[Bug libstdc++/72847] New: vector<bool> copy-assignment basic exception safety

["dyp-cpp at gmx dot net" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=72847

            Bug ID: 72847
           Summary: vector<bool> copy-assignment basic exception safety
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dyp-cpp at gmx dot net
  Target Milestone: ---

vector<bool>'s copy-assignment operator uses a very simple algorithm if
resizing is required: first, free the current allocation, then create a new
allocation. The pointer data member that holds the allocation is not touched by
the first step, then assigned-to by the second step. Therefore, if the second
step (the allocation) fails via exception, that pointer (_M_end_of_storage -
size()) is dangling. Destruction of a vector<bool> in such a state leads to a
double deletion.