National Instruments 320685D-01 Using LoadExternalModule on DLL Files under Windows 95/NT, Using LoadExternalModule on DLL and Path Files under Windows 3.1

Chapter 7 Creating and Distributing Standalone Executables and DLLs

National Instruments Corporation 7-17 LabWindows/CVI Programmer Reference Manual

Using LoadExternalModule on DLL Files under Windows 95/NT

Under Windows 95/NT, you cannot pass the pathname of a DLL directly into

LoadExternalModule. Instead, you must pass the pathname of a DLL import library. You

can link the import library into your executable or DLL or distribute it separately and load it

dynamically. For import libraries that you link into your executable or DLL, refer to the Using

LoadExternalModule on Files in the Project section earlier in this chapter. For import

libraries that you load dynamically, refer to the Using LoadExternalModule on Library and

Object Files Notin theProject section earlier in this chap ter.

You must always distribute DLLs as separate files. The operating system finds the DLL

associated with the loaded import library using the standard Windows DLL search algorithm.

The search precedence is as follows.

1. The directory from which the application loads

2. The current working directory

3. Under Windows 95, the Windows system directory. Under Windows NT, the W i nd ows

system32 and system directories

4. The Windows directory

5. The directories the PATH environment variable lists

Using LoadExternalModule on DLL and Path Files under Windows 3.1

DLL files and DLL path files are never linked into the executable, so you must distribute them

as separate files.

Your executable can call LoadExternalModule directly on a DLL or DLL path file only if

you include the DLL or DLL path file in the project. When you select Create Standalone

Executable File, LabWindows/CVI automatically creates the DLL glue code and links it into

the executable.

Also, you can pass the DLL glue object module filename to LoadExternalModule. You can

generate the DLL glue object module by opening the .hfile for the DLL in a Source window

of LabWindows/CVI and selecting Generate DLL Glue Object from the Options menu.

If you include the DLL, the DLL path file, or the DLL glue object module as a file in the

project, you must pass LoadExternalModule a simple filename, and it uses the following

search method to find the DLL.

1. Look for a .pth file in the directory of the executable. The .pth file must have the same

base name as the file you passed to LoadExternalModule. If the .pth file contains an

absolute path to the DLL, use that path to find the DLL. If the .pth file contains a simple

filename, use the standard Windows DLL search algorithm: directory of executables,