What It Means & How to Fix It in UE5 C++

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🧠 Why You’re Seeing This Error

LNK2016 is a linker error that means a symbol (usually a variable or function) has been defined as absolute in multiple object files — which is illegal.

This is extremely rare in standard UE5 development but can happen if you’re using custom linker directives, __declspec(allocate(...)), or inline assembly, or if a library is compiled with conflicting settings.

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💥 Example Error Message

error LNK2016: absolute symbol '??_C@_01@...' defined in multiple objects: MyActor.cpp.obj and AnotherFile.cpp.obj

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🛠️ Common UE5 Triggers

• Declaring global/static variables with const in headers without inline or extern
• Using #pragma data_seg or __declspec(allocate(...)) to put variables in specific memory segments
• Mixing compiler or linker settings across modules or third-party libraries
• Including a .cpp file in another .cpp file (instead of proper header include)

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✅ How to Fix LNK2016 in UE5 – Step-by-Step

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✔️ 1. Avoid Defining const Globals in Headers Without inline or extern

Wrong:

// In a header
const int32 GlobalValue = 42; // ❌ Defined in every translation unit

Fix:

// In header
extern const int32 GlobalValue;

// In one .cpp file
const int32 GlobalValue = 42; // ✅ Single definition

Or use inline (C++17+):

inline constexpr int32 GlobalValue = 42; // ✅ OK in headers

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✔️ 2. Never include .cpp Files

Never do this:

#include "MyActor.cpp" // ❌ Triggers multiple definitions

Instead, only include header files.

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✔️ 3. Don’t Mix Linker Sections or Use Absolute Symbols Without Care

Avoid low-level memory directives like:

#pragma data_seg(".MYSEG")
__declspec(allocate(".MYSEG")) int32 GlobalData = 1; // ⚠️ Can trigger LNK2016

Unless you absolutely know what you’re doing — this is not typical in UE5 development.

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✅ Summary: How to Fix LNK2016 in UE5

Cause	Fix Example
Const global defined in header	Use extern in header, define once in .cpp
Misuse of __declspec(allocate)	Avoid custom memory segment directives unless required
Including .cpp files	Only include .h files in other sources
Compiler/linker setting mismatch	Ensure consistent build settings across all modules/libraries