National Instruments 320685D-01 Debugging Levels , User Protection

Chapter 1 LabWindows/CVI Compiler

LabWindows/CVI Programmer Reference Manual 1-8

National Instruments Corporation

Debugging Levels

You can compile the source modules in your application to include debugging information. If

you do so, you can use breakpoints and view or modify v ariable s and ex press ions whil e you r

program is suspended. You set the debugging level by selecting Options»Run Options in the

Project window. Refer to the Run Options section in Chapter 3, Project Window, of the

LabWindows/CVI User Manual for information on debugging levels.

User Protection

User protection detects invalid program behavior that LabWindows/CVI cannot otherwise

detect during compilation. LabWindows/CVI reports such invalid program behavior as user

protection errors. When you set the debugging level to Standard or Extended,

LabWindows/CVI maintains extra information for arrays, structures, and pointers, and uses

the information at run time to determine the validity of addresses.

Two groups of user protection errors exist based upon two characteristics: severity level and

error category. In each case, the ANSI C standard states that programs with these errors have

undefined behavior. The two severity levels are as follows:

•Non-Fatal errors include expressions that are likely to cause problems, but do not

directly affect program execution. Examples include bad pointer arithmetic, attempts to

free pointers more than once, and comparisons of pointers to different array objects. The

expression is invalid and its behavior is undefined, but execution can continue.

•Fatal errors include expressions that LabWindows/CVI cannot execute without causing

major problems, such as causing a general protection fault. For example, dereferencing

an invalid pointer value is a fatal error.

Error categories include pointer protection, dynamic memory protection, library protection,

and general protection errors. Each of these categories includes subgroups as described in the

following sections.

The pointer protection errors catch invalid operations with pointers and arrays. In this section,

these errors are grouped by the type of expression that causes the error or the type of invalid

pointer involved.

Pointer arithmetic expressions involve a pointer sub-expression and an integer

sub-expression. LabWindows/CVI generates an error when the pointer sub- expression is