[Bug fortran/66775] New: Allocatable function result type(t) produces segfault when uninitialized

[vehre at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66775

            Bug ID: 66775
           Summary: Allocatable function result type(t) produces segfault
                    when uninitialized
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vehre at gcc dot gnu.org
  Target Milestone: ---

Created attachment 35917
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35917&action=edit
Full pseudo code of failing example.

The following code produces a segfault:

! { dg-do run }

module test_alloc_func_mod
  implicit none

  type t
    integer :: i = 5
  end type

contains

  type(t) function t_init() ! { dg-warning "not set" }
    allocatable :: t_init
  end function

end module test_alloc_func_mod

program test_alloc_func
  use test_alloc_func_mod

  type(t), allocatable :: temp

  temp = t_init() ! <-- This derefs a null-pointer currently
  if (allocated (temp)) call abort()
end program


The pseudo code in question is:
t_init ()
{
  struct t * __result_t_init;

  __result_t_init = 0B;    // Setting NULL-pointer.
  return __result_t_init;
}

for t_init, and reduced to the essential line (full pseudo code is attached)

  struct t * temp;
  struct t * D.3388;
  temp = (struct t *) __builtin_malloc (4);
  D.3388 = t_init ();
  *temp = *D.3388;      // D.3388 is NULL; dereferencing it here is hazardous.

This error was experienced during patching of pr58586.