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type: add c99 variable length array support

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The dwarf standard allow certain attributes to be expressed as dwarf
expressions rather than constants. For instance upper-/lowerbound attributes.
In case of a c99 variable length array the upperbound is a dynamic attribute.

With this change c99 vla behave the same as with static arrays.

1| void foo (size_t n) {
2|   int ary[n];
3|   memset(ary, 0, sizeof(ary));
4| }

(gdb) print ary
$1 = {0 <repeats 42 times>}

	* dwarf2loc.c (dwarf2_locexpr_baton_eval): New function.
	(dwarf2_evaluate_property): New function.
	* dwarf2loc.h (dwarf2_evaluate_property): New function prototype.
	* dwarf2read.c (attr_to_dynamic_prop): New function.
	(read_subrange_type): Use attr_to_dynamic_prop to read high bound
	attribute.
	* gdbtypes.c: Include dwarf2loc.h.
	(is_dynamic_type): New function.
	(resolve_dynamic_type): New function.
	(resolve_dynamic_bounds): New function.
	(get_type_length): New function.
	(check_typedef): Use get_type_length to compute type length.
	* gdbtypes.h (TYPE_HIGH_BOUND_KIND): New macro.
	(TYPE_LOW_BOUND_KIND): New macro.
	(is_dynamic_type): New function prototype.
	* value.c (value_from_contents_and_address): Call resolve_dynamic_type
	to resolve dynamic properties of the type. Update comment.
	* valops.c (get_value_at, value_at, value_at_lazy): Update comment.
This commit is contained in:
Sanimir Agovic 2013-10-09 15:28:22 +01:00
parent 729efb1317
commit 37c1ab67a3
8 changed files with 437 additions and 90 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

21
gdb/ChangeLog
View file

@ -1,3 +1,24 @@
2014-04-11 Sanimir Agovic <sanimir.agovic@intel.com>
* dwarf2loc.c (dwarf2_locexpr_baton_eval): New function.
(dwarf2_evaluate_property): New function.
* dwarf2loc.h (dwarf2_evaluate_property): New function prototype.
* dwarf2read.c (attr_to_dynamic_prop): New function.
(read_subrange_type): Use attr_to_dynamic_prop to read high bound
attribute.
* gdbtypes.c: Include dwarf2loc.h.
(is_dynamic_type): New function.
(resolve_dynamic_type): New function.
(resolve_dynamic_bounds): New function.
(get_type_length): New function.
(check_typedef): Use get_type_length to compute type length.
* gdbtypes.h (TYPE_HIGH_BOUND_KIND): New macro.
(TYPE_LOW_BOUND_KIND): New macro.
(is_dynamic_type): New function prototype.
* value.c (value_from_contents_and_address): Call resolve_dynamic_type
to resolve dynamic properties of the type. Update comment.
* valops.c (get_value_at, value_at, value_at_lazy): Update comment.
2014-04-11 Sanimir Agovic <sanimir.agovic@intel.com>
* dwarf2read.c (read_subrange_type): Use struct bound_prop for

