[Click] %{element} syntax

[Ian Rose]

Hmm really?  That's a bit worrisome.  Is it vsnprintf that you think may 
crash or code that's actually in some elements themselves?

I note that in line 112 of glue.cc, you fall back on just a simple 
vsnprintf if ErrorHandler::default_handler() returns NULL:

>  112   if (ErrorHandler *errh = ErrorHandler::default_handler()) {
>  113     errh->xmessage(ErrorHandler::e_info, fmt, val);
>  114   } else {
 > [...]

So is this behavior also dangerous?  Now admittedly, I'm not sure why 
default_handler would ever be NULL, so maybe this is just a "this should 
never happen but if it does let's do our best to print something even if 
its unsafe" type thing?

All I am actually trying to do is make click_chatter go to stdout while 
leaving all other errors going to stderr.  I guess I could create a new 
FileErrorHandler using stdout instead of stderr and then change line 112 
above to be something like:

if (ErrorHandler *errh = <my-stdout-handler>) {

thanks,
Ian


Eddie Kohler wrote:
> Ah, OK.
> 
> Whatever you're doing, I would definitely do it by subclassing 
> ErrorHandler.  Elements definitely expect the %{..} syntax to work and 
> you will get crashes if it is ignored.
> 
> E
> 
> 
> On 3/10/10 5:47 PM, Ian Rose wrote:
>> AH HA!
>>
>> My mistake - I totally forgot that (normally) click_chatter calls
>> through an ErrorHandler rather than directly to vsnprintf or the like. I
>> have changed my glue.cc to NOT use ErrorHandler::default_handler(),
>> which is why this special syntax is not working for me.
>>
>> Sorry about the false alarm there!
>>
>> - Ian
>>
>>
>> Eddie Kohler wrote:
>>> The code that handles this case starts at error.cc:690, if you're
>>> interested in single stepping.
>>>
>>>
>>> On 3/10/10 4:54 PM, Ian Rose wrote:
>>>> Hi all -
>>>>
>>>> In various places (such as simplequeue.cc), there are lines like this:
>>>>
>>>>> click_chatter("%{element}: overflow", this);
>>>>
>>>> I'm guessing that this is supposed to print some kind of
>>>> description/representation of the element, followed by ": overflow", 
>>>> but
>>>> on my machine (userspace click, FreeBSD 7.2-STABLE) it just prints
>>>> "{element}: overflow".
>>>>
>>>> Does this "work" (as I am assuming its supposed to) for other people or
>>>> does it print oddly for everyone?
>>>>
>>>> - Ian
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