Linker Support for Delay-Loaded DLLs

The Visual C++ linker now supports the delayed loading of DLLs. This relieves you of the need to use the Windows SDK functions LoadLibrary and GetProcAddress to implement DLL delayed loading.

Before Visual C++ 6.0, the only way to load a DLL at run time was by using LoadLibrary and GetProcAddress; the operating system would load the DLL when the executable or DLL using it was loaded.

Beginning with Visual C++ 6.0, when statically linking with a DLL, the linker provides options to delay load the DLL until the program calls a function in that DLL.

An application can delay load a DLL using the /DELAYLOAD (Delay Load Import) linker option with a helper function (default implementation provided by Visual C++). The helper function will load the DLL at run time by calling LoadLibrary and GetProcAddress for you.

You should consider delay loading a DLL if:

• Your program may not call a function in the DLL.

• A function in the DLL may not get called until late in your program's execution.

The delayed loading of a DLL can be specified during the build of either a .EXE or .DLL project. A .DLL project that delays the loading of one or more DLLs should not itself call a delay-loaded entry point in Dllmain.

The following topics describe delay loading DLLs:

• Specifying DLLs to Delay Load

• Explicitly Unloading a Delay-Loaded DLL

• Loading All Imports for a Delay-Loaded DLL

• Binding Imports

• Error Handling and Notification

• Dumping Delay-Loaded Imports

• Constraints of Delay Loading DLLs

• Understanding the Helper Function

• Developing Your Own Helper Function

See Also

Concepts

DLLs

Linking