was always zero-terminated without your patch. It's fine to 
call create_string with NULL str argument as long as len is 0 and 
current implementation works fine in this case.


Jacek

jscript: Do not call memcpy() with a NULL pointer argument

[Andrew Talbot]

Jacek Caban wrote:
> The string was always zero-terminated without your patch. It's fine to
> call create_string with NULL str argument as long as len is 0 and
> current implementation works fine in this case.
>
> Jacek

Hi Jacek,

Technically, behavior is undefined if the pointers do not each point to an
object, even if the size parameter has a value of zero (see
http://tinyurl.com/6eqo3n, third post). Though I concede that it would be a
rare implementation that touched its pointers (or copies of them) in that
case.

-- 
Andy.

jscript: Do not call memcpy() with a NULL pointer argument

[Jacek Caban]

Hi Andrew,

Andrew Talbot wrote:
> Jacek Caban wrote:
> > The string was always zero-terminated without your patch. It's fine to
> > call create_string with NULL str argument as long as len is 0 and
> > current implementation works fine in this case.
> >
> > Jacek
>
> Hi Jacek,
>
> Technically, behavior is undefined if the pointers do not each point to an
> object, even if the size parameter has a value of zero (see
> http://tinyurl.com/6eqo3n, third post). Though I concede that it would be a
> rare implementation that touched its pointers (or copies of them) in that
> case.

I'm not fan of such fixes, but if you want to fix it, you should check 
len, not str, in your patch and you may move zero-terminating outside 
if..else statement.


Jacek

jscript: Do not call memcpy() with a NULL pointer argument

[Andrew Talbot]

Jacek Caban wrote:
> I'm not fan of such fixes, but if you want to fix it, you should check
> len, not str, in your patch and you may move zero-terminating outside
> if..else statement.
>
> Jacek

Thank you, I shall fix it in the better way that you describe here.

-- 
Andy.