| MQL5 Reference / Constants, Enumerations and Structures / Codes of Errors and Warnings / Compilation Errors |
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Compilation Errors
MetaEdtior 5 shows error messages about the program errors detected by the built-in compiler during compilation. The list of these errors is given below in table. To compile a source code into an executable one, press F7. Programs that contain errors cannot be compiled until the errors identified by the compiler are eliminated.
Code |
Description |
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File reading error |
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Error of opening an *. EX5 for writing |
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Not enough free memory to complete compilation |
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Empty syntactic unit unrecognized by compiler |
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Incorrect file name in #include |
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Error accessing a file in #include (probably the file does not exist) |
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Inappropriate name for #define |
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Unknown command of preprocessor (valid #include, #define, #property, #import) |
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Symbol unknown to compiler |
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Function not implemented (description is present, but no body) |
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Double quote (") omitted |
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Opening angle bracket (<) or double quote (") omitted |
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Single quote (') omitted |
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Closing angle bracket ">" omitted |
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Type not specified in declaration |
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No return operator or return is found not in all branches of the implementation |
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Opening bracket of call parameters was expected |
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Error writing EX5 |
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Invalid access to an array |
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The function is not of void type and the return operator must return a value |
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Incorrect declaration of the destructor |
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Colon ":" is missing |
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Variable is already declared |
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Variable with such identifier already declared |
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Variable name is too long (> 250 characters) |
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Structure with such identifier already defined |
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Structure is not defined |
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Structure member with the same name already defined |
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No such structure member |
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Breached pairing of brackets |
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Opening parenthesis "(" expected |
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Unbalanced braces (no "}") |
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Difficult to compile (too much branching, internal stack levels are overfilled) |
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Error of file opening for reading |
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Not enough memory to download the source file into memory |
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Variable is expected |
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Reference cannot be initialized |
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Assignment expected (appears at declaration) |
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Opening brace "{" expected |
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Parameter can be a dynamic array only |
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Use of "void" type is unacceptable |
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No pair for ")" or "]", i.e. "(or" [ " is absent |
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No pair for "(or" [ ", i.e. ") "or"] " is absent |
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Incorrect array size |
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Too many parameters (> 64) |
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This token is not expected here |
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Invalid use of operation (invalid operands) |
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Expression of void type not allowed |
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Operator is expected |
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Misuse of break |
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Semicolon ";" expected |
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Comma "," expected |
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Must be a class type, not struct |
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Expression is expected |
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"non HEX character" found in HEX or too long number (number of digits> 511) |
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String-constant has more than 65534 characters |
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Function definition is unacceptable here |
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Unexpected end of program |
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Forward declaration is prohibited for structures |
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Function with this name is already defined and has another return type |
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Function with this name is already defined and has a different set of parameters |
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Function with this name is already defined and implemented |
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Function overload for this call was not found |
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Function with a return value of void type cannot return a value |
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Function is not defined |
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Value is expected |
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In case expression only integer constants are valid |
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The value of case in this switch is already used |
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Integer is expected |
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In #import expression file name is expected |
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Expressions are not allowed on global level |
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Omitted parenthesis ")" before ";" |
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To the left of equality sign a variable is expected |
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The result of expression is not used |
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Declaring of variables is not allowed in case |
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Implicit conversion from a string to a number |
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Implicit conversion of a number to a string |
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Ambiguous call of an overloaded function (several overloads fit) |
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Illegal else without proper if |
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Invalid case or default without a switch |
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Inappropriate use of ellipsis |
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The initializing sequence has more elements than the initialized variable |
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A constant for case expected |
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A constant expression required |
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A constant variable cannot be changed |
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Closing bracket or a comma is expected (declaring array member) |
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Enumerator identifier already defined |
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Enumeration cannot have access modifiers (const, extern, static) |
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Enumeration member already declared with a different value |
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There is a variable defined with the same name |
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There is a structure defined with the same name |
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Name of enumeration member expected |
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Integer expression expected |
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Division by zero in constant expression |
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Wrong number of parameters in the function |
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Parameter by reference must be a variable |
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Variable of the same type to pass by reference expected |
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A constant variable cannot be passed by a non-constant reference |
