Craig Berry wrote:
On Monday, January 23, 2006, at 09:18AM, John E. Malmberg <[EMAIL PROTECTED]> wrote:
The puzzling thing is that the statement "-e $Null" will only cause an
access violation for $Null = '_NLA0:'. Replacing it with "-e '_NLA0:'
eliminates the access violation.
Now the one place where that code should be taking a different path
under those two conditions that I can find is in doio.c.
Remember Perl is a dynamic language. If $Null is never assigned to,
the Perl compiler may optimize it away. A very slightly different memory
allocation signature could make a difference in whether we trigger the
bug. You can watch memory allocation and deallocation happen by running
with -"Dm" :
$ perl -"Dm" [.op]stat.t
$Null is definitely assigned to, I have a debugging statement that
prints out it's value.
I can add statements for "-e '_NLA0:' to the test script before the
access violation occurs and they execute with out affecting the access
violation for "-e $Null".
It is curious, as for a reproducer, I ended up with code that
opens/create the temporary file, and then closes it.
Then it opens it and leaves it open.
1 while unlink $tmpfile;
open(FOO, ">$tmpfile") || DIE("Can't open temp test file: $!");
close FOO;
open(FOO, ">$tmpfile") || DIE("Can't open temp test file: $!");
It does not seem to make a difference if $Null is set from the
File::Spec->devnull; or from $Null = '_NLA0:'.
$Null = '/dev/null' does not cause an access violation either.
After that the "-e $Null" statement causes a access violation.
In the test file, if I close that temporary file, no access violation,
but in the real stat.t the temporary file should be closed at this
point, and I do not see a way around it in the Perl script, so I do not
know why that makes a difference.
If I do not open and close the file once before opening it and leaving
it open, I do not get the access violation.
If I extract what is left of uncommented of the script out into a new
script, I do not get the access violation.
I think this one is going to be a bit painful to find as it does not
show up in the VMS debugger.
Some of the other -"D" flags may help isolate what routines that Perl
was in just before the access violation as a first pass in zeroing in on it.
-John
[EMAIL PROTECTED]
Personal Opinion Only
