[Bug fortran/94788] [10 Regression] Severe regression leading to double free in tcache

[simon.brass at desy dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94788

--- Comment #7 from Simon Braß <simon.brass at desy dot de> ---
(In reply to Simon Braß from comment #6)
> (In reply to Richard Biener from comment #3)
> > Can you maybe bisect this to a specific (fortran) commit in GCC?
> 
> FYI, I'm hooking up with the bisect (I'm a colleague of Jürgen).
> I will post an update as fast as possible, reasonably, tomorrow.
> 
> Cheers,
> Simon.

After bisecting the commits of the last 8 days, the offending commit is:

Author: Thomas König <tkoenig@gcc.gnu.org>  2020-04-23 20:30:01
Committer: Thomas König <tkoenig@gcc.gnu.org>  2020-04-23 20:30:01
Parent: dcf69ac5448fd6a16137cfe9fe6deadd0ec0243d (coroutines, libstdc++-v3:
Update to n4861 C++20 DIS.)
Child:  bca558de2a24b2a78c6a321d6cec384e07759d77 (tree: Fix up get_narrower
[PR94724])
Branches: master, remotes/origin/devel/c++-coroutines, remotes/origin/master
Follows: misc/cutover-git
Precedes: 

    Fix PR 93956, wrong pointer when returned via function.

    This one took a bit of detective work.  When array pointers point
    to components of derived types, we currently set the span field
    and then create an array temporary when we pass the array
    pointer to a procedure as a non-pointer or non-target argument.
    (This is inefficient, but that's for another release).

    Now, the compiler detected this case when there was a direct assignment
    like p => a%b, but not when p was returned either as a function result
    or via an argument.  This patch fixes that.

    2020-04-23  Thomas Koenig  <tkoenig@gcc.gnu.org>

        PR fortran/93956
        * expr.c (gfc_check_pointer_assign): Also set subref_array_pointer
        when a function returns a pointer.
        * interface.c (gfc_set_subref_array_pointer_arg): New function.
        (gfc_procedure_use): Call it.

    2020-04-23  Thomas Koenig  <tkoenig@gcc.gnu.org>

        PR fortran/93956
        * gfortran.dg/pointer_assign_13.f90: New test.