What would cause Perl to dump core?

Question

What are the most common reasons that I would be getting this error from running a Perl script:

Memory fault(coredump)

I am running two SQL commands beforehand that only store ~1500 rows each with 6 fields. The SQL works fine out of the script, so I don't think I'm getting the error from that. And half of my code runs before it takes a bomb and gives me that error.

So what are the most common reasons for this error and what might my reason be?

EDIT - heres the code that works

my $i;
$i = 0;    
while ($DBS->SQLFetch() == *PLibdata::RET_OK)
    {
        while ($i != $colnamelen)
        {
         if ($i == 1)
         {
          $rowfetch = $DBS->{Row}->GetCharValue($colname[$i]);
          $rowfetch =~ s/(?=..$)/:/;
          printline($rowfetch);
          $i++;  
         }
         if ($i == 2)
         {
          $rowfetch = $DBS->{Row}->GetCharValue($colname[$i]);
          $rowfetch =~ s/(?=..$)/:/;
          printline($rowfetch);
          $i++;  
         }
         if ($i == 10)
         {
          $rowfetch = $DBS->{Row}->GetCharValue("meetdays");
          $rowfetch =~ s/-//gi;
          printline($rowfetch);
          $i++;
         }
         if ($i == 12)
         {
          $rowfetch = $DBS->{Row}->GetCharValue("fullname");
          my ($lname, $fname) = split /,\s*/, $rowfetch;
          $rowfetch = $fname;
          printline($rowfetch);
          $rowfetch = $lname;
          printline($rowfetch);
          $i=$i+2;
         }
         else
         {
          $rowfetch = $DBS->{Row}->GetCharValue($colname[$i]);
          printline($rowfetch);
          $i++;
         }
        }
        $i=0; 
        printf $fh "\n";
    }

Heres the code that doesnt work - All that was done was optimizing the sql fetch command

my $i;
$i = 0;      
while ($DBS->SQLFetch() == *PLibdata::RET_OK)
    {
        while ($i != $colnamelen)
        {
                $rowfetch = $DBS->{Row}->GetCharValue($colname[$i]);
         if ($i == 1)
         {
          $rowfetch =~ s/(?=..$)/:/;
          printline($rowfetch);
          $i++;  
         }
         if ($i == 2)
         {
          $rowfetch =~ s/(?=..$)/:/;
          printline($rowfetch);
          $i++;  
         }
         if ($i == 10)
         {
          $rowfetch =~ s/-//gi;
          printline($rowfetch);
          $i++;
         }
         if ($i == 12)
         {
          my ($lname, $fname) = split /,\s*/, $rowfetch;
          $rowfetch = $fname;
          printline($rowfetch);
          $rowfetch = $lname;
          printline($rowfetch);
          $i=$i+2;
         }
         else
         {
          printline($rowfetch);
          $i++;
         }
        }
        $i=0; 
        printf $fh "\n";
    }

Oh and by the way, there is a functioning SQL statement before this while loop goes into action.. I just didnt want to waste space.

Answer 1

You're tickling a bug in the Perl interpreter or one of its C modules. If your Perl binary doesn't have debugging symbols, compile a version that does and make a core dump. Load the core dump into gdb and do a back trace. Find the bug, see if it's in the latest version, and if it isn't, then submit a patch that fixes it.

Answer 2

I have seen similar events when the DBD driver is compiled against a different version of the shared library than is currently on the system. (Such as would be the case of having MySQL4, and then upgrading to MySQL5 without recompiling the DBD)

Answer 3

Can you reduce the problematic script to something short that shows the same error? Where in the script does it dump core?

My first suspect would be one of the modules you are using has an XS component that isn't playing nicely. Find out where the script blows up, then start investigating the parts around there. Keep cutting out parts until you can come up with the smallest script which reproduces the problem.

Answer 4

Before the code change, you called GetCharValue after checking if $i was as value you wanted. After the change, you call it even if it's not 1,2,10,12. Is it possible that the values for $i other than those 4 is causing the issue?