Stacktraces from dynamically-constructed functions not as expected

[Hannes Wallnoefer]

Hi Vivin,

What you see is some fuzziness in the translation from JS functions to 
Java methods and from there to the stack traces you see.

When we compile a JS function, we create a Java method with the name of 
the function concatenated to the names of its parent functions, using 
'$' as separator. For anonymous functions we use something like L:123 as 
name where 123 is the line of code where the function begins.

This method naming scheme helps a lot in making bytecode easier to 
debug, and to create unique method names within a compilation unit. 
However, it also leads to the stack traces you see, getting f$foo in the 
first case and something like L1:foo in the second case, which is 
rendered as <anonymous> in the stack trace.

Ideally we should reverse this when printing stack traces, displaying 
only the name of the function itself, e.g. "bar" for "foo$bar" and 
"<anonymous>" for "foo$L:3". Unfortunately, "$" is a valid character in 
a JS identifier, so it's not that easy, "foo$bar" may also be the name 
of the original function.

I'm thinking about how to solve this and will probably file an issue for it.

Hannes

Am 2016-05-12 um 15:59 schrieb Vivin Suresh Paliath:
> I tried this out on in chrome and I get the expected stack trace there. Is
> this a bug?
> On May 6, 2016 3:39 PM, "Vivin Suresh Paliath" <vivin.paliath at gmail.com>
> wrote:
>
>> I have the following code:
>>
>> *var f = (function() {*
>> *    return function foo() {*
>> *        try {*
>> *            throw new Error();*
>> *        } catch(e) {*
>> *            print(e.stack);*
>> *        }*
>> *    }*
>> *})();*
>>
>>
>> When I call the function, I get the following stacktrace as expected
>> (mostly; I was expecting *foo* instead of *f$foo*).
>>
>> *Error*
>> *        at f$foo (<shell>:1)*
>> *        at <program> (<shell>:1)*
>>
>>
>> However, if I dynamically construct the function as follows:
>>
>> *var f = new Function([], "return function foo() { try { throw new
>> Error(); } catch(e) { print(e.stack); } }")()*
>>
>>
>> I get:
>>
>>
>> *Error*
>> *        at <anonymous> (<function>:2)*
>> *        at <program> (<shell>:1)*
>>
>>
>> Is there a reason for this discrepancy? Isn't the second version
>> effectively the same as the first? Also, why is it *f$foo* instead of
>> *foo* in the first case?
>>
>> I am running jdk8u92.
>>
>> Thanks!
>>
>> --
>> Ruin untold;
>> And thine own sadness,
>> Sing in the grass,
>> When eve has forgot, that no more hear common things that gleam and pass;
>> But seek alone to lip, sad Rose of love and ruin untold;
>> And thine own mother
>> Can know it as I know
>> More than another
>> What makes your own sadness,
>> Set in her eyes.
>>
>> map{@n=split//;$j.=$n[0]x$n[1]}split/:/,"01:11:02".
>> ":11:01:11:02:13:01:11:01:11:01:13:02:12:01:13:01".
>> ":11:04:11:06:12:04:11:01:12:01:13:02:12:01:14:01".
>> ":13:01:11:03:12:01:11:04:12:02:11:01:11:01:13:02".
>> ":11:03:11:06:11:01:11:05:12:02:11:01:11:01:13:02".
>> ":11:02:12:01:12:04:11:06:12:01:11:04:12:04:11:01".
>> ":12:03:12:01:12:01:11:01:12:01:12:02:11:01:11:01".
>> ":13:02:11:01:02:11:01:12:02";map{print chr unpack"
>> i",pack"B32",$_}$j=~m/.{8}/g
>>