c++ - Returning Strings from DLL Functions

Question

For some reason, returning a string from a DLL function crashes my program on runtime with the error Unhandled exception at 0x775dfbae in Cranberry Library Tester.exe: Microsoft C++ exception: std::out_of_range at memory location 0x001ef604...

I have verified it's not a problem with the function itself by compiling the DLL code as an .exe and doing a few simple tests in the main function.

Functions with other return types (int, double, etc.) work perfectly.

• Why does this happen?
• Is there a way to work around this behavior?

Source code for DLL:

// Library.h
#include <string>

std::string GetGreeting();

.

// Library.cpp
#include "Library.h"

std::string GetGreeting()
{
    return "Hello, world!";
}

Source code for tester:

// Tester.cpp
#include <iostream>
#include <Library.h>

int main()
{
    std::cout << GetGreeting()
}

EDIT: I'm using VS2010.

---

Conclusion

A workaround is to make sure the library and source are compiled using the same compiler with the same options, etc.

Answer 1

This occurs because you're allocating memory in one DLL (using std::string's constructor), and freeing it in another DLL. You can't do that because each DLL typically sets up it's own heap.