National Instruments 320685D-01 Resolving Run-Time Module References to Symbols Not Exported from a DLL, Run State Change Callbacks Are Not Available in External Compilers

Chapter 3 Windows95/NT Compiler/Linker Issues

National Instruments Corporation 3-13 LabWindows/CVI Programmer Reference Manual

module references any of the commonly used Windows SDK functions, you can use the

cvi\sdk\include\basicsdk.h file.

Execute the External Compiler Support command in the Build menu of the Project window.

A dialog box appears. Enable the Using Load External Module option. Enable the Other

Symbols checkbox if it is not already enabled. Enter the pathname of the include file in the

Header File control. Enter the pathname of the object file to generate in the Object File

control. Click on the Create button to the right of the Object File control.

Include the object file in the external compiler project you use to create your executable. Also,

you must call InitCVIRTE at the beginning of your main or WinMain function. Refer to the

Calling InitCVIRTE and CloseCVIRTE section later in this chapter.

Resolving Run-Time Module References to Symbols Not Exported from a DLL

When you load an object or static library file from a DLL, you might want to resolve

references from that module using global symbols the DLL contains, but does not export. You

can do this by calling LoadExternalModuleEx. When you pass the DLL module handle to

LoadExternalModuleEx, the Utility Library searches the symbol table the DLL contains

before searching the table that the executable contains. Refer to Chapter8, Utility Library, of

the LabWindows/CVI Standard Libraries Reference Manual for detailed information on

LoadExternalModuleEx.

If you create your DLL in LabWindows/CVI, LabWindo ws/CVI includes the table of symbol s

in the DLL automatically. If you create your DLL using an external compiler, the external

compiler does not make such a table available to the Utility Library. Thus, when you use an

external compiler, you must include in your DLL one or more object files that contain the

necessary symbol tables. You can do this using the technique that the previous section,

Resolving References to Symbols Not in Run-Time Engine, describes. You must call

InitCVIRTE and CloseCVIRTE in your DLLMain function. Refer to the Calling InitCVIRTE

and CloseCVIRTE section later in this chapter.

Run State Change Callbacks Are Not Available in External Compilers

When you use a compiled module in LabWindows/CVI, you can arrange for

LabWindows/CVI to notify the module of a change in the execution status such as start, stop,

suspend, or resume. You do this through a callback function that is always named

__RunStateChangeCallback. The Notification of Changes in Run State section, in

Chapter 2, Using Loadable CompiledModules, of this manual, describes this in detail.

The run state change callback capability in LabWindows/CVI is necessary because the

LabWindows/CVI development environment executes your program as part of the

LabWindows/CVI process. When your program terminates, the operating system does not

release resources as it does when a process terminates. LabWindows/CVI attempts to release