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Diagnosing Memory Leaks in Managed Windows Store Apps

There is so much material on the web (and even on this blog) about memory leak diagnostics in managed code, and a considerable number of tools that make diagnostics increasingly easier. Modern memory profilers can open application dumps, attach to live processes, display live memory graphs, compare snapshots, identify problematic retention patterns, and so much more. Unfortunately, these tools presently don’t work with Windows Store apps. Moreover, the UI model of Windows Store apps poses a significant...

Under the Covers of WinRT Using C++

The WinRT type system relies strongly on WinRT components, which are COM objects implementing a specific set of interfaces and adhering to a certain ABI (Application Binary Interface). We will examine here this ABI and how C++ compiler extensions help reference that ABI without exposing the nitty-gritty details of dealing with COM interfaces and COM activation. A WinRT component implements the IInspectable interface , which derives from IUnknown (however, WinRT components do not have dual interfaces...

Detecting the STA Thread from GetToSTA

When a thread makes a method call through an appropriately marshaled COM proxy that points to a thread in a different STA (Single-Threaded Apartment) , ole32.dll kicks in and implements the minute details of marshaling input parameters across the required boundary, waiting for the call to return, and unmarshaling the return value and output parameters. In a debugger, a thread making a COM call to another STA will have a native call stack similar to the following: 0:002> kb ChildEBP RetAddr ...

STA Objects and the Finalizer Thread: Tale of a Deadlock

Here’s a non-trivial deadlock that manifests from using a non-pumping wait API and a finalizer. It is another example of why finalizers are a dangerous cleanup mechanism and why you should avoid them at all costs. Let’s say that you have an STA COM object called NativeComObject that your managed application is using, and you wrap the COM object with a class called FinalizableResource . This latter class has a finalizer that cleans up resources associated with the COM object by calling a cleanup method...