[Bug c++/60750] [4.8/4.9 Regression] double free after std::move on string inside throw when compiled with optimization

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60750

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org

--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
For some reason thrower() is pure(!?) (no vdef) and thus FRE maybe does some
invalid transform.  Oh.

      /* A 'pure' or a 'const' function never call-clobbers anything.
         A 'noreturn' function might, but since we don't return anyway
         there is no point in recording that.  */
      if (!(call_flags & (ECF_PURE | ECF_CONST | ECF_NORETURN)))
        add_virtual_operand (fn, stmt, opf_def);

that's of course "true", but only if the function doesn't return otherwise
(like via EH):

  # VUSE <.MEM_11>
  thrower (&D.20915);
;;    succ:       5 (EH)

it doesn't save us much when we remove that optimization (we "save" a
VDEF), but I can imagine other analyses being confused about this because
generally "no VDEF" -> doesn't store.