Re: [Openexr-devel] Memory leaks in 2.01

[Richard Addison-Wood]

Indeed, under Linux there would be issues that are dependent on how the plug-in is compiled and linked.  (Others could speak to issues related to other operating systems.) For instance, if a plug-in does link against OpenEXR statically but does not do anything about limiting where it finds global symbols (like not using -Wl,-Bsymbolic or other related options) then the plug-in can end up binding to OpenEXR symbols from elsewhere in the process. With namespaces, at least we have a mechanism to make sure that those additional copies of those symbols are related to a compatible implementation.  But it does mean that there can be additional unrelated code piggy-backing on static data that might otherwise be controlled by initialization and clean-up that expects only one call each. If we were to add clean-up, we would need to have a corresponding count of the number explicit requests to initialize. On 11/07/13 10:04, Peter Hillman wrote: It should work most of the time. I was more concerned about edge cases causing unpredictable crashes depending on link flags, dlopen flags and the like, and the implications of introducing the change so that some versions of OpenEXR uninitialize and others do not. On 07/11/13 09:48, Christopher Horvath wrote: If both plugins are statically linked, they'll each have their own copy of any global variables, with their own addresses. Does that fix this, in any way? On Wed, Nov 6, 2013 at 12:44 PM, Peter Hillman <pet...@wetafx.co.nz> wrote: Would this still be safe if one or both plugins were statically linked against OpenEXR? On 07/11/13 09:41, Halfdan Ingvarsson wrote: The call to uninitialize would be done inside of OpenEXR, and not by any calling plugin. Therefore would only be called once IlmImf.so unloads, which would only happen when all users are done with it. Basically, this function should both be internal to OpenEXR and OpenEXR alone should be responsible. This also alleviates a potential race-condition with using a local static Mutex in staticInitialize -- which, prior to C++11 is not guaranteed to be thread-safe -- since DSO load sequences are guaranteed to be single-threaded (although another fix is to move the Mutex to file scope). Hope this clears it up.  - ½ On 13-11-06 03:25 PM, Peter Hillman wrote: Calling Uninitialize automatically seems dangerous. What happens if a package loads two plugins, both of which are dependent on OpenEXR? If only one is unloaded, there's a danger it would unitialize the attributes for the other, causing a segfault when it tries to parse a header. Alternatively, if both are unloaded, the second might try to free memory already freed by the first. It seems safer only to call this function manually, and only in a build intended for leak analysis, since the memory returned is insignificant. _______________________________________________ Openexr-devel mailing list Openexr-devel@nongnu.org https://lists.nongnu.org/mailman/listinfo/openexr-devel -- I think this situation absolutely requires that a really futile and stupid gesture be done on somebody's part. And we're just the guys to do it.

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