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 declaration:

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
Fast call naming convention (__fastcall)	@test@0	?test@@YIXXZ
Standard call naming convention (__stdcall)	_test@0	?test@@YGXXZ
Vector call 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 linker names you don't 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 don't match those in the function declaration may also cause LNK2001.

There are currently no standards for C++ naming between compiler vendors or even between different versions of a compiler. Linking object files compiled by other compilers may not produce the same naming scheme, and can cause unresolved externals.

See also

Linker Tools Error LNK2001