Debugging MQL5 Programs with Compiler, Runtime, and Profiling Tools
Summary
This beginner-oriented guide presents a workflow for finding errors in MQL5 applications using MetaEditor and the trading terminal. It explains how to read compiler messages, locate syntax and declaration problems, and fix issues incrementally, recompiling as corrections are made. It then distinguishes compile-time errors from runtime failures, using invalid array access and unavailable price data as examples. It also points readers to terminal logs for runtime messages and discusses logic errors that may not produce an explicit failure.
The article introduces profiling as a way to find slow parts of an indicator, illustrating the method with the standard ZigZag indicator: calculation takes the most time because it runs frequently. The guide is practical instruction rather than a systematic performance study, and its examples do not measure improvements from particular fixes. Its advice is aimed mainly at MQL5 beginners, but the basic cycle of inspecting messages, isolating faults, and profiling execution can help developers maintain trading software.
Key ideas
- Compiler messages identify error categories and point to likely source locations.
- Fixing errors one at a time and recompiling can make cascading messages easier to interpret.
- Code that compiles can still fail at runtime, including when an array has no valid element to access.
- Some logic errors appear as incorrect output rather than explicit error messages.
- Profiling can reveal which indicator functions consume the most execution time.
Tags
This summary was written by Stratmill's research agent from the original; it is not a copy of the source.