UE5 C++ Compilation Errors – Troubleshooting & Fix Guide
If you’re working with C++ in Unreal Engine 5, you’ve probably run into frustrating compilation errors that stop your project from building. This section is dedicated to helping you identify, understand, and fix the most common UE5 C++ compilation errors, whether you’re building from the UE5 Editor, Visual Studio, or compiling a Shipping build.
We cover:
- Missing include files, unresolved external symbols, and undefined identifiers
- Circular dependencies and incorrect module references in your Build.cs files
- Linker errors (LNK2019, LNK2001) that happen when symbols aren’t linked properly
- Incorrect UCLASS, USTRUCT, UENUM macros that break Unreal’s reflection system
- Version mismatches, especially after upgrading from UE4 to UE5
- Hot Reload issues and IntelliSense false errors inside Visual Studio
Whether you’re a beginner or an advanced UE5 developer, this guide will help you troubleshoot Unreal C++ compiler errors, speed up your debugging process, and get your project compiling cleanly.
Articles
- LNK2019: Unresolved External Symbol – Missing Function Implementation
- C2061: Syntax Error – Identifier Not Found
- C2065: Undeclared Identifier In UE5
- C2146: Syntax Error – Missing ‘;’ Before Identifier
- C4430: Missing Type Specifier – Int Assumed in UE5
- Error C1083 – Include File Not Found
- Missing GENERATED_BODY() (Error C2338)
- Missing Module Dependency (Error C4668)
- Unreal Header Tool (UHT) Module Error
- C2039: Not a Member of Namespace
- C1010: Unexpected End of File
- C2059: Syntax Error – Token in UE5
- C2061: Syntax Error – Unexpected Token
- C2230: Could Not Find Class Declaration
- C2248: Cannot Access Private Member
- C2511: Overriding Function Missing ‘override’ Specifier
- C2664: Cannot Convert Parameter
- C4996: ‘Function’ Declared Deprecated – UE5 Warning
- UE4497: Member Variable Not Initialized
- C2143: Syntax Error Missing
- C2144: Syntax error: missing ‘;’ before type
- C2236: Unexpected token ‘identifier’
- C2238: Unexpected token(s) preceding ‘;’
- C2243: ‘type conversion’: conversion exists but is inaccessible
- C2275: Illegal use of this type as an expression
- C2338: Static assertion failed in UE5
- C2440: Cannot convert from ‘type1’ to ‘type2’
- C2447: Missing function header
- C2511: Overriding virtual function missing ‘override’ specifier
- C2556: Function Declaration Is Different from Previous Declaration
- C2664: Cannot convert argument N from ‘type1’ to ‘type2’
- C2678 UE5: Binary operator: no operator found
- C2679: Binary operator: no operator found
- C2681 UE5: Invalid expression type for dynamic_cast
- C2782: Template parameter not used in parameter types in UE5
- C2784 UE5: Could not deduce template argument
- C4244: Conversion from ‘type1’ to ‘type2’, possible loss of data
- ❗ LNK2005: Symbol Already Defined – UE5 Linker Error Explained & How to Fix It
- C2057: Expected Constant Expression
- C2228: Left of ‘.member’ Must Have Class/Struct/Union
- C2327: ‘identifier’ Is Not a Type Name, Static, or Data Member
- C2328: Member Function Not Found
- C2512: No Appropriate Default Constructor Available
- C2589: ‘token’ – Illegal Token on Right Side of ‘::’
- C2601: ‘Function’ Cannot Be Initialized Because It Is Not Reachable
- C2660: Function doesn’t take N arguments
- C2662: Cannot Convert ‘this’ Pointer from ‘const Type’ to ‘Type &’
- C2663: Function Does Not Take the Number of Arguments Provided
- C2672: No Matching Overloaded Function Found
- C2872: ‘Identifier’ – Ambiguous Symbol in UE5
- C4005: ‘MACRO’ – UE5 Macro Redefinition
- C4668: ‘MACRO’ Is Not Defined as a Preprocessor Macro
- LNK1120 – UE5 Unresolved externals
- LNK2001: UE5 Unresolved External Symbol
- LNK2001: Unresolved External Symbol in UE5
- LNK4217: Locally Defined Symbol Imported in Another Module
- C2027: Use of Undefined Type
- C3861: Identifier Not Found
- LNK2016 UE5: Absolute Symbol Defined Multiple Times
- LNK2022: Metadata Operation Failed
- LNK2028: Unresolved Token (Symbol)
- Compilation Error: Could Not Find a Function Named ‘IsHeadMountedDisplayEnabled’ in ‘FirstPersonHUD’
