[imp] IMP5 hangs opening messages with multiple pdf attachments

[Peter Woit]

On 03/21/2012 07:09 PM, Peter Woit wrote:
> We've been using Horde/Imp for years, recently installed Horde4/Imp5.
> Everything seems to work fine (traditional, not dynamic interface),
> except for one major problem: when a user tries to open certain e-mail
> messages their session hangs, and they have to restart their browser.
>
> This is completely reproducible, the messages that cause the problem
> seem to be ones with multiple pdf attachments.
>
> The problem leads to a lot of hung-up httpd processes, which when killed
> give an error message to the log of
>
> zend_mm_heap corrupted
>
> Running apache with USE_ZEND_ALLOC=0 doesn't fix the problem, but just
> causes that error message to not be there when the httpd is killed.
>
> Nothing unusual shows up in horde or apache logs.
>
> Perhaps the problem has to do with how IMP is handling pdf attachments,
> but I don't see any way to change its behavior to test this.
>
> Any advice about what to try, or how to generate enough debugging info
> for a useful bug report, would be appreciated.
>
> Peter Woit

To follow up, in case anyone else is having this problem, I've found 
that a work-around is to turn off image manipulation capabilities, i.e.

$conf['image']['driver'] = false

I'm guessing the problem is with pdf thumbnail creation on our system. 
The same problem could be generated by changing from the image driver 
from the PECL imagick one to our Imagemagick installation on the server 
(which seems otherwise fine). When this is done, the problem again 
appears when opening an e-mail with multiple image attachments.