smart exceptions

Serge Aleynikov <>
Thu Mar 23 16:21:13 CET 2006


Thomas,

I believe this might be a bug in the parse_transform causing a compiler 
warning in cases like the one attached.

$ erlc -W +'{parse_transform, smart_exceptions}' t.erl
./t.erl:12: variable 'Result' unsafe in 'case' (line 6)

$ erlc -W t.erl
[no warnings]

Serge

Thomas Lindgren wrote:
> 
> --- Serge Aleynikov <> wrote:
> 
> 
>>Thomas, thanks for your tips.
>>
>>Another question: In the attached example when an
>>undefined function is 
>>called (test case 0) the line number doesn't get
>>written as you can see 
>>below.  Is this expected?
> 
> 
> Yes. There are some cases that can't be (cheaply)
> caught by smart_exceptions. At compile-time, we don't
> know if the function is supposed to be defined or not,
> and wrapping a catch around every function call to
> handle if it's undefined seems like overkill.
> 
> You will see the same thing when calling bad funs, I
> believe. And calling code that wasn't compiler with
> smart exceptions will throw dumb old exceptions. 
> 
> All of these appear because this sort of checking
> seemed too expensive.
> 
> Oh yes, there is another case where you will get dumb
> exceptions: when a binary expression fails (e.g., A =
> {foo}, <<A:32>>). This one is something that should be
> fixed, but I've put it off.
> 
> Finally, there is a fundamental weakness:
> smart_exceptions do not handle expressions with
> exported variables well. This is a thorny issue, but
> if erlc reports that variables are mysteriously
> undefined, that may be the cause.
> 
> (And as you can see, smart exceptions is really
> functionality that sits better integrated in the VM
> :-)
> 
> If you have any usage/features feedback, send me a
> mail.
> 
> Best,
> Thomas
> 
> 
> __________________________________________________
> Do You Yahoo!?
> Tired of spam?  Yahoo! Mail has the best spam protection around 
> http://mail.yahoo.com 
> 

-- 
Serge Aleynikov
R&D Telecom, IDT Corp.
Tel: (973) 438-3436
Fax: (973) 438-1464

-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: t.erl
URL: <http://erlang.org/pipermail/erlang-questions/attachments/20060323/228f1fb4/attachment.ksh>


More information about the erlang-questions mailing list