Re: [PATCH 01/10] lib/mbalign: fix unsigned integer overflow [AddressSanitizer]

["Pádraig Brady" <P@draigBrady.com>]

On 30/11/14 13:57, Sami Kerola wrote:
> This error was reported 155 times.
> 
> lib/mbsalign.c:322:18: runtime error: unsigned integer overflow: 0 - 1
> cannot be represented in type 'size_t' (aka 'unsigned long')
> 
> Signed-off-by: Sami Kerola <kerolasa@iki.fi>
> ---
>  lib/mbsalign.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/mbsalign.c b/lib/mbsalign.c
> index b307d19..052fec6 100644
> --- a/lib/mbsalign.c
> +++ b/lib/mbsalign.c
> @@ -319,7 +319,7 @@ mbs_align_pad (char *dest, const char* dest_end, size_t n_spaces)
>  {
>    /* FIXME: Should we pad with "figure space" (\u2007)
>       if non ascii data present?  */
> -  while (n_spaces-- && (dest < dest_end))
> +  for (/* nothing */; n_spaces && (dest < dest_end); n_spaces--)
>      *dest++ = ' ';
>    *dest = '\0';
>    return dest;

What compiler and version are you using for this?
I don't get the error with gcc 4.9.2 with -fsanitize=undefined
Note the error is incorrect I think as the variable is not read
after the overflow.

thanks,
Pádraig.