Re: jsdIScript.functionName semantics

Here's another way to think about the "empty-function-name" functions.

Consider the code:
---
var a = 1;        // 1: not in named function body
a += 1;           // 2: ditto
function foo() {
   return 2;       // 4: Function "foo"
}
--

If this code is in a web page, then lines 1 and 2 are part of the
__top_level__ function with an empty name.

If this code is eval()ed, then lines 1 and 2 are part of ... ah, er,
the eval-level function with an empty name.

In both cases the bytecodes for this out-of-body code can only be
executed once, which I suppose is why the engine does not keep it
around. Also in both cases the function "foo" is a JavaScript function
with a name that can be called.

The top-level function runs at the top of the stack while the eval-level 
function with an empty name runs in a stack frame with at least one 
caller. Of course a significant difference between these cases is the 
subject of bug #332176: the debugger does not have the source for the 
eval-level or for foo() in the eval case.

John.

James Ross wrote:
> John J. Barton wrote:
>> James Ross wrote:
>>> Venkman identifies __top_level__ scripts by their name (i.e. empty), 
>>> but uses some logic about sealed scripts I don't follow to pick out 
>>> the eval scripts.
>>
>> Oh that's a great hint.  I could not figure out what Venkman was up 
>> to. But now I have a guess.  It analyzes all scripts on creation.  It 
>> uses the first empty name to mark __top_level__.  Because it knows 
>> that no function at compile time will be empty name except top level 
>> and that script comes last in the compile sequence. At the same time 
>> it marks the page ("instance") as "sealed", ie "I saw the top level".  
>> After that all scripts that are created must be EvalScript. (Granted 
>> there is some funky code about _lastScriptWrapper but it seems 
>> consistent with this model).
>>
>> The key assertion is "no function at compile time will be empty name 
>> except top level". Or "every empty name other than top level must be 
>> from runtime, ie eval".
>>
>> You buying that ;-)
> 
> I'll buy that alright; I never did log all the script wrapper and 
> instances and sealing stuff, but counting all non-function scripts after 
> the first as evals would fit.
>