Re: How can LoadLibrary fail?

From:

"Ben Voigt [C++ MVP]" <rbv@nospam.nospam>

Newsgroups:

microsoft.public.vc.language

Date:

Thu, 25 Oct 2007 09:51:26 -0500

Message-ID:

<epO$AaxFIHA.3548@TK2MSFTNGP06.phx.gbl>

"David Webber" <dave@musical-dot-demon-dot-co.uk> wrote in message
news:u86XnYvFIHA.1188@TK2MSFTNGP04.phx.gbl...

I have a project which attempts to load a DLL with

HINSTANCE hInstance = LoadLibrary( pszPath );

where pszPath is the full path name of the DLL.

Just occasionally it fails and returns NULL. It has done it for others,
but just this week it happened to me for the first time, and so i was able
to check one or two things.

The path is correct and the DLL is there.
The path name is not longer than _MAX_PATH characters.

The library in question is a resource-only DLL which has one C++ function
in a .cpp file which reads in its entirety:

You may want to use LoadLibraryEx with the LOAD_LIBRARY_AS_IMAGE_RESOURCE
flag, to avoid worrying about dependencies, platform match, etc.

#include "stdafx.h"

BOOL APIENTRY DllMain( HANDLE hModule,
                      DWORD ul_reason_for_call,
                      LPVOID lpReserved
     )
{
   return TRUE;
}

How can it fail?

[In my case rebuilding the resource-only DLL made it work again, but this
does not necessarily work for others with the problem, and so I need to
understand what can go wrong!]

A bit more detail:

Immediately prior to attempting to load the DLL I do a loop using
FindFirstFile() FindNextFile() [and I don't forget FileClose()] to store
a collection of names of resource DLLs which are present (all of the
above content), and have names of a certain form. Then I try to open each
one of them, and extract a string from it with a given ID, which tells me
more about it. But sometimes, just occasionally, one or more fails to
open.

[The calling DLL is linked dynamically with MFC and using AfxLoadLibrary()
makes absolutely no difference.]

Any ideas?

Dave
--
David Webber
Author of 'Mozart the Music Processor'
http://www.mozart.co.uk
For discussion/support see
http://www.mozart.co.uk/mozartists/mailinglist.htm