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Re: [PATCH v5 03/15] type: add c99 variable length array support
- From: Joel Brobecker <brobecker at adacore dot com>
- To: Sanimir Agovic <sanimir dot agovic at intel dot com>
- Cc: tromey at redhat dot com, keven dot boell at intel dot com, gdb-patches at sourceware dot org
- Date: Fri, 28 Feb 2014 08:27:22 -0800
- Subject: Re: [PATCH v5 03/15] type: add c99 variable length array support
- Authentication-results: sourceware.org; auth=none
- References: <1391704056-25246-1-git-send-email-sanimir dot agovic at intel dot com> <1391704056-25246-4-git-send-email-sanimir dot agovic at intel dot com>
Hi Sanimir,
> 2013-10-18 Sanimir Agovic <sanimir.agovic@intel.com>
> Keven Boell <keven.boell@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.
Tough review (took a while). Some questions and comments, but nothing
too serious. See below.
I apologize in advance if I appear to nit-pick - I only allow myself to
do so when touching the patch for other reasons too. Thank you!
> Signed-off-by: Sanimir Agovic <sanimir.agovic@intel.com>
> ---
> gdb/dwarf2loc.c | 120 +++++++++++++++++++++++++
> gdb/dwarf2loc.h | 24 +++++
> gdb/dwarf2read.c | 100 +++++++++++++++------
> gdb/gdbtypes.c | 264 ++++++++++++++++++++++++++++++++++++++++++++-----------
> gdb/gdbtypes.h | 10 +++
> gdb/valops.c | 12 ++-
> gdb/value.c | 17 ++--
> 7 files changed, 459 insertions(+), 88 deletions(-)
>
> diff --git a/gdb/dwarf2loc.c b/gdb/dwarf2loc.c
> index 2b1f323..72bc727 100644
> --- a/gdb/dwarf2loc.c
> +++ b/gdb/dwarf2loc.c
> @@ -2431,6 +2431,126 @@ 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;
> + /* Not supported dwarf values. */
> + case DWARF_VALUE_OPTIMIZED_OUT:
> + case DWARF_VALUE_IMPLICIT_POINTER:
Would "Unsupported" be more idiomatic? I'm not a native English
speaker, so I am not sure. But "unsupported" somehow sounds better.
Feel free to choose either option.
> + break;
> + }
> +
> + do_cleanups (cleanup);
> +
> + return 0;
Can you remove the empty line betwee do_cleanups and return?
It's not very important, but compresses a bit the code, I think.
> +}
> +
> +/* 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. */
>
> diff --git a/gdb/dwarf2loc.h b/gdb/dwarf2loc.h
> index 9bc8ca5..9be3e24 100644
> --- a/gdb/dwarf2loc.h
> +++ b/gdb/dwarf2loc.h
> @@ -90,6 +90,13 @@ 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);
> +
Would you mind adding an empty line betwee documentation and
declaration? It's a bit of a nit-pick, but since we're adjusting
this patch, we might as well.
> CORE_ADDR dwarf2_read_addr_index (struct dwarf2_per_cu_data *per_cu,
> unsigned int addr_index);
>
> @@ -135,6 +142,23 @@ struct dwarf2_loclist_baton
> unsigned char from_dwo;
> };
>
> +/* A dynamic property is either expressed as a single location expression
> + or a location list in the context of TYPE. */
> +
> +struct dwarf2_property_baton
> +{
> + /* Keep track of referenced type. */
> + struct type *referenced_type;
Can you explain in this comment what the referenced type is?
If it helps, giving an example could be used.
> + union
> + {
> + /* Location expression. */
> + struct dwarf2_locexpr_baton locexpr;
> +
> + /* Location list to be evaluated in the context of TYPE. */
> + struct dwarf2_loclist_baton loclist;
> + };
> +};
> +
> extern const struct symbol_computed_ops dwarf2_locexpr_funcs;
> extern const struct symbol_computed_ops dwarf2_loclist_funcs;
>
> diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
> index 101065b..1d5fa3d 100644
> --- a/gdb/dwarf2read.c
> +++ b/gdb/dwarf2read.c
> @@ -14252,6 +14252,78 @@ 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);
> + }
It looks like, if TARGET_ATTR is neither a section offset
nor a block, you're getting through to the "return 1" at the end
of the function even though you've haven't set PROP. From my
reading of the DWARF v4 standard, DW_AT_location attributes
should not have any other forms, but let's protect ourselves
against it. I would add a complaint and then 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 *
> @@ -14325,27 +14397,7 @@ 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)
I know that in the testcase you are trying to support, the bounds
are necessarily starting at zero and therefore constant/non-dynamic.
