subject:"Re\: \[v8\-users\] Re\: Debugging wrapped C\+\+ object"

Re: [v8-users] Re: Debugging wrapped C++ object

2018-05-11 Thread Ben Noordhuis

On Thu, May 10, 2018 at 11:18 AM, Anoop R. S.  wrote:
> Thank you for the reply, Ben.
>>
>> Instead of v8::IndexedPropertyHandlerConfiguration, you may
>> want to use v8::NamedPropertyHandlerConfiguration.
>
> I am already using it. What I noticed is that, when I run the code without
> devtools debugging, only the callback GenericNamedPropertyGetterCallback,
> (of NamedPropertyHandlerConfiguration) is invoked.
> IndexedPropertyHandlerConfiguration callbacks are not called even though
> they are implemented. But when I run the code through the debugger, I can
> see the IndexedPropertyHandlerConfiguration callback is called and whatever
> I am populating inside it, is visible in the debugger. After that,
> GenericNamedPropertyGetterCallback, (of NamedPropertyHandlerConfiguration)
> is called, for resolving the names which I am putting into the array in
> GenericNamedPropertyGetterCallback implementation.

Just to make sure we're on the same page:
IndexedPropertyHandlerConfiguration is for number-as-key operations,
i.e., obj[42]; obj.x and obj['x'] on the other hand are named property
operations.

What the debugger does is (mostly) equivalent to `Object.keys(obj)`
and `Object.getOwnPropertyNames(obj)`, operations that include
enumerable element indices _and_ enumerable named properties in their
output.  That's why you observe your IndexedPropertyEnumeratorCallback
getting invoked.  It's asked to list the object's enumerable element
indices.

Interceptor callbacks need to conform to some fairly strict semantics
(that isn't always explained well in v8.h), otherwise you can get
unintuitive behavior.  If unsure, take a look at
test/cctest/test-api-interceptors.cc.

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Re: [v8-users] Re: Debugging wrapped C++ object

2018-05-10 Thread Anoop R. S.

Thank you for the reply, Ben.

> Instead of v8::IndexedPropertyHandlerConfiguration, you may 
> want to use v8::NamedPropertyHandlerConfiguration. 
>

I am already using it. 
What I noticed is that, when I run the code without devtools debugging, 
only the callback *GenericNamedPropertyGetterCallback, (*of 
*NamedPropertyHandlerConfiguration**) *is invoked. 
*IndexedPropertyHandlerConfiguration *callbacks are not called even though 
they are implemented. 
But when I run the code through the debugger, I can see the 
*IndexedPropertyHandlerConfiguration *callback is called and whatever I am 
populating inside it, is visible in the debugger. After that, 
*GenericNamedPropertyGetterCallback, 
(*of *NamedPropertyHandlerConfiguration**) *is called, for resolving the 
names which I am putting into the array in *GenericNamedPropertyGetterCallback 
*implementation. 

Based on this behaviour, I would assume that *evaluateOnCallFrame *(similar 
behaviour is shown by the message *Runtime.getProperties* also, which I 
think fetches the variable values for the overlay display) treats the 
variable as an indexed property. 

regards,
Anoop R. S.

