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From: "mikael at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug fortran/106050] ICE in reject_statement, at
 fortran/parse.cc:2879 since r8-3056-g5bab4c9631c478b7
Date: Mon, 10 Jul 2023 18:15:27 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106050

Mikael Morin <mikael at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mikael at gcc dot gnu.org

--- Comment #5 from Mikael Morin <mikael at gcc dot gnu.org> ---
When matching statement "type t(k)", two symbols are created, one for t and=
 one
for k.
t is in gfc_current_ns and k is in t's f2k_derived namespace.
If the statement is rejected, both t and k need to be freed.
But one should care about ordering, as the release of t frees f2k_derived,
which is k's namespace, so k should be released before t.

I haven't checked that the above actually is the problem here, but it might=
 be.
Possibly walking the symbols in reverse order to release them would fix thi=
s.

Regarding the patches posted, if sym->refs < 0 is true, then the memory for=
 sym
has already been released and may be garbage (including sym->refs).  A cras=
h is
as good as anything else at this point IMHO.=