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LabVIEW Debugging Techniques to Find and Squash Software Bugs

Rejwan Ali

Marketing Engineer

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Photo Credit: Bugs / Brian Searle / CC BY 2.0

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LabVIEW Edit-Time Bugs

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LabVIEW Edit-Time Bugs

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LabVIEW Run-Time Bugs

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1. Use Error Wires

• Surfaces run-time errors so you can fix them

• Search ni.com “Structured Error Handler” for a more

structured error handling strategy

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1. Use Error Wires

• Surfaces run-time errors so you can fix them

• Search for “Structured Error Handler” on ni.com for a

more structured error handling strategy

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2. Highlight Execution

• Animation of the block diagram data flow

• LabVIEW Idea Exchange (ni.com/ideas) on “User

Defined Partial Highlight Execution”

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3. Single-Stepping

• Walk through each block diagram interaction one at a time

• If you single-step through a VI with execution highlighting

on, an execution glyph appears on the icons of the

subVIs that are currently running.

Step Into Step Over Step Out

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4. Probes

• Watch data values on wires in “real time”

• SAPHIR - VIBox Probes free add-on for custom probes

available on the LabVIEW Tools Network

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4. Probes

• Watch data values on wires in “real time”

• SAPHIR - VIBox Probes free add-on for custom probes

available on the LabVIEW Tools Network

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4. Probes

• Watch data values on wires in “real-time”

• SAPHIR - VIBox Probes free add-on for custom probes

available on the LabVIEW Tools Network

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5. Breakpoints

• Pause execution of a VI at a certain block diagram location

• LabVIEW Idea Exchange (ni.com/ideas) on “Allow Data in

Wires to be Forced During Development”

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5. Breakpoints

• Pause execution of a VI at a certain block diagram location

• LabVIEW Idea Exchange (ni.com/ideas) on “Allow Data

in Wires to be Forced During Development”

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6. Suspend When Called

• Suspends execution of subVI when it is called

• Determine where the subVI is being called from by using

the Call list pull-down menu on the toolbar (Call Chain

function also would work programmatically)

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6. Suspend When Called

• Suspends execution of subVI when it is called

• Determine where the subVI is being called from by using

the Call list pull-down menu on the toolbar (Call Chain

function also would work programmatically)

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6. Suspend When Called

• Suspends execution of subVI when it is called

• Determine where the subVI is being called from by using

the Call list pull-down menu on the toolbar (Call Chain

function also would work programmatically)

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6. Suspend When Called

• Suspends execution of subVI when it is called

• Determine where the subVI is being called from by using

the Call list pull-down menu on the toolbar (Call Chain

function also would work programmatically)

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6. Suspend When Called

• Suspends execution of subVI when it is called

• Determine where the subVI is being called from by using

the Call list pull-down menu on the toolbar (Call Chain

function also would work programmatically)

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7. Debugging with “Binary Search” method

• Comment out half of your code and see if the problem still

persists. Keep going until you narrow in on the offending

code

• LabVIEW Idea Exchange (ni.com/ideas) on “Conditional

Disable Symbols settable in Application Builder”

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7. Debugging with “Binary Search” method

• Comment out half of your code and see if the problem still

persists. Keep going until you narrow in on the offending

code

• LabVIEW Idea Exchange (ni.com/ideas) on “Conditional

Disable Symbols settable in Application Builder”

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7. Debugging with “Binary Search” method

• Comment out half of your code and see if the problem still

persists. Keep going until you narrow in on the offending

code

• LabVIEW Idea Exchange (ni.com/ideas) on “Conditional

Disable Symbols settable in Application Builder”

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8. VI Debug File

• Write values to a “debug file” periodically so that you can

read about the VI execution later

• This will show the values in more real execution timing

compared to other tools like Highlight Execution

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8. VI Debug File

• Write values to a “debug file” periodically so that you can

read about the VI execution later

• This will show the values in more real execution timing

compared to other options like Highlight Execution

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8. VI Debug File

• Write values to a “debug file” periodically so that you can

read about the VI execution later

• This will show the values in more real execution timing

compared to other options like Highlight Execution

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8. VI Debug File

• Write values to a “debug file” periodically so that you can

read about the VI execution later

• For this example, search ni.com/community for “Simple

Debug File Troubleshooting in LabVIEW”

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9. Desktop Execution Trace Toolkit

• Even code that is syntactically correct and functionally

complete is often still contaminated with problems such

as memory leaks or daemon tasks that can impact

performance or lead to incorrect behavior

• Debugging large, highly parallel applications is difficult

• Code that crashes LabVIEW needs another process to

help it debug

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9. Desktop Execution Trace Toolkit

• Good for memory leaks, event sources, last call before

error, and remote execution tracing

• It can trace VI Execution, Event Structure, Queues and

Notifers, User Logged Strings, Reference Leaks, Error

I/O, Memory Allocations, and Thread and CPU IDs

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10. Catch All

• Make sure and initialize appropriate shift registers (There

is a VI Analyzer test for this)

• Hidden or unwired subVIs could happen if you place

structures on top of VIs and could cause the VI to perform

extra functions. Use View»VI Hierarchy, to look for extra

VIs or change the environmental setting so that terminals

are “required” by default.

• What else is missing from this list?

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Want to Learn More?

• ni.com/training

• “LabVIEW Core 1” – LabVIEW Debugging Basics

• “LabVIEW Core 2” – Debugging a LabVIEW Application

• “LabVIEW Performance” – Identify and Improve Performance

Issues; VI Profiler, VI Analyzer, Desktop Execution Trace Toolkit

• ni.com/training/self-paced (For LabVIEW Core 1 & 2)

• “Debugging Techniques” in-product whitepaper

(Help»LabVIEW Help) and also online if you search

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Plan Your ProficiencyVisit the Proficiency Booth and complete the short questionnaire to see your custom plan

for recommended Training and Certification

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Let us help you identify

the skills your LabVIEW

project requires today

Visit the LabVIEW

Proficiency Booth for details

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Thanks for attending!