[1/2] jscript: Return NULL if jsstr_substr fails.

[Sebastian Lackner]

On 06.09.2016 15:26, Sebastian Lackner wrote:
> On 06.09.2016 12:27, Jacek Caban wrote:
>> Hi Sebastian,
>>
>> I took a deeper look at this. It seems that we have at least two more
>> jsstr_alloc_buf callers to fix (jsstr_concat and
>> JSGlobal_decodeURIComponent). All those seem to be mistakes caused by
>> wrong choice of function signature, requiring not intuitive error
>> handling. I'd prefer to change the root of those problems, making the
>> function:
>> jsstr_t *jsstr_alloc_buf(unsigned,WCHAR**)
>> This should avoid similar mistakes in the future.
>>
>> This will be much larger patch than you originally meant, so please let
>> me know if you'd like to prepare a patch or should I take care of that.
>>
>> Thanks,
>> Jacek
>>
>>
> 
> Good catch. Yes, the current function signature makes it very easy to do
> things wrong. If you want me to prepare an updated patch I can do that,
> but I also don't mind if you want to prepare a patch yourself.
> 
> Best regards,
> Sebastian
> 

I've just sent a patch, but feel free to ignore it if you have already been
working on your own version.

By the way, there is another aspect which makes jsstr_alloc_buf very hard to
use, which is that we have to know the exact buffer size in advance. As a
result there are also places where it is done wrong, for example
Date_toTimeString which passes the maximum required buffer size, but does not
update ->length_flags afterwards. Are you fine with adding something like

jsstr_shrink_buf(jsstr_t *)
or
jsstr_shrink_buf(jsstr_t *, unsigned)

to fix this, or do we really want to fix the length calculation instead?

Regards,
Sebastian