[Bug fortran/41478] Corrupted memory using PACK for derived-types with allocated components

["burnus at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #8 from burnus at gcc dot gnu dot org  2009-10-01 21:21 -------
Minimal test case:

program main
type :: container_t
  integer, allocatable :: entry
end type container_t
type(container_t), dimension(1) :: a1, a2
allocate (a1(1)%entry, a2(1)%entry)
a2(1)%entry = 1
a1(1:1) = pack (a2(1:1), mask = [.true.])
end program main

I think what happens is the following: In pack one copies (memcpy) the bytes
from A2 to A1 - that whay A1 is a one-to-one copy of A2. At the end automatic
deallocation happens. First one frees (and nullifies) A1. Then one moves on to
A2, which is an exact copy of A1; thus A2%entry points to the same memory as
A1%entry - but the memory was already freed.

Thus we are obviously mishandling derived types with allocatable (or pointer)
components. Adding "print *, loc()" before and after pack illustrates this:
              6307888 ! loc(a2(1)%entry - before pack
              6307856 ! loc(a1(1)%entry - before pack
              6307888 ! loc(a2(1)%entry - after pack
              6307888 ! loc(a1(1)%entry - after pack

Actually, ifort shows the same result:
               7020672
               7020640
               7020672
               7020672
(and openf95 and pathf95 crash in pack).

While both NAG 95, sunf95 and g95 seem to handle it correctly:
 6722520
 6722456
 6722520
 6722456

That those handle it correctly, can also be seen if one adds:
  a1(1)%entry = 2
  print *, a2(1)%entry, a1(1)%entry
It should print "1 2" (as with NAG f95, g95 and sunf95) but gfortran and ifort
print "2 2".


-- 

burnus at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|function "pack" causes      |Corrupted memory using PACK
                   |double free violation       |for derived-types with
                   |                            |allocated components


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41478