Plugin API passes memory ownership

[mixxxbot]

Reported by: bkgood
Date: 2011-07-21T18:16:33Z
Status: Fix Released
Importance: Critical
Launchpad Issue: lp814215
Tags: plugin, soundsource

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The plugin API defines a function which returns a null-terminated array of c-style strings. This memory is allocated (by malloc) in the plugin, and then expected to be freed using free() in the calling code (SoundSourceProxy::something).

This works well where the plugin and mixxx binary are linked to the same C runtime DSO, as is typically the case in Linux, but Windows has more MSVCRT DSOs in the wild than the galaxy has stars (give or take) and different CRT DSOs can use different memory structures in their malloc implementation; this manifests itself in segmentation faults/access violations on plugin usage in Windows. Because we can't guarantee (and shouldn't expect) the two objects to be linked to the same CRT DSO, it's imperative that the unit allocating the memory also be responsible for freeing it; therefore, the plugin API must be modified 
so that this is the case.

See https://code.launchpad.net/~mixxxdevelopers/mixxx/features_m4a_win7/+merge/67111

[mixxxbot]

Commented by: bkgood
Date: 2011-10-09T19:27:46Z

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Changed to crit because if this is encountered segfault does happen. Fixed in lp:~mixxxdevelopers/mixxx/fixes-plugins-mempassing r2847.

[mixxxbot]

Issue closed with status Fix Released.