inconsistency in Get/set private data

[rethish]

Hi;

If I do the following operation

a = PRIVATE_TO_JSVAL(7);

b = JSVAL_TO_PRIVATE(a);

I get b's value as '6'. !

Can't I set anyt integar value to private?

Can this operation be done only on pointers?

Thanks & regards

Rethish

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[John Bandhauer]

You (and everyone else who uses JSAPI) would be wise to read and
understand the JSVAL macros at the top of jsapi.h.

John.

[Boris Zbarsky]

rethish wrote:
> Can't I set anyt integar value to private?
>
> Can this operation be done only on pointers?

Yes. In fact, the private pointer needs to be 8-byte aligned.

-Boris

[John Bandhauer]

Hey Boris,

I'm curious why you added the comment about 8-byte alignment. The
PRIVATE macros just tag and untag the 0th bit. From the engine's
perspective, this makes a private jsval indistinguishable from any
other int jsval. That bit is all it takes for the engine to know this
is not a gcthing. Why would the 'full' 31 bits not be available to the
api user? I can't think of any way that the engine would care about
the state of the other 2 low bits. Am I missing something?

John.

>
> -Boris

[Boris Zbarsky]

John Bandhauer wrote:
> I'm curious why you added the comment about 8-byte alignment. The
> PRIVATE macros just tag and untag the 0th bit.

Ah, right. We're talking about private pointers, not gcthing pointers being
stored in a jsval. The latter need to be 8-byte aligned. The private pointers
just need to be 2-byte aligned...

-Boris