From: Phillip Wood <phillip.wood123@gmail.com>
To: Roland Illig <roland.illig@gmx.de>, git@vger.kernel.org
Subject: Re: undefined behavior in builtin/am.c
Date: Fri, 1 Jul 2022 18:54:29 +0100 [thread overview]
Message-ID: <d717324b-d7dc-fc5c-7bd7-2b74c4dfb644@gmail.com> (raw)
In-Reply-To: <130c3636-b978-1600-df53-6a38c3414a88@gmx.de>
Hi Roland
On 01/07/2022 18:03, Roland Illig wrote:
> Hi,
>
> builtin/am.c says:
> > static int str_isspace(const char *str)
> > {
> > for (; *str; str++)
> > if (!isspace(*str))
> > return 0;
> >
> > return 1;
> > }
>
> The macro 'isspace' must only be called with an integer representable as
> an 'unsigned char', or with the value of the macro EOF.
Thanks for reporting this. Git uses its own version of isspace() (see
git-compat-util.h & ctype.c) which does not suffer from this limitation
as it casts its argument to an unsigned char.
Best Wishes
Phillip
> On platforms where plain 'char' is a signed integer type, any character
> whose value is negative invokes undefined behavior (except for the one
> character that by coincidence has the same value as the macro EOF).
>
> To fix this, write '!isspace((unsigned char)*str)' instead.
>
> I have no idea how to trigger this part of the code but for someone who
> knows this part of Git, it should be easy. Depending on the platform,
> this kind of error may be silently ignored or crash the program, as
> always with undefined behavior.
>
> Roland
prev parent reply other threads:[~2022-07-01 17:56 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-01 17:03 undefined behavior in builtin/am.c Roland Illig
2022-07-01 17:53 ` Jeff King
2022-07-01 18:58 ` Roland Illig
2022-07-01 17:54 ` Phillip Wood [this message]
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