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From: "mikpelinux at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/64294] invalid code, zero check gets optimized away
Date: Sat, 20 Dec 2014 15:24:00 -0000 [thread overview]
Message-ID: <bug-64294-4-Yc8k4cetil@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-64294-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64294
--- Comment #10 from Mikael Pettersson <mikpelinux at gmail dot com> ---
You're invoking undefined behaviour due to overflow in signed integer
arithmetic.
Running it after compiling with -fsanitize=undefined produces:
petite.c:391:28: runtime error: signed integer overflow: 2147483647 * 2 cannot
be represented in type 'int'
Fixing that in the following crude way:
--- petite.c 2014-12-20 16:02:59.786063515 +0100
+++ petite-fixed.c 2014-12-20 16:15:05.030889115 +0100
@@ -388,7 +388,7 @@
free(usects);
return 1;
}
- backbytes = backbytes*2 + oob;
+ backbytes = (int)((unsigned
int)backbytes*2 + (unsigned int)oob);
if ( (oob = doubledl(&ssrc,
&mydl, buf, bufsz)) == -1 ) {
free(usects);
return 1;
allows the testcase to work at -O2 and -O3.
next prev parent reply other threads:[~2014-12-20 15:24 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-12 22:25 [Bug rtl-optimization/64294] New: " gcc at breakpoint dot cc
2014-12-12 22:43 ` [Bug rtl-optimization/64294] " schwab@linux-m68k.org
2014-12-12 22:54 ` gcc at breakpoint dot cc
2014-12-13 20:58 ` gcc at breakpoint dot cc
2014-12-13 20:59 ` gcc at breakpoint dot cc
2014-12-13 21:12 ` gcc at breakpoint dot cc
2014-12-20 11:53 ` mikpelinux at gmail dot com
2014-12-20 14:30 ` gcc at breakpoint dot cc
2014-12-20 14:35 ` gcc at breakpoint dot cc
2014-12-20 15:24 ` mikpelinux at gmail dot com [this message]
2014-12-20 21:21 ` gcc at breakpoint dot cc
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