#38273 [Opn]: Incorrect return address after the execution of a signal handler?

[axelluttgens at swing dot be]

 ID:               38273
 User updated by:  axelluttgens at swing dot be
 Reported By:      axelluttgens at swing dot be
 Status:           Open
 Bug Type:         PCNTL related
 Operating System: Mac OS 10.4.7
 PHP Version:      4.4.2
 New Comment:

As a follow-up: a "switch" statement, instead of reproduce code's "if"
statement, does not seem to be affected by the problem.

So, replacing the while loop in reproduce code with this one:

while (!socket_select($r = array($endpoint), $w = NULL, $e = NULL,
NULL))
        switch ($err = socket_last_error())
        {
                case SOCKET_EINTR:
                        socket_clear_error();
                        PollSigs();
                        break;
                default:
                        echo "socket_select() failed with $err\n";
                        break 2;
        }


I get the expected behavior back (without having to resort to the
"dummy statement" kludge):

$ /Volumes/Data/Sources/sigtest.php 

^C
Warning: socket_select() unable to select [4]: Interrupted system call
in /Volumes/Data/Sources/sigtest.php on line 32
Received SIGINT
Handling SIGINT
^C
Warning: socket_select() unable to select [4]: Interrupted system call
in /Volumes/Data/Sources/sigtest.php on line 32
Received SIGINT
Handling SIGINT

Could this be of some help for narrowing the cause?


Previous Comments:
------------------------------------------------------------------------

[2006-08-01 11:59:14] axelluttgens at swing dot be

Hello Tony, thanks again for your follow up!

For various reasons, I am currently really stuck with PHP 4 here. In
that sense, PHP 5 isn't an alternative for me yet.

But perhaps were you considering a very precise point?
Do you want me to try something else?

TIA,
Axel

------------------------------------------------------------------------

[2006-07-31 20:13:53] [EMAIL PROTECTED]

Please try using this CVS snapshot:

  http://snaps.php.net/php5.2-latest.tar.gz
 
For Windows:
 
  http://snaps.php.net/win32/php5.2-win32-latest.zip



------------------------------------------------------------------------

[2006-07-31 19:40:17] axelluttgens at swing dot be

Description:
------------
It seems there is a problem with the construction of the return address
to be used after an interrupt handler.

Now, I'm not sure whether the problem is a general one, or more
precisely located in the socket_xxx() family of functions.
I used the socket_select() function for building the example, as I
needed a function whose execution is liable to be suspended until the
occurence of an interrupt.

But the "workaround" described hereafter anyway seems to reveal some
misbehavior.

Reproduce code:
---------------
Create an executable file, say "sigtest.php", with following contents:

#!/usr/local/bin/php

<?php

declare(ticks = 1);

$gotINT = FALSE;

function SaveINT()
{
        $GLOBALS['gotINT'] = TRUE;
        echo "Received SIGINT\n";
}

function HandleINT()
{
        echo "Handling SIGINT\n";
}

function PollSigs()
{
        if ($GLOBALS['gotINT'])
                HandleINT();
}

pcntl_signal(SIGINT, 'SaveINT');

$endpoint = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
socket_bind($endpoint, '127.0.0.1', 12345);
socket_listen($endpoint, 10);
while (!socket_select($r = array($endpoint), $w = NULL, $e = NULL,
NULL))
        if (($err = socket_last_error()) === SOCKET_EINTR)
        {
                # $err = $err;
                PollSigs();
        }
        else
        {
                echo "socket_select() failed with $err\n";
                exit(1);
        }

?>

Expected result:
----------------
During execution of above file on the terminal, a break (^C) should
result in:

1. the capture of SIGINT, and thus the execution of SaveINT(),
2. the continuation of execution after socket_select(), and thus the
execution of HandleINT() consecutively to the call of PollSigs(). 

Actual result:
--------------
[1] With above code, launching the executable yields:

$ /Volumes/Data/Sources/sigtest.php 

^C
Warning: socket_select() unable to select [4]: Interrupted system call
in /Volumes/Data/Sources/sigtest.php on line 31
Received SIGINT
^C
Warning: socket_select() unable to select [4]: Interrupted system call
in /Volumes/Data/Sources/sigtest.php on line 31
Handling SIGINT
Received SIGINT

[2] Now, uncomment the
   # $err = $err;
line in the source and launch the executable again:

$ /Volumes/Data/Sources/sigtest.php 

^C
Warning: socket_select() unable to select [4]: Interrupted system call
in /Volumes/Data/Sources/sigtest.php on line 31
Received SIGINT
Handling SIGINT
^C
Warning: socket_select() unable to select [4]: Interrupted system call
in /Volumes/Data/Sources/sigtest.php on line 31
Received SIGINT
Handling SIGINT

The dummy instruction (ie, $err = $err;) thus allows to restore
exepected behavior.


------------------------------------------------------------------------


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Edit this bug report at http://bugs.php.net/?id=38273&edit=1