[Bug libstdc++/89763] New: Making iterator's operator== breaks existing code

[dan at stahlke dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89763

            Bug ID: 89763
           Summary: Making iterator's operator== breaks existing code
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dan at stahlke dot org
  Target Milestone: ---

gcc 9 has made operator== and operator!= free functions for std::map (and
probably other) iterators.  Probably this is considered an implementation
detail and not a violation of the standard, but I thought I'd bring it to your
attention that this breaks CINT.

CINT does things like this:

./src/gcc3strm.cxx:     
G__letint(result7,103,(long)((fpos<mbstate_t>*)(G__getstructoffset()))->operator==(*(fpos<mbstate_t>*)libp->para[0].ref));
./src/Apiifold.cxx:     
G__letint(result7,105,(long)((G__ClassInfo*)(G__getstructoffset()))->operator==(*(G__ClassInfo*)libp->para[0].ref));
./src/Apiifold.cxx:     
G__letint(result7,105,(long)((G__TypeInfo*)(G__getstructoffset()))->operator==(*(G__TypeInfo*)libp->para[0].ref));
./src/Apiif.cxx:     
G__letint(result7,105,(long)((G__ClassInfo*)(G__getstructoffset()))->operator==(*(G__ClassInfo*)libp->para[0].ref));
./src/Apiif.cxx:     
G__letint(result7,105,(long)((G__TypeInfo*)(G__getstructoffset()))->operator==(*(G__TypeInfo*)libp->para[0].ref));

Given that CINT is no longer supported, CERN is not likely to release any
patches for this.

Here is a standalone demonstration of the issue:

#include <map>

bool f()
{
    std::map<int, int> m;
    auto it = m.begin();
    return it.operator==(it);
}