Add support for dynamic DW_AT_byte_stride.
This patch adds support for DW_AT_byte_stride, using Ada as one
example of where this would be useful. However, the implementation
is language-agnostic.
Consider the following Ada code:
procedure Nested (L, U : Integer) is
subtype Small_Type is Integer range L .. U;
type Record_Type (I : Small_Type := L) is record
S : String (1 .. I);
end record;
type Array_Type is array (Integer range <>) of Record_Type;
A1 : Array_Type :=
(1 => (I => 0, S => <>),
2 => (I => 1, S => "A"),
3 => (I => 2, S => "AB"));
procedure Discard (R : Record_Type) is
begin
null;
end Discard;
begin
Discard (A1 (1)); -- STOP
end;
It defines an array A1 of Record_Type, which is a variant record
type whose maximum size actually depends on the value of the
parameters passed when calling Nested. As a result, the stride
of the array A1 cannot be known statically, which leads the compiler
to generate a dynamic DW_AT_byte_stride attribute for our type.
Here is what the debugging info looks like with GNAT:
.uleb128 0x10 # (DIE (0x14e) DW_TAG_array_type)
.long .LASF17 # DW_AT_name: "foo__nested__T18b"
.long 0x141 # DW_AT_byte_stride
.long 0xdc # DW_AT_type
.uleb128 0x11 # (DIE (0x15f) DW_TAG_subrange_type)
.long 0x166 # DW_AT_type
.byte 0x3 # DW_AT_upper_bound
.byte 0 # end of children of DIE 0x14e
There DW_AT_byte_stride is a reference to a local (internal)
variable:
.uleb128 0x9 # (DIE (0x141) DW_TAG_variable)
.long .LASF6 # DW_AT_name: "foo__nested__T18b___PAD___XVZ"
This patch enhances GDB to handle this dynamic byte stride attribute
by first adding a new dynamic_prop_node_kind (DYN_PROP_BYTE_STRIDE)
to store the array dynamic stride info (when dynamic). It then enhances
the dynamic type resolver to handle this dynamic property.
Before applying this patch, trying to print the value of some of
A1's elements after having stopped at the "STOP" comment does not
work. For instance:
(gdb) p a1(2)
Cannot access memory at address 0x80000268dec0
With this patch applied, GDB now prints the value of all 3 elements
correctly:
(gdb) print A1(1)
$1 = (i => 0, s => "")
(gdb) print A1(2)
$2 = (i => 1, s => "A")
(gdb) print A1(3)
$3 = (i => 2, s => "AB")
gdb/ChangeLog:
* gdbtypes.h (enum dynamic_prop_node_kind) <DYN_PROP_BYTE_STRIDE>:
New enum value.
(create_array_type_with_stride): Add byte_stride_prop parameter.
* gdbtypes.c (create_array_type_with_stride) <byte_stride_prop>:
New parameter. Update all callers in this file.
(array_type_has_dynamic_stride): New function.
(is_dynamic_type_internal, resolve_dynamic_array): Add handling
of arrays with dynamic byte strides.
* dwarf2read.c (read_array_type): Add support for dynamic
DW_AT_byte_stride attributes.
gdb/testsuite/ChangeLog:
* gdb.ada/dyn_stride: New testcase.
Tested on x86_64-linux.
This commit is contained in:
Joel Brobecker
parent
74a2f8ffb8
commit
a405673cc5
7 changed files with 197 additions and 13 deletions
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@ -1090,6 +1090,14 @@ discrete_position (struct type *type, LONGEST val, LONGEST *pos)
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Elements will be of type ELEMENT_TYPE, the indices will be of type
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RANGE_TYPE.
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BYTE_STRIDE_PROP, when not NULL, provides the array's byte stride.
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This byte stride property is added to the resulting array type
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as a DYN_PROP_BYTE_STRIDE. As a consequence, the BYTE_STRIDE_PROP
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argument can only be used to create types that are objfile-owned
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(see add_dyn_prop), meaning that either this function must be called
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with an objfile-owned RESULT_TYPE, or an objfile-owned RANGE_TYPE.
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BIT_STRIDE is taken into account only when BYTE_STRIDE_PROP is NULL.
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If BIT_STRIDE is not zero, build a packed array type whose element
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size is BIT_STRIDE. Otherwise, ignore this parameter.
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@ -1101,14 +1109,27 @@ struct type *
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create_array_type_with_stride (struct type *result_type,
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struct type *element_type,
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struct type *range_type,
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struct dynamic_prop *byte_stride_prop,
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unsigned int bit_stride)
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{
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if (byte_stride_prop != NULL
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&& byte_stride_prop->kind == PROP_CONST)
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{
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/* The byte stride is actually not dynamic. Pretend we were
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called with bit_stride set instead of byte_stride_prop.
