[geos-devel] Exceptions

[Paul Ramsey]

Martin Davis wrote:
> Yes, absolutely.  The whole idea behind structured exception handling
> is so that higher layers of client code can catch some or all of them
> and handle them intelligently.  To do this, exceptions need to be
> typed, and they often need to carry extra information about the
> nature of the error.
> 
> If every exception thrown is a string, the only handling strategy
> possible is to abort printing out the string.
> 
> It's easy to degrade exceptions to strings, but very hard to make
> them back into typed exceptions.  If typed exceptions are causing a
> problem, the answer is to catch them all in the "C PostgresQL
> wrapper" and convert them to strings.

Unfortunately that is not an option for us, because the act of throwing 
the exception also sends the backend a sigabort. The backend is dead 
before it can catch the exception.

Don't worry about making any changes until Dave gets back and can 
provide more detailed guidance. I don't know that there is any guarantee 
that string-based exceptions would be any more catchable and any less 
deadly to us.

> Martin Davis, Senior Technical Architect Vivid Solutions Inc. Suite
> #1A-2328 Government Street   Victoria, B.C.   V8T 5G5 Phone: (250)
> 385 6040    Fax: (250) 385 6046 EMail: mbdavis at vividsolutions.com
> Web: www.vividsolutions.com
> 
> 
> 
>> -----Original Message----- From: Paul Ramsey
>> [mailto:pramsey at refractions.net] Sent: Saturday, April 19, 2003
>> 12:23 AM To: GEOS List Subject: [geos-devel] Exceptions
>> 
>> 
>> The exceptions continue to muck with us. Exceptions thrown in geos
>> have not been catchable, and are taking down the postgres backend
>> with sigabort. I did a grep for "throw" in the source code, and the
>>  exceptions are a bit of a mishmash. Most of them are of the form,
>> 
>> throw "PointCoordinateList exception: can't retrieve element\n";
>> 
>> But some are of the form,
>> 
>> throw new ParseException(e.toString());
>> 
>> or
>> 
>> throw ParseException("Expected number but encountered ')'")
>> 
>> So, sometimes we are throwing strings, sometimes we are throwing
>> new exception objects and other times just static things?
>> 
>> Anyhow, we have had better luck catching the simple throws (the 
>> strings). Is there a reason for throwing specially constructed 
>> exception objects?
>> 
>> 
>> Paul Ramsey Refractions Research Email: pramsey at refractions.net 
>> Phone: (250) 885-0632
>> 
>> 
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>> 
> 
> 
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-- 
       __
      /
      | Paul Ramsey
      | Refractions Research
      | Email: pramsey at refractions.net
      | Phone: (250) 885-0632
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