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Handy Tips & Tricks for Debugging
LabWindows/CVI Code
Johannes Turner
National Instruments
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Agenda
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2.
3.
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6.
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Catching bugs at compile time
Catching bugs at run time
LabWindows/CVI Debugging Tools
Debugging Release Executables
Summary
Q&A
About Me
Working at National Instruments Romania (NIR) located in Cluj-Napoca.
With NI for 5 years.
Worked in CVI R&D since the CVI 2012 SP2 release.
LabWindows/CVI User Group Community interaction:
LabWindows/CVI Discussion Forums
LabWindows/CVI Idea Exchange
Interests: source code editors, music.
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Catching Bugs at Compile Time: Compiler Warnings
Customize using predefined warning level in Options Build Options.
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Catching Bugs at Compile Time: Compiler Warnings
Customize warnings for each warning level preset.
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Catching Bugs at Compile Time: Compiler Warnings
Assignments in conditionals
Uninitialized local variables
Unreferenced local variables
Unreachable code
Pointer and sign conversions
Improper char array initialization
Static array bounds checking
Dangling else constructs
Macro redefinition
Operator precedence problems
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Catching Bugs at Compile Time: Compiler Warnings
Improper char array initialization
char foo[2] = "bar";
int bar[10];
return bar[10];
Operator precedence problems
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Dangling else constructs
Static array bounds checking
int i;
i = 100 << 10+2;
if (a == 1)
if (b == 1)
a = 42;
else
b = 42;
Catching Bugs at Compile Time: Compiler Warnings
Assignments in conditionals
Uninitialized local variables
Unreferenced local variables
Unreachable code
Pointer and sign conversions
Improper char array initialization
Static array bounds checking
Dangling else constructs
Macro redefinition
Operator precedence problems
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Catching Bugs at Compile Time: Example 1
Using and customizing LabWindows/CVI compiler warnings when
diagnosing issues in your application.
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Catching Bugs at Run Time: Automatic Checking
Invalid pointer arithmetic or array indexing
Dereferencing invalid or freed pointers
Use of uninitialized local variables
Library function argument type checking
printf, SetCtrlAttribute
Library functions return error values
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Run Break On Library Errors
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Catching Bugs at Run Time: Manual Checking
Asserts
Standard C macro (assert.h): assert(condition);
Tips:
o
o
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Test expectations and program invariants
Explicitly enforce assumptions your code makes
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Catching Bugs at Run Time: Manual Checking
Error checking!
Check function return values for errors
Null-check memory allocations
errChk, nullChk
o
int Initialize (int panel, int ctrl) {
int error = 0;
errChk(SetCtrlVal(panel, ctrl, Hello, world!));
Error:
return error;
}
Automatic run-time checking is not a substitute for checking error
conditions in your code!
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Debugging Tools: The Bread and Butter
Inspect and modify variables
Examine stack trace
Variables window
Detect when values change
Variables window
Editable data tooltips
Watch expressions
Break On Change
Detect special cases
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Conditional breakpoints
Regular watch expression
Watch expression with Break On Change enabled
Watch expression with Break On Change enabled (HW).
Watch expression with Break On Change enabled (SW).
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Debugging Tools: Other Handy Features
Change the point of execution
Inspect/modify memory
Memory window
Examine arrays graphically
Set Next Statement
Graphical Array View
Redraw UI while suspended
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Run Refresh User Interface (Ctrl + R)
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Catching Bugs at Run-Time Time: Example 1 (Cont.)
Using the Graphical Array View
Debugging common C language pitfalls.
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More LabWindows/CVI-Specific Debugging Tips
Get more insight about symbols
with Watch Window Specific Type
1.
2.
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Add symbol to Watch Window
(Add Watch Expression
menu item)
Right-click watchpoint
Specific Type
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Debugging Release Executables
Which EXE or DLL did the crash occur in?
Where in the EXE or DLL did the crash occur?
1.
2.
Look at the module list in the LabWindows/CVI debugger
Generate a map file for the EXE or DLL
Look up the address in the map file
Trace the execution of your EXE or DLL
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DebugPrintf
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Debugging Release Executables: Example 2
List of loaded modules
Map files
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Debugging Release Executables
Understanding why does my project work in the debug configuration
but does not in the release configuration?
Data initialization in debug builds.
Code generation optimization
o
Conditional compilation
o
o
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Options Build Options Optimization level
Examine the preprocessor output
Compare different preprocessor outputs
Examine values and trace macro expansion: #pragma message, #error
Race conditions
Different timing of processed events
Communication with hardware
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Debugging Release Executables: Example 2 (Cont.)
Analyzing the preprocessor output
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Other Advanced Debugging Tools
Windows Sysinternals
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http://www.sysinternals.com
DebugView
ProcessExplorer
Many more
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Summary
Early detection of bugs at compile time using compiler warnings
Catching bugs at run time
Using the debugger
Debugging release executables
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Questions and Answers
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Thank you!
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