Windows 10, Visual Studio C++

I can successfully load an .exe file and find exported functions in it.
However, when I try to execute a function in the loaded .exe file I get an Access Violation.

The ExeExport.exe to be loaded and called:

#include <string>

extern "C" // Avoid name mangling
{
    __declspec(dllexport) int MyExternal()
    {
        std::string s;  // Access violation here
        return 0;
    }
}
int main()  // Dummy, not called
{
    return 0;
}

The .exe that loads and calls ExeExport:

#include <windows.h>
#include "stdio.h"

typedef int (*StartExternal)();

int main()
{
    HMODULE hModule;

    hModule = LoadLibrary("ExeExport.exe");
    StartExternal startExternal = (StartExternal)GetProcAddress(hModule, "MyExternal");
    if (startExternal)
        printf("Success: %dn", startExternal());   // To here it works but crashes in MyExternal()
    else
        printf("Error %dn", GetLastError());
    FreeLibrary(hModule);
    return 0;
}

I get Access Violation when executing this line in ExeExport.exe:

std::string s;  // Access violation here

I suspect it has something to do with the fact that ExeExport is loaded but not executed or initialized
but I don’t what to call to initialize it.