Your PLC project compiles. That doesn't mean it works.

PLC Lint reads a PLCopenXML export and finds what the compiler accepts without a word: a timer nobody calls, a setpoint truncated before it is used, a division by a variable that is zero, a branch that can never run. 34 checks, about 10 seconds, no signup.

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Your customer's export is their property, and sending it to somebody else's server is rarely your call. So don't: the local build is one .exe — no install, no Python, no network calls at all. Drop an export onto it and the same report appears next to the file.

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Linux/macOS: python cli.py project.xml · MIT on GitHub

Project in git? uses: caspershes/plc-lint@v1 — the GitHub Action breaks the build on high-severity findings.

Check the whole project in batch (Pro) → · Compare versions → · Bugs explained one by one →

What we check · 34 checks in total

Will stop the controller or send it out of control (13)

Analog input without a plausibility checka broken Pt1000 reaches the controller as a solid 0 °C (profile)

Array index out of boundsreaching the line reads memory that isn't yours

CFC: division by a literal zeroin CFC the block divisor is wired to a literal 0

Channel never written — gap in a channel familydeclared for all four boilers, written for three

Channel parameter fed from another channelpump 1's alarm arrives on pump 2's input

Command depends on its own feedbackstopped → no permission → no command → stopped

Division by a literal zeroliteral /0 and an unguarded divisor variable

Duplicate Modbus address on moduleswhich of the two answers the poll?

Global name typo (gvl.*)references to globals not declared in the GVL

Implicit check does not protecta Check function exists but its guard is gutted

Infinite loop with no exitWHILE TRUE with no exit — the scan stalls

Uncalled timer/triggerTON/TP/R_TRIG read, but the FB is never called

Unreachable IF/ELSIF branchdead ELSIF — the classic heating-curve bug

Quiet defects: it runs, but not as intended (11)

Assignment of a variable to itselfx := x — a typo or lost logic

CASE without an ELSE branch (no default)unhandled selector values

Check present but not activethe check exists but is not registered

Empty IF/loop branchlogic forgotten in an IF or a loop

Integer division (lost fraction?)5/2 yields 2 — the fraction is dropped

Line indexes differently from its groupeleven lines write to their own channel, the twelfth does not

No POUs for implicit checks (runtime guards)the runtime will not intercept a bad index or /0

REAL_TO_TIME(...)*N — setpoint truncationa fractional time setpoint is lost before conversion

REAL_TO_WORD(...)*N — WORD overflow?the product overflows 0..65535

Task watchdog disabledthe task watchdog is switched off

Timer with zero delay (PT := T#0)PT := T#0S — effectively no delay

Style and maintainability (10)

Bloated routine (decomposition candidate)extract the repeated logic into a FUNCTION_BLOCK

Cryptic variable namecryptic single-character names

Dead code — POU is never calledleftovers — or a rename someone forgot to finish

Deep IF nestingdeeply nested IFs

Double `;;` (empty statement)stray ;; and similar litter

Duplicated logic block (copy-paste)structurally duplicated blocks and loops

Magic number — raw constant in coderaw constants in logic, with no name

Name off the PLCopen standardtype prefixes in names (profile)

POU without a single commentnothing explains the logic to the next engineer

Unused local variabledeclared but never used

Every finding comes with suggested fixes and code examples.

5 bugs the compiler doesn't catch →

Processing happens in memory — the uploaded code is not stored. The tool advises; code changes are up to the engineer (see what the linter can't see). What happens to your code → · Your code & privacy · Industry benchmark · Feedback · GitHub