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Requires a positive integer constant |
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Failed to access protected class member |
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Import already defined in another way |
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Executable file not created |
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'OnCalculate' entry point not found for the indicator |
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The continue operation can be used only inside a loop |
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Error accessing private (closed) class member |
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Method of structure or class is not declared |
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Error accessing private (closed) class method |
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Copying of structures with objects is not allowed |
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Index out of array range |
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Array initialization in structure or class declaration not allowed |
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Class constructor cannot have parameters |
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Class destructor can not have parameters |
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Class method or structure with the same name and parameters have already been declared |
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Operand expected |
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Class method or structure with the same name exists, but with different parameters (declaration!=implementation) |
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Imported function is not described |
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ZeroMemory() is not allowed for objects with protected members or inheritance |
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Ambiguous call of the overloaded function (exact match of parameters for several overloads) |
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Variable name expected |
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A reference cannot be declared in this place |
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Already used as the enumeration name |
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Class or structure expected |
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Cannot call 'delete' operator to delete the array |
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Operator ' while' expected |
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Operator 'delete' must have a pointer |
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There is 'default' for this 'switch' already |
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Syntax error |
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Escape-sequence can occur only in strings (starts with '\') |
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Array required - square bracket '[' does not apply to an array, or non arrays are passed as array parameters |
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Can not be initialized through the initialization sequence |
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Import is not defined |
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Optimizer error on the syntactic tree |
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Declared too many structures (try to simplify the program) |
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Conversion of the parameter is not allowed |
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Incorrect use of the 'delete' operator |
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It's not allowed to declare a pointer to a reference |
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It's not allowed to declare a reference to a reference |
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It's not allowed to declare a pointer to a pointer |
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Structure declaration in the list of parameter is not allowed |
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Invalid operation of typecasting |
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A pointer can be declared only for a class or structure |
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Undeclared identifier |
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Executable code optimizer error |
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Executable code generation error |
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Invalid expression for the 'switch' operator |
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Pool of string constants overfilled, simplify program |
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Cannot convert to enumeration |
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Do not use 'virtual' for data (members of a class or structure) |
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Cannot call protected method of class |
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Overridden virtual functions return a different type |
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Class cannot be inherited from a structure |
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Structure cannot be inherited from a class |
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Constructor cannot be virtual (virtual specifier is not allowed) |
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Method of structure cannot be virtual |
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Function must have a body |
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Overloading of system functions (terminal functions) is prohibited |
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Const specifier is invalid for functions that are not members of a class or structure |
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Not allowed to change class members in constant method |
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Inappropriate initialization sequence |
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Missed default value for the parameter (specific declaration of default parameters) |
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Overriding the default parameter (different values in declaration and implementation) |
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Not allowed to call non-constant method for a constant object |
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An object is necessary for accessing members (a dot for a non class/structure is specified) |
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The name of an already declared structure cannot be used in declaration |
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Unauthorized conversion (at closed inheritance) |
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Structures and arrays cannot be used as input variables |
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Const specifier is not valid for constructor/destructor |
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Incorrect string expression for a datetime |
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Unknown property (#property) |
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Incorrect value of a property |
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Invalid index for a property in #property |
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Call parameter omitted - <func (x,)> |
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Object must be passed by reference |
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Array must be passed by reference |
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Function was declared as exportable |
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Function was not declared as exportable |
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It is prohibited to export imported function |
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Imported function cannot have this parameter (prohibited to pass a pointer, class or structure containing a dynamic array, pointer, class, etc.) |
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Must be a class |
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#import was not closed |
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Type mismatch |
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Extern variable is already initialized |
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No exported function or entry point found |
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Explicit constructor call is not allowed |
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Method was declared as constant |
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Method was not declared as constant |
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Incorrect size of the resource file |
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Incorrect resource name |
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Resource file opening error |
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Resource file reading error |
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Unknown resource type |
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Incorrect path to the resource file |
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The specified resource name is already used |
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Argument expected for the function-like macro |
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Unexpected symbol in macro definition |
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Error in formal parameters of the macro |
