Base support for <unavailable> value contents.

gdb/
	* value.h (value_bytes_available): Declare.
	(mark_value_bytes_unavailable): Declare.
	* value.c (struct range): New struct.
	(range_s): New typedef.
	(ranges_overlap): New function.
	(range_lessthan): New function.
	(ranges_contain_p): New function.
	(struct value) <unavailable>: New field.
	(value_bytes_available): New function.
	(mark_value_bytes_unavailable): New function.
	(require_not_optimized_out): Constify parameter.
	(require_available): New function.
	(value_contents_all, value_contents): Require all bytes be
	available.
	(value_free): Free `unavailable'.
	(value_copy): Copy `unavailable'.
	* valprint.h (val_print_unavailable): Declare.
	* valprint.c (valprint_check_validity): Rename `offset' parameter
	to `embedded_offset'.  If printing a scalar, check whether the
	value chunk is available.
	(val_print_unavailable): New.
	(val_print_scalar_formatted): Check whether the value is
	available.
	* python/py-prettyprint.c (apply_val_pretty_printer): Refuse
	pretty-printing unavailable values.

gdb/ChangeLog

@@ -1,3 +1,34 @@
+2011-02-14  Pedro Alves  <pedro@codesourcery.com>
+
+	Base support for <unavailable> value contents.
+
+	gdb/
+	* value.h (value_bytes_available): Declare.
+	(mark_value_bytes_unavailable): Declare.
+	* value.c (struct range): New struct.
+	(range_s): New typedef.
+	(ranges_overlap): New function.
+	(range_lessthan): New function.
+	(ranges_contain_p): New function.
+	(struct value) <unavailable>: New field.
+	(value_bytes_available): New function.
+	(mark_value_bytes_unavailable): New function.
+	(require_not_optimized_out): Constify parameter.
+	(require_available): New function.
+	(value_contents_all, value_contents): Require all bytes be
+	available.
+	(value_free): Free `unavailable'.
+	(value_copy): Copy `unavailable'.
+	* valprint.h (val_print_unavailable): Declare.
+	* valprint.c (valprint_check_validity): Rename `offset' parameter
+	to `embedded_offset'.  If printing a scalar, check whether the
+	value chunk is available.
+	(val_print_unavailable): New.
+	(val_print_scalar_formatted): Check whether the value is
+	available.
+	* python/py-prettyprint.c (apply_val_pretty_printer): Refuse
+	pretty-printing unavailable values.
+
 2011-02-13  Jan Kratochvil  <jan.kratochvil@redhat.com>
 
 	Fix const/volatile qualifiers of C++ types, PR c++/12328.

gdb/python/py-prettyprint.c

@@ -690,6 +690,11 @@ apply_val_pretty_printer (struct type *type, const gdb_byte *valaddr,
   struct cleanup *cleanups;
   int result = 0;
   enum string_repr_result print_result;
+
+  /* No pretty-printer support for unavailable values.  */
+  if (!value_bytes_available (val, embedded_offset, TYPE_LENGTH (type)))
+    return 0;
+
   cleanups = ensure_python_env (gdbarch, language);
 
   /* Instantiate the printer.  */

gdb/valprint.c

@@ -260,7 +260,7 @@ scalar_type_p (struct type *type)
 static int
 valprint_check_validity (struct ui_file *stream,
 			 struct type *type,
-			 int offset,
+			 int embedded_offset,
 			 const struct value *val)
 {
   CHECK_TYPEDEF (type);
@@ -269,19 +269,25 @@ valprint_check_validity (struct ui_file *stream,
       && TYPE_CODE (type) != TYPE_CODE_STRUCT
       && TYPE_CODE (type) != TYPE_CODE_ARRAY)
     {
-      if (! value_bits_valid (val, TARGET_CHAR_BIT * offset,
+      if (!value_bits_valid (val, TARGET_CHAR_BIT * embedded_offset,
-			      TARGET_CHAR_BIT * TYPE_LENGTH (type)))
+			     TARGET_CHAR_BIT * TYPE_LENGTH (type)))
 	{
 	  val_print_optimized_out (stream);
 	  return 0;
 	}
 
