[Bug fortran/107426] [12/13/14 Regression] ICE in gfc_compare_derived_types, at fortran/interface.cc:636

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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107426

--- Comment #8 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:a44d7e8a52007c2d45217709ca02947c6600de87

commit r14-9619-ga44d7e8a52007c2d45217709ca02947c6600de87
Author: Mikael Morin <mikael@gcc.gnu.org>
Date:   Thu Mar 21 17:27:54 2024 +0100

    fortran: Ignore use statements on error [PR107426]

    This fixes an access to freed memory on the testcase from the PR.
    The problem comes from an invalid subroutine statement in an interface,
    which is ignored and causes the following statements forming the procedure
    body to be rejected.  One of them use-associates the intrinsic
ISO_C_BINDING
    module, which imports new symbols in a namespace that is freed at the time
    the statement is rejected.  However, this creates dangling pointers as
    ISO_C_BINDING is special and its import creates a reference to the imported
    C_PTR symbol in the return type of the global intrinsic symbol for C_LOC
    (see the function create_intrinsic_function).

    This change saves and restores the list of use statements, so that rejected
    use statements are removed before they have a chance to be applied to the
    current namespace and create dangling pointers.

            PR fortran/107426

    gcc/fortran/ChangeLog:

            * gfortran.h (gfc_save_module_list, gfc_restore_old_module_list):
            New declarations.
            * module.cc (old_module_list_tail): New global variable.
            (gfc_save_module_list, gfc_restore_old_module_list): New functions.
            (gfc_use_modules): Set module_list and old_module_list_tail.
            * parse.cc (next_statement): Save module_list before doing any
work.
            (reject_statement): Restore module_list to its saved value.

    gcc/testsuite/ChangeLog:

            * gfortran.dg/pr89943_3.f90: Update error pattern.
            * gfortran.dg/pr89943_4.f90: Likewise.
            * gfortran.dg/use_31.f90: New test.