从 ASM（64 位汇编）C++ 中获取价值

Question

I am having problems with Assembly & C++, I was just playing around and learning how to use Assembly in C++ but I couldn't seem to be able to get a function in asm to return the value I wanted it to. My C++ code:

#include <iostream>

using namespace std;

extern "C" int GetValueFromASM();

int main()
{
    cout << GetValueFromASM();
    cin.ignore();
    return 0;
}

And my asm code in another file:

.code
GetValueFromASM proc
    move eax, 489
    ret
GetValueFromASM endp

end

The errors I recieve are

Error2 error LNK1120: 1 unresolved externals    
Error1 error LNK2019: unresolved external symbol GetValueFromASM referenced in function main

I am using Visual Studio 2013 & and masm for the assembly & I selected x64 in the Configuration Manager, just some extra info there.

I would be very thankful for any help as I am new to asm.

Answer 1

One way

You have to change this:

extern "C" int GetValueFromASM();

to his:

extern "C" int __stdcall GetValueFromASM();

Another way

Or in asm-file define this

.model flat, c

instead of this

.model flat, stdcall