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Invalid number of parameters for a macro |
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Too many parameters for a macro |
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Too complex, simplify the macro |
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Parameter for EnumToString() can be only an enumeration |
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The resource name is too long |
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Unsupported image format (only BMP with 24 or 32 bit color depth is supported) |
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An array cannot be declared in operator |
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The function can be declared only in the global scope |
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The declaration is not allowed for the current scope |
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Initialization of static variables with the values of local variables is not allowed |
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Illegal declaration of an array of objects that do not have a default constructor |
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Initialization list allowed only for constructors |
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No function definition after initialization list |
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Initialization list is empty |
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Array initialization in a constructor is not allowed |
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Initializing members of a parent class in the initialization list is not allowed |
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Expression of the integer type expected |
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Memory required for the array exceeds the maximum value |
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Memory required for the structure exceeds the maximum value |
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Memory required for the variables declared on the global level exceeds the maximum value |
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Memory required for local variables exceeds the maximum value |
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Constructor not defined |
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Invalid name of the icon file |
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Could not open the icon file at the specified path |
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Reinitialization of a member in a class/structure constructor using the initialization list |
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Initialization of static members in the constructor initialization list is not allowed |
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Initialization of a non-static member of a class/structure on a global level is not allowed |
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The name of the class/structure method matches the name of an earlier declared member |
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The name of the class/structure member matches the name of an earlier declared method |
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Constructor or destructor cannot be static |
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Non-static member/method of a class or a structure cannot be accessed from a static function |
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An overload operation (+,-,[],++,-- etc.) is expected after the operator keyword |
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Not all operations can be overloaded in MQL5 |
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Definition does not match declaration |
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An invalid number of parameters is specified for the operator |
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Event handling function not found |
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Method cannot be exported |
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A pointer to the constant object cannot be normalized by a non-constant object |
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Class templates are not supported yet |
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Function template overload is not supported yet |
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Function template cannot be applied |
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Ambiguous parameter in function template (several parameter types can be applied) |
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Unable to determine the parameter type, by which the function template argument should be normalized |
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Incorrect number of parameters in the function template |
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Function template cannot be virtual |
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Function templates cannot be exported |
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Function templates cannot be imported |
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Structures containing the objects are not allowed |
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String arrays and structures containing the objects are not allowed |
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A static class/structure member must be explicitly initialized |
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Compiler limitation: the string cannot contain more than 65 535 characters |
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Inconsistent #ifdef/#endif |
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Object of class cannot be returned, copy constructor not found |
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Non-static members and methods cannot be used |
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OnTesterInit() impossible to use without OnTesterDeinit() |
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Redefinition of formal parameter '%s' |
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Macro __FUNCSIG__ and __FUNCTION__ cannot appear outside of a function body |
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Invalid returned type. For example, this error will be produced for functions imported from DLL that return structure or pointer. |
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Template usage error |
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Not used |
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Illegal syntax when declaring pure virtual function, only "=NULL" or "=0" are allowed |
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Only virtual functions can be declared with the pure-specifier ("=NULL" or "=0") |
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Abstract class cannot be instantiated |
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A pointer to a user-defined type should be applied as a target type for dynamic casting using the dynamic_cast operator |
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"Pointer to function" type is expected |
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Pointers to methods are not supported |
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Error – cannot define the type of a pointer to function |
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Type cast is not available due to private inheritance |
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A variable with const modifier should be initialized during declaration |
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Only methods with public access can be declared in an interface |
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Invalid nesting of an interface inside of another interface |
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An interface can only be derived from another interface |
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An interface is expected |
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Interfaces only support public inheritance |
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An interface cannot contain members |
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Interface objects cannot be created directly, only use inheritance |
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A specifier cannot be used in a forward declaration |
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Inheritance from the class is impossible, since it is declared with the final specifier |
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The final specifier can be applied only to virtual functions |
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The method marked by the override specifier actually does not override any base class function |
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A specifier is not allowed in defining a function, but only in declaring |
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Cannot cast the type to the specified one |
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The type cannot be used for a resource variable |
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Error in the project file |
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Cannot be used as a union member |
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Ambiguous choice for the name, the usage context should be explicitly defined |
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The structure cannot be used from DLL |
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Cannot call a function marked by the delete specifier |
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MQL4 is not supported. To compile this program, use MetaEditor from your MetaTrader 4 installation folder |