But can you modify the function to also handle the DW_AT_lower_bound
the same way? Other languages such as Ada will need that also, and
that seems like the logical time to be doing it.
> @@ -14409,12 +14461,6 @@ 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;
> diff --git a/gdb/gdbtypes.c b/gdb/gdbtypes.c
> index 7f0269c..f5bd236 100644
> --- a/gdb/gdbtypes.c
> +++ b/gdb/gdbtypes.c
> @@ -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. */
> @@ -982,24 +993,28 @@ create_array_type (struct type *result_type,
> struct type *element_type,
> struct type *range_type)
> {
> - 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 (get_discrete_bounds (range_type, &low_bound, &high_bound) < 0)
> - low_bound = high_bound = 0;
> - CHECK_TYPEDEF (element_type);
> - /* Be careful when setting the array length. Ada arrays can be
> - empty arrays with the high_bound being smaller than the low_bound.
> - In such cases, the array length should be zero. */
> - if (high_bound < low_bound)
> - TYPE_LENGTH (result_type) = 0;
> - else
> - TYPE_LENGTH (result_type) =
> - TYPE_LENGTH (element_type) * (high_bound - low_bound + 1);
> +
> + 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);
> + /* Be careful when setting the array length. Ada arrays can be
> + empty arrays with the high_bound being smaller than the low_bound.
> + In such cases, the array length should be zero. */
> + if (high_bound < low_bound)
> + TYPE_LENGTH (result_type) = 0;
> + else
> + TYPE_LENGTH (result_type) =
> + TYPE_LENGTH (element_type) * (high_bound - low_bound + 1);
> + }
> TYPE_NFIELDS (result_type) = 1;
> TYPE_FIELDS (result_type) =
> (struct field *) TYPE_ZALLOC (result_type, sizeof (struct field));
Does it look like you might be leaving the TYPE_LENGTH undefined
for the case of the non-static array index? (Eg when result_type
is not passed as NULL).
It may not matter in practice, as we are probably supposed to ignore
that field for those arrays anyway. But in the case we're not, leaving
the length undefined could cause all sorts of nastiness. For instance,
a struct value fetching its contents could allocate a buffer using
that size, which potentially means randomly large memory regions,
leading to a memory error, always very scary for the typical user.
Any objection to setting the length to 0 in this case?
> @@ -1530,7 +1545,181 @@ stub_noname_complaint (void)
> complaint (&symfile_complaints, _("stub type has NULL name"));
> }
>
> -/* Find the real type of TYPE. This function returns the real type,
> +/* Calculates the size of a type. If TYPE has static bound values takes upper
> + and lower bound into account, otherwise only the TYPE length is returned.
> + TYPE is expected not to be a typedef. */
Would you mind explaining this part to me?
Intuitively, if it is an array with static bounds, then haven't we
already set the correct array length during the call to "create_array_type"?
And if the type is indeed dynamic, is the TYPE's TYPE_LENGTH correct?
