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Bug #46024 stream_select() doesn't return the correct number
Submitted: 2008-09-08 14:33 UTC Modified: 2008-11-04 00:43 UTC
From: mike at silverorange dot com Assigned:
Status: Closed Package: Streams related
PHP Version: 5.2CVS-2008-09-09 (snap) OS: linux
Private report: No CVE-ID: None
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 [2008-09-08 14:33 UTC] mike at silverorange dot com 
Description:
------------
The stream_select function should return the number of streams ready in the read and write arrays. Sometimes it does and sometimes it doesn't.

Reproduce code:
---------------
http://labs.silverorange.com/files/stream-select-bug/

Expected result:
----------------
selecting ... got 2
Array (     [0] => Resource id #5 ) 
Array (     [0] => Resource id #6 ) 
selecting ... got 2
Array (     [0] => Resource id #5 ) 
Array (     [0] => Resource id #6 )

Actual result:
--------------
selecting ... got 2
Array (     [0] => Resource id #5 ) 
Array (     [0] => Resource id #6 ) 
selecting ... got 1
Array (     [0] => Resource id #5 ) 
Array (     [0] => Resource id #6 )

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 [2008-09-09 03:30 UTC] mike at silverorange dot com 
The test also fails on the provided snapshot.
 [2008-09-15 02:58 UTC] mike at silverorange dot com 
If I use 8192 as the number of bytes for fread(), the correct value is returned. Examining the program with strace() reveals:

 - PHP always reads 8192 bytes from fread
 - the requested bytes are returned and the remaining bytes are buffered
 - stream_select() only invokes a system select() call if the internal buffer is empty
 - stream_select() returns the wrong value if no actual system select() call is performed.

See additional test cases at the above link.
 [2008-11-04 00:43 UTC] lbarnaud@php.net 
This bug has been fixed in CVS.

Snapshots of the sources are packaged every three hours; this change
will be in the next snapshot. You can grab the snapshot at
http://snaps.php.net/.
 
Thank you for the report, and for helping us make PHP better.
 
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