Weak symbol in VC

msvc_weak.cpp

#include <stdio.h>

extern const char * pWeakValue;
static const char * pDefaultWeakValue = "nullptr";
// #pragma comment(linker, "/alternatename:_pWeakValue=_pDefaultWeakValue")

#define DEFINE_WEAK(Type, Name) \
    extern Type Name; \
    static Type Name##Default; \
    __pragma(warning(push)) \
    __pragma(comment(linker, "/alternatename:_" #Name "=_" #Name "Default"))

#define PRAGMA_ENABLE_SHADOW_VARIABLE_WARNINGS \
    __pragma(warning(pop))

PRAGMA_ENABLE_SHADOW_VARIABLE_WARNINGS

DEFINE_WEAK(int, N);

int main() {
    extern int X;
    printf("pWeakValue=%p\n", &X);
}