Hi All,

In the latest CVS I can get the backend to terminate quite
easily with a divide by 0.

postgres=> select 1/0;
pqReadData() -- backend closed the channel unexpectedly.
        This probably means the backend terminated abnormally before or while 
processing the request.
We have lost the connection to the backend, so further processing is impossible. 
 Terminating.
[postgres@sparclinux pgsql]$ 

A bt on the core shows:-

Program received signal SIGILL, Illegal instruction.
0xe0155718 in .div ()
(gdb) bt 
#0  0xe0155718 in .div ()
#1  0xc6bcc in int4div (arg1=1, arg2=0) at int.c:523

I don't know if this is recently introduced behaviour or if
it's platform dependant. I can't recall trying this before
so maybe it's always happened on S/Linux.

My immediate thought is to include a check for divide by 0
in the intXXdiv() functions and do something like an elog(WARN,...)

Firstly, what do other people get on their platform?

Keith.


Mon, 22 Jun 1998 20:40:15 +0100 (BST)
Keith Parks <emkxp01@mtcc.demon.co.uk>
Divide by zero error on SPARC/Linux.
> 
> Hi All,
> 
> In the latest CVS I can get the backend to terminate quite
> easily with a divide by 0.
> 
> postgres=> select 1/0;
> pqReadData() -- backend closed the channel unexpectedly.
>         This probably means the backend terminated abnormally before or while 
> processing the request.
> We have lost the connection to the backend, so further processing is impossible. 
>  Terminating.
> [postgres@sparclinux pgsql]$ 
> 
> A bt on the core shows:-
> 
> I don't know if this is recently introduced behaviour or if
> it's platform dependant. I can't recall trying this before
> so maybe it's always happened on S/Linux.
> 
> My immediate thought is to include a check for divide by 0
> in the intXXdiv() functions and do something like an elog(WARN,...)
> 
> Firstly, what do other people get on their platform?

I get:

ttest=> select 1/0;
ERROR:  floating point exception! The last floating point operation
either exceeded legal ranges or was a divide by zero

so it looks like the signal.  Check these lines:

#$ gid FloatExceptionHandler
backend/postmaster/postmaster.c:1247:   pqsignal(SIGFPE, FloatExceptionHandler);
backend/tcop/postgres.c:772: FloatExceptionHandler(SIGNAL_ARGS)
include/tcop/tcopprot.h:37: extern void FloatExceptionHandler(SIGNAL_ARGS);


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Mon, 22 Jun 1998 17:07:47 -0400 (EDT)
Bruce Momjian <maillist@candle.pha.pa.us>
Re: [HACKERS] Divide by zero error on SPARC/Linux.