Create a c++ library without a class name - c++

Question

I'm trying to create a C++ dynamic library that won't have a class. I'd like it to work similar to how you can include <string.h> and call strlen directly.
I can create a class that will compile, but won't link correctly with my library.
Here's the test library I'm working on now:
Header
#ifndef _DLL_H_
#define _DLL_H_
BOOL APIENTRY DllMain(HANDLE hModule, DWORD dwReason, LPVOID lpReserved);
extern "C" __declspec(dllexport) int testMethod(int a);
#endif
Cpp
#include "dll.h"
int testMethod(int num)
{
std::cout << "test message" << std::endl;
return 1;
}
BOOL APIENTRY DllMain (HINSTANCE hInst, // Library instance handle. ,
DWORD reason, // Reason this function is being called. ,
LPVOID reserved) // Not used. )
{
switch (reason)
{
case DLL_PROCESS_ATTACH:
break;
case DLL_PROCESS_DETACH:
break;
case DLL_THREAD_ATTACH:
break;
case DLL_THREAD_DETACH:
break;
}
// Returns TRUE on success, FALSE on failure
return TRUE;
}
Finally, here's the class I'm using to test the Dll, which is told to link against the lib mingw outputs
#include <iostream>
#include "../Dll/dll.h"
using namespace std;
int main(int argc, char *argv[])
{
testMethod(5);
}
I haven't used C++ in about a year so I'm pretty rusty

Answer 1

extern "C" __declspec(dllexport) int testMethod(int a);
This needs to be dllimport in the application which is linking against the DLL. Most people compile their DLL with a #define which controls if it is an export or an import.
#ifdef INSIDE_MYDLL
#define MYDLLAPI __declspec(dllexport)
#else
#define MYDLLAPI __declspec(dllimport)
#endif
extern "C" MYDLLAPI int testMethod(int a);