[Bug fortran/82721] [13/14/15/16 Regression] Error message with corrupted text, sometimes ICE

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82721

--- Comment #25 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-13 branch has been updated by Paul Thomas <pault@gcc.gnu.org>:

https://gcc.gnu.org/g:7103afbdd74ff57fb4cc226704b2acd89dc4e0d0

commit r13-10230-g7103afbdd74ff57fb4cc226704b2acd89dc4e0d0
Author: Christopher Albert <albert@tugraz.at>
Date:   Tue Mar 10 18:17:32 2026 +0100

    Fortran: Fix ICE after rejected CHARACTER duplicate declaration [PR82721]

    When a CHARACTER declaration is rejected because the symbol already has
    a different basic type, declaration parsing may already have created a
    fresh gfc_charlen node for the rejected entity.  reject_statement()
    undoes symbol-table changes, but it does not roll back the namespace
    charlen list, so the stale len(...) expression can survive and later be
    resolved through dangling symtree pointers, causing corrupted
    diagnostics or an ICE.

    Fix this in build_sym by discarding only the unattached gfc_charlen
    node created for the rejected declaration before it is ever attached to
    any surviving symbol.  Keep shared charlen nodes intact so other
    invalid-code diagnostics still see the state they expect.  Also add a
    regression test that uses MALLOC_PERTURB_ to make the old crash
    reproducible.

    gcc/fortran/ChangeLog:

            PR fortran/82721
            * decl.cc (discard_pending_charlen): New helper.
            (build_sym): Discard unattached CHARACTER length nodes when
            gfc_add_type rejects the declaration.

    gcc/testsuite/ChangeLog:

            PR fortran/82721
            * gfortran.dg/pr82721.f90: New test.

    Signed-off-by: Christopher Albert <albert@tugraz.at>
    (cherry picked from commit 5cfaad50af7dc25f6174044cdc05ebd56b6c4e3c)