pushed: [Ada 1/2] Crash with references to GNAT packed arrays handling
Commit Message
From: Pierre-Marie de Rodat <derodat@adacore.com>
Consider the following declarations:
type Packed_Array is array (Natural range <>) of Boolean;
pragma Pack (Packed_Array);
function Make (H, L : Natural) return Packed_Array is
begin
return (H .. L => False);
end Make;
A1 : Packed_Array := Make (1, 2);
A2 : Packed_Array renames A1;
One possible DWARF translation for A2 is:
<3><1e4>: Abbrev Number: 21 (DW_TAG_variable)
<1e5> DW_AT_name : a2
<1ea> DW_AT_type : <0x1d9>
<3><1d9>: Abbrev Number: 22 (DW_TAG_const_type)
<1da> DW_AT_type : <0x1de>
<3><1de>: Abbrev Number: 23 (DW_TAG_reference_type)
<1e0> DW_AT_type : <0x1a3>
<3><1a3>: Abbrev Number: 17 (DW_TAG_array_type)
<1a4> DW_AT_name : foo__Ta1S___XP1
<1a8> DW_AT_GNAT_descriptive_type: <0x16b>
<3><16b>: Abbrev Number: 6 (DW_TAG_typedef)
<16c> DW_AT_name : foo__Ta1S
<172> DW_AT_type : <0x176>
<3><176>: Abbrev Number: 17 (DW_TAG_array_type)
<177> DW_AT_name : foo__Ta1S
<17b> DW_AT_GNAT_descriptive_type: <0x223>
Here, foo__Ta1S___XP1 is the type used for the code generation while
foo__Ta1S is the source-level type. Both form a valid GNAT encoding for
a packed array type.
Trying to print A2 (1) can make GDB crash. This is because A2 is defined
as a reference to a GNAT encoding for a packed array. When decoding
constrained packed arrays, the ada_coerce_ref subprogram follows
references and returns a fixed type from the target type, peeling
the GNAT encoding for packed arrays. The remaining code assumes that
the resulting type is still such an encoding while we only have
a standard GDB array type, hence the crash:
arr = ada_coerce_ref (arr);
[...]
type = decode_constrained_packed_array_type (value_type (arr));
decode_constrained_packed_array_type assumes that its argument is
such an encoding. From its front comment:
/* The array type encoded by TYPE, where
ada_is_constrained_packed_array_type (TYPE). */
This patch simply replaces the call to ada_coerce_ref with a call
to coerce_ref in order to avoid prematurely transforming
the packed array type as a side-effect. This way, the remaining code
will always work with a GNAT encoding.
gdb/ChangeLog:
* ada-lang.c (decode_constrained_packed_array): Perform a
minimal coercion for reference with coerce_ref instead of
ada_coerce_ref.
Tested on x86_64-linux. Pushed.
---
gdb/ChangeLog | 6 ++++++
gdb/ada-lang.c | 16 ++++++++--------
2 files changed, 14 insertions(+), 8 deletions(-)
@@ -1,3 +1,9 @@
+2014-03-17 Pierre-Marie de Rodat <derodat@adacore.com>
+
+ * ada-lang.c (decode_constrained_packed_array): Perform a
+ minimal coercion for reference with coerce_ref instead of
+ ada_coerce_ref.
+
2014-03-17 Tristan Gingold <gingold@adacore.com>
* solib-darwin.c (DYLD_VERSION_MAX): Increase value.
@@ -2250,14 +2250,14 @@ decode_constrained_packed_array (struct value *arr)
{
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 our value is a pointer, then dereference it. Likewise if
+ the value is a reference. 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 "coerce_ref"
+ and "value_ind" routines to perform the dereferencing, as opposed
+ to using "ada_coerce_ref" or "ada_value_ind". */
+ arr = coerce_ref (arr);
if (TYPE_CODE (ada_check_typedef (value_type (arr))) == TYPE_CODE_PTR)
arr = value_ind (arr);