Name Decoration

Name decoration usually refers to C++ naming conventions, but can apply to a number of C cases as well. By default, C++ uses the function name, parameters, and return type to create a linker name for the function. Consider the following function:

void CALLTYPE test(void)

The following table shows the linker name for various calling conventions.

Calling convention extern "C" or .c file .cpp, .cxx or /TP
C naming convention (__cdecl) _test ?test@@ZAXXZ
Fastcall naming convention (__fastcall) @test@0 ?test@@YIXXZ
Standard Call naming convention (__stdcall) _test@0 ?test@@YGXXZ
Vectorcall naming convention (__vectorcall) test@@0 ?test@@YQXXZ

Use extern "C" to call a C function from C++. Extern "C" forces use of the C naming convention for non-class C++ functions. Be aware of compiler switches /Tc or /Tp, which tell the compiler to ignore the filename extension and compile the file as C or C++, respectively. These options may cause names you do not expect.

Having function prototypes that have mismatched parameters can also cause this error. Name decoration incorporates the parameters of a function into the final decorated function name. Calling a function with the parameter types that do not match those in the function declaration may also cause LNK2001.

There is currently no standard for C++ naming between compiler vendors or even between different versions of a compiler. Therefore linking object files compiled with other compilers may not produce the same naming scheme and thus causes unresolved externals.

See Also

Linker Tools Error LNK2001