Testing Your Cygwin Installation

You can now test your Cygwin installation by compiling a simple DLL with the gcc utility and calling it from a C# .NET program. Here is an example of how to do this.

Create the following C source code file named MyDll.c . This will be compiled with the gcc utility to create a Windows DLL.

 //MyDll.c #include <windows.h> int WINAPI DllMain(    HANDLE hInst,    ULONG reason,    LPVOID lpReserved) {    return 1; }  __declspec(dllexport) char* SomeDllFunction()  {    return "SomeDllFunction called!"; } 

Here is the command line for compiling and generating MyDll.dll . This can be executed at an ordinary Windows command prompt or at the Cygwin Bash Shell prompt.

 gcc -shared MyDll.c -o MyDll.dll -e DllMain@12 

Here is the C# client program that will be used to test MyDll.dll .

 //MyDllClient.cs using System;  using System.Runtime.InteropServices;  class MyDllClient {    //NOTE: MyDll.dll must be in dll search path  [DllImport("MyDll.dll")]   public static extern String SomeDllFunction();  static void Main(string[] args)    {  String str = SomeDllFunction();  Console.WriteLine(          "SomeDllFunction in MyDll.dll returned: " +          str);    } } 

The result of running this C# client program is shown in Figure C-11. If you achieve this result, then you have set up your Cygwin installation properly.

Figure C-11. The result of running the C# client program.

If this simple example worked, you should now install and test the GMP library.