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Q50519: Loader Uses Return Value from a DLL’s Initialization Routine

Article: Q50519
Product(s): See article
Version(s): 5.10
Operating System(s): OS/2
Keyword(s): ENDUSER | | mspl13_c
Last Modified: 21-MAR-1990

Question:

How is the return value from a DLL's initialization routine used?

Response:

The return value from a DLL's initialization is used by the loader.

Using an initialization routine for your DLL is optional. The
initialization routine can be global or instance. The initialization
routine is called when the DLL is loaded. [This is not necessarily the
same time as when a DLL-exported function is called. For example, if
you load the DLL using DosLoadModule() and DosGetProcAddr(), the
initialization routine is run and the return value is examined at that
time.]

Every time you run a program that uses DLLs, the loader goes through
the import list in the exehdr and attempts to load all the DLLs. As it
tries to load each DLL, it runs its initialization routine (depending
on whether the init routine is instance or global). If the
initialization routine fails (even if the DLL is found) the system may
display a message, or simply terminate at that point.

Initialization routines are mentioned in Ray Duncan's book, "Advanced
OS/2 Programming," in Chapter 19, "Dynamic Link Libraries," Pages
459-469.

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