[Bug libstdc++/61217] New: pop_heap can't guarantee At most 2 * log(last - first) comparisons

["kan.liu.229 at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61217

            Bug ID: 61217
           Summary: pop_heap can't guarantee At most 2 * log(last - first)
                    comparisons
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: minor
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: kan.liu.229 at gmail dot com

pop_heap uses __adjust_heap to percolate down the hole. 

Inside __adjust_heap, it uses __value stores the value where was in position
__result(__last). After percolating down the hole, it uses __push_heap to push
back the __value. Process of percolatiing down takes 2 * logN comparasion, and
__push_heap takes another 2 * logN, 4 * logN in total, which excceed the
requirement "2 * log(last - first) comparisons" of standard.