c++ - iostream linker error

I have some old C code that I would like to combine with some C++ code.

The C code used to have has the following includes:

#include 
#include 
#include 
#include "mysql.h"

Now I'm trying to make it use C++ with iostream like this:

#include 

#include 
#include 
#include 
#include "mysql.h"

But I keep getting the following linker errors when I compile:

[Linker error] undefined reference to `std::string::size() const'

[Linker error] undefined reference to `std::string::operator[](unsigned int) const'

[Linker error] undefined reference to `std::string::operator[](unsigned int) const'

[Linker error] undefined reference to `std::string::operator[](unsigned int) const'

[Linker error] undefined reference to `std::ios_base::Init::Init()'

[Linker error] undefined reference to `std::ios_base::Init::~Init()'

ld returned 1 exit status

How do I resolve this?

Edit: My compiler is Dev-C++ 4.9.9.2

Answer

The C string.h header and the C++ string header are not interchangeable.

Overall, though, your problem is that the file is getting properly compiled, but the wrong runtime library is getting linked in.

Dev-C++ uses GCC. GCC can correctly determine the language in a file based on file extension, but won't link the right runtime library in unless you specifically ask it to (-lstdc++ at the command line). Calling GCC as "g++" (or, in your case, "mingwin32-g++") will also get the right language and will link the needed library.