Fix MQL4 and MQL5 errors, and check your EA before it trades
MetaEditor says "undeclared identifier", "function already defined" or "unexpected end of program", and the EA will not compile. Upload the code, paste the errors if you have them, and the Lab finds the real cause, fixes it, compiles again and shows what changed.
How fixing works
- MetaEditor compiles your code first, so you do not need to copy errors by hand.
- Many errors come from one cause: the Lab groups them and fixes the cause, not each symptom.
- Each fix is checked by compiling again, a few rounds at most.
- Only what is broken changes: the rest of your code stays exactly as it was.
- The result is a new version; you can compare it line by line with the original.
A verification certificate in plain words
Check my code runs ten checks: compile, platform, program kind, whether the trading code is reached, real-broker issues (filling mode, stop levels, lot step), inputs, risk protection, the confirmed strategy, safety, and an AI dry run. Each finding says what it means for trading and how much it matters, with a short summary at the top. The same code always gets the same certificate.
Common MetaTrader errors the Lab fixes
- Undeclared identifiers and missing includes.
- Functions or variables defined twice, and variables that hide global ones.
- MT4 functions used in an MT5 file, or MT5 functions in an MT4 file.
- Wrong parameter counts and type mismatches.
- Unbalanced brackets and unexpected end of program.
- Orders refused by the broker: filling mode, stop distance, lot step and trading permission.
Questions
Do I need to paste the MetaEditor errors?
No. When MetaEditor is connected, the Lab compiles your code itself and fixes what it finds. You can still paste errors or terminal logs to point at a specific problem.
Will the fix change my strategy?
No. Fixes change only what is broken. Notes such as "stop distance not checked" are suggestions; the Lab never changes how your EA trades unless you ask it to.
What does "Needs fixes" mean on a certificate?
At least one check found something that should be fixed, such as a compile error or a mistake that stops trades. Notes that do not block are listed separately with their impact.