[Bug fortran/125998] Wrong shape/bounds for TRANSPOSE() passed to a CONTIGUOUS dummy argument

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125998

--- Comment #17 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Mikael Morin <mikael@gcc.gnu.org>:

https://gcc.gnu.org/g:6658c2347d4a88d82e80f44a450b14dc7287bcef

commit r17-2111-g6658c2347d4a88d82e80f44a450b14dc7287bcef
Author: Mikael Morin <mikael@gcc.gnu.org>
Date:   Fri Jul 3 11:16:04 2026 +0200

    fortran: Don't reuse original descriptors for packed arrays [PR125998]

    Don't try to reuse the original descriptor when creating a descriptor
    for packed data in gfc_conv_array_parameter.

    For a non-transposed array (anything but TRANSPOSE(VAR)) the original
    descriptor was reused, and only the data was reset to the result of
    packing.  This is wrong because the original descriptor can be
    non-contiguous, it can't be correct as the descriptor of packed data.
    In the testcase, a dummy array associated with a transposed array actual
    argument matches this case.  Reusing the descriptor in that case would
    cause the packed data to be used transposed, that is not in the normal
    array element order.  This change removes this case to always fallback
    to what was previously the transposed case (see next).

    For the transposed case (TRANSPOSE(VAR)), the full dimensions of the
    original untransposed descriptor were reused (in other words, the
    dimensions of VAR).  This is wrong because packing doesn't change the
    shape, so the packed array should have the same bounds as the bounds
    of TRANSPOSE(VAR), not the same bounds as VAR.  Reusing the strides of
    an unpacked array for a packed array doesn't seem right either.  This
    change uses matching dimensions when copying from the original
    descriptor, and only copies the lbound and ubound.  The strides are
    recalculated.  And then the offset is recalculated as well (even though
    I couldn't find a testcase where it made a difference).

            PR fortran/97592
            PR fortran/125998

    gcc/fortran/ChangeLog:

            * trans-array.cc (gfc_conv_array_parameter): Always create a new
            descriptor.  Copy lbound and ubound from the original descriptor
            using matching dimension indexes.  Recalculate stride and
            offset.

    gcc/testsuite/ChangeLog:

            * gfortran.dg/contiguous_17.f90: New test.