struct type *type;
arr = ada_coerce_ref (arr);
+
+ /* If our value is a pointer, then dererence it. Make sure that
+ this operation does not cause the target type to be fixed, as
+ this would indirectly cause this array to be decoded. The rest
+ of the routine assumes that the array hasn't been decoded yet,
+ so we use the basic "value_ind" routine to perform the dereferencing,
+ as opposed to using "ada_value_ind". */
if (TYPE_CODE (value_type (arr)) == TYPE_CODE_PTR)
- arr = ada_value_ind (arr);
+ arr = value_ind (arr);
type = decode_packed_array_type (value_type (arr));
if (type == NULL)
}
else if (is_dynamic_field (type, f))
{
+ const gdb_byte *field_valaddr = valaddr;
+ CORE_ADDR field_address = address;
+ struct type *field_type =
+ TYPE_TARGET_TYPE (TYPE_FIELD_TYPE (type, f));
+
if (dval0 == NULL)
{
/* rtype's length is computed based on the run-time
else
dval = dval0;
- /* Get the fixed type of the field. Note that, in this case, we
- do not want to get the real type out of the tag: if the current
- field is the parent part of a tagged record, we will get the
- tag of the object. Clearly wrong: the real type of the parent
- is not the real type of the child. We would end up in an infinite
- loop. */
- TYPE_FIELD_TYPE (rtype, f) =
- ada_to_fixed_type
- (ada_get_base_type
- (TYPE_TARGET_TYPE (TYPE_FIELD_TYPE (type, f))),
- cond_offset_host (valaddr, off / TARGET_CHAR_BIT),
- cond_offset_target (address, off / TARGET_CHAR_BIT), dval, 0);
+ /* If the type referenced by this field is an aligner type, we need
+ to unwrap that aligner type, because its size might not be set.
+ Keeping the aligner type would cause us to compute the wrong
+ size for this field, impacting the offset of the all the fields
+ that follow this one. */
+ if (ada_is_aligner_type (field_type))
+ {
+ long field_offset = TYPE_FIELD_BITPOS (field_type, f);
+
+ field_valaddr = cond_offset_host (field_valaddr, field_offset);
+ field_address = cond_offset_target (field_address, field_offset);
+ field_type = ada_aligned_type (field_type);
+ }
+
+ field_valaddr = cond_offset_host (field_valaddr,
+ off / TARGET_CHAR_BIT);
+ field_address = cond_offset_target (field_address,
+ off / TARGET_CHAR_BIT);
+
+ /* Get the fixed type of the field. Note that, in this case,
+ we do not want to get the real type out of the tag: if
+ the current field is the parent part of a tagged record,
+ we will get the tag of the object. Clearly wrong: the real
+ type of the parent is not the real type of the child. We
+ would end up in an infinite loop. */
+ field_type = ada_get_base_type (field_type);
+ field_type = ada_to_fixed_type (field_type, field_valaddr,
+ field_address, dval, 0);
+
+ TYPE_FIELD_TYPE (rtype, f) = field_type;
TYPE_FIELD_NAME (rtype, f) = TYPE_FIELD_NAME (type, f);
bit_incr = fld_bit_len =
TYPE_LENGTH (TYPE_FIELD_TYPE (rtype, f)) * TARGET_CHAR_BIT;
{
struct type *index_type_desc;
struct type *result;
+ int packed_array_p;
- if (ada_is_packed_array_type (type0) /* revisit? */
- || TYPE_FIXED_INSTANCE (type0))
+ if (TYPE_FIXED_INSTANCE (type0))
return type0;
+ packed_array_p = ada_is_packed_array_type (type0);
+ if (packed_array_p)
+ type0 = decode_packed_array_type (type0);
+
index_type_desc = ada_find_parallel_type (type0, "___XA");
if (index_type_desc == NULL)
{
consult the object tag. */
struct type *elt_type = ada_to_fixed_type (elt_type0, 0, 0, dval, 1);
- if (elt_type0 == elt_type)
+ /* Make sure we always create a new array type when dealing with
+ packed array types, since we're going to fix-up the array
+ type length and element bitsize a little further down. */
+ if (elt_type0 == elt_type && !packed_array_p)
result = type0;
else
result = create_array_type (alloc_type (TYPE_OBJFILE (type0)),
error (_("array type with dynamic size is larger than varsize-limit"));
}
+ if (packed_array_p)
+ {
+ /* So far, the resulting type has been created as if the original
+ type was a regular (non-packed) array type. As a result, the
