old-cross-binutils/gdb/testsuite/gdb.ada
Joel Brobecker dddc0e16ef [Ada] GDB crash during "finish" of function with out parameters
Consider a function with the following signature...

   function F (R : out Rec_Type) return Enum_Type;

... where Rec_Type is a simple record:

   type Rec_Type is record
      Cur : Integer;
   end record;

Trying to "finish" from that function causes GDB to SEGV:

    (gdb) fin
    Run till exit from #0  bar.f (r=...) at bar.adb:5
    0x00000000004022fe in foo () at foo.adb:5
    5          I : Enum_Type := F (R);
    [1]    18949 segmentation fault (core dumped)  /[..]/gdb

This is related to the fact that funtion F has a parameter (R)
which is an "out" parameter being passed by copy. For those,
GNAT transforms the return value to be a record with multiple
fields: The first one is called "RETVAL" and contains the return
value shown in the source, and the remaining fields have the same
name as the "out" or "in out" parameters which are passed by copy.
So, in the example above, function F returns a struct that has
one field who name is "r".

Because "RETVAL" starts with "R", GDB thinks it's a wrapper field,
because it looks like the encoding used for  variant records:

   --    member_name ::= {choice} | others_choice
   --    choice ::= simple_choice | range_choice
   --    simple_choice ::= S number
   --    range_choice  ::= R number T number   <<<<<-----  here
   --    number ::= {decimal_digit} [m]
   --    others_choice ::= O (upper case letter O)

See ada_is_wrapper_field:

  return (name != NULL
          && (startswith (name, "PARENT")
              || strcmp (name, "REP") == 0
              || startswith (name, "_parent")
              || name[0] == 'S' || name[0] == 'R' || name[0] == 'O'));

As a result of this, when trying to print the RETURN value,
we think that RETVAL is a wrapper, and thus recurse into
print_field_values...

      if (ada_is_wrapper_field (type, i))
        {
          comma_needed =
            print_field_values (TYPE_FIELD_TYPE (type, i),
                                valaddr,
                                (offset
                                 + TYPE_FIELD_BITPOS (type, i) / HOST_CHAR_BIT),
                                stream, recurse, val, options,
                                comma_needed, type, offset, language);

... which is a problem since print_field_values assumes that
the type it is given ("TYPE_FIELD_TYPE (type, i)" here), is also
a record type. However, that's not the case, since RETVAL is
an enum. That eventually leads GDB to a NULL type when trying to
extract fields out of the enum, which then leads to a SEGV when
trying to dereference it.

Ideally, we'd want to be a little more careful in identifying
wrapper fields, by enhancing ada_is_wrapper_field to be a little
more complete in its analysis of the field name before declaring
it a variant record wrapper. However, it's not super easy to do
so, considering that the choices can be combined together when
complex choices are used. Eg:

   -- [...] the choice 1 .. 4 | 7 | -10 would be represented by
   --    R1T4S7S10m

Given that we are working towards getting rid of GNAT encodings,
which means that the above will eventually disappear, we took
the more pragmatic approach is just treating  RETVAL as a special
case.

gdb/ChangeLog:

        * ada-lang.c (ada_is_wrapper_field): Add special handling
        for fields called "RETVAL".

gdb/testsuite/ChangeLog:

