Perl Packager - Free to wrong pool error

[google]

perl -v
This is perl, v5.8.8 built for MSWin32-x86-multi-thread
....

== Begin of test.pl ==
use strict;
use warnings;

my $pid;

LaunchHostname();

print "waiting for child $pid to complete...\n";
my $waitstat = waitpid($pid,0);
print "waitpid returned $waitstat\n";
exit;

sub LaunchHostname {
$pid = fork ();
if (!defined($pid)) {
die "Failed to fork: $!\n";
}
elsif ($pid == 0) {
# This is the child
exec('hostname.exe'); # LINE 22
die "exec failed\n";
}
return;
}
== END of test.pl ==

perl test.pl

waiting for child -3592 to complete...
fileserver123
waitpid returned -3592

pp -o test.exe test.pl

test.exe

waiting for child -1600 to complete...
fileserver123
Free to wrong pool fac720 not 8367c0 at script/test.pl line 22.

When I execute test.exe, the above error message is accompanied by a
pop up indicating "test.exe has encountered a problem and needs to
close. We are sorry for the inconvenience."

When I do all the above on a system with perl v5.10.0 installed, I do
not get the "Free to wrong pool" message but get a pop up that says:
'The instruction at "0x2800cd70" referenced memory at "0x00000028".
The memory could not be "read"'.

Any ideas why I get these errors?

 

[sln]

perl -v

This is perl, v5.8.8 built for MSWin32-x86-multi-thread
...
[snip]
Free to wrong pool fac720 not 8367c0 at script/test.pl line 22.

When I execute test.exe, the above error message is accompanied by a
pop up indicating "test.exe has encountered a problem and needs to
close. We are sorry for the inconvenience."

When I do all the above on a system with perl v5.10.0 installed, I do
not get the "Free to wrong pool" message but get a pop up that says:
'The instruction at "0x2800cd70" referenced memory at "0x00000028".
The memory could not be "read"'.

Any ideas why I get these errors?

I got that message when I tried out of range unicode chars in regular expression tests.
But the windows MB says Perl encounterred an error and needs to close.
I press OK and the command prompt returns.
I do the very same command line again and get a different address, same result though.

Looks like its not nice to exec a program from Perl that will crash.

-sln

 

[google]

Quoth (e-mail address removed):







Since you're on Win32, is there a good reason for using fork/exec rather
than system(1, ...) or Win32:rocess? fork on Win32 is a rather
complicated emulation, and fork+exec ends up being a convoluted way of
calling spawnvp(3). Since the whole fork API is only present on Win32
for compatibility with Unix scripts, it's better to use the native
method.

I was unaware that system() could be made to run asynchroneously.
Thank you for the excellent suggestion, but I don't think it will work
for my situation.

With the fork/exec, I am starting a GUI application and then
manipulating it in my perl code using Win32::GuiTest. This GUI
application MUST be run from a specified directory, so in my actual
perl program, I do a chdir() to that directory in the child process
before the child calls exec() make the child perl process become the
application. I don't think there is any way to do that using system
(1,...).

It is interesting to note that no errors occur when the perl program
is run directly. The errors occur only when I run the executable I've
created using pp. This makes me suspect that the problem may be
related to something in PAR:acker.

I was able to work around the problem (in an non-portable way) by
using Win32:rocess::Create() instead of fork/exec. Fortunately for
me, Win32:rocess::Create() takes the working directory as in input
argument.

 

[A. Sinan Unur]

(e-mail address removed) wrote in (e-mail address removed):

With the fork/exec, I am starting a GUI application and then
manipulating it in my perl code using Win32::GuiTest.
....

I was able to work around the problem (in an non-portable way) by
using Win32:rocess::Create() instead of fork/exec.

I do not think portability to any other system than Win32 should be a
concern in this case.

Sinan
--
A. Sinan Unur <[email protected]>
(remove .invalid and reverse each component for email address)

comp.lang.perl.misc guidelines on the WWW:
http://www.rehabitation.com/clpmisc/

 

[sln]

Quoth (e-mail address removed):

Well, the obvious way would be

use Cwd qw/cwd/;

my $oldcwd = cwd or die "can't find cwd: $!";
chdir "c:/wherever" or die "can't chdir to 'c:/wherever': $!";
system 1, "command";
chdir $oldcwd or die "can't chdir to '$oldcwd': $!";

This of course assumes that you can determine your current directory and
chdir back into it, so if Win32 supports fchdir(2) something like

opendir my $OLDCWD, "." or die "can't opendir '.': $!";
chdir "c:/wherever" or die "...";
system 1, "command";
chdir $OLDCWD;

might be safer (substitute File::Spec->curdir if you like). You can
check if you have fchdir(2) with

perl -V:d_fchdir

or

use Config;

if ($Config{d_fchdir} eq "define") {
...
}


Yes, me too. I have had numerous problems with pp on Win32 in the past;
the peculiarities of perl and of Win32's dll model combine to mean PAR
has to do some very strange things to get the program to work.
Apparently they don't always work successfully.


Yes, whatever you do it will end up calling CreateProcess(2) eventually,
so you might as well call it directly.

Ben

Which variable is '2'?

BOOL CreateProcess(
LPCTSTR lpApplicationName,
LPTSTR lpCommandLine,
LPSECURITY_ATTRIBUTES lpProcessAttributes,
LPSECURITY_ATTRIBUTES lpThreadAttributes,
BOOL bInheritHandles,
DWORD dwCreationFlags,
LPVOID lpEnvironment,
LPCTSTR lpCurrentDirectory,
LPSTARTUPINFO lpStartupInfo,
LPPROCESS_INFORMATION lpProcessInformation
);

-sln

 

[Tim McDaniel]

....

I was unaware that system() could be made to run asynchroneously.

I'd never heard of it either. I Googled and found
<http://www.mail-archive.com/[email protected]/msg35810.html>
explaining things.

It's not documented in "perlfunc system" but in "man perlport". The
text (the trailing "(Win32)" apparently means "this paragraph applies
to Windows 32-bit"):

As an optimization, may not call the command shell specified in
$ENV{PERL5SHELL}. "system(1, @args)" spawns an external process
and immediately returns its process designator, without waiting
for it to terminate. Return value may be used subsequently in
"wait" or "waitpid". Failure to spawn() a subprocess is indicated
by setting $? to "255 << 8". $? is set in a way compatible with
Unix (i.e. the exitstatus of the subprocess is obtained by "$? >>
8", as described in the documentation). (Win32)

The Jan Dubois, in that note above, also wrote "

One thing that may not be obvious from the documentation is that
Perl keeps track of the process ids returned by system(1, ...), and
the call will fail once you have created more than 63 processes.

Check here for a "workaround" to make sure you at least reclaim
handles of processes no longer running:

http://aspn.activestate.com/ASPN/Mail/Message/pdk/3122771

You will still be limited to about 63 concurrent processes.

I haven't looked further for a few minutes, but I found no other
gotchas.