Re: [RFC, v2] Fix PR symtab/15391

[Pedro Alves <palves@redhat.com>]

On 05/14/2013 02:50 PM, Tom Tromey wrote:
> +  if (TYPE_LENGTH (value_type (value)) < sizeof (LONGEST))
> +    {
> +      LONGEST nbits = 8 * TYPE_LENGTH (value_type (value));
> +      LONGEST m1 = -1;
> +
> +      if (((byte_offset >> (nbits - 1)) & 1) != 0)
> +	byte_offset |= m1 << nbits;
> +    }

I believe left-shifting a negative number is actually undefined
behavior.  It's more usual/idiomatic to do sign extension like:

LONGEST nbits = 8 * TYPE_LENGTH (value_type (value));
int signbit = 1U << nbits;
byte_offset = (byte_offset ^ signbit) - signbit;

-- 
Pedro Alves