119
gdb/dwarf2loc.c
View file

@ -2432,6 +2432,125 @@ dwarf2_evaluate_loc_desc (struct type *type, struct frame_info *frame,
return dwarf2_evaluate_loc_desc_full (type, frame, data, size, per_cu, 0);
}
/* Evaluates a dwarf expression and stores the result in VAL, expecting
that the dwarf expression only produces a single CORE_ADDR. ADDR is a
context (location of a variable) and might be needed to evaluate the
location expression.
Returns 1 on success, 0 otherwise. */
static int
dwarf2_locexpr_baton_eval (const struct dwarf2_locexpr_baton *dlbaton,
CORE_ADDR addr, CORE_ADDR *valp)
{
struct dwarf_expr_context *ctx;
struct dwarf_expr_baton baton;
struct objfile *objfile;
struct cleanup *cleanup;
if (dlbaton == NULL || dlbaton->size == 0)
return 0;
ctx = new_dwarf_expr_context ();
cleanup = make_cleanup_free_dwarf_expr_context (ctx);
baton.frame = get_selected_frame (NULL);
baton.per_cu = dlbaton->per_cu;
objfile = dwarf2_per_cu_objfile (dlbaton->per_cu);
ctx->gdbarch = get_objfile_arch (objfile);
ctx->addr_size = dwarf2_per_cu_addr_size (dlbaton->per_cu);
ctx->ref_addr_size = dwarf2_per_cu_ref_addr_size (dlbaton->per_cu);
ctx->offset = dwarf2_per_cu_text_offset (dlbaton->per_cu);
ctx->funcs = &dwarf_expr_ctx_funcs;
ctx->baton = &baton;
dwarf_expr_eval (ctx, dlbaton->data, dlbaton->size);
switch (ctx->location)
{
case DWARF_VALUE_REGISTER:
case DWARF_VALUE_MEMORY:
case DWARF_VALUE_STACK:
*valp = dwarf_expr_fetch_address (ctx, 0);
if (ctx->location == DWARF_VALUE_REGISTER)
*valp = dwarf_expr_read_addr_from_reg (&baton, *valp);
do_cleanups (cleanup);
return 1;
case DWARF_VALUE_LITERAL:
*valp = extract_signed_integer (ctx->data, ctx->len,
gdbarch_byte_order (ctx->gdbarch));
do_cleanups (cleanup);
return 1;
/* Unsupported dwarf values. */
case DWARF_VALUE_OPTIMIZED_OUT:
case DWARF_VALUE_IMPLICIT_POINTER:
break;
}
do_cleanups (cleanup);
return 0;
}
/* See dwarf2loc.h. */
int
dwarf2_evaluate_property (const struct dynamic_prop *prop, CORE_ADDR address,
CORE_ADDR *value)
{
if (prop == NULL)
return 0;
switch (prop->kind)
{
case PROP_LOCEXPR:
{
const struct dwarf2_property_baton *baton = prop->data.baton;
if (dwarf2_locexpr_baton_eval (&baton->locexpr, address, value))
{
if (baton->referenced_type)
{
struct value *val = value_at (baton->referenced_type, *value);
*value = value_as_address (val);
}
return 1;
}
}
break;
case PROP_LOCLIST:
{
struct dwarf2_property_baton *baton = prop->data.baton;
struct frame_info *frame = get_selected_frame (NULL);
CORE_ADDR pc = get_frame_address_in_block (frame);
const gdb_byte *data;
struct value *val;
size_t size;
data = dwarf2_find_location_expression (&baton->loclist, &size, pc);
if (data != NULL)
{
val = dwarf2_evaluate_loc_desc (baton->referenced_type, frame, data,
size, baton->loclist.per_cu);
if (!value_optimized_out (val))
{
*value = value_as_address (val);
return 1;
}
}
}
break;
case PROP_CONST:
*value = prop->data.const_val;
return 1;
}
return 0;
}
/* Helper functions and baton for dwarf2_loc_desc_needs_frame. */

28
gdb/dwarf2loc.h
View file

@ -90,6 +90,14 @@ struct value *dwarf2_evaluate_loc_desc (struct type *type,
size_t size,
struct dwarf2_per_cu_data *per_cu);
/* Converts a dynamic property into a static one. ADDR is the address of
the object currently being evaluated and might be nedded.
Returns 1 if PROP could be converted and the static value is passed back
into VALUE, otherwise returns 0. */
int dwarf2_evaluate_property (const struct dynamic_prop *prop,
CORE_ADDR addr, CORE_ADDR *value);
CORE_ADDR dwarf2_read_addr_index (struct dwarf2_per_cu_data *per_cu,
unsigned int addr_index);
@ -135,6 +143,26 @@ struct dwarf2_loclist_baton
unsigned char from_dwo;
};
/* A dynamic property is either expressed as a single location expression
or a location list. If the property is an indirection, pointing to
another die, keep track of the targeted type in REFERENCED_TYPE. */
struct dwarf2_property_baton
{
/* If the property is an indirection, we need to evaluate the location
LOCEXPR or LOCLIST in the context of the type REFERENCED_TYPE.
If NULL, the location is the actual value of the property. */
struct type *referenced_type;
union
{
/* Location expression. */
struct dwarf2_locexpr_baton locexpr;
/* Location list to be evaluated in the context of REFERENCED_TYPE. */
struct dwarf2_loclist_baton loclist;
};
};
extern const struct symbol_computed_ops dwarf2_locexpr_funcs;
extern const struct symbol_computed_ops dwarf2_loclist_funcs;

