Today I noticed the StringObj manpage (from tcl) says that the bytes
that represent an tcl object should be treated as read-only (although it
uses char *) so this issue1028.diff may very well cause a segfault at
some point.

I'm attaching a new patch that fixes this and also uses
Tcl_GetStringFromObj, instead of directly accessing the bytes member of
a tcl object, so we know its string representation is not invalid.