iostream linker error
c, c++, iostream, linker
Solution
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.
Problem
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 <windows.h> #include <stdio.h> #include <string.h> #include "mysql.h" ``` Now I'm trying to make it use C++ with iostream like this: ``` #include <windows.h> #include <stdio.h> #include <string> #include <iostream> #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