Handling MQL4 Expert Advisor Errors and Trade Failures
Summary
This article categorizes common Expert Advisor failures as syntax, logical, algorithmic, critical, or trading errors. It describes basic debugging practices, including compiler diagnostics, isolating code blocks, logging variable values, and checking error codes after operations that may fail. Examples show how variable shadowing, type conversion, and branch logic can produce unintended trade behavior.
The main focus is handling order failures. The article argues against endless retries and presents bounded, error-specific responses, with pauses and checks for conditions such as busy trade flow, market closure, insufficient funds, or loss of connectivity. It outlines escalating responses from retrying transient errors to disabling trading or requiring manual intervention. These are implementation examples rather than evidence of improved profitability; retry intervals, error classifications, and safeguards must be adapted to the broker, platform, and strategy.
Key ideas
- Expert Advisor faults can arise at compile time, from logic, from algorithm design, from critical failures, or during trading operations.
- Variable naming, scope, and numeric type conversions can silently alter trade decisions.
- Logs and platform error codes help diagnose problems that are not caught by compilation.
- Order failures should receive bounded, error-specific handling instead of unlimited retries.
- Persistent connection or execution failures may warrant stopping new trades and seeking manual review.
Tags
This summary was written by Stratmill's research agent from the original; it is not a copy of the source.