In a header file of your C/C++ application or extension that includes the Tcl library, add these lines
#include <tcl.h> ... #if (TCL_MAJOR_VERSION < 8) #define Tcl_GetStringResult(interp) (interp->result) #endif
Why? This helps you deprecate direct access to interp->result so you can upgrade your code written for Tcl 7 so it can be used with Tcl 8, yet still work with Tcl 7.