(Ada) crash assigning to record component which is an array

Consider the following code, which declares a variabled called "input"
of type "parameter", which is a record with one component called "u2",
where the type of that component is a simple 3-element array of
floating point values:

   type Float_Array_3 is array (1 .. 3) of Float;
   type parameters is record
      u2 : Float_Array_3;
   end record;
   input : parameters;

Trying to assign a value to input.u2 causes GDB to crash:

    (gdb) p input.u2 := (0.25,0.5,0.75)
    [1]    20228 segmentation fault (core dumped) [...]/gdb

The crash occurs because input.u2 is described in the debugging
info as a typedef of an array. Indeed, input's type is:

 <1><ae9>: Abbrev Number: 7 (DW_TAG_structure_type)
    <aea>   DW_AT_name        : (indirect string, offset: 0x1045): target_wrapper__parameters
    [...]
 <2><af5>: Abbrev Number: 8 (DW_TAG_member)
    <af6>   DW_AT_name        : u2
    [...]
    <afb>   DW_AT_type        : <0xaca>

and, looking at DIE 0xaca to get input.u2's type, we see:

 <1><aca>: Abbrev Number: 4 (DW_TAG_typedef)
    <acb>   DW_AT_name        : (indirect string, offset: 0x1060): target_wrapper__float_array_3
    [...]
    <ad1>   DW_AT_type        : <0xad5>

We can also confirm, following the DW_AT_type attribute (0xad5), that
it's a typedef of our array:

 <1><ad5>: Abbrev Number: 5 (DW_TAG_array_type)
    <ad6>   DW_AT_name        : (indirect string, offset: 0x1060): target_wrapper__float_array_3
    [...]

In fact, this scenario uncovered 2 areas where typedef handling
is missing, thus causing a crash. The first happens inside
assign_aggregate:

   if (ada_is_direct_array_type (lhs_type))
     {
       lhs = ada_coerce_to_simple_array (lhs);
       lhs_type = value_type (lhs);
       low_index = TYPE_ARRAY_LOWER_BOUND_VALUE (lhs_type);
       high_index = TYPE_ARRAY_UPPER_BOUND_VALUE (lhs_type);
     }

Here, lhs_type is a TYPE_CODE_TYPEDEF. ada_is_direct_array_type
knows how to handle it, but TYPE_ARRAY_LOWER_BOUND_VALUE assumes
that the given type is a TYPE_CODE_ARRAY. As such, it ends up
accessing some fields in lhs_type which it shouldn't, and kaboom.

We fixed this issue by making sure that the TYPE_CODE_TYPEDEF
layer gets stripped.

Once this is done, we hit a different kind of error, also leading to
a SEGV, this time in assign_component. The code looks like this:

  if (TYPE_CODE (value_type (lhs)) == TYPE_CODE_ARRAY)
    [...]
  else
    [...]

Because once again lhs is a TYPE_CODE_TYPEDEF, the check fail,
and we end up assuming that lhs is a struct, executing the "else"
block, which is:

  else
    {
      elt = ada_index_struct_field (index, lhs, 0, value_type (lhs));
      elt = ada_to_fixed_value (elt);
    }

Since lhs is not a struct, ada_index_struct_field returns NULL,
which ada_to_fixed_value does not handle well, hence another crash.

This patch fixes this other issue the same way, by stripping
TYPE_CODE_TYPEDEF layers.

gdb/ChangeLog:

        * ada-lang.c (assign_component): Strip any TYPE_CODE_TYPEDEF
        layer from lhs' type.
        (assign_aggregate): Likewise.

gdb/testsuite:

        * gdb.ada/assign_arr: New testcase.

Tested on x86_64-linux.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index fd2700d..5e65e5f 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2017-12-18  Joel Brobecker  <brobecker@adacore.com>
+
+       * ada-lang.c (assign_component): Strip any TYPE_CODE_TYPEDEF
+       layer from lhs' type.
+       (assign_aggregate): Likewise.
+
 2017-12-18  Xavier Roirand  <roirand@adacore.com>
 
        * ada-lang.c (ada_convert_actual): Change the way actual value

diff --git a/gdb/ada-lang.c b/gdb/ada-lang.c
index 8a0423e..14a0bd6 100644 (file)
--- a/gdb/ada-lang.c
+++ b/gdb/ada-lang.c
@@ -9960,8 +9960,9 @@ assign_component (struct value *container, struct value *lhs, LONGEST index,
 {
   struct value *mark = value_mark ();
   struct value *elt;
+  struct type *lhs_type = check_typedef (value_type (lhs));
 
-  if (TYPE_CODE (value_type (lhs)) == