National Instruments 320685D-01 Using LoadExternalModule on Library and Object Files Not in the Project

Chapter 7 Creating and Distributing Standalone Executables and DL Ls

LabWindows/CVI Programmer Reference Manual 7-16

National Instruments Corporation

• If you want to force only specific mo dules from th e library into the executable,

reference them statically in your program. For example, you could have an array

of void pointers and initialize them to the names of the necessary symbols.

• If you link in an external compiler under Windo ws 95/NT , the LabW indows/CVI Utility

library does not know the location of symbols in the externally linked executable or DLL.

Consequently, without further action on your part, you cannot call

GetExternalModuleAddr or RunExternalModule on modules that you link directly

into your executable or DLL. Your alternatives are as follows.

1. Remove the file from the project and distribute it as a separate .obj, .lib,

or .dll.

2. Use the Other Symbols section of the External Compiler Support dialog box in

the Build menu of the Project window to create an object module that contains

a table of symbols you want GetExternalModuleAddr to find. If you use this

method, pass the empty string ("") to LoadExternalModule as the module

pathname. The empty string indicates that you linked the module directly into

your executable or DLL using an external compiler.

Using LoadExternalModule on Library and Object Files Not in the Project

If you call LoadExternalModule on a library or object file not in the project, you must keep

the library or object file separate in your distribution.

When you keep an object or library file separate, you can manage memory more efficiently

and replace it without having to replace the executable. For this reason, if you call

LoadExternalModule on a library or object in the project, remove or exclude the file from

the project before you select Create Standalone Executable File or Create Dynamic Link

Library, and then include it as a separate file when you use Create Distribution Kit.

However, remember that you cannot statically reference functions defined in a separate

library or object file from the executable or DLL. You must use LoadExternalModule and

GetExternalModuleAddr to make such references.

When you distribute the library or object file as a separate file, it is a good idea to place the

file in the same directory as the executable or DLL. If you place the file in the same directory,

you can pass a simple filename to LoadExternalModule. If you do not want the file to be

in the same directory as your executable, you must pass a pathname to

LoadExternalModule. LoadExternalModule interprets relative pathnames as being

relative to the directory that contains the executable or DLL.