On Thursday, 10 May 2018 13:10:03 UTC+5:30, Ben Noordhuis wrote:
>
> On Thu, May 10, 2018 at 8:42 AM, Anoop R. S.  > wrote: 
> > Ok. I figured out that if v8::IndexedPropertyHandlerConfiguration is 
> set, 
> > and IndexedPropertyEnumeratorCallback is implemented, I can configure 
> what 
> > is displayed on mouse over action (Debugger.evaluateOnCallFrame is 
>  passed 
> > from devtools on doing that operation.) 
> > 
> > The implementation is provided below. 
> > void IndexedPropertyEnumeratorCallbackFunction( 
> >  const v8::PropertyCallbackInfo& p_callbackInfo) 
> > { 
> >  v8::Local IndexArray = 
> > v8::Array::New(p_callbackInfo.GetIsolate(), 2); 
> >  IndexArray->Set( 
> >  v8::Integer::New(p_callbackInfo.GetIsolate(), 0), 
> >  v8::String::NewFromUtf8(p_callbackInfo.GetIsolate(), u8"x")); 
> >  IndexArray->Set( 
> >  v8::Integer::New(p_callbackInfo.GetIsolate(), 1), 
> >  v8::String::NewFromUtf8(p_callbackInfo.GetIsolate(), u8"y")); 
> >  p_callbackInfo.GetReturnValue().Set(IndexArray); 
> > } 
> > 
> > From reading the embedder's guide, my understanding is that 
> >> 
> >> indexed property interceptors - called when accessing indexed 
> properties. 
> >> An example of this, in a browser environment, is 
> document.forms.elements[0]. 
> > 
> > 
> > Why is it called on evaluateOnCallFrame action? Also, I tried with other 
> > callback s of v8::IndexedPropertyHandlerConfiguration, but they are not 
> > called. Can I know why? Also, since the signature of callback is as 
> below : 
> > 
> > void (*IndexedPropertyEnumeratorCallback)( const 
> > PropertyCallbackInfo& info); 
> > 
> > I can set only arrays into the result and nothing else. 
> > I am not an expert in v8, hence these questions. Please let me know 
> about 
> > it/ point me to some documentation regarding this. 
> > 
> > regards, 
> > Anoop R. S. 
>
> IndexedPropertyEnumeratorCallback - is called for Object.keys()-like 
> operations; i.e., to list the enumerable properties of the object but 
> not non-enumerable or prototype properties.  The 'Indexed' refers to 
> the fact that it's intended for numeric keys, i.e., array-like 
> objects.  Instead of v8::IndexedPropertyHandlerConfiguration, you may 
> want to use v8::NamedPropertyHandlerConfiguration. 
>
> evaluateOnCallFrame - V8 cannot know whether your callback has any 
> side effects (it could create objects, call into JS code, etc.), hence 
> it evaluates it as if it were a snippet of regular JS code.  Newer 
> versions of V8 let you register callbacks with kHasNoSideEffect but as 
> far as I know that has no effect (hah!) on whether or not 
> evaluateOnCallFrame is used.  Maybe in the future. 
>

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Re: [v8-users] Re: Debugging wrapped C++ object

2018-05-10 Thread Anoop R. S.

Thank you for the reply, Ben.

> Instead of v8::IndexedPropertyHandlerConfiguration, you may 
> want to use v8::NamedPropertyHandlerConfiguration. 
>

I am already using it. What I noticed is that, when I run the code without 
devtools debugging, only the callback *GenericNamedPropertyGetterCallback, 
(*of *NamedPropertyHandlerConfiguration**) *is invoked. 
*IndexedPropertyHandlerConfiguration *callbacks are not called even though 
they are implemented. But when I run the code through the debugger, I can 
see the *IndexedPropertyHandlerConfiguration *callback is called and 
whatever I am populating inside it, is visible in the debugger. After that, 
*GenericNamedPropertyGetterCallback, 
(*of *NamedPropertyHandlerConfiguration**) *is called, for resolving the 
names which I am putting into the array in *GenericNamedPropertyGetterCallback 
*implementation. 

Based on this behaviour, I would assume that *evaluateOnCallFrame *(similar 
behaviour is shown by the message *Runtime.getProperties* also, which I 
think fetches the variable values for the overlay display) treats the 
variable as an indexed property. 

regards,
Anoop R. S.

