[Bug fortran/53015] New: free_pi_tree(): Unresolved fixup is back

["brainschrat at gmx dot de" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53015

             Bug #: 53015
           Summary: free_pi_tree(): Unresolved fixup is back
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: brainschrat@gmx.de


Bug 47546 was fixed some time ago, but I get "Internal error - free_pi_tree():
Unresolved fixup" all over the place again, with versions 4.6.2, 4.7.0 and
4.8.0 of gfortran from svn.

I have a project that uses many Fortran 2003 features, like polymorphism,
type-bound procedures etc. Some sub-classes are in different modules, which did
not cause problems before and is supported by the standard. I also use OpenMPI
and PETSc, so there are some preprocessor macros. The code compiles and runs
fine withe the Intel Fortran compiler, which is the only other Fortran compiler
I have access to.

Like in 47546 , the issue is very elusive: Sometimes it happens when compiling
the modules themselves, sometimes when compiling a program that uses the
modules. Sometimes commenting out one arbitrary line of code fixes the error,
and it remains fixed after putting the line in again. Sometimes removing all
modules and object files and re-compiling (even files that remain unchanged)
fixes the error. On some days, I cannot compile my code at all, but using an
different version of gfortran works. But then the issue pops up again after
adding a new line of code.

Because of this, I am not able to provide a test case as I have no clue what
the error means and the rest of the case seems non-deterministic. Maybe someone
can assist me in narrowing down the possibilities.