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From: "dmalcolm at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug analyzer/108968] fanalyzer false positive with the uninitalised-ness of the stack pointer
Date: Thu, 02 Mar 2023 21:29:05 +0000 [thread overview]
Message-ID: <bug-108968-4-JRp5coTHnv@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-108968-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108968
--- Comment #12 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
(In reply to Andrew Cooper from comment #9)
[...snip...]
> Our code does fundamentally rely on get_cpu_info() always returning the same
> pointer (on a single CPU). For example, `current` is defined as
> `get_cpu_info()->current` and we do expect that to yield the same pointer
> when used multiple times.
>
> Even if the analyser was interpreting the generated asm, there's no way it
> could prove this without knowing the size/alignment constraints of our
> stacks.
Another issue is that even if the analyzer "knows" that get_cpu_info() always
returns the same value, it doesn't know what memory is being pointed to, and so
has to assume that in:
T old_value = get_cpu_info()->current;
some_function_call ();
T new_value = get_cpu_info()->current;
that old_value doesn't necessarily equal new_value, since some_function_call ()
could have modified the value of "current".
next prev parent reply other threads:[~2023-03-02 21:29 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-28 12:41 [Bug c/108968] New: " andrew.cooper3 at citrix dot com
2023-02-28 13:12 ` [Bug c/108968] " schwab@linux-m68k.org
2023-02-28 13:44 ` andrew.cooper3 at citrix dot com
2023-02-28 13:59 ` schwab@linux-m68k.org
2023-02-28 15:41 ` andrew.cooper3 at citrix dot com
2023-02-28 18:56 ` [Bug analyzer/108968] " dmalcolm at gcc dot gnu.org
2023-02-28 19:04 ` andrew.cooper3 at citrix dot com
2023-03-02 19:02 ` cvs-commit at gcc dot gnu.org
2023-03-02 19:25 ` dmalcolm at gcc dot gnu.org
2023-03-02 21:15 ` andrew.cooper3 at citrix dot com
2023-03-02 21:20 ` andrew.cooper3 at citrix dot com
2023-03-02 21:25 ` dmalcolm at gcc dot gnu.org
2023-03-02 21:29 ` dmalcolm at gcc dot gnu.org [this message]
2023-03-02 21:34 ` andrew.cooper3 at citrix dot com
2023-03-02 21:35 ` andrew.cooper3 at citrix dot com
2023-03-02 21:41 ` andrew.cooper3 at citrix dot com
2023-03-02 21:46 ` dmalcolm at gcc dot gnu.org
2023-03-02 21:48 ` dmalcolm at gcc dot gnu.org
2023-03-02 21:52 ` dmalcolm at gcc dot gnu.org
2023-03-29 18:19 ` cvs-commit at gcc dot gnu.org
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