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This will give us the same result type, while avoiding
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the need to handle this as a special case. */
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bit_stride = byte_stride_prop->data.const_val * 8;
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byte_stride_prop = NULL;
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}
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if (result_type == NULL)
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result_type = alloc_type_copy (range_type);
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TYPE_CODE (result_type) = TYPE_CODE_ARRAY;
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TYPE_TARGET_TYPE (result_type) = element_type;
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if (has_static_range (TYPE_RANGE_DATA (range_type))
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if (byte_stride_prop == NULL
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&& has_static_range (TYPE_RANGE_DATA (range_type))
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&& (!type_not_associated (result_type)
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&& !type_not_allocated (result_type)))
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{
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@ -1144,7 +1165,10 @@ create_array_type_with_stride (struct type *result_type,
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TYPE_FIELDS (result_type) =
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(struct field *) TYPE_ZALLOC (result_type, sizeof (struct field));
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TYPE_INDEX_TYPE (result_type) = range_type;
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if (bit_stride > 0)
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if (byte_stride_prop != NULL)
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add_dyn_prop (DYN_PROP_BYTE_STRIDE, *byte_stride_prop, result_type,
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TYPE_OBJFILE (result_type));
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else if (bit_stride > 0)
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TYPE_FIELD_BITSIZE (result_type, 0) = bit_stride;
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/* TYPE_TARGET_STUB will take care of zero length arrays. */
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@ -1163,7 +1187,7 @@ create_array_type (struct type *result_type,
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struct type *range_type)
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{
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return create_array_type_with_stride (result_type, element_type,
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range_type, 0);
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range_type, NULL, 0);
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}
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struct type *
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@ -1824,6 +1848,17 @@ stub_noname_complaint (void)
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complaint (&symfile_complaints, _("stub type has NULL name"));
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}
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/* Return nonzero if TYPE has a DYN_PROP_BYTE_STRIDE dynamic property
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attached to it, and that property has a non-constant value. */
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static int
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array_type_has_dynamic_stride (struct type *type)
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{
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struct dynamic_prop *prop = get_dyn_prop (DYN_PROP_BYTE_STRIDE, type);
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return (prop != NULL && prop->kind != PROP_CONST);
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}
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/* Worker for is_dynamic_type. */
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static int
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@ -1869,11 +1904,16 @@ is_dynamic_type_internal (struct type *type, int top_level)
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{
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gdb_assert (TYPE_NFIELDS (type) == 1);
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/* The array is dynamic if either the bounds are dynamic,
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or the elements it contains have a dynamic contents. */
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/* The array is dynamic if either the bounds are dynamic... */
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if (is_dynamic_type_internal (TYPE_INDEX_TYPE (type), 0))
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return 1;
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return is_dynamic_type_internal (TYPE_TARGET_TYPE (type), 0);
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/* ... or the elements it contains have a dynamic contents... */
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if (is_dynamic_type_internal (TYPE_TARGET_TYPE (type), 0))
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return 1;
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/* ... or if it has a dynamic stride... */
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if (array_type_has_dynamic_stride (type))
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return 1;
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return 0;
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}
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case TYPE_CODE_STRUCT:
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@ -1969,6 +2009,7 @@ resolve_dynamic_array (struct type *type,
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struct type *range_type;
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struct type *ary_dim;
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struct dynamic_prop *prop;
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unsigned int bit_stride = 0;
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gdb_assert (TYPE_CODE (type) == TYPE_CODE_ARRAY);
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@ -2000,8 +2041,31 @@ resolve_dynamic_array (struct type *type,
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else
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elt_type = TYPE_TARGET_TYPE (type);
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return create_array_type_with_stride (type, elt_type, range_type,
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TYPE_FIELD_BITSIZE (type, 0));
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prop = get_dyn_prop (DYN_PROP_BYTE_STRIDE, type);
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if (prop != NULL)
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{
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int prop_eval_ok
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= dwarf2_evaluate_property (prop, NULL, addr_stack, &value);
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if (prop_eval_ok)
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{
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remove_dyn_prop (DYN_PROP_BYTE_STRIDE, type);
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bit_stride = (unsigned int) (value * 8);
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}
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else
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{
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/* Could be a bug in our code, but it could also happen
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if the DWARF info is not correct. Issue a warning,
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and assume no byte/bit stride (leave bit_stride = 0). */
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warning (_("cannot determine array stride for type %s"),
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TYPE_NAME (type) ? TYPE_NAME (type) : "<no name>");
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}
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}
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else
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bit_stride = TYPE_FIELD_BITSIZE (type, 0);
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return create_array_type_with_stride (type, elt_type, range_type, NULL,
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bit_stride);
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}
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/* Resolve dynamic bounds of members of the union TYPE to static
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