> +
> +static ULONGEST
> +get_type_length (const struct type *type)
> +{
> + const struct type *range_type, *target_type;
> + ULONGEST len = TYPE_LENGTH (type);
> + LONGEST low_bound, high_bound;
> +
> + gdb_assert (TYPE_CODE (type) != TYPE_CODE_TYPEDEF);
> +
> + if (TYPE_CODE (type) != TYPE_CODE_ARRAY
> + && TYPE_CODE (type) != TYPE_CODE_STRING)
> + return len;
> +
> + range_type = check_typedef (TYPE_INDEX_TYPE (type));
> +
> + if (!has_static_range (TYPE_RANGE_DATA (range_type)))
> + return len;
> +
> + target_type = check_typedef (TYPE_TARGET_TYPE (type));
> +
> + /* 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. */
> + low_bound = TYPE_LOW_BOUND (range_type);
> + high_bound = TYPE_HIGH_BOUND (range_type);
> +
> + 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 = get_type_length (target_type);
> +
> + len = tlen * (uhigh - ulow + 1);
> + if (tlen == 0 || (len / tlen - 1 + ulow) != uhigh || len > UINT_MAX)
> + len = 0;
> + }
> +
> + return len;
> +}
> +
> +/* See gdbtypes.h. */
> +
> +int
> +is_dynamic_type (const struct type *type)
> +{
> + if (TYPE_CODE (type) == TYPE_CODE_ARRAY
> + && TYPE_NFIELDS (type) == 1)
> + {
> + const struct type *range_type = TYPE_INDEX_TYPE (type);
> +
> + if (!has_static_range (TYPE_RANGE_DATA (range_type)))
> + return 1;
> + }
> +
> + if (TYPE_CODE (type) == TYPE_CODE_ARRAY
> + || TYPE_CODE (type) == TYPE_CODE_PTR
> + || TYPE_CODE (type) == TYPE_CODE_REF
> + || TYPE_CODE (type) == TYPE_CODE_TYPEDEF)
> + return is_dynamic_type (check_typedef (TYPE_TARGET_TYPE (type)));
As discussed on IRC, I think that TYPE_NFIELDS should always
be 1 for TYPE_CODE_ARRAY. So let's transform that into an assert,
if you don't mind, and see what happens?
Can you explain why you included TYPE_CODE_PTR in the list?
This is not clear to me based on the function's description.
The risk I see with this is trying to print the value of a pointer
to a dynamic array - the printing really only needs to display
the address, and not resolve the underlying array. Also, from
a logical standpoint, pointers are not dynamic types.
In the case of TYPE_CODE_TYPEDEF, I think it would be better to do
the unwrapping at the end, as it would be more consistent with what
we do, and also avoid an additional level of recursion. In fact,
the only recursion that's only really needed, I think, is for arrays,
no? Thus...
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:
gdb_assert (TYPE_NFIELDS (type) == 1);
range_type = TYPE_INDEX_TYPE (type);
if (!has_static_range (TYPE_INDEX_TYPE (type)))
return 1;
else
return is_dynamic_type (TYPE_TARGET_TYPE (type));
break;
default:
return 0;
break;
}
... for instance.
> +
> + return 0;
> +}
> +
> +/* Resolves dynamic bound values of an array type to static ones.
> + TYPE is modified in place and is expected not to be a typedef.
> + ADDRESS might be needed to resolve the subrange bounds, it is the location
> + of the associated array. */
In this description, you mention that TYPE is expected NOT to be
a typedef, and yet the code tests for it...
> +
> +static struct type *
> +resolve_dynamic_bounds (struct type *type, CORE_ADDR addr)
> +{
> + CORE_ADDR value;
> + struct type *array_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
> + || TYPE_CODE (type) == TYPE_CODE_PTR)
> + {
> + struct type *copy = copy_type (type);
> +
> + TYPE_TARGET_TYPE (copy)
> + = resolve_dynamic_bounds (TYPE_TARGET_TYPE (type), addr);
> +
> + return copy;
> + }
Same remark as above for the handling of typedefs. I think this will
help avoid an unnecessary type copy.
Also, same question about handling pointers. Why do it here?
> +
> + gdb_assert (TYPE_CODE (type) == TYPE_CODE_ARRAY);
> +
> + array_type = check_typedef (type);
> + range_type = check_typedef (TYPE_INDEX_TYPE (array_type));
If the assert above passed, you should not need the check_typedef
on TYPE to get ARRAY_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 (array_type));
> +
> + if (ary_dim != NULL && TYPE_CODE (ary_dim) == TYPE_CODE_ARRAY)
> + array_type = resolve_dynamic_bounds (TYPE_TARGET_TYPE (type), addr);
> + else
> + array_type = TYPE_TARGET_TYPE (type);
I know this is going to sound a little silly, but would you mind
calling "array_type" something like "elt_type" instead. The else
block where you have "array_type = TYPE_TARGET_TYPE" really threw me
at first, thinking you had a bug in your code.
