Examples: Common Errors in MQL4 Programs and How to Avoid Them

[MetaQuotes]

New article Common Errors in MQL4 Programs and How to Avoid Them has been published:

To avoid critical completion of programs, the previous version compiler handled many errors in the runtime environment. For example, division by zero or array out of range are critical errors and usually lead to program crash. The new compiler can detect actual or potential sources of errors and improve code quality. In this article, we discuss possible errors that can be detected during compilation of old programs and see how to fix them.

Author: MetaQuotes Software Corp.

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these enum data identifiers are NOT recognized in mql4, even though they are documented in the MQL4 Reference

ENUM_ACCOUNT_STOPOUT_MODE, ENUM_ACCOUNT_TRADE_MODE, ENUM_APPLIED_VOLUME, ENUM_DRAW_TYPE, ENUM_SYMBOL_TRADE_EXECUTION, ENUM_SYMBOL_TRADE_MODE, ENUM_TRADE_RETURN_CODES

for example if I compile a script with this line

Print("MQL_PROGRAM_TYPE = "+MQLInfoInteger(MQL_PROGRAM_TYPE)+" = "+EnumToString((ENUM_PROGRAM_TYPE)MQLInfoInteger(MQL_PROGRAM_TYPE)));

it's all correct and Script prints: MQL_PROGRAM_TYPE = 1 = PROGRAM_SCRIPT

but, if i try to compile this other line

Print("SYMBOL_TRADE_MODE = "+SymbolInfoInteger(Symbol(), SYMBOL_TRADE_MODE)+" = "+EnumToString((ENUM_SYMBOL_TRADE_MODE)SymbolInfoInteger(Symbol(), SYMBOL_TRADE_MODE)));

there are errors! 'NUM_SYMBOL_TRADE_MODE' - undeclared identifier

and so on with 'ENUM_SYMBOL_TRADE_EXECUTION' - undeclared identifier, 'ENUM_ACCOUNT_TRADE_MODE' - undeclared identifier, ..., ...

[madmaxbd]

Help me this not working 

 <code removed>

[Alain Verleyen]

madmaxbd:

Help me this not working 

 <code removed>

Please attach your code as a file, it is too big.

[Miroslav Randa]

Hi, with the new version I am unable to compile my code, receiving the message "expression of 'void' type is illegal" with reference to line 1 column 1 (see attached pictures). The line 1 and column 1 as shown on other attached pict. Any idea what I have to look for?

Thanks for help