Good morning, when writing a reference counting scheme, I cam across this slightly intricate bug. I suspect this is related to a problem in the type bound assignment but I could not pin it down. The problem: Type(Inner) has type bound assignment and Final. -assignment associates output reference counter to input reference counter and incrments -final decrements reference counter and deallocates reference count pointer when 0 Type(outer) has type(inner) as member. If Type(inner) is used by itself everything works correctly However, if assignment of type(outer) to type(outer) is made, an additional finalization is invoked (the third with an unassociated reference counter). Here is the simplest test code I could produce: ! ============================== BEGIN TEST CODE ======================== MODULE Classes IMPLICIT NONE TYPE :: Inner INTEGER, POINTER :: icount CONTAINS PROCEDURE :: init PROCEDURE :: assignMe GENERIC :: assignment(=) => assignMe FINAL :: deleteIt END TYPE TYPE Outer TYPE(Inner) :: ext END TYPE CONTAINS SUBROUTINE init(self) CLASS(Inner), INTENT(INOUT) :: self ALLOCATE(self%icount) self%icount=1 END SUBROUTINE ! Destrutor, if data is assigned decrement counter and delete once we reach 0 SUBROUTINE deleteIt(self) TYPE(Inner) :: self WRITE(*,*)"FINAL CALLED with icount =", self%icount, "LOC =",LOC(self%icount) self%icount=self%icount-1 IF(self%icount<=0)THEN ! usually == 0 but <=0 better shows the problem self%icount=-100 WRITE(*,*)" DEALLOCATING ICOUNT at LOC=", LOC(self%icount) DEALLOCATE(self%icount) END IF END SUBROUTINE ! The basic assigment routine, set pointer to input data pointer and increment counter SUBROUTINE assignMe(self, input) CLASS(Inner), INTENT(INOUT) :: self CLASS(Inner), INTENT(IN) :: input self%icount => input%icount self%icount=self%icount+1 END SUBROUTINE END MODULE PROGRAM test USE Classes IMPLICIT NONE WRITE(*,*)"Direct Call on inner performs only 2 FINALIZATIONS" BLOCK TYPE(Inner) :: inner1, inner2 CALL inner1%init() inner2=inner1 END BLOCK WRITE(*,*) WRITE(*,*)"Indirect Call, 3 FINALIZATIONS, last with dangling pointer on TYPE(inner)%icount" BLOCK TYPE(Outer) :: Outer1, Outer2 CALL Outer1%ext%init() Outer2=Outer1 END BLOCK END !========================= END TEST CODE ================================ Note: in Final comparison is for <= 0 to cause double free best regards Flo
Confirmed.
This might be related to bug 88735, at least the ingredients are very similar and final routine is called wrongly.
The master branch has been updated by Paul Thomas <pault@gcc.gnu.org>: https://gcc.gnu.org/g:d7caf313525a46f200d7f5db1ba893f853774aee commit r13-6747-gd7caf313525a46f200d7f5db1ba893f853774aee Author: Paul Thomas <pault@gcc.gnu.org> Date: Sat Mar 18 07:56:23 2023 +0000 Fortran: Fix bugs and missing features in finalization [PR37336] 2023-03-18 Paul Thomas <pault@gcc.gnu.org> gcc/fortran PR fortran/103854 PR fortran/96122 PR fortran/37336 * class.cc (finalize_component): Include the missing arguments in the call to the component's finalizer wrapper. (has_finalizer_component): Do not return true for procedure pointer components. (finalizer_insert_packed_call): Remove the redundant argument in the call to the final subroutine. (generate_finalization_wrapper): Add support for assumed rank finalizers. (gfc_may_be_finalized): New helper function. * dump-parse-tree.cc (write_proc): Whitespace. * gfortran.h : Add prototype for gfc_may_be_finalized. * resolve.cc (resolve_function): Correct derived types that have an incomplete namespace. (resolve_where, gfc_resolve_where_code_in_forall, gfc_resolve_forall_body, gfc_resolve_code): Check that the op code is still EXEC_ASSIGN. If it is set lhs to must finalize. (is_finalizable_type): New function. (generate_component_assignments): Set must_finalize if needed. (gfc_resolve_finalizers): Error if assumed rank finalizer is not the only one. Warning on lack of scalar finalizer modified to account for assumed rank finalizers. (generate_final_call): New function. (generate_component_assignments): Enclose the outermost call in a block to capture automatic deallocation and final calls. Set must_finalize as required to satisfy the standards. Use an explicit pointer assignment for pointer components to capture finalization of the target. Likewise use explicit assignment for allocatable components. Do not use the temporary copy of the lhs in defined assignment if the component is allocatable. Put the temporary in the same namespace as the lhs symbol if the component may be finalized. Remove the leading assignment from the expansion of assignment of components that have their own defined assignment components. Suppress finalization of assignment of temporary components to the lhs. Make an explicit final call for the rhs function temporary if it exists. (gfc_resolve_code): Set must_finalize for assignments with an array constructor on the rhs. (gfc_resolve_finalizers): Ensure that an assumed rank finalizer is the only finalizer for that type and correct the surprising warning for the lack of a scalar finalizer. (check_defined_assignments): Handle allocatable components. (resolve_fl_derived): Set referenced the vtab for use associated symbols. (resolve_symbol): Set referenced an unreferenced symbol that will be finalized. * trans-array.cc (gfc_trans_array_constructor_value): Add code to finalize the constructor result. Warn that this feature was removed in F2018 and that it is suppressed by -std=2018. (trans_array_constructor): Add finalblock, pass to previous and apply to loop->post if filled. (gfc_add_loop_ss_code): Add se finalblock to outer loop post. (gfc_trans_array_cobounds, gfc_trans_array_bounds): Add any generated finalization code to the main block. (structure_alloc_comps): Add boolean argument to suppress finalization and use it for calls from gfc_deallocate_alloc_comp_no_caf. Otherwise it defaults to false. (gfc_copy_alloc_comp_no_fini): New wrapper for structure_alloc_comps. (gfc_alloc_allocatable_for_assignment): Suppress finalization by setting new arg in call to gfc_deallocate_alloc_comp_no_caf. (gfc_trans_deferred_array): Use gfc_may_be_finalized and do not deallocate the components of entities with a leading '_' in the name that are also marked as artificial. * trans-array.h : Add the new boolean argument to the prototype of gfc_deallocate_alloc_comp_no_caf with a default of false. Add prototype for gfc_copy_alloc_comp_no_fini. * trans-decl.cc(init_intent_out_dt): Tidy up the code. * trans-expr.cc (gfc_init_se): Initialize finalblock. (gfc_conv_procedure_call): Use gfc_finalize_tree_expr to finalize function results. Replace in-line block for class results with call to new function. (gfc_conv_expr): Finalize structure constructors for F2003 and F2008. Warn that this feature was deleted in F2018 and, unlike array constructors, is not default. Add array constructor finalblock to the post block. (gfc_trans_scalar_assign): Suppress finalization by setting new argument in call to gfc_deallocate_alloc_comp_no_caf. Add the finalization blocks to the main block. (gfc_trans_arrayfunc_assign): Use gfc_assignment_finalizer_call and ensure that finalization occurs after the evaluation of the rhs but using the initial value for the lhs. Finalize rhs function results using gfc_finalize_tree_expr. (trans_class_assignment, gfc_trans_assignment_1): As previous function, taking care to order evaluation, assignment and finalization correctly. * trans-io.cc (gfc_trans_transfer): Add the final block. * trans-stmt.cc (gfc_trans_call, gfc_trans_allocate): likewise. (trans_associate_var): Nullify derived allocatable components and finalize function targets with defined assignment components on leaving the block scope. (trans_allocate): Finalize source expressions, if required, and set init_expr artificial temporarily to suppress the finalization in gfc_trans_assignment. * trans.cc (gfc_add_finalizer_call): Do not finalize the temporaries generated in type assignment with defined assignment components. (gfc_assignment_finalizer_call): New function. (gfc_finalize_tree_expr): New function. * trans.h: Add finalblock to gfc_se. Add the prototypes for gfc_finalize_tree_expr and gfc_assignment_finalizer_call. gcc/testsuite/ PR fortran/64290 * gfortran.dg/finalize_38.f90 : New test. * gfortran.dg/finalize_38a.f90 : New test. * gfortran.dg/allocate_with_source_25.f90 : The number of final calls goes down from 6 to 4. * gfortran.dg/associate_25.f90 : Remove the incorrect comment. * gfortran.dg/auto_dealloc_2.f90 : Change the tree dump expr but the final count remains the same. * gfortran.dg/unlimited_polymorphic_8.f90 : Tree dump reveals foo.1.x rather than foo.0.x PR fortran/67444 * gfortran.dg/finalize_39.f90 : New test. PR fortran/67471 * gfortran.dg/finalize_40.f90 : New test. PR fortran/69298 PR fortran/70863 * gfortran.dg/finalize_41.f90 : New test. PR fortran/71798 * gfortran.dg/finalize_42.f90 : New test. PR fortran/80524 * gfortran.dg/finalize_43.f90 : New test. PR fortran/82996 * gfortran.dg/finalize_44.f90 : New test. PR fortran/84472 * gfortran.dg/finalize_45.f90 : New test. PR fortran/88735 PR fortran/93691 * gfortran.dg/finalize_46.f90 : New test. PR fortran/91316 * gfortran.dg/finalize_47.f90 : New test. PR fortran/106576 * gfortran.dg/finalize_48.f90 : New test. PR fortran/37336 * gfortran.dg/finalize_49.f90 : New test. * gfortran.dg/finalize_50.f90 : New test. * gfortran.dg/finalize_51.f90 : New test.
Hi Florian, I am closing this as fixed, even though it runs to the third finalization and then segfaults, because both nagfor and ifort behave in the same way. The dump of the code shows that Outer2 is finalized before the assignment and that both Outer1 and Outer2 are finalized on leaving the block scope. Thus, alll is as it should be. Default initializing icount to NULL(), guarding for unassociated icount in deleteIt gets rid of the segfault. Thanks for the report. Paul