> +
> + range_type
> + = create_range_type (NULL,
> + TYPE_TARGET_TYPE (range_type),
> + &low_bound, &high_bound);
Small formatting nit-pick (while we're touching this code):
range_type = create_range_type (NULL,
TYPE_TARGET_TYPE (range_type),
&low_bound, &high_bound);
> + array_type = create_array_type (copy_type (type),
> + array_type,
> + range_type);
> +
> + return array_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 (!TYPE_OBJFILE_OWNED (real_type))
> + return type;
Can you explain this? This definitely deserves a comment.
> + if (!is_dynamic_type (real_type))
> + return type;
> +
> + resolved_type = resolve_dynamic_bounds (type, addr);
> + resolved_type->length = get_type_length (check_typedef (resolved_type));
Same as above regarding get_type_length. It seems to me that the length
should have already been correctly computed by create_array_type,
called from resolve_dynamic_bounds.
> +
> + return resolved_type;
> +}
> +
> +/* find the real type of TYPE. This function returns the real type,
^^^^
I think you unintentionally modified the first line of this comment...
This line should not be part of the diff.
> after removing all layers of typedefs, and completing opaque or stub
> types. Completion changes the TYPE argument, but stripping of
> typedefs does not.
> @@ -1706,44 +1895,15 @@ 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;
> - }
> + || TYPE_CODE (type) == TYPE_CODE_STRING)
> + {
> + range_type = TYPE_INDEX_TYPE (type);
> + if (has_static_range (TYPE_RANGE_DATA (range_type)))
> + {
> + TYPE_LENGTH (type) = get_type_length (type);
> + TYPE_TARGET_STUB (type) = 0;
> + }
> + }
> else if (TYPE_CODE (type) == TYPE_CODE_RANGE)
> {
> TYPE_LENGTH (type) = TYPE_LENGTH (target_type);
> diff --git a/gdb/gdbtypes.h b/gdb/gdbtypes.h
> index f6e68c5..38cd240 100644
> --- a/gdb/gdbtypes.h
> +++ b/gdb/gdbtypes.h
> @@ -1,3 +1,4 @@
> +
> /* Internal type definitions for GDB.
>
> Copyright (C) 1992-2013 Free Software Foundation, Inc.
> @@ -1574,6 +1575,15 @@ extern struct type *lookup_unsigned_typename (const struct language_defn *,
> extern struct type *lookup_signed_typename (const struct language_defn *,
> struct gdbarch *, const char *);
>
> +/* Resolves 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 values returns TYPE otherwise a new type with static
> + values is returned. */
> +extern struct type *resolve_dynamic_type (struct type *type, CORE_ADDR addr);
> +
> +/* Predicates if the type has dynamic values, which are not resolved yet. */
> +extern int is_dynamic_type (const struct type *type);
> +
While making adjustments to this patch, would you mind adjusting
the style of the function descriptions, please. We use the imperative
style when describing the actions of the function. For instance:
/* Resolve (no s) all dynamic values of a type.
"ADDR specifies" should still be with an 's'...
> extern struct type *check_typedef (struct type *);
>
> #define CHECK_TYPEDEF(TYPE) \
> diff --git a/gdb/valops.c b/gdb/valops.c
> index 5c7bb89..a7260b9 100644
> --- a/gdb/valops.c
> +++ b/gdb/valops.c
> @@ -902,7 +902,9 @@ 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 values new type after this call. */
^^^^^^^^
Suggest: Make sure to retrieve the returned value's new type after
this call.
I'd suggest also an example of when the value's type might be
different...
> static struct value *
> get_value_at (struct type *type, CORE_ADDR addr, int lazy)
> @@ -927,7 +929,9 @@ 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 values
> + new type after this call.
>
> Note: value_at does *NOT* handle embedded offsets; perform such
> adjustments before or after calling it. */
> @@ -938,7 +942,9 @@ 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 values new type after this call. */
Same remark as above. And in value.c below as well.
>
> struct value *
> value_at_lazy (struct type *type, CORE_ADDR addr)
> diff --git a/gdb/value.c b/gdb/value.c
> index a64e7e1..12726a1 100644
> --- a/gdb/value.c
> +++ b/gdb/value.c
> @@ -3178,32 +3178,37 @@ 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 values new type after this call. */
> 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;
> --
> 1.8.4.2
--
Joel