+ bitsize of the array elements needs to be set again, and the array
+ length needs to be recomputed based on that bitsize. */
+ int len = TYPE_LENGTH (result) / TYPE_LENGTH (TYPE_TARGET_TYPE (result));
+ int elt_bitsize = TYPE_FIELD_BITSIZE (type0, 0);
+
+ TYPE_FIELD_BITSIZE (result, 0) = TYPE_FIELD_BITSIZE (type0, 0);
+ TYPE_LENGTH (result) = len * elt_bitsize / HOST_CHAR_BIT;
+ if (TYPE_LENGTH (result) * HOST_CHAR_BIT < len * elt_bitsize)
+ TYPE_LENGTH (result)++;
+ }
+
TYPE_FIXED_INSTANCE (result) = 1;
return result;
}
if (raw_type == NULL || TYPE_CODE (raw_type) != TYPE_CODE_STRUCT)
return raw_type;
+ if (ada_is_aligner_type (raw_type))
+ /* The encoding specifies that we should always use the aligner type.
+ So, even if this aligner type has an associated XVS type, we should
+ simply ignore it.
+
+ According to the compiler gurus, an XVS type parallel to an aligner
+ type may exist because of a stabs limitation. In stabs, aligner
+ types are empty because the field has a variable-sized type, and
+ thus cannot actually be used as an aligner type. As a result,
+ we need the associated parallel XVS type to decode the type.
+ Since the policy in the compiler is to not change the internal
+ representation based on the debugging info format, we sometimes
+ end up having a redundant XVS type parallel to the aligner type. */
+ return raw_type;
+
real_type_namer = ada_find_parallel_type (raw_type, "___XVS");
if (real_type_namer == NULL
|| TYPE_CODE (real_type_namer) != TYPE_CODE_STRUCT
return value_cast (type, arg2);
}
+/* Evaluating Ada expressions, and printing their result.
+ ------------------------------------------------------
+
+ We usually evaluate an Ada expression in order to print its value.
+ We also evaluate an expression in order to print its type, which
+ happens during the EVAL_AVOID_SIDE_EFFECTS phase of the evaluation,
+ but we'll focus mostly on the EVAL_NORMAL phase. In practice, the
+ EVAL_AVOID_SIDE_EFFECTS phase allows us to simplify certain aspects of
+ the evaluation compared to the EVAL_NORMAL, but is otherwise very
+ similar.
+
+ Evaluating expressions is a little more complicated for Ada entities
+ than it is for entities in languages such as C. The main reason for
+ this is that Ada provides types whose definition might be dynamic.
+ One example of such types is variant records. Or another example
+ would be an array whose bounds can only be known at run time.
+
+ The following description is a general guide as to what should be
+ done (and what should NOT be done) in order to evaluate an expression
+ involving such types, and when. This does not cover how the semantic
+ information is encoded by GNAT as this is covered separatly. For the
+ document used as the reference for the GNAT encoding, see exp_dbug.ads
+ in the GNAT sources.
+
+ Ideally, we should embed each part of this description next to its
+ associated code. Unfortunately, the amount of code is so vast right
+ now that it's hard to see whether the code handling a particular
+ situation might be duplicated or not. One day, when the code is
+ cleaned up, this guide might become redundant with the comments
+ inserted in the code, and we might want to remove it.
+
+ When evaluating Ada expressions, the tricky issue is that they may
+ reference entities whose type contents and size are not statically
+ known. Consider for instance a variant record:
+
+ type Rec (Empty : Boolean := True) is record
+ case Empty is
+ when True => null;
+ when False => Value : Integer;
+ end case;
+ end record;
+ Yes : Rec := (Empty => False, Value => 1);
+ No : Rec := (empty => True);
+
+ The size and contents of that record depends on the value of the
+ descriminant (Rec.Empty). At this point, neither the debugging
+ information nor the associated type structure in GDB are able to
+ express such dynamic types. So what the debugger does is to create
+ "fixed" versions of the type that applies to the specific object.
