DllMain

The DllMain function is an optional method of entry into a dynamic-link library (DLL). If the function is used, it is called by the system when processes and threads are initialized and terminated, or upon calls to LoadLibrary and FreeLibrary.

Syntax

BOOL DllMain(
    HINSTANCE hinstDLL,
    DWORD fdwReason,
    LPVOID lpvReserved
);

Parameters

HinstDLL

A handle to the RTDLL. HINSTANCE of a RTDLL is the same as the HMODULE of the RTDLL, so hinstDLL can be used in subsequent calls to functions that require a module handle.

fdwReason

Specifies a flag indicating why the RTDLL entry-point function is being called. This parameter can be one of the following values:

Value	Definition
DLL_PROCESS_ATTACH	Indicates that the RTDLL is being loaded into the virtual address space of the current process as a result of a call to LoadLibrary. DLL_PROCESS_ATTACH is only called for the first process that attaches to it.
DLL_THREAD_ATTACH	This value is not used in the RTSS Environment.
DLL_THREAD_DETACH	This value is not used in the RTSS Environment
DLL_PROCESS_DETACH	Indicates that the RTDLL is being unloaded from the virtual address space of the calling process as a result of either a process exit or a call to FreeLibrary.

lpvReserved

lpvReserved is NULL.

Return Value

When the system calls DllMain with the DLL_PROCESS_ATTACH value, the function returns:

TRUE if initialization succeeds, FALSE if initialization fails

NOTE: When the system calls DllMain with any value other than DLL_PROCESS_ATTACH, the return value is ignored.

If the return value is FALSE, LoadLibrary returns NULL.

To get extended error information, call GetLastError.

Remarks

On attach, the body of the RTDLL entry-point function should perform only simple initialization tasks such as creating synchronization objects, and opening files. Do not call LoadLibrary in the entry-point function, because this may create dependency loops in the RTDLL load order. This can result in an RTDLL being used before the system has executed its initialization code. Similarly, do not call FreeLibrary in the entry-point function on detach because this can result in an RTDLL being used after the system has executed its termination code.

Calling other functions other than synchronization, and file functions may result in problems that are difficult to diagnose. To provide more complex initialization, create an initialization routine for the RTDLL and require applications to call the initialization routine before calling any other routines in the RTDLL. Otherwise, have the initialization routine create a named mutex, and have each routine in the RTDLL call the initialization routine if the mutex does not exist.

Requirements

Minimum Supported Version	RTX64 2013
Header	windows.h
Library	Rtx_Rtss.lib