CommandBarFlyout static initialization creates winrt objects using COM API prohibited during DllMain() #6826
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ghost
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kmahone
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Mar 14, 2022
| // IsCompact and LabelPosition have no effect on an AppBarButton's rendering, when used as a secondary command, they are not present in the list. | ||
| // These two arrays are initialized in the constructor instead of being statically initialized here because that would result in the initialization happening during | ||
| // dllmain and it is not valid to call COM apis at that time. | ||
| winrt::DependencyProperty CommandBarFlyout::s_appBarButtonDependencyProperties[s_commandBarElementDependencyPropertiesCount]{ nullptr, nullptr, nullptr }; |
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I don't love that this is required to initialize the array to nullptrs.
It is not possible to just use "{}", because the default construction of a winrt::Foo object is not null - it creates a new instance of the object. Or at least it does if the winrt type itself has a default constructor. DependencyProperty does not have a constructor, since they are never instantiated directly (instead they are returned by DependencyProperty::Register). So in this case "{}" would be a compiler error.
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/azp run |
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RBrid
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Mar 14, 2022
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This is an issue that was caught by AppVerifier.
When Microsoft.UI.Xaml.dll is loaded, during DllMain is instantiates winrt objects, which is invalid. This is due to a pair of static arrays defined on CommandBarFlyout that were adding in PR #5347.
The fix is to initialize these arrays to nullptr, and populate them on the first creation of a CommandBarFlyout in its ctor.