-      if (value_bits_synthetic_pointer (val, TARGET_CHAR_BIT * offset,
+      if (value_bits_synthetic_pointer (val, TARGET_CHAR_BIT * embedded_offset,
 					TARGET_CHAR_BIT * TYPE_LENGTH (type)))
 	{
 	  fputs_filtered (_("<synthetic pointer>"), stream);
 	  return 0;
 	}
+
+      if (!value_bytes_available (val, embedded_offset, TYPE_LENGTH (type)))
+	{
+	  val_print_unavailable (stream);
+	  return 0;
+	}
     }
 
   return 1;
@@ -293,6 +299,12 @@ val_print_optimized_out (struct ui_file *stream)
   fprintf_filtered (stream, _("<optimized out>"));
 }
 
+void
+val_print_unavailable (struct ui_file *stream)
+{
+  fprintf_filtered (stream, _("<unavailable>"));
+}
+
 /* Print using the given LANGUAGE the data of type TYPE located at
    VALADDR + EMBEDDED_OFFSET (within GDB), which came from the
    inferior at address ADDRESS + EMBEDDED_OFFSET, onto stdio stream
@@ -560,6 +572,8 @@ val_print_scalar_formatted (struct type *type,
   if (!value_bits_valid (val, TARGET_CHAR_BIT * embedded_offset,
 			      TARGET_CHAR_BIT * TYPE_LENGTH (type)))
     val_print_optimized_out (stream);
+  else if (!value_bytes_available (val, embedded_offset, TYPE_LENGTH (type)))
+    val_print_unavailable (stream);
   else
     print_scalar_formatted (valaddr + embedded_offset, type,
 			    options, size, stream);

gdb/valprint.h

@@ -154,4 +154,6 @@ int read_string (CORE_ADDR addr, int len, int width, unsigned int fetchlimit,
 
 extern void val_print_optimized_out (struct ui_file *stream);
 
+extern void val_print_unavailable (struct ui_file *stream);
+
 #endif

gdb/value.c

@@ -63,6 +63,110 @@ struct internal_function
   void *cookie;
 };
 
+/* Defines an [OFFSET, OFFSET + LENGTH) range.  */
+
+struct range
+{
+  /* Lowest offset in the range.  */
+  int offset;
+
+  /* Length of the range.  */
+  int length;
+};
+
+typedef struct range range_s;
+
+DEF_VEC_O(range_s);
+
+/* Returns true if the ranges defined by [offset1, offset1+len1) and
+   [offset2, offset2+len2) overlap.  */
+
+static int
+ranges_overlap (int offset1, int len1,
+		int offset2, int len2)
+{
+  ULONGEST h, l;
+
+  l = max (offset1, offset2);
+  h = min (offset1 + len1, offset2 + len2);
+  return (l < h);
+}
+
+/* Returns true if the first argument is strictly less than the
+   second, useful for VEC_lower_bound.  We keep ranges sorted by
+   offset and coalesce overlapping and contiguous ranges, so this just
+   compares the starting offset.  */
+
+static int
+range_lessthan (const range_s *r1, const range_s *r2)
+{
+  return r1->offset < r2->offset;
+}
+
+/* Returns true if RANGES contains any range that overlaps [OFFSET,
+   OFFSET+LENGTH).  */
+
+static int
+ranges_contain (VEC(range_s) *ranges, int offset, int length)
+{
+  range_s what;
+  int i;
+
+  what.offset = offset;
+  what.length = length;
+
+  /* We keep ranges sorted by offset and coalesce overlapping and
+     contiguous ranges, so to check if a range list contains a given
+     range, we can do a binary search for the position the given range
+     would be inserted if we only considered the starting OFFSET of
+     ranges.  We call that position I.  Since we also have LENGTH to
+     care for (this is a range afterall), we need to check if the
+     _previous_ range overlaps the I range.  E.g.,
+
+         R
+         |---|
+       |---|    |---|  |------| ... |--|
+       0        1      2            N
+
+       I=1
+
+     In the case above, the binary search would return `I=1', meaning,
+     this OFFSET should be inserted at position 1, and the current
+     position 1 should be pushed further (and before 2).  But, `0'
+     overlaps with R.
+
+     Then we need to check if the I range overlaps the I range itself.
+     E.g.,
+
+              R
+              |---|
+       |---|    |---|  |-------| ... |--|
+       0        1      2             N
+
+       I=1
+  */
+
+  i = VEC_lower_bound (range_s, ranges, &what, range_lessthan);
+
+  if (i > 0)
+    {
+      struct range *bef = VEC_index (range_s, ranges, i - 1);
+
+      if (ranges_overlap (bef->offset, bef->length, offset, length))
+	return 1;
+    }
+
+  if (i < VEC_length (range_s, ranges))
+    {
+      struct range *r = VEC_index (range_s, ranges, i);
+
+      if (ranges_overlap (r->offset, r->length, offset, length))
+	return 1;
+    }
+
+  return 0;
+}
+
 static struct cmd_list_element *functionlist;
 
