Sorry, you're right -- I should have researched the history and behavior of
CreateDataProperty and DefineOwnProperty. And, in fact, it does appear that
they will not replace an exisiting object property. Given that, it seems
like you have no choice other than to use ForceSet (until
CreateDataProperty and DefineOwnProperty are fixed?).
While I guess ForceSet was a little uncool in that it allowed replacing
even non-configurable (v8::DontDelete) properties, IMO CreateDataProperty
and DefineOwnProperty seem to go too far in the other direction.
Just out of curiosity, were your examples of read and print used for
simplicity or are these really the functions you're lazily instantiating?
If the latter, is an accessor really that much cheaper to set up then just
adding the function right away as an object property? I can definitely see
using lazy instantiation for a function if it's a constructor and comes
along with a bunch of other stuff but if it's just a simple function, I
would think the FunctionTemplate::New()->GetFunction() isn't going to be
noticably slower than SetAccessor. Of course, you might be doing tricky
stuff like dynamically loading the functions or maybe compiling JavaScript
callbacks with your function or whatever, in which case lazy instantiation
would make perfect sense.
On Saturday, October 31, 2015 at 11:03:10 AM UTC-7, Jane Chen wrote:
>
> Yes, the first time the property is accessed, it gets the correct native
> function. In my accessor before I return, I have:
>
> global->SetAccessor(context,property,0);
> global->CreateDataProperty(context,property,obj);
>
> Then the property becomes undefined the second time on.
>
> On Saturday, October 31, 2015 at 10:04:24 AM UTC-7, Alex Kodat wrote:
>>
>> CreateDataProperty or DefineOwnProperty should work. Of course, you have
>> to make sure that the first time the function is accessed via the accessor
>> when you do your override, you have to return the function from the
>> accessor. But I assume you're doing that?
>>
>> On Friday, October 30, 2015 at 3:03:27 PM UTC-7, Jane Chen wrote:
>>>
>>> Is there anyway to use something like CreateDataProperty to override the
>>> accessor so that the actual function is associated with the property,
>>> albeit lazily created?
>>>
>>> I tried to use CreateDataProperty in place of ForceSet, since ForceSet
>>> is deprecated, but that didn't do it, and my property becomes undefined.
>>>
>>> On Friday, October 30, 2015 at 2:12:12 AM UTC-7, Jakob Kummerow wrote:
>>>>
>>>> Well, the profile tells you which function was executed. It doesn't
>>>> know or care what name you used to refer to this function -- it can't, as
>>>> it's a sampling profiler. Pure-JS example:
>>>>
>>>> function f() { /* long-running stuff */ }
>>>> var g = f;
>>>> g(); // Shows up as "f" in the profile.
>>>>
>>>> In your example, the function is a C++ object, so it doesn't even have
>>>> a name, so V8 tries to infer a name that it hopes is meaningful to a human
>>>> reader. The point is that for a single function, it can only infer a
>>>> single
>>>> name.
>>>>
>>>> I think this is working as intended.
>>>>
>>>> On Thu, Oct 29, 2015 at 11:57 PM, Jane Chen <jxch...@gmail.com> wrote:
>>>>
>>>>> A test case to demonstrate the issue can be found at:
>>>>>
>>>>> https://code.google.com/p/v8/issues/detail?id=4527
>>>>>
>>>>>
>>>>> On Thursday, October 29, 2015 at 3:46:21 PM UTC-7, Jane Chen wrote:
>>>>>>
>>>>>> Testing profiling against v8 4.6.88.
>>>>>>
>>>>>> I have functions that are exposed through accessor callbacks. If a
>>>>>> native function is set for multiple accessor properties, the last
>>>>>> property
>>>>>> shows up as the function name in the CpuProfileNode, regardless what
>>>>>> name
>>>>>> you set to the function returned by the accessor function. For example:
>>>>>>
>>>>>> global->SetAccessor(
>>>>>> v8::String::NewFromUtf8(isolate, "print",
>>>>>> v8::NewStringType::kNormal)
>>>>>> .ToLocalChecked(),
>>>>>> getFunction);
>>>>>> global->SetAccessor(
>>>>>> v8::String::NewFromUtf8(isolate, "read",
>>>>>> v8::NewStringType::kNormal)
>>>>>> .ToLocalChecked(),
>>>>>> getFunction);
>>>>>>
>>>>>> Now "get read" is the function name in CpuProfileNode although print
>>>>>> is called.
>>>>>>
>>>>>> Test script:
>>>>>>
>>>>>> function isPrime(num) {
>>>>>> for (var count = 2; count < num; count++)
>>>>>> if (num % count == 0) return false;
>>>>>> return true;
>>>>>> };
>>>>>>
>>>>>> var total = 0;
>>>>>> for (var i = 2; i < 100000; i++) {
>>>>>> if (isPrime(i)) {
>>>>>> print(i);
>>>>>> total++
>>>>>> }
>>>>>> };
>>>>>> total;
>>>>>>
>>>>>> TotalHitCount:2233
>>>>>>
>>>>>> FunctionName:(root)
>>>>>> LineNumber:0
>>>>>> ColumnNumber:0
>>>>>> HitCount:0
>>>>>> FunctionName:(program)
>>>>>> LineNumber:0
>>>>>> ColumnNumber:0
>>>>>> HitCount:7
>>>>>> FunctionName:
>>>>>> LineNumber:0
>>>>>> ColumnNumber:0
>>>>>> HitCount:13
>>>>>> FunctionName:isPrime
>>>>>> LineNumber:1
>>>>>> ColumnNumber:17
>>>>>> HitCount:8
>>>>>> FunctionName:
>>>>>> LineNumber:1
>>>>>> ColumnNumber:1
>>>>>> HitCount:2196
>>>>>> FunctionName:get read
>>>>>> LineNumber:0
>>>>>> ColumnNumber:0
>>>>>> HitCount:2
>>>>>> FunctionName:(garbage collector)
>>>>>> LineNumber:0
>>>>>> ColumnNumber:0
>>>>>> HitCount:7
>>>>>>
>>>>>>
>>>>>> Given that an accessor callback takes a property name, it should
>>>>>> allow one native function to handle multiple properties. Is this a bug,
>>>>>> or
>>>>>> am I doing something wrong?
>>>>>>
>>>>> --
>>>>> --
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>>>>>
>>>>
>>>>
>>>>
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