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Re: [Public WebGL] TypedArray constructors and zero length



On Thu, Jun 10, 2010 at 2:12 AM, Cedric Vivier <cedricv@neonux.com> wrote:
> On Thu, Jun 10, 2010 at 06:44, Cedric Vivier <cedricv@neonux.com> wrote:
>>> While -1 will convert
>>> to a large number, implementations are expected to attempt the
>>> allocation, fail, and return a buffer with zero length.
>>
>> Are you implying TypedArray construction can never fail then ?
>> IF returning a zero-length array is the behavior only when "a large
>> number" is passed, how implementations should differentiate "a large
>> number" which couldn't be allocated from "out of memory (within the
>> resource limits of the Javascript context or GC)" ?
>>
>
> FWIW I wrote some tests on this today, Mozilla has the sane behavior
> of throwing an exception ("invalid array size") when length is
> negative while WebKit swaps like crazy attempting to allocate
> memory... and in the end returns "undefined".

After looking back at the JavaScript bindings in WebKit, the intended
behavior is that this should throw an INDEX_SIZE_ERR exception. See
http://trac.webkit.org/browser/trunk/WebCore/bindings/js/JSArrayBufferConstructor.cpp
, line 61, and http://trac.webkit.org/browser/trunk/WebCore/bindings/v8/custom/V8ArrayBufferCustom.cpp
, line 77. I'm not sure why this isn't happening. Feel free to file a
bug on http://bugs.webkit.org/ .

-Ken

> If we do not simply go for changing length type in constructors (only
> [1]) to 'long', I guess we should somehow specify stricter conversion
> rules in WebIDL so that passing an out of range value to a unsigned
> parameter throws as expected (and therefore provide consistent defined
> behavior).
>
>
> Regards,
>
>
> [1] : other attributes are not an issue since they are "readonly" or
> have specified behavior wrt values are out of range (e.g slice,...),
> the issue is only present for constructor as it is an "in" value.
>
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