From: Collin Funk <collin.funk1@gmail.com>
To: Eli Zaretskii <eliz@gnu.org>
Cc: Paul Eggert <eggert@cs.ucla.edu>, emacs-devel@gnu.org
Subject: Re: master a86c25c91f3 11/13: Prefer -I to -isystem
Date: Wed, 17 Jul 2024 09:20:06 -0700 [thread overview]
Message-ID: <87ed7suh1l.fsf@gmail.com> (raw)
In-Reply-To: <868qy0gmjp.fsf@gnu.org> (Eli Zaretskii's message of "Wed, 17 Jul 2024 16:44:58 +0300")
Eli Zaretskii <eliz@gnu.org> writes:
> d:/usr/include/glib-2.0/gobject/gparam.h:157:35: warning: result of '1 << 31' requires 33 bits to represent, but 'int' only has 32 bits [-Wshift-overflow=]
> 157 | G_PARAM_DEPRECATED = 1 << 31
> | ^~
>
> While arguably a bug in Glib, the diagnostic is an annoyance, so I'd
> like to avoid it. I've verified that -Wno-system-headers doesn't
> remove it. -Wno-shift-overflow does, but I don't think suppressing
> that globally is a good idea.
It is a bug since (1 * 2^31) is equal to INT_MAX + 1 on most platforms.
C23 § 6.5.7 says this is undefined behavior [1].
GCC and Clang both seem to handle it fine but the warning is correct.
Although it is annoying when it occurs in included headers. I ran into a
similar issue with GCC intrinsic doing (1 << 31) too. The glib bug was
fixed at some point since my system has:
G_PARAM_DEPRECATED = (gint)(1u << 31)
Which is the same as I did for GCC.
Collin
[1] https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3096.pdf
prev parent reply other threads:[~2024-07-17 16:20 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-07-17 13:44 master a86c25c91f3 11/13: Prefer -I to -isystem Eli Zaretskii
2024-07-17 15:31 ` Paul Eggert
2024-07-17 16:04 ` Eli Zaretskii
2024-07-17 16:20 ` Collin Funk [this message]
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