From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
	id ED9C33895FC3; Tue, 15 Nov 2022 13:14:42 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org ED9C33895FC3
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1668518082;
	bh=ZDX7prCxLCSKJm6TUr6VXNCrYWQ7nYe31DU9z7Zf5qM=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=ap03/5AJPJeYlSlI5msL5bN3IL1oRLYovQUoyTQtx2aVMBQ6xrxdLBWBNfccWvSjJ
	 dBzHc7rcWAnpL6Ne+1aVPOi3nuOoKmbQQEKiVd3urP4unhgpQfitohlqRz4CWqH+8u
	 g3QVUeDOBFt/nbG79QGwwbkMXPb9yM1C9gdfk6qs=
From: "carlosgalvezp at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/107677] -Warray-bounds: unclear what exactly it's
 meant to detect
Date: Tue, 15 Nov 2022 13:14:42 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: middle-end
X-Bugzilla-Version: 13.0
X-Bugzilla-Keywords: diagnostic, documentation
X-Bugzilla-Severity: normal
X-Bugzilla-Who: carlosgalvezp at gmail dot com
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-107677-4-ro0hXdQjkm@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-107677-4@http.gcc.gnu.org/bugzilla/>
References: <bug-107677-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
List-Id: <gcc-bugs.sourceware.org>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107677

--- Comment #5 from Carlos Galvez <carlosgalvezp at gmail dot com> ---
Wow, that was mind blowing, thanks for the clarification! Such thing I'd li=
ke
to have in the docs, it's very easy to confuse with the other message:

note: at offset 48 into object '<anonymous>' of size 48

So one offset is an actual index, and the other is a "mathematical range of
indices".

Back to my example:

error: array subscript [-536870912, -1] is outside array bounds

I don't see these numbers in my code. Therefore I wonder: how does GCC comp=
ute
these numbers? Are they based on my code, or are they based on: "if the user
pass you the number -536870912 as input at runtime, then you'll do
out-of-bounds"?=