AddDllDirectory

AddDllDirectory is a function in the Windows API that modifies the DLL search order for the current process. When an application attempts to load a dynamic-link library (DLL), the operating system searches for the DLL in a predefined set of locations. By calling AddDllDirectory, an application can add a specific directory to this search path. This is particularly useful for applications that use custom DLLs located in non-standard directories, preventing the need to place these DLLs in the application's executable directory or the system directories.

When AddDllDirectory is called with a valid directory path, that path is prepended to the DLL search order for the current process. Subsequent DLL loads will check the newly added directory before the standard locations. This function is designed to be more secure than older methods like SetDllDirectory, as it does not interfere with the global DLL search path. It also allows for more granular control over where DLLs are loaded from.

It is important to note that directories added using AddDllDirectory are only effective for the process that calls the function. They do not affect other processes or the system-wide DLL search path. When the process terminates, these added directories are removed from the DLL search order. To remove a directory added by AddDllDirectory before the process terminates, the RemoveDllDirectory function should be used, passing the handle returned by AddDllDirectory.