National Instruments 320685D-01 Run State Change Callbacks Are Not Available in Executables

Chapter 5 UNIX Compiler/Linker Issues

National Instruments Corporation 5-5 LabWindows/CVI Programmer Reference Manual

National Instruments recommends that you always include source code similar to the

following example in your program.

int main(int argc, char *argv[])

{if (InitCVIRTE(0, argv, 0) == 0) {

return 1;/* Failed to initialize */

}

/* your program code here */

}

If you pass NULL for the second argument to InitCVIRTE, your program might still work,

but with the following limitations:

• Your executable cannot accept the -display command line argument. As a result, you

cannot specify an X display on the command line for your program to use. You still can

use the DISPLAY environment variable to specify a different X display.

•LoadPanel, LoadExternalModule, DisplayImageFile, SavePanelState,

RecallPanelState, and other functions that normally use the directory of the

executable to search for files, use the current working directory instead. If you run the

executable from a directory other than the one that contains your executable, some of

these functions might fail to find files.

Run State Change Callbacks Are Not Available in Executables

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

LabWindows/CVI to notify it of a change in execution status (start, stop, suspend, resume).

You do this through a function called __RunStateChangeCallback. The Notification of

Changes in Run State section, in Chapter2, Using Loadable Compiled Modules, describes

this in detail.

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

run a program in the LabWindows/CVI development environment, it executes 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 releases as many

resources as it can, but your compiled module might have to do more. Also, if the program

suspends for debugging purposes, your compiled module might have to disable interrupts.

When you run a standalone executable, it always executes as a separate process. Thus, the run

state change callback facility is not necessary and doesnot work. External compilers report

link errors when you define __RunStateChangeCallback in more than one object file. If

you require a run state change callback in a compiled module that you intend to use both in

LabWindows/CVI and an external compiler, National Instruments recommends that you put

the callback function in a separate source file and create a library (.a) instead of an object file.