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From: "shaohua.li at inf dot ethz.ch" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug sanitizer/108481] [13 Regression] UBsan missed a signed integer overflow
Date: Tue, 31 Jan 2023 08:05:58 +0000	[thread overview]
Message-ID: <bug-108481-4-IX4UmmcHMj@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-108481-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108481

--- Comment #4 from Li Shaohua <shaohua.li at inf dot ethz.ch> ---
(In reply to Andrew Pinski from comment #2)
>       i = i - 6822162149299574294;
> 
> Is not being invoked on the executable code.
> 
> If we look at look at the original code:
> 
> 
>     if ((i * (unsigned long)7 <= 1) << j)
>       ;
>     else {
>       i = i - 6822162149299574294;
>       if (j) {
>         if (*g)
>           break;
>         continue;
>       }
>       return 8;
>     }
> ...
>   return h;
> 
> The only path where the undefined behavior even matters is inside the path
> that had continue in it. Which is where the subtraction is pushed to now.
> 
> I don't know if we should declear this as a valid thing to do or not.

When I compiled the source code with `-O1 -fsanitize=undefined` and then used
gdb to check the execution trace of the binary, I indeed observed that `i = i -
6822162149299574294` was executed.

  parent reply	other threads:[~2023-01-31  8:05 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-20 14:17 [Bug sanitizer/108481] New: " shaohua.li at inf dot ethz.ch
2023-01-23 12:41 ` [Bug sanitizer/108481] " marxin at gcc dot gnu.org
2023-01-31  3:50 ` [Bug sanitizer/108481] [13 Regression] " pinskia at gcc dot gnu.org
2023-01-31  3:57 ` pinskia at gcc dot gnu.org
2023-01-31  4:00 ` pinskia at gcc dot gnu.org
2023-01-31  8:05 ` shaohua.li at inf dot ethz.ch [this message]
2023-02-01 13:11 ` [Bug sanitizer/108481] [10/11/12/13 " jakub at gcc dot gnu.org
2023-02-01 13:16 ` jakub at gcc dot gnu.org
2023-02-09 13:28 ` jakub at gcc dot gnu.org

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