106
gdb/dwarf2read.c
View file

@ -14405,6 +14405,84 @@ read_base_type (struct die_info *die, struct dwarf2_cu *cu)
return set_die_type (die, type, cu);
}
/* Parse dwarf attribute if it's a block, reference or constant and put the
resulting value of the attribute into struct bound_prop.
Returns 1 if ATTR could be resolved into PROP, 0 otherwise. */
static int
attr_to_dynamic_prop (const struct attribute *attr, struct die_info *die,
struct dwarf2_cu *cu, struct dynamic_prop *prop)
{
struct dwarf2_property_baton *baton;
struct obstack *obstack = &cu->objfile->objfile_obstack;
if (attr == NULL || prop == NULL)
return 0;
if (attr_form_is_block (attr))
{
baton = obstack_alloc (obstack, sizeof (*baton));
baton->referenced_type = NULL;
baton->locexpr.per_cu = cu->per_cu;
baton->locexpr.size = DW_BLOCK (attr)->size;
baton->locexpr.data = DW_BLOCK (attr)->data;
prop->data.baton = baton;
prop->kind = PROP_LOCEXPR;
gdb_assert (prop->data.baton != NULL);
}
else if (attr_form_is_ref (attr))
{
struct dwarf2_cu *target_cu = cu;
struct die_info *target_die;
struct attribute *target_attr;
target_die = follow_die_ref (die, attr, &target_cu);
target_attr = dwarf2_attr (target_die, DW_AT_location, target_cu);
if (target_attr == NULL)
return 0;
if (attr_form_is_section_offset (target_attr))
{
baton = obstack_alloc (obstack, sizeof (*baton));
baton->referenced_type = die_type (target_die, target_cu);
fill_in_loclist_baton (cu, &baton->loclist, target_attr);
prop->data.baton = baton;
prop->kind = PROP_LOCLIST;
gdb_assert (prop->data.baton != NULL);
}
else if (attr_form_is_block (target_attr))
{
baton = obstack_alloc (obstack, sizeof (*baton));
baton->referenced_type = die_type (target_die, target_cu);
baton->locexpr.per_cu = cu->per_cu;
baton->locexpr.size = DW_BLOCK (target_attr)->size;
baton->locexpr.data = DW_BLOCK (target_attr)->data;
prop->data.baton = baton;
prop->kind = PROP_LOCEXPR;
gdb_assert (prop->data.baton != NULL);
}
else
{
dwarf2_invalid_attrib_class_complaint ("DW_AT_location",
"dynamic property");
return 0;
}
}
else if (attr_form_is_constant (attr))
{
prop->data.const_val = dwarf2_get_attr_constant_value (attr, 0);
prop->kind = PROP_CONST;
}
else
{
dwarf2_invalid_attrib_class_complaint (dwarf_form_name (attr->form),
dwarf2_name (die, cu));
return 0;
}
return 1;
}
/* Read the given DW_AT_subrange DIE. */
static struct type *
@ -14478,27 +14556,7 @@ read_subrange_type (struct die_info *die, struct dwarf2_cu *cu)
die->offset.sect_off, objfile_name (cu->objfile));
attr = dwarf2_attr (die, DW_AT_upper_bound, cu);
if (attr)
{
if (attr_form_is_block (attr) || attr_form_is_ref (attr))
{
/* GCC encodes arrays with unspecified or dynamic length
with a DW_FORM_block1 attribute or a reference attribute.
FIXME: GDB does not yet know how to handle dynamic
arrays properly, treat them as arrays with unspecified
length for now.
FIXME: jimb/2003-09-22: GDB does not really know
how to handle arrays of unspecified length
either; we just represent them as zero-length
arrays. Choose an appropriate upper bound given
the lower bound we've computed above. */
high.data.const_val = low.data.const_val - 1;
}
else
high.data.const_val = dwarf2_get_attr_constant_value (attr, 1);
}
else
if (!attr_to_dynamic_prop (attr, die, cu, &high))
{
attr = dwarf2_attr (die, DW_AT_count, cu);
if (attr)
@ -14569,12 +14627,6 @@ read_subrange_type (struct die_info *die, struct dwarf2_cu *cu)
range_type = create_range_type (NULL, orig_base_type, &low, &high);
/* Mark arrays with dynamic length at least as an array of unspecified
length. GDB could check the boundary but before it gets implemented at
least allow accessing the array elements. */
if (attr && attr_form_is_block (attr))
TYPE_HIGH_BOUND_KIND (range_type) = PROP_UNDEFINED;
/* Ada expects an empty array on no boundary attributes. */
if (attr == NULL && cu->language != language_ada)
TYPE_HIGH_BOUND_KIND (range_type) = PROP_UNDEFINED;

