Unsafe Operations with STL !!!

It is UNSAFE to do any operation on an STL container that will modify its size while holding a reference to one of its exisiting element. What could happen is, when you do an operation, say push_back on a vector, it determines if there is enough space available to add a new element. If there is not sufficient space available, it allocates new space for whole of the data structure and deletes the old buffer. At this point, any reference to one of its elements created prior to push_back would have gotten corrupted.

For example, the following usage of code is dangerous when used within a single scope.

SomeClass &sc = m_Vector.back();
m_Vector.push_back(someotherobject);
.
.
.
sc.SomeMethodCall(); // Code might crash here.

Comments

Extension Methods - A Polished C++ Feature !!!

Extension Method is an excellent feature in C# 3.0. It is a mechanism by which new methods can be exposed from an existing type (interface or class) without directly adding the method to the type. Why do we need extension methods anyway ? Ok, that is the big story of lamba and LINQ. But from a conceptual standpoint, the extension methods establish a mechanism to extend the public interface of a type. The compiler is smart enough to make the method a part of the public interface of the type. Yeah, that is what it does, and the intellisense is very cool in making us believe that. It is cleaner and easier (for the library developers and for us programmers even) to add extra functionality (methods) not provided in the type. That is the intent. And we know that was exercised extravagantly in LINQ. The IEnumerable was extended with a whole lot set of methods to aid the LINQ design. Remember the Where, Select etc methods on IEnumerable. An example code snippet is worth a thousand ...

Implementing COM OutOfProc Servers in C# .NET !!!

Had to implement our COM OOP Server project in .NET, and I found this solution from the internet after a great deal of search, but unfortunately the whole idea was ruled out, and we wrapped it as a .NET assembly. This is worth knowing. Step 1: Implement IClassFactory in a class in .NET. Use the following definition for IClassFactory. namespace COM { static class Guids { public const string IClassFactory = "00000001-0000-0000-C000-000000000046"; public const string IUnknown = "00000000-0000-0000-C000-000000000046"; } /// /// IClassFactory declaration /// [ComImport(), InterfaceType(ComInterfaceType.InterfaceIsIUnknown), Guid(COM.Guids.IClassFactory)] internal interface IClassFactory { [PreserveSig] int CreateInstance(IntPtr pUnkOuter, ref Guid riid, out IntPtr ppvObject); [PreserveSig] int LockServer(bool fLock); } } Step 2: [DllImport("ole32.dll")] private static extern int CoR...

Passing CComPtr By Value !!!

This is about a killer bug identified by our chief software engineer in our software. What was devised for ease of use and write smart code ended up in this killer defect due to improper perception. Ok, let us go! CComPtr is a template class in ATL designed to wrap the discrete functionality of COM object management - AddRef and Release. Technically it is a smart pointer for a COM object. void SomeMethod() { CComPtr siPtr; HRESULT hr = siPtr.CoCreateInstance(CLSID_SomeComponent); siPtr->MethodOne(20, L"Hello"); } Without CComPtr, the code wouldn't be as elegant as above. The code would be spilled with AddRef and Release. Besides, writing code to Release after use under any circumstance is either hard or ugly. CComPtr automatically takes care of releasing in its destructor just like std::auto_ptr . As a C++ programmer, we must be able to appreciate the inevitability of the destructor and its immense use in writing smart code. However there is a difference...

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