From: visa <visa@openbsd.org>
Date: Mon, 31 May 2021 12:45:33 +0000 (+0000)
Subject: Redefine ADJFREQ_MIN to avoid undefined behaviour (when not using -fwrapv)
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=b9e7483a798ae4a21090f07a3cc474a7547c6d8f;p=openbsd

Redefine ADJFREQ_MIN to avoid undefined behaviour (when not using -fwrapv)

Change the definition of ADJFREQ_MIN so that it does not shift
a negative value. Such shifting is undefined in standard C.

This came up when cross-compiling the kernel using ports clang.
The shifting becomes defined when compiling with option -fwrapv.
Base clang enables this option by default.

OK naddy@ cheloha@
---

diff --git a/sys/kern/kern_time.c b/sys/kern/kern_time.c
index aa380e0a525..37771cc02f0 100644
--- a/sys/kern/kern_time.c
+++ b/sys/kern/kern_time.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: kern_time.c,v 1.151 2020/12/23 20:45:02 cheloha Exp $	*/
+/*	$OpenBSD: kern_time.c,v 1.152 2021/05/31 12:45:33 visa Exp $	*/
 /*	$NetBSD: kern_time.c,v 1.20 1996/02/18 11:57:06 fvdl Exp $	*/
 
 /*
@@ -396,7 +396,7 @@ sys_settimeofday(struct proc *p, void *v, register_t *retval)
 }
 
 #define ADJFREQ_MAX (500000000LL << 32)
-#define ADJFREQ_MIN (-500000000LL << 32)
+#define ADJFREQ_MIN (-ADJFREQ_MAX)
 
 int
 sys_adjfreq(struct proc *p, void *v, register_t *retval)