CODEWITHSUNDEEP
windowswinapifunction-calls
Srikan
Srikan

Reputation: 2241

Stop looking for the entry point at runtime in a DLL

I have an application which runs on windows 2003, window 2008 and windows small business server.

There is a windows call that I make to reboot the system.All the calls mentioned below come from advapi32.dll

InitiateSystemshutdown - This is fine in windows 2003 and windows 2008 but for some reason not working in Windows aurora

InitiateShutdown - since the above call is not working in windows aurora we used this call and minimum supported OS for this call is windows 2008

Now my application fails to run in windows 2003 since the InitiateShutDown is not present in the advapi32.dll on Windows 2003

I get a failed to find procedure entry point for Initiateshutdown in advapi32.dll

I have already put a condition also so that the proper function calls are called with respect to the windows version.

Is there way to stop looking for the entry point in the dll when the application launches.The condition will make sure that the proper function call are called?

OR

I should be asking Microsoft why the old call InitiateSystemshutdown is not working properly ?

Upvotes: 0

Views: 1013

Answers (2)

selbie
selbie

Reputation: 104569

Rather that explicitly calling that function in your code (such that your app will fail to load if the function can't be loaded from the expected DLL), call it implicitly via LoadLibrary and GetProcAddress.

Do a "LoadLibrary" on advapi32.dll. And then call GetProcAddress for "InitiateShutdown". Fail gracefully if the function doesn't exist, otherwise cast it to an appropriate function pointer and invoke it.

typedef DWORD (WINAPI *InitiateSystemShutdownTypeA) (char*, char*, DWORD, DWORD, DWORD);
typedef DWORD (WINAPI *InitiateSystemShutdownTypeW) (wchar_t*, wchar_t*, DWORD, DWORD, DWORD);

InitiateShutdownTypeA func = NULL;
HMODULE hMod = LoadLibrary("advapi32.dll"); 
if (hMod)
    func = (InitiateShutdownTypeA)GetProcAddress("InitiateShutdownW");

if (func)
    func(pwszMachineName, pwszMessage, dwGracePeriod, dwFlags, dwReason);

Upvotes: 1

James Johnston
James Johnston

Reputation: 9492

You have to use GetProcAddress and set your preprocessor variables for the earlier version of Windows. See http://msdn.microsoft.com/en-us/library/aa383745(VS.85).aspx#setting_winver_or__win32_winnt

Basically, you should:

  1. Set WINVER to the earliest version of Windows you must support so you don't accidentally use something newer.

  2. Some API calls and definitions won't work anymore (like InitiateShutdown in your case) in your code, because they aren't included by header files. For these, you must use them dynamically. Typically you use the GetProcAddress API and use a "typedef" to define the function's signature (since it isn't in the header files you're including anymore). An example is here: http://msdn.microsoft.com/en-us/library/ms683212(VS.85).aspx. In your case you would use the InitiateShutdown API instead of the given GetNativeSystemInfo. If the call to GetProcAddress fails then you can assume that the API is not supported on that version of Windows.

Upvotes: 2

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