Why is function definition not found?

Question

assembler

Hello, I'm writing my first masm calculator function that squares
a number.

//cpp-file
#include <iostream>

extern "C"
{
  int square(int num);
}

int main()
{
  int num;
  std::cin >> num;
  std::cout << square(num);
}

;masm32-file

.386
.model tiny, C

.code
    square PROC
         push    ebp
         mov     ebp, esp
         mov     eax, DWORD PTR [ebp+8]
         imul    eax, DWORD PTR [ebp+8]
         pop     ebp
         ret
    square ENDP
end

there are no errors, but the compiler says that the function has no definition, although it is in the asm file, how can I fix this

Answer 1

the function does not have a definition, although it is in the asm file, how can I fix this

change in the assembler source square PROCto square PROC PUBLIC.
Make sure that the assembler source is compiled and linked with the project.