        * gdb.ada/fin_fun_out: New testcase.
2015-11-09 09:58:16 -08:00
..
access_to_packed_array
addr_arith
aliased_array
arr_arr
array_bounds
array_char_idx
array_of_variable_length
array_ptr_renaming
array_return
array_subscript_addr
arraydim
arrayidx
arrayparam
arrayptr
atomic_enum
attr_ref_and_charlit
bad-task-bp-keyword
bp_enum_homonym
bp_on_var
bp_range_type
bp_reset
byte_packed_arr
call_pn
catch_ex
char_enum
char_param
complete
cond_lang
disc_arr_bound
dot_all
dyn_arrayidx
dyn_loc
enum_idx_packed
exec_changed
expr_delims
exprs
fin_fun_out [Ada] GDB crash during "finish" of function with out parameters 2015-11-09 09:58:16 -08:00
fixed_cmp
fixed_points
float_param
formatted_ref
frame_args
fullname_bp
fun_addr
fun_in_declare
fun_renaming
funcall_char
funcall_param
funcall_ref
homonym
info_exc
info_locals_renaming
int_deref
interface
iwide
lang_switch
mi_catch_ex
mi_dyn_arr
mi_ex_cond
mi_exc_info
mi_interface
mi_task_arg
mi_task_info
mi_var_array
mod_from_name
n_arr_bound
nested
null_array
null_record
O2_float_param
operator_bp
optim_drec
out_of_line_in_inlined
packed_array
packed_tagged
pckd_arr_ren
pckd_neg
pkd_arr_elem
pp-rec-component
print_chars
ptr_typedef
ptype_field
ptype_tagged_param
py_range
rdv_wait
rec_comp
rec_return
ref_param
ref_tick_size
same_enum
set_pckd_arr_elt
set_wstr
small_reg_param
start
str_ref_cmp
str_uninit
sym_print_name
taft_type
tagged
tagged_access
tagged_not_init
task_bp
tasks
tick_last_segv
tick_length_array_enum_idx
type_coercion
unc_arr_ptr_in_var_rec
uninitialized_vars
var_arr_attrs
var_arr_typedef
var_rec_arr
variant_record_packed_array
watch_arg
whatis_array_val
widewide
win_fu_syms
access_to_packed_array.exp
addr_arith.exp
aliased_array.exp
arr_arr.exp
array_bounds.exp
array_char_idx.exp
array_of_variable_length.exp
array_ptr_renaming.exp
array_return.exp
array_subscript_addr.exp
arraydim.exp
arrayidx.exp
arrayparam.exp
arrayptr.exp
assign_1.exp
atomic_enum.exp
attr_ref_and_charlit.exp
bad-task-bp-keyword.exp
boolean_expr.exp
bp_enum_homonym.exp
bp_on_var.exp
bp_range_type.exp
bp_reset.exp
byte_packed_arr.exp
call_pn.exp
catch_ex.exp
char_enum.exp
char_param.exp
complete.exp
cond_lang.exp
disc_arr_bound.exp
dot_all.exp
dyn_arrayidx.exp
dyn_loc.exp
enum_idx_packed.exp
exec_changed.exp
expr_delims.exp
exprs.exp
fin_fun_out.exp [Ada] GDB crash during "finish" of function with out parameters 2015-11-09 09:58:16 -08:00
fixed_cmp.exp
fixed_points.exp
float_param.exp
formatted_ref.exp
frame_args.exp
fullname_bp.exp
fun_addr.exp
fun_in_declare.exp
fun_renaming.exp
funcall_char.exp
funcall_param.exp
funcall_ref.exp
gnat_ada.gpr
homonym.exp
info_exc.exp
info_locals_renaming.exp
info_types.c
info_types.exp
int_deref.exp
interface.exp
iwide.exp
lang_switch.exp
Makefile.in
mi_catch_ex.exp
mi_dyn_arr.exp
mi_ex_cond.exp
mi_exc_info.exp
mi_interface.exp
mi_task_arg.exp
mi_task_info.exp
mi_var_array.exp
mod_from_name.exp
n_arr_bound.exp
nested.exp
null_array.exp
null_record.exp
O2_float_param.exp
operator_bp.exp
optim_drec.exp
out_of_line_in_inlined.exp
packed_array.exp
packed_tagged.exp
pckd_arr_ren.exp
pckd_neg.exp
pkd_arr_elem.exp
pp-rec-component.exp
pp-rec-component.py
print_chars.exp
print_pc.exp
ptr_typedef.exp
ptype_arith_binop.exp
ptype_field.exp
ptype_tagged_param.exp
py_range.exp
rdv_wait.exp
rec_comp.exp
rec_return.exp
ref_param.exp
ref_tick_size.exp
same_enum.exp
set_pckd_arr_elt.exp
set_wstr.exp
small_reg_param.exp
start.exp
str_ref_cmp.exp
str_uninit.exp
sym_print_name.exp
taft_type.exp
tagged.exp
tagged_access.exp
tagged_not_init.exp
task_bp.exp
tasks.exp
tick_last_segv.exp
tick_length_array_enum_idx.exp
type_coercion.exp
unc_arr_ptr_in_var_rec.exp
uninitialized_vars.exp
var_arr_attrs.exp
var_arr_typedef.exp
var_rec_arr.exp
variant_record_packed_array.exp
watch_arg.exp
whatis_array_val.exp
widewide.exp
win_fu_syms.exp