183
gdb/gdbtypes.c
View file

@ -853,6 +853,17 @@ create_static_range_type (struct type *result_type, struct type *index_type,
return result_type;
}
/* Predicate tests whether BOUNDS are static. Returns 1 if all bounds values
are static, otherwise returns 0. */
static int
has_static_range (const struct range_bounds *bounds)
{
return (bounds->low.kind == PROP_CONST
&& bounds->high.kind == PROP_CONST);
}
/* Set *LOWP and *HIGHP to the lower and upper bounds of discrete type
TYPE. Return 1 if type is a range type, 0 if it is discrete (and
bounds will fit in LONGEST), or -1 otherwise. */
@ -986,13 +997,15 @@ create_array_type_with_stride (struct type *result_type,
struct type *range_type,
unsigned int bit_stride)
{
LONGEST low_bound, high_bound;
if (result_type == NULL)
result_type = alloc_type_copy (range_type);
TYPE_CODE (result_type) = TYPE_CODE_ARRAY;
TYPE_TARGET_TYPE (result_type) = element_type;
if (has_static_range (TYPE_RANGE_DATA (range_type)))
{
LONGEST low_bound, high_bound;
if (get_discrete_bounds (range_type, &low_bound, &high_bound) < 0)
low_bound = high_bound = 0;
CHECK_TYPEDEF (element_type);
@ -1007,6 +1020,18 @@ create_array_type_with_stride (struct type *result_type,
else
TYPE_LENGTH (result_type) =
TYPE_LENGTH (element_type) * (high_bound - low_bound + 1);
}
else
{
/* This type is dynamic and its length needs to be computed
on demand. In the meantime, avoid leaving the TYPE_LENGTH
undefined by setting it to zero. Although we are not expected
to trust TYPE_LENGTH in this case, setting the size to zero
allows us to avoid allocating objects of random sizes in case
we accidently do. */
TYPE_LENGTH (result_type) = 0;
}
TYPE_NFIELDS (result_type) = 1;
TYPE_FIELDS (result_type) =
(struct field *) TYPE_ZALLOC (result_type, sizeof (struct field));
@ -1585,6 +1610,121 @@ stub_noname_complaint (void)
complaint (&symfile_complaints, _("stub type has NULL name"));
}
/* See gdbtypes.h. */
int
is_dynamic_type (struct type *type)
{
type = check_typedef (type);
if (TYPE_CODE (type) == TYPE_CODE_REF)
type = check_typedef (TYPE_TARGET_TYPE (type));
switch (TYPE_CODE (type))
{
case TYPE_CODE_ARRAY:
{
const struct type *range_type;
gdb_assert (TYPE_NFIELDS (type) == 1);
range_type = TYPE_INDEX_TYPE (type);
if (!has_static_range (TYPE_RANGE_DATA (range_type)))
return 1;
else
return is_dynamic_type (TYPE_TARGET_TYPE (type));
break;
}
default:
return 0;
break;
}
}
/* Resolves dynamic bound values of an array type TYPE to static ones.
ADDRESS might be needed to resolve the subrange bounds, it is the location
of the associated array. */
static struct type *
resolve_dynamic_bounds (struct type *type, CORE_ADDR addr)
{
CORE_ADDR value;
struct type *elt_type;
struct type *range_type;
struct type *ary_dim;
const struct dynamic_prop *prop;
const struct dwarf2_locexpr_baton *baton;
struct dynamic_prop low_bound, high_bound;
if (TYPE_CODE (type) == TYPE_CODE_TYPEDEF)
{
struct type *copy = copy_type (type);
TYPE_TARGET_TYPE (copy)
= resolve_dynamic_bounds (TYPE_TARGET_TYPE (type), addr);
