The programmer has simply forgotten to define the object.Ĭonsider the following C++ program. This is the simplest reason for causing an “undefined reference” error. There are various reasons that cause an “undefined reference” error. As clear from definition, this error occurs in the later stages of the linking process. Thus when the linker cannot find the definition of a linked object, it issues an “undefined reference” error. We will discuss the possible causes of each of these errors and along with the precautions that we can take as a programmer to prevent these errors.Īn “Undefined Reference” error occurs when we have a reference to object name (class, function, variable, etc.) in our program and the linker cannot find its definition when it tries to search for it in all the linked object files and libraries. P.S.In this tutorial, we will discuss three types of errors that are critical from any C++ programmer’s point of view.

Did you use one outside the file it was created in incorrectly? I would give this page a good long read, and I'm sure your solution will be come rather obvious quickly =] Type or number of parameters, declaration without definition, function declaration and function definition are not the same, to name a few.įirst steps, go through your code, look at it for the obvious fixes is this function declaration the same as its definition and is its implementation scoped to its owning class (.h)/is the type the same? Check the scope of other variables that are used in places other than the same file. Sometimes this is either caused by scoping issues, not implementing functions with correct scope or owner, etc.

LNK2019 is an error the linker throws when it cannot resolve or find the definition of a function or variable.

Visual studio code c++ lnk2019