+ We also informally refer to this opperation as "fixing" an object,
+ which means creating its associated fixed type.
+
+ Example: when printing the value of variable "Yes" above, its fixed
+ type would look like this:
+
+ type Rec is record
+ Empty : Boolean;
+ Value : Integer;
+ end record;
+
+ On the other hand, if we printed the value of "No", its fixed type
+ would become:
+
+ type Rec is record
+ Empty : Boolean;
+ end record;
+
+ Things become a little more complicated when trying to fix an entity
+ with a dynamic type that directly contains another dynamic type,
+ such as an array of variant records, for instance. There are
+ two possible cases: Arrays, and records.
+
+ Arrays are a little simpler to handle, because the same amount of
+ memory is allocated for each element of the array, even if the amount
+ of space used by each element changes from element to element.
+ Consider for instance the following array of type Rec:
+
+ type Rec_Array is array (1 .. 2) of Rec;
+
+ The type structure in GDB describes an array in terms of its
+ bounds, and the type of its elements. By design, all elements
+ in the array have the same type. So we cannot use a fixed type
+ for the array elements in this case, since the fixed type depends
+ on the actual value of each element.
+
+ Fortunately, what happens in practice is that each element of
+ the array has the same size, which is the maximum size that
+ might be needed in order to hold an object of the element type.
+ And the compiler shows it in the debugging information by wrapping
+ the array element inside a private PAD type. This type should not
+ be shown to the user, and must be "unwrap"'ed before printing. Note
+ that we also use the adjective "aligner" in our code to designate
+ these wrapper types.
+
+ These wrapper types should have a constant size, which is the size
+ of each element of the array. In the case when the size is statically
+ known, the PAD type will already have the right size, and the array
+ element type should remain unfixed. But there are cases when
+ this size is not statically known. For instance, assuming that
+ "Five" is an integer variable:
+
+ type Dynamic is array (1 .. Five) of Integer;
+ type Wrapper (Has_Length : Boolean := False) is record
+ Data : Dynamic;
+ case Has_Length is
+ when True => Length : Integer;
+ when False => null;
+ end case;
+ end record;
+ type Wrapper_Array is array (1 .. 2) of Wrapper;
+
+ Hello : Wrapper_Array := (others => (Has_Length => True,
+ Data => (others => 17),
+ Length => 1));
+
+
+ The debugging info would describe variable Hello as being an
+ array of a PAD type. The size of that PAD type is not statically
+ known, but can be determined using a parallel XVZ variable.
+ In that case, a copy of the PAD type with the correct size should
+ be used for the fixed array.
+
+ However, things are slightly different in the case of dynamic
+ record types. In this case, in order to compute the associated
+ fixed type, we need to determine the size and offset of each of
+ its components. This, in turn, requires us to compute the fixed
+ type of each of these components.
+
+ Consider for instance the example:
+
+ type Bounded_String (Max_Size : Natural) is record
+ Str : String (1 .. Max_Size);
+ Length : Natural;
+ end record;
+ My_String : Bounded_String (Max_Size => 10);
+
+ In that case, the position of field "Length" depends on the size
+ of field Str, which itself depends on the value of the Max_Size
+ discriminant. In order to fix the type of variable My_String,
+ we need to fix the type of field Str. Therefore, fixing a variant
+ record requires us to fix each of its components.
+
+ However, if a component does not have a dynamic size, the component
+ should not be fixed. In particular, fields that use a PAD type
+ should not fixed. Here is an example where this might happen
+ (assuming type Rec above):
+
+ type Container (Big : Boolean) is record
+ First : Rec;
+ After : Integer;
+ case Big is
+ when True => Another : Integer;
+ when False => null;
+ end case;
+ end record;
+ My_Container : Container := (Big => False,
+ First => (Empty => True),
+ After => 42);
+
+ In that example, the compiler creates a PAD type for component First,
+ whose size is constant, and then positions the component After just
+ right after it. The offset of component After is therefore constant
+ in this case.