return copy;
}
gdb_assert (TYPE_CODE (type) == TYPE_CODE_ARRAY);
elt_type = type;
range_type = check_typedef (TYPE_INDEX_TYPE (elt_type));
prop = &TYPE_RANGE_DATA (range_type)->low;
if (dwarf2_evaluate_property (prop, addr, &value))
{
low_bound.kind = PROP_CONST;
low_bound.data.const_val = value;
}
else
{
low_bound.kind = PROP_UNDEFINED;
low_bound.data.const_val = 0;
}
prop = &TYPE_RANGE_DATA (range_type)->high;
if (dwarf2_evaluate_property (prop, addr, &value))
{
high_bound.kind = PROP_CONST;
high_bound.data.const_val = value;
}
else
{
high_bound.kind = PROP_UNDEFINED;
high_bound.data.const_val = 0;
}
ary_dim = check_typedef (TYPE_TARGET_TYPE (elt_type));
if (ary_dim != NULL && TYPE_CODE (ary_dim) == TYPE_CODE_ARRAY)
elt_type = resolve_dynamic_bounds (TYPE_TARGET_TYPE (type), addr);
else
elt_type = TYPE_TARGET_TYPE (type);
range_type = create_range_type (NULL,
TYPE_TARGET_TYPE (range_type),
&low_bound, &high_bound);
return create_array_type (copy_type (type),
elt_type,
range_type);
}
/* See gdbtypes.h */
struct type *
resolve_dynamic_type (struct type *type, CORE_ADDR addr)
{
struct type *real_type = check_typedef (type);
struct type *resolved_type;
if (!is_dynamic_type (real_type))
return type;
resolved_type = resolve_dynamic_bounds (type, addr);
return resolved_type;
}
/* Find the real type of TYPE. This function returns the real type,
after removing all layers of typedefs, and completing opaque or stub
types. Completion changes the TYPE argument, but stripping of
@ -1760,45 +1900,6 @@ check_typedef (struct type *type)
{
/* Nothing we can do. */
}
else if (TYPE_CODE (type) == TYPE_CODE_ARRAY
&& TYPE_NFIELDS (type) == 1
&& (TYPE_CODE (range_type = TYPE_INDEX_TYPE (type))
== TYPE_CODE_RANGE))
{
/* Now recompute the length of the array type, based on its
number of elements and the target type's length.
Watch out for Ada null Ada arrays where the high bound
is smaller than the low bound. */
const LONGEST low_bound = TYPE_LOW_BOUND (range_type);
const LONGEST high_bound = TYPE_HIGH_BOUND (range_type);
ULONGEST len;
if (high_bound < low_bound)
len = 0;
else
{
/* For now, we conservatively take the array length to be 0
if its length exceeds UINT_MAX. The code below assumes
that for x < 0, (ULONGEST) x == -x + ULONGEST_MAX + 1,
which is technically not guaranteed by C, but is usually true
(because it would be true if x were unsigned with its
high-order bit on). It uses the fact that
high_bound-low_bound is always representable in
ULONGEST and that if high_bound-low_bound+1 overflows,
it overflows to 0. We must change these tests if we
decide to increase the representation of TYPE_LENGTH
from unsigned int to ULONGEST. */
ULONGEST ulow = low_bound, uhigh = high_bound;
ULONGEST tlen = TYPE_LENGTH (target_type);
len = tlen * (uhigh - ulow + 1);
if (tlen == 0 || (len / tlen - 1 + ulow) != uhigh
|| len > UINT_MAX)
len = 0;
}
TYPE_LENGTH (type) = len;
TYPE_TARGET_STUB (type) = 0;
}
else if (TYPE_CODE (type) == TYPE_CODE_RANGE)
{
TYPE_LENGTH (type) = TYPE_LENGTH (target_type);