On Thursday, 10 May 2018 13:10:03 UTC+5:30, Ben Noordhuis wrote:
>
> On Thu, May 10, 2018 at 8:42 AM, Anoop R. S.  > wrote: 
> > Ok. I figured out that if v8::IndexedPropertyHandlerConfiguration is 
> set, 
> > and IndexedPropertyEnumeratorCallback is implemented, I can configure 
> what 
> > is displayed on mouse over action (Debugger.evaluateOnCallFrame is 
>  passed 
> > from devtools on doing that operation.) 
> > 
> > The implementation is provided below. 
> > void IndexedPropertyEnumeratorCallbackFunction( 
> >  const v8::PropertyCallbackInfo& p_callbackInfo) 
> > { 
> >  v8::Local IndexArray = 
> > v8::Array::New(p_callbackInfo.GetIsolate(), 2); 
> >  IndexArray->Set( 
> >  v8::Integer::New(p_callbackInfo.GetIsolate(), 0), 
> >  v8::String::NewFromUtf8(p_callbackInfo.GetIsolate(), u8"x")); 
> >  IndexArray->Set( 
> >  v8::Integer::New(p_callbackInfo.GetIsolate(), 1), 
> >  v8::String::NewFromUtf8(p_callbackInfo.GetIsolate(), u8"y")); 
> >  p_callbackInfo.GetReturnValue().Set(IndexArray); 
> > } 
> > 
> > From reading the embedder's guide, my understanding is that 
> >> 
> >> indexed property interceptors - called when accessing indexed 
> properties. 
> >> An example of this, in a browser environment, is 
> document.forms.elements[0]. 
> > 
> > 
> > Why is it called on evaluateOnCallFrame action? Also, I tried with other 
> > callback s of v8::IndexedPropertyHandlerConfiguration, but they are not 
> > called. Can I know why? Also, since the signature of callback is as 
> below : 
> > 
> > void (*IndexedPropertyEnumeratorCallback)( const 
> > PropertyCallbackInfo& info); 
> > 
> > I can set only arrays into the result and nothing else. 
> > I am not an expert in v8, hence these questions. Please let me know 
> about 
> > it/ point me to some documentation regarding this. 
> > 
> > regards, 
> > Anoop R. S. 
>
> IndexedPropertyEnumeratorCallback - is called for Object.keys()-like 
> operations; i.e., to list the enumerable properties of the object but 
> not non-enumerable or prototype properties.  The 'Indexed' refers to 
> the fact that it's intended for numeric keys, i.e., array-like 
> objects.  Instead of v8::IndexedPropertyHandlerConfiguration, you may 
> want to use v8::NamedPropertyHandlerConfiguration. 
>
> evaluateOnCallFrame - V8 cannot know whether your callback has any 
> side effects (it could create objects, call into JS code, etc.), hence 
> it evaluates it as if it were a snippet of regular JS code.  Newer 
> versions of V8 let you register callbacks with kHasNoSideEffect but as 
> far as I know that has no effect (hah!) on whether or not 
> evaluateOnCallFrame is used.  Maybe in the future. 
>

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Re: [v8-users] Re: Debugging wrapped C++ object

2018-05-10 Thread Anoop R. S.

Thank you for the reply, Ben.

> Instead of v8::IndexedPropertyHandlerConfiguration, you may 
> want to use v8::NamedPropertyHandlerConfiguration. 
>

I am already using it. What I noticed is that, when I run the code without 
devtools debugging, only the callback *GenericNamedPropertyGetterCallback *is 
invoked. *IndexedPropertyHandlerConfiguration *callbacks are not called 
even though they are implemented. But when I run the code through the 
debugger, I can see the *IndexedPropertyHandlerConfiguration *callback is 
called and whatever I am populating inside it, is visible in the debugger.
Based on the behaviour, I would assume that *evaluateOnCallFrame (*similar 
behaviour is shown by the message *Runtime.getProperties* also, which I 
think fetches the variable values for the overlay display*) *treats the 
variable as an indexed property. 

On Thursday, 10 May 2018 13:10:03 UTC+5:30, Ben Noordhuis wrote:
>
> On Thu, May 10, 2018 at 8:42 AM, Anoop R. S.  > wrote: 
> > Ok. I figured out that if v8::IndexedPropertyHandlerConfiguration is 
> set, 
> > and IndexedPropertyEnumeratorCallback is implemented, I can configure 
> what 
> > is displayed on mouse over action (Debugger.evaluateOnCallFrame is 
>  passed 
> > from devtools on doing that operation.) 
> > 
> > The implementation is provided below. 
> > void IndexedPropertyEnumeratorCallbackFunction( 
> >  const v8::PropertyCallbackInfo& p_callbackInfo) 
> > { 
> >  v8::Local IndexArray = 
> > v8::Array::New(p_callbackInfo.GetIsolate(), 2); 
> >  IndexArray->Set( 
> >  v8::Integer::New(p_callbackInfo.GetIsolate(), 0), 
> >  v8::String::NewFromUtf8(p_callbackInfo.GetIsolate(), u8"x")); 
> >  IndexArray->Set( 
> >  v8::Integer::New(p_callbackInfo.GetIsolate(), 1), 
> >  v8::String::NewFromUtf8(p_callbackInfo.GetIsolate(), u8"y")); 
> >  p_callbackInfo.GetReturnValue().Set(IndexArray); 
> > } 
> > 
> > From reading the embedder's guide, my understanding is that 
> >> 
> >> indexed property interceptors - called when accessing indexed 
> properties. 
> >> An example of this, in a browser environment, is 
> document.forms.elements[0]. 
> > 
> > 
> > Why is it called on evaluateOnCallFrame action? Also, I tried with other 
> > callback s of v8::IndexedPropertyHandlerConfiguration, but they are not 
> > called. Can I know why? Also, since the signature of callback is as 
> below : 
> > 
> > void (*IndexedPropertyEnumeratorCallback)( const 
> > PropertyCallbackInfo& info); 
> > 
> > I can set only arrays into the result and nothing else. 
> > I am not an expert in v8, hence these questions. Please let me know 
> about 
> > it/ point me to some documentation regarding this. 
> > 
> > regards, 
> > Anoop R. S. 
>
> IndexedPropertyEnumeratorCallback - is called for Object.keys()-like 
> operations; i.e., to list the enumerable properties of the object but 
> not non-enumerable or prototype properties.  The 'Indexed' refers to 
> the fact that it's intended for numeric keys, i.e., array-like 
> objects.  Instead of v8::IndexedPropertyHandlerConfiguration, you may 
> want to use v8::NamedPropertyHandlerConfiguration. 
>
> evaluateOnCallFrame - V8 cannot know whether your callback has any 
> side effects (it could create objects, call into JS code, etc.), hence 
> it evaluates it as if it were a snippet of regular JS code.  Newer 
> versions of V8 let you register callbacks with kHasNoSideEffect but as 
> far as I know that has no effect (hah!) on whether or not 
> evaluateOnCallFrame is used.  Maybe in the future. 
>

