[Bug fortran/110677] UBSAN error: load of value 1818451807, which is not a valid value for type 'expr_t' when compiling pr49213.f90

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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110677

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Martin Jambor <jamborm@gcc.gnu.org>:

https://gcc.gnu.org/g:84e122c34834d9dea189c10fe0bf60c4d1a99fae

commit r14-3224-g84e122c34834d9dea189c10fe0bf60c4d1a99fae
Author: Martin Jambor <mjambor@suse.cz>
Date:   Tue Aug 15 17:13:44 2023 +0200

    Fortran: Avoid accessing gfc_charlen when not looking at BT_CHARACTER (PR
110677)

    This patch addresses an issue uncovered by the undefined behavior
    sanitizer.  In function resolve_structure_cons in resolve.cc there is
    a test starting with:

          if (cons->expr->ts.type == BT_CHARACTER && comp->ts.u.cl
              && comp->ts.u.cl->length
              && comp->ts.u.cl->length->expr_type == EXPR_CONSTANT

    and UBSAN complained of loads from comp->ts.u.cl->length->expr_type of
    integer value 1818451807 which is outside of the value range expr_t
    enum.  If I understand the code correctly it the entire load was
    unwanted because comp->ts.type in those cases is BT_CLASS and not
    BT_CHARACTER.  This patch simply adds a check to make sure it is only
    accessed in those cases.

    During review, Harald Anlauf noticed that length types also need to be
    checked and so I added also checks that he suggested to the condition.

    Co-authored-by: Harald Anlauf <anlauf@gmx.de>

    gcc/fortran/ChangeLog:

    2023-08-14  Martin Jambor  <mjambor@suse.cz>

            PR fortran/110677
            * resolve.cc (resolve_structure_cons): Check comp->ts is character
            type before accessing stuff through comp->ts.u.cl.