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.

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[Category Porting]