+
+ The debugger computes the position of each field based on an algorithm
+ that uses, among other things, the actual position and size of the field
+ preceding it. Let's now imagine that the user is trying to print the
+ value of My_Container. If the type fixing was recursive, we would
+ end up computing the offset of field After based on the size of the
+ fixed version of field First. And since in our example First has
+ only one actual field, the size of the fixed type is actually smaller
+ than the amount of space allocated to that field, and thus we would
+ compute the wrong offset of field After.
+
+ Unfortunately, we need to watch out for dynamic components of variant
+ records (identified by the ___XVL suffix in the component name).
+ Even if the target type is a PAD type, the size of that type might
+ not be statically known. So the PAD type needs to be unwrapped and
+ the resulting type needs to be fixed. Otherwise, we might end up
+ with the wrong size for our component. This can be observed with
+ the following type declarations:
+
+ type Octal is new Integer range 0 .. 7;
+ type Octal_Array is array (Positive range <>) of Octal;
+ pragma Pack (Octal_Array);
+
+ type Octal_Buffer (Size : Positive) is record
+ Buffer : Octal_Array (1 .. Size);
+ Length : Integer;
+ end record;
+
+ In that case, Buffer is a PAD type whose size is unset and needs
+ to be computed by fixing the unwrapped type.
+
+ Lastly, when should the sub-elements of a type that remained unfixed
+ thus far, be actually fixed?
+
+ The answer is: Only when referencing that element. For instance
+ when selecting one component of a record, this specific component
+ should be fixed at that point in time. Or when printing the value
+ of a record, each component should be fixed before its value gets
+ printed. Similarly for arrays, the element of the array should be
+ fixed when printing each element of the array, or when extracting
+ one element out of that array. On the other hand, fixing should
+ not be performed on the elements when taking a slice of an array!
+
+ Note that one of the side-effects of miscomputing the offset and
+ size of each field is that we end up also miscomputing the size
+ of the containing type. This can have adverse results when computing
+ the value of an entity. GDB fetches the value of an entity based
+ on the size of its type, and thus a wrong size causes GDB to fetch
+ the wrong amount of memory. In the case where the computed size is
+ too small, GDB fetches too little data to print the value of our
+ entiry. Results in this case as unpredicatble, as we usually read
+ past the buffer containing the data =:-o. */
+
+/* Implement the evaluate_exp routine in the exp_descriptor structure
+ for the Ada language. */
+
static struct value *
ada_evaluate_subexp (struct type *expect_type, struct expression *exp,
int *pos, enum noside noside)
}
else
{
- arg1 =
- unwrap_value (evaluate_subexp_standard
- (expect_type, exp, pos, noside));
+ arg1 = evaluate_subexp_standard (expect_type, exp, pos, noside);
+ arg1 = unwrap_value (arg1);
return ada_to_fixed_value (arg1);
}
if (ada_is_packed_array_type (desc_base_type (value_type (argvec[0]))))
argvec[0] = ada_coerce_to_simple_array (argvec[0]);
+ else if (TYPE_CODE (value_type (argvec[0])) == TYPE_CODE_ARRAY
+ && TYPE_FIELD_BITSIZE (value_type (argvec[0]), 0) != 0)
+ /* This is a packed array that has already been fixed, and
+ therefore already coerced to a simple array. Nothing further
+ to do. */
+ ;
else if (TYPE_CODE (value_type (argvec[0])) == TYPE_CODE_REF
|| (TYPE_CODE (value_type (argvec[0])) == TYPE_CODE_ARRAY
&& VALUE_LVAL (argvec[0]) == lval_memory))
return value_zero (ada_aligned_type (type), lval_memory);
}
else
- return
- ada_to_fixed_value (unwrap_value
- (ada_value_struct_elt
- (arg1, &exp->elts[pc + 2].string, 0)));
+ arg1 = ada_value_struct_elt (arg1, &exp->elts[pc + 2].string, 0);
+ arg1 = unwrap_value (arg1);
+ return ada_to_fixed_value (arg1);
+
case OP_TYPE:
/* The value is not supposed to be used. This is here to make it
easier to accommodate expressions that contain types. */
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