Re: [GM-core] Fwd: Magick++ Bug Report

[Bob F. <bfr...@si...>]

On Tue, 17 Feb 2015, Hyrum Wright wrote:

> See below for a bug in ImageMagick that Dirk thinks may also be in GraphicsMagick.

Thanks for the heads-up.  If the locking was not actually working, 
then one would think that a problem with locking would have been 
reported during the 16+ years this code has been in use.  Indeed, I do 
not recall any bug reports regarding locking issues in Magick++.

Have the object lifetime/scoping rules/behavior changed in more modern 
C++?

Bob

> 
> ---------- Forwarded message ----------
> From: Dirk Lemstra <di...@le...>
> Date: Tue, Feb 17, 2015 at 6:28 PM
> Subject: Re: Magick++ Bug Report
> To: Hyrum Wright <hw...@go...>
> 
> 
> Hyrum,
> 
> You might also want to contact the maintainer of GraphicsMagick. Their code has the same issue.
> 
> Dirk
> 
> On 18-02-2015 00:07, Lexie Parsimoniae wrote:
>
>       From: Hyrum Wright <hw...@go...>
>       Reply-To: Hyrum Wright <hw...@go...>
>       X-Mailer: PHP/5.3.3
>       Origin: 72.14.228.1
>
>       On the 6.9.0 branch, Magick++/lib/Blob.cpp and Magick++/lib/Image.cpp don't do proper locking. 
>       Specifically, the line of the form:
>
>         Lock(&_imgRef->_mutexLock);
>
>       or
>
>         Lock(&_blobRef->_mutexLock);
>
>       are wrong.  These lines look like they are attempting to use RAII to ensure the mutex is unlocked when the
>       relevant functions return, but instead these lines create a *temporary* unnamed lock that is immediately
>       released.  The proper fix looks something like:
>
>         Lock lock(&_imgRef->_mutexLock);
>
>       I count 6 instances of this bug in Blob.cpp and 8 in Image.cpp.  These were found using the
>       misc-unused-raii check from clang-tidy.
>
>       It doesn't look like this problem exists on trunk, since the locking has been moved to BlobRef.cpp and
>       ImageRef.cpp and made manual.
>
>       -Hyrum
> 
> 
> 
>

-- 
Bob Friesenhahn
bfr...@si..., http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/