fix(client_openxr): 🐛 Fix crash caused by undefined behavior #2391
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The-personified-devil
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This PR attempts to fix a crash reported when enabling face tracking on the Quest Pro.
This PR fixes undefined behavior using a specific solution. Before we were calling
System<props>::out()which returns aMaybeUninit, and immediately callassume_uninit(). Doing so only the correspondingBaseOutStructurefields are initialized, that istyandnext. The other fields are filled with random values. Beside this, callingassume_uninit()after attempting to get the properties withget_system_propertiesis not enough. The OpenXR spec doesn't say to return an error if thenextpointer is populated with an unknown structure. So after theget_system_propertiescall, theSystem<props>struct might still contain random values. Because of this we should ditch theout()method and manually initialize the structure. The upstreamopenxrscrate suffers from the same bug, but only concerning the hand tracking extension. That instance of the bug hasn't surfaced yet.