Re: [unavailable values part 1, 06/17] array element repeats, <unavailable> confused with 0.

[Jan Kratochvil <jan.kratochvil@redhat.com>]

> --- src.orig/gdb/value.h	2011-02-07 11:15:02.926705996 +0000
> +++ src/gdb/value.h	2011-02-07 11:15:23.176706001 +0000
> @@ -374,6 +374,31 @@ extern int value_bytes_available (const
>  extern void mark_value_bytes_unavailable (struct value *value,
>  					  int offset, int length);
>  
> +/* Compare LENGTH bytes of VAL1's contents starting at OFFSET1 with
> +   LENGTH bytes of VAL2's contents starting at OFFSET2.  Returns true

/* OFFSET1 and OFFSET2 should include possible EMBEDDED_OFFSET.  */


> +   iff the set of available contents match.  Unavailable contents
> +   compare equal with unavailable contents, and different with any
> +   available byte.  For example, if 'x's represent an unavailable
> +   byte, and 'V' and 'Z' represent different available bytes, in a
> +   value with length 16:
> +
> +   offset:   0   4   8   12  16
> +   contents: xxxxVVVVxxxxVVZZ
> +
> +   then:
> +
> +   value_available_contents_eq(val, 0, val, 8, 6) => 1
> +   value_available_contents_eq(val, 0, val, 4, 4) => 1
> +   value_available_contents_eq(val, 0, val, 8, 8) => 0
> +   value_available_contents_eq(val, 4, val, 12, 2) => 1
> +   value_available_contents_eq(val, 4, val, 12, 4) => 0
> +   value_available_contents_eq(val, 3, val, 4, 4) => 0
> +*/
> +
> +extern int value_available_contents_eq (const struct value *val1, int offset1,
> +					const struct value *val2, int offset2,
> +					int length);


> +/* Find the first range in RANGES that overlaps the range defined by
> +   OFFSET and LENGTH, starting at element POS in the RANGES vector,
> +   Returns the index into RANGES where such overlapping range was
> +   found, or -1 if none was found.  */
> +
> +static int
> +find_first_range_overlap (VEC(range_s) *ranges, int pos,
> +			  int offset, int length)
> +{
> +  range_s *r;
> +  int i;
> +
> +  for (i = pos; VEC_iterate (range_s, ranges, i, r); i++)
> +    if (ranges_overlap (r->offset, r->length, offset, length))
> +      return i;
> +
> +  return -1;
> +}
> +
> +int
> +value_available_contents_eq (const struct value *val1, int offset1,
> +			     const struct value *val2, int offset2,
> +			     int length)
> +{
> +  int org_len = length;
> +  int org_offset1 = offset1;
> +  int org_offset2 = offset2;

All the org_* fields can be dropped by reusing other variables making the code
more readable.


> +  int idx1 = 0, idx2 = 0;
> +  int prev_avail;
> +
> +  /* This routine is used by printing routines, where we should
> +     already have read the value.  Note that we only know whether a
> +     value chunk is available if we've tried to read it.  */
> +  gdb_assert (!val1->lazy && !val2->lazy);
> +
> +  /* The offset from either ORG_OFFSET1 or ORG_OFFSET2 where the
> +     available contents we haven't compared yet start.  */
> +  prev_avail = 0;
> +
> +  while (length > 0)
> +    {
> +      range_s *r1, *r2;
> +      ULONGEST l1, h1;
> +      ULONGEST l2, h2;
> +
> +      idx1 = find_first_range_overlap (val1->unavailable, idx1,
> +				       offset1, length);
> +      idx2 = find_first_range_overlap (val2->unavailable, idx2,
> +				       offset2, length);
> +
> +      /* The usual case is for both values to be completely available.  */
> +      if (idx1 == -1 && idx2 == -1)
> +	return (memcmp (val1->contents + org_offset1 + prev_avail,

`org_offset1 + prev_avail' -> `offset1'.

> +			val2->contents + org_offset2 + prev_avail,
> +			org_len - prev_avail) == 0);

`org_len - prev_avail' -> `length' to drop `org_len'.


> +      /* The contents only match equal if the available set matches as
> +	 well.  */
> +      else if (idx1 == -1 || idx2 == -1)
> +	return 0;
> +
> +      gdb_assert (idx1 != -1 && idx2 != -1);
> +
> +      r1 = VEC_index (range_s, val1->unavailable, idx1);
> +      r2 = VEC_index (range_s, val2->unavailable, idx2);
> +
> +      /* Get the unavailable windows intersected by the incoming
> +	 ranges.  The first and last ranges that overlap the argument
> +	 range may be wider than said incoming arguments ranges.  */
> +      l1 = max (offset1, r1->offset);
> +      h1 = min (offset1 + length, r1->offset + r1->length);
> +
> +      l2 = max (offset2, r2->offset);
> +      h2 = min (offset2 + length, r2->offset + r2->length);
> +
> +      /* Make them relative to the respective start offsets, so we can
> +	 compare them for equality.  */
> +      l1 -= offset1;
> +      h1 -= offset1;
> +
> +      l2 -= offset2;
> +      h2 -= offset2;
> +
> +      /* Different availability, no match.  */
> +      if (l1 != l2 || h1 != h2)
> +	return 0;
> +
> +      /* Compare the _available_ contents.  */
> +      if (memcmp (val1->contents + org_offset1 + prev_avail,
> +		  val2->contents + org_offset2 + prev_avail,
> +		  l2 - prev_avail) != 0)

`l2 - prev_avail' is not right.  `l2' is already this available chunk size,
`prev_avail' can be much larger covering all the preceding ranges,
`prev_avail' is already subtracted from `l2' by `offset1'/`offset2' above.


> +	return 0;
> +
> +      prev_avail += h1;
> +      length -= h1;
> +      offset1 += h1;
> +      offset2 += h1;
> +    }
> +
> +  return 1;
> +}


Thanks,
Jan