[patch] Fix -fsanitize=address on unreadable inferior strings

[Joel Brobecker]

> gdb/
> 2014-08-18  Jan Kratochvil  <jan.kratochvil@redhat.com>
> 
> 	Fix -fsanitize=address on unreadable inferior strings.
> 	* valprint.c (val_print_string): Fix access before BUFFER.

LGTM. I actually don't see why this wouldn't be a possible bug.
Couldn't LEN be 0, in which case BYTES_READ would be zero, making
WIDTH > BYTES_READ?

> 
> diff --git a/gdb/valprint.c b/gdb/valprint.c
> index d3ab267..a87d67c 100644
> --- a/gdb/valprint.c
> +++ b/gdb/valprint.c
> @@ -2510,8 +2510,10 @@ val_print_string (struct type *elttype, const char *encoding,
>       LEN is -1.  */
>  
>    /* Determine found_nul by looking at the last character read.  */
> -  found_nul = extract_unsigned_integer (buffer + bytes_read - width, width,
> -					byte_order) == 0;
> +  found_nul = 0;
> +  if (bytes_read >= width)
> +    found_nul = extract_unsigned_integer (buffer + bytes_read - width, width,
> +					  byte_order) == 0;
>    if (len == -1 && !found_nul)
>      {
>        gdb_byte *peekbuf;


-- 
Joel