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Re: [v8-users] Re: Debugging wrapped C++ object

2018-05-10 Thread Ben Noordhuis

On Thu, May 10, 2018 at 8:42 AM, Anoop R. S.  wrote:
> Ok. I figured out that if v8::IndexedPropertyHandlerConfiguration is set,
> and IndexedPropertyEnumeratorCallback is implemented, I can configure what
> is displayed on mouse over action (Debugger.evaluateOnCallFrame is  passed
> from devtools on doing that operation.)
>
> The implementation is provided below.
> void IndexedPropertyEnumeratorCallbackFunction(
>  const v8::PropertyCallbackInfo& p_callbackInfo)
> {
>  v8::Local IndexArray =
> v8::Array::New(p_callbackInfo.GetIsolate(), 2);
>  IndexArray->Set(
>  v8::Integer::New(p_callbackInfo.GetIsolate(), 0),
>  v8::String::NewFromUtf8(p_callbackInfo.GetIsolate(), u8"x"));
>  IndexArray->Set(
>  v8::Integer::New(p_callbackInfo.GetIsolate(), 1),
>  v8::String::NewFromUtf8(p_callbackInfo.GetIsolate(), u8"y"));
>  p_callbackInfo.GetReturnValue().Set(IndexArray);
> }
>
> From reading the embedder's guide, my understanding is that
>>
>> indexed property interceptors - called when accessing indexed properties.
>> An example of this, in a browser environment, is document.forms.elements[0].
>
>
> Why is it called on evaluateOnCallFrame action? Also, I tried with other
> callback s of v8::IndexedPropertyHandlerConfiguration, but they are not
> called. Can I know why? Also, since the signature of callback is as below :
>
> void (*IndexedPropertyEnumeratorCallback)( const
> PropertyCallbackInfo& info);
>
> I can set only arrays into the result and nothing else.
> I am not an expert in v8, hence these questions. Please let me know about
> it/ point me to some documentation regarding this.
>
> regards,
> Anoop R. S.

IndexedPropertyEnumeratorCallback - is called for Object.keys()-like
operations; i.e., to list the enumerable properties of the object but
not non-enumerable or prototype properties.  The 'Indexed' refers to
the fact that it's intended for numeric keys, i.e., array-like
objects.  Instead of v8::IndexedPropertyHandlerConfiguration, you may
want to use v8::NamedPropertyHandlerConfiguration.

evaluateOnCallFrame - V8 cannot know whether your callback has any
side effects (it could create objects, call into JS code, etc.), hence
it evaluates it as if it were a snippet of regular JS code.  Newer
versions of V8 let you register callbacks with kHasNoSideEffect but as
far as I know that has no effect (hah!) on whether or not
evaluateOnCallFrame is used.  Maybe in the future.

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Re: [v8-users] Re: Debugging wrapped C++ object

Re: [v8-users] Re: Debugging wrapped C++ object

Re: [v8-users] Re: Debugging wrapped C++ object

Re: [v8-users] Re: Debugging wrapped C++ object

Re: [v8-users] Re: Debugging wrapped C++ object

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