10
gdb/gdbtypes.h
View file

@ -1,3 +1,4 @@
/* Internal type definitions for GDB.
Copyright (C) 1992-2014 Free Software Foundation, Inc.
@ -1682,6 +1683,15 @@ extern void get_unsigned_type_max (struct type *, ULONGEST *);
extern void get_signed_type_minmax (struct type *, LONGEST *, LONGEST *);
/* * Resolve all dynamic values of a type e.g. array bounds to static values.
ADDR specifies the location of the variable the type is bound to.
If TYPE has no dynamic properties return TYPE; otherwise a new type with
static properties is returned. */
extern struct type *resolve_dynamic_type (struct type *type, CORE_ADDR addr);
/* * Predicate if the type has dynamic values, which are not resolved yet. */
extern int is_dynamic_type (struct type *type);
extern struct type *check_typedef (struct type *);
#define CHECK_TYPEDEF(TYPE) \

15
gdb/valops.c
View file

@ -900,7 +900,10 @@ value_one (struct type *type)
return val;
}
/* Helper function for value_at, value_at_lazy, and value_at_lazy_stack. */
/* Helper function for value_at, value_at_lazy, and value_at_lazy_stack.
The type of the created value may differ from the passed type TYPE.
Make sure to retrieve the returned values's new type after this call
e.g. in case the type is a variable length array. */
static struct value *
get_value_at (struct type *type, CORE_ADDR addr, int lazy)
@ -925,7 +928,10 @@ get_value_at (struct type *type, CORE_ADDR addr, int lazy)
value_at_lazy instead. value_at_lazy simply records the address of
the data and sets the lazy-evaluation-required flag. The lazy flag
is tested in the value_contents macro, which is used if and when
the contents are actually required.
the contents are actually required. The type of the created value
may differ from the passed type TYPE. Make sure to retrieve the
returned values's new type after this call e.g. in case the type
is a variable length array.
Note: value_at does *NOT* handle embedded offsets; perform such
adjustments before or after calling it. */
@ -936,7 +942,10 @@ value_at (struct type *type, CORE_ADDR addr)
return get_value_at (type, addr, 0);
}
/* Return a lazy value with type TYPE located at ADDR (cf. value_at). */
/* Return a lazy value with type TYPE located at ADDR (cf. value_at).
The type of the created value may differ from the passed type TYPE.
Make sure to retrieve the returned values's new type after this call
e.g. in case the type is a variable length array. */
struct value *
value_at_lazy (struct type *type, CORE_ADDR addr)

19
gdb/value.c
View file

@ -3319,32 +3319,39 @@ value_from_ulongest (struct type *type, ULONGEST num)
/* Create a value representing a pointer of type TYPE to the address
ADDR. */
ADDR. The type of the created value may differ from the passed
type TYPE. Make sure to retrieve the returned values's new type
after this call e.g. in case of an variable length array. */
struct value *
value_from_pointer (struct type *type, CORE_ADDR addr)
{
struct value *val = allocate_value (type);
struct type *resolved_type = resolve_dynamic_type (type, addr);
struct value *val = allocate_value (resolved_type);
store_typed_address (value_contents_raw (val), check_typedef (type), addr);
store_typed_address (value_contents_raw (val),
check_typedef (resolved_type), addr);
return val;
}
/* Create a value of type TYPE whose contents come from VALADDR, if it
is non-null, and whose memory address (in the inferior) is
ADDRESS. */
ADDRESS. The type of the created value may differ from the passed
type TYPE. Make sure to retrieve values new type after this call. */
struct value *
value_from_contents_and_address (struct type *type,
const gdb_byte *valaddr,
CORE_ADDR address)
{
struct type *resolved_type = resolve_dynamic_type (type, address);
struct value *v;
if (valaddr == NULL)
v = allocate_value_lazy (type);
v = allocate_value_lazy (resolved_type);
else
v = value_from_contents (type, valaddr);
v = value_from_contents (resolved_type, valaddr);
set_value_address (v, address);
VALUE_LVAL (v) = lval_memory;
return v;