The MI command "var-info-path-expression varN.[N]" for a set:<int> returns an empty string "" where it should return "int". This is likely related to but 10252, which concerns var-info-path-expression for vectors. I looked at the cplus_path_expr_of_child() function in varobj.c, and its "struct varobj *child" argument actually contains the correct type, but the function delegates its work to cplus_describe_child(), which is looking at the set/map object as a C++ class rather than a collection. For indices > 2, gdb gets an out of bounds exception for the index and exits.
This is really the same as 10252. The issue is that we need to give the printers a way to supply the path expression to varobj. *** This bug has been marked as a duplicate of 10252 ***