 struct value
@@ -206,6 +310,11 @@ struct value
      valid if lazy is nonzero.  */
   gdb_byte *contents;
 
+  /* Unavailable ranges in CONTENTS.  We mark unavailable ranges,
+     rather than available, since the common and default case is for a
+     value to be available.  This is filled in at value read time.  */
+  VEC(range_s) *unavailable;
+
   /* The number of references to this value.  When a value is created,
      the value chain holds a reference, so REFERENCE_COUNT is 1.  If
      release_value is called, this value is removed from the chain but
@@ -214,6 +323,179 @@ struct value
   int reference_count;
 };
 
+int
+value_bytes_available (const struct value *value, int offset, int length)
+{
+  gdb_assert (!value->lazy);
+
+  return !ranges_contain (value->unavailable, offset, length);
+}
+
+void
+mark_value_bytes_unavailable (struct value *value, int offset, int length)
+{
+  range_s newr;
+  int i;
+
+  /* Insert the range sorted.  If there's overlap or the new range
+     would be contiguous with an existing range, merge.  */
+
+  newr.offset = offset;
+  newr.length = length;
+
+  /* Do a binary search for the position the given range would be
+     inserted if we only considered the starting OFFSET of ranges.
+     Call that position I.  Since we also have LENGTH to care for
+     (this is a range afterall), we need to check if the _previous_
+     range overlaps the I range.  E.g., calling R the new range:
+
+       #1 - overlaps with previous
+
+	   R
+	   |-...-|
+	 |---|     |---|  |------| ... |--|
+	 0         1      2            N
+
+	 I=1
+
+     In the case #1 above, the binary search would return `I=1',
+     meaning, this OFFSET should be inserted at position 1, and the
+     current position 1 should be pushed further (and become 2).  But,
+     note that `0' overlaps with R, so we want to merge them.
+
+     A similar consideration needs to be taken if the new range would
+     be contiguous with the previous range:
+
+       #2 - contiguous with previous
+
+	    R
+	    |-...-|
+	 |--|       |---|  |------| ... |--|
+	 0          1      2            N
+
+	 I=1
+
+     If there's no overlap with the previous range, as in:
+
+       #3 - not overlapping and not contiguous
+
+	       R
+	       |-...-|
+	  |--|         |---|  |------| ... |--|
+	  0            1      2            N
+
+	 I=1
+
+     or if I is 0:
+
+       #4 - R is the range with lowest offset
+
+	  R
+	 |-...-|
+	         |--|       |---|  |------| ... |--|
+	         0          1      2            N
+
+	 I=0
+
+     ... we just push the new range to I.
+
+     All the 4 cases above need to consider that the new range may
+     also overlap several of the ranges that follow, or that R may be
+     contiguous with the following range, and merge.  E.g.,
+
+       #5 - overlapping following ranges
+
+	  R
+	 |------------------------|
+	         |--|       |---|  |------| ... |--|
+	         0          1      2            N
+
+	 I=0
+
+       or:
+
+	    R
+	    |-------|
+	 |--|       |---|  |------| ... |--|
+	 0          1      2            N
+
+	 I=1
+
+  */
+
+  i = VEC_lower_bound (range_s, value->unavailable, &newr, range_lessthan);
+  if (i > 0)
+    {
+      struct range *bef = VEC_index (range_s, value->unavailable, i - i);
+
+      if (ranges_overlap (bef->offset, bef->length, offset, length))
+	{
+	  /* #1 */
+	  ULONGEST l = min (bef->offset, offset);
+	  ULONGEST h = max (bef->offset + bef->length, offset + length);
+
+	  bef->offset = l;
+	  bef->length = h - l;
+	  i--;
+	}
+      else if (offset == bef->offset + bef->length)
+	{
+	  /* #2 */
+	  bef->length += length;
+	  i--;
+	}
+      else
+	{
+	  /* #3 */
+	  VEC_safe_insert (range_s, value->unavailable, i, &newr);
+	}
+    }
+  else
+    {
+      /* #4 */
+      VEC_safe_insert (range_s, value->unavailable, i, &newr);
+    }
+
+  /* Check whether the ranges following the one we've just added or
+     touched can be folded in (#5 above).  */
+  if (i + 1 < VEC_length (range_s, value->unavailable))
+    {
+      struct range *t;
+      struct range *r;
+      int removed = 0;
+      int next = i + 1;
+
+      /* Get the range we just touched.  */
+      t = VEC_index (range_s, value->unavailable, i);
+      removed = 0;
+
+      i = next;
+      for (; VEC_iterate (range_s, value->unavailable, i, r); i++)
+	if (r->offset <= t->offset + t->length)
+	  {
+	    ULONGEST l, h;
+
+	    l = min (t->offset, r->offset);
+	    h = max (t->offset + t->length, r->offset + r->length);
+
+	    t->offset = l;
+	    t->length = h - l;
+
+	    removed++;
+	  }
+	else
+	  {
+	    /* If we couldn't merge this one, we won't be able to
+	       merge following ones either, since the ranges are
+	       always sorted by OFFSET.  */
+	    break;
+	  }
+
+      if (removed != 0)
+	VEC_block_remove (range_s, value->unavailable, next, removed);
+    }
+}
+
 /* Prototypes for local functions.  */
 
 static void show_values (char *, int);
@@ -420,12 +702,19 @@ value_enclosing_type (struct value *value)
 }
 
 static void
-require_not_optimized_out (struct value *value)
+require_not_optimized_out (const struct value *value)
 {
   if (value->optimized_out)
     error (_("value has been optimized out"));
 }
 
+static void
+require_available (const struct value *value)
+{
+  if (!VEC_empty (range_s, value->unavailable))
+    error (_("value is not available"));
+}
+
 const gdb_byte *
 value_contents_for_printing (struct value *value)
 {
@@ -446,6 +735,7 @@ value_contents_all (struct value *value)
 {
   const gdb_byte *result = value_contents_for_printing (value);
   require_not_optimized_out (value);
+  require_available (value);
   return result;
 }
 
@@ -478,6 +768,7 @@ value_contents (struct value *value)
 {
   const gdb_byte *result = value_contents_writeable (value);
   require_not_optimized_out (value);
+  require_available (value);
   return result;
 }
 
@@ -703,6 +994,7 @@ value_free (struct value *val)
 	}
 
       xfree (val->contents);
+      VEC_free (range_s, val->unavailable);
     }
   xfree (val);
 }
@@ -833,6 +1125,7 @@ value_copy (struct value *arg)
 	      TYPE_LENGTH (value_enclosing_type (arg)));
 
     }
+  val->unavailable = VEC_copy (range_s, arg->unavailable);
   val->parent = arg->parent;
   if (val->parent)
     value_incref (val->parent);

gdb/value.h

@@ -360,6 +360,20 @@ extern int value_bits_valid (const struct value *value,
 extern int value_bits_synthetic_pointer (const struct value *value,
 					 int offset, int length);
 
+/* Given a value, determine whether the contents bytes starting at
+   OFFSET and extending for LENGTH bytes are available.  This returns
+   nonzero if all bytes in the given range are available, zero if any
+   byte is unavailable.  */
+
+extern int value_bytes_available (const struct value *value,
+				  int offset, int length);
+
+/* Mark VALUE's content bytes starting at OFFSET and extending for
+   LENGTH bytes as unavailable.  */
+
+extern void mark_value_bytes_unavailable (struct value *value,
+					  int offset, int length);
+
 
 
 #include "symtab.h"