https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110626
Bug ID: 110626 Summary: Duplicated finalization in derived Product: gcc Version: 13.1.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: fortran Assignee: unassigned at gcc dot gnu.org Reporter: habbit89 at hotmail dot es Target Milestone: --- Created attachment 55520 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=55520&action=edit Example module and test program After the changes to finalization in gfortran 13 there seems to be an issue under the following circumstances: * A derived type A has custom assignment and finalization * It is used as a component (or as a base) of another type B Then, assignment of type B will call the assignment of A only once, but the final subroutine twice, which breaks resource holding code such as reference counting. The example has two subroutines, one where two objects of type A are used directly, and one where objects of type B are used. In both cases, o1 is initialized to some value, then it is copied to o2, then o2 is overwritten again. The expected result would, in both cases, be a finalization of the target before the assignment, then the assignment call. Compiling and running the example will give the following correct results on gfortran 11 > $ gfortran-11 -Wall -Wextra -o a-11.out testmod.f90 > $ ./a-11.out > o1: 7FFFA5E1BD2C > o2: 7FFFA5E1BD28 > dtor: -1 7FFFA5E1BD28 > copy: 15 from 7FFFA5E1BD2C to 7FFFA5E1BD28 > dtor: 16 7FFFA5E1BD28 > copy: 15 from 7FFFA5E1BD2C to 7FFFA5E1BD28 > dtor: 16 7FFFA5E1BD28 > dtor: 15 7FFFA5E1BD2C > objects of type B in subroutine > o1: 7FFFA5E1BD2C > o2: 7FFFA5E1BD28 > dtor: 15 7FFFA5E1BD28 > copy: 15 from 7FFFA5E1BD2C to 7FFFA5E1BD28 > dtor: 15 7FFFA5E1BD28 > copy: 15 from 7FFFA5E1BD2C to 7FFFA5E1BD28 > dtor: 16 7FFFA5E1BD28 > dtor: 15 7FFFA5E1BD2C But the following *invalid* results in gfortran 13: > $ gfortran-13 -Wall -Wextra -o a-13.out testmod.f90 > $ ./a-13.out > objects of type A in subroutine > o1: 7FFFCEEDBC2C > o2: 7FFFCEEDBC28 > dtor: -1 7FFFCEEDBC28 > copy: 15 from 7FFFCEEDBC2C to 7FFFCEEDBC28 > dtor: 16 7FFFCEEDBC28 > copy: 15 from 7FFFCEEDBC2C to 7FFFCEEDBC28 > dtor: 16 7FFFCEEDBC28 > dtor: 15 7FFFCEEDBC2C > objects of type B in subroutine > o1: 7FFFCEEDBC24 > o2: 7FFFCEEDBC20 > dtor: -1 7FFFCEEDBC20 > dtor: -1 7FFFCEEDBC2C > copy: 15 from 7FFFCEEDBC24 to 7FFFCEEDBC2C > dtor: 16 7FFFCEEDBC20 > dtor: 16 7FFFCEEDBC28 > copy: 15 from 7FFFCEEDBC24 to 7FFFCEEDBC28 > dtor: 16 7FFFCEEDBC20 > dtor: 15 7FFFCEEDBC24 The part where objects of type A are used directly works in both versions. However, when objects of type *B* are used, gfortran 13 shows the following behaviour: * There seems to be a "shadow"/temporary object created at a different location which is neither o1 nor o2, probably at a stack address. * The assignment operator runs only once, from o1 to this shadow object. * The value is then apparently blitted onto/used for o2, which might be okay except that... * Before the next assignment, the final subroutine of A runs *twice*, once with the actual o2 and once with this shadow object. Thus, given that the assignment code runs once but the finalization runs *twice*, using this scheme to hold resources (e.g. via ref counting) breaks. In particular, it is very weird that I am _assuming_ that the two separate finalizations may be conceptually come from 1. the overall finalization of B before the assignment, and 2. the intent(out) for A in subroutine copy. However, both calls use the values _prior_ to the finalization (since it sets the value to -2 but the calls both print 16)