From: "R. Diez" <rdiezmail-2005@yahoo.de>
To: Mike Frysinger <vapier@gentoo.org>
Cc: Richard Earnshaw <Richard.Earnshaw@foss.arm.com>, newlib@sourceware.org
Subject: Re: [PATCH v2] newlib: fix build with <gcc-5 versions
Date: Wed, 16 Mar 2022 08:12:04 +0100 [thread overview]
Message-ID: <e8076dd4-5977-4cfd-a968-2ce5f85ca905@yahoo.de> (raw)
In-Reply-To: <YjEnGIyU31Kl6zYJ@vapier>
> __builtin_mul_overflow showed up with gcc-5, so stub it out for older
> versions.
> [...]
> +#if !__GNUC_PREREQ__(5, 0)
> +#define __builtin_mul_overflow(a, b, size) ({ *(size) = (a) * (b); 0; })
I do not understand why Newlib needs to "stub it out" like this.
According to the GCC documentation, this kind of built-in routines allow the caller to check whether the operations overflowes. But the code above performs no overflow checking at all.
Therefore, compiling your code with GCC < 5 will silently break your application. After all, the only reason to use __builtin_mul_overflow() is that you need to check for overflow, is it?
Regards,
rdiez
next prev parent reply other threads:[~2022-03-16 7:12 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-14 3:25 [PATCH] " Mike Frysinger
2022-03-14 7:36 ` Sebastian Huber
2022-03-14 16:58 ` Mike Frysinger
2022-03-15 3:25 ` [PATCH v2] " Mike Frysinger
2022-03-15 12:41 ` Richard Earnshaw
2022-03-15 23:54 ` Mike Frysinger
2022-03-16 7:12 ` R. Diez [this message]
2022-03-16 8:30 ` Mike Frysinger
2022-03-16 9:17 ` R. Diez
2022-03-17 2:41 ` Mike Frysinger
2022-03-17 9:49 ` Corinna Vinschen
2022-03-17 11:26 ` Richard Earnshaw
2022-03-18 7:24 ` Corinna Vinschen
2022-03-18 8:30 ` R. Diez
2022-03-18 9:26 ` Corinna Vinschen
2022-03-18 9:45 ` R. Diez
2022-03-20 1:22 ` Mike Frysinger
2022-03-20 1:21 ` Mike Frysinger
2022-03-20 13:57 ` Jordi Sanfeliu
2022-03-20 12:52 ` Eric Bresie
2022-03-20 14:16 ` Mike Frysinger
2022-03-15 23:53 ` [PATCH v3] " Mike Frysinger
[not found] <1647792834.2524.0.ref@smtp.mail.att.net>
2022-03-20 16:13 ` [PATCH v2] " Steven J Abner
[not found] <1647807849.2524.1.ref@smtp.mail.att.net>
2022-03-20 20:24 ` Steven J Abner
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