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POpossible reasons for excessive memory consumption when instantiating a generic list of a managed VisualC++ type vs C# type?
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copied!<p>I've spent the last couple of days attempting to pinpoint the source of a memory leak on a .NET application I'm responsible for maintaining.</p> <p>The application is mostly written in C#, but some parts reference a Visual C++ assembly. The memory leaks seem to center around the parts of the code that interact with the types defined in the Visual C++ assembly.</p> <p>It could very well be that the Visual C++ assembly is using unmanaged resources that are not being disposed properly, but I'm intrigued by the fact that merely initializing a generic list of Visual C++ types increases memory usage (perfmon.exe: Process|Private Bytes) significantly, even if no elements are added to the list.</p> <p>Please see the following sample code:</p> <pre><code>//defined in a referenced Visual CPP assembly public class ref VisualCPPType { private: String ^ a; String ^ b; public: VisualCppType(String ^ a, String ^ b) { this->a = a; this->b = b; } } //defined in the CSharp assembly public class CSharpType { private String a; private String b; public CSharpType(String a, String b) { this.a = a; this.b = b; } } //defined in the CSharp assembly public class ListWrapper { public List<VisualCPPType> _visualCppElementList; public List<CSharpType> _cSharpElementList; public ListWrapper(bool trueToInitVisualCppListOnly_falseToInitCSharpListOnly) { if (trueToInitVisualCppListOnly_falseToInitCSharpListOnly) { //Process|Working Set - Private -> increases by ~5000K //Process|Private Bytes -> increases by ~5000K //.NET CLR Memory|Bytes In All Heaps -> remains constant _visualCppElementList = new List<VisualCPPType>(); } else { //Process|Working Set - Private -> increases by ~750K //Process|Private Bytes -> increases by ~500K //.NET CLR Memory|Bytes In All Heaps -> remains constant _cSharpElementList = new List<CSharpType>(); } } } //defined in the CSharp assembly public class EntryPoint { public static void Main(String[] args) { //a utility class that can be used to obtain the same data displayed by perfmon.exe MemoryMonitor monitor = MemoryMonitor.NewMonitor(); ListWrapper list = new ListWrapper(Boolean.parse(args[0]); monitor.PrintMemoryDiff(); } } </code></pre> <p>As I noted in the comments, the mere act of instantiating a generic list of a Visual C++ element type appears to be a much more expensive operation than instantiating a generic list of a similar C# type.</p> <p>Can someone please explain this behavior? And if it seems like this could be one of the possible causes of the memory leak, offer some hints as to how I could go about fixing it?</p>

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