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 the LoadLibrary
is a placeholder for the library-defined function name. The actual name must
be specified at build time. For more information, see the documentation
included with your development tools.
BOOL WINAPI DllEntryPoint(
| HINSTANCE hinstDLL,
||// handle to DLL module
| DWORD fdwReason,
||// reason for calling function
| LPVOID lpvReserved
A handle to the DLL. The value is the base address of the DLL. The HINSTANCE
of a DLL is the same as the HMODULE of the DLL, so hinstDLL
can be used in subsequent calls to the GetModuleFileName
function and other functions that require a module handle.
Specifies a flag indicating why the DLL entry-point function is being called.
This parameter can be one of the following values:
||Indicates that the DLL is attaching to the address space of the current
process as a result of the process starting up or as a result of a call to LoadLibrary. DLLs can use this opportunity to initialize any instance data or to use the TlsAlloc function to allocate a thread local storage (TLS) index.
||During initial process startup or after a call to LoadLibrary, the operating system scans the list of loaded DLLs for the process. For each
DLL that has not already been called with the DLL_PROCESS_ATTACH value, the
system calls the DLL's entry-point function. This call is made in the context of
the thread that caused the process address space to change, such as the primary
thread of the process or the thread that called LoadLibrary.
||Indicates that the current process is creating a new thread. When this occurs,
the system calls the entry-point function of all DLLs currently attached to
the process. The call is made in the context of the new thread. DLLs can use this
opportunity to initialize a TLS slot for the thread. A thread calling the DLL
entry-point function with the DLL_PROCESS_ATTACH value does not call the DLL
entry-point function with the DLL_THREAD_ATTACH value.
||Note that a DLL's entry-point function is called with this value only by
threads created after the DLL is attached to the process. When a DLL is attached by LoadLibrary, existing threads do not call the entry-point function of the newly loaded
||Indicates that a thread is exiting cleanly. If the DLL has stored a pointer to
allocated memory in a TLS slot, it uses this opportunity to free the memory.
The operating system calls the entry-point function of all currently loaded DLLs
with this value. The call is made in the context of the exiting thread. There
are cases in which the entry-point function is called for a terminating thread
even if the DLL never attached to the thread for example, the entry-point function was never called with the
DLL_THREAD_ATTACH value in the context of the thread in either of these two situations:
- The thread was the initial thread in the process, so the system called the
entry-point function with the DLL_PROCESS_ATTACH value.
- The thread was already running when a call to the LoadLibrary function was made, so the system never called the entry-point function for
||Indicates that the DLL is detaching from the address space of the calling
process as a result of either a clean process exit or of a call to FreeLibrary. The DLL can use this opportunity to call the TlsFree function to free any TLS indices allocated by using TlsAlloc and to free any thread local data. When a DLL detaches from a process as a
result of process termination or as a result of a call to FreeLibrary, the operating system does not call the DLL's entry-point function with the
DLL_THREAD_DETACH value for the individual threads of the process. The DLL is
only given DLL_PROCESS_DETACH notification. DLLs can take this opportunity to
clean up all resources for all threads attached and known to the DLL.
Specifies further aspects of DLL initialization and cleanup.
is DLL_PROCESS_ATTACH, lpvReserved
is NULL for dynamic loads and non-NULL for static loads.
is DLL_PROCESS_DETACH, lpvReserved
is NULL if DllEntryPoint
has been called by using FreeLibrary
and non-NULL if DllEntryPoint
has been called during process termination.
When the system calls the DllEntryPoint
function with the DLL_PROCESS_ATTACH value, the function returns TRUE if it
succeeds or FALSE if initialization fails. If the return value is FALSE when DllEntryPoint
is called because the process uses the LoadLibrary
returns NULL. If the return value is FALSE when DllEntryPoint
is called during process initialization, the process terminates with an
error. To get extended error information, call GetLastError
When the system calls the DllEntryPoint
function with any value other than DLL_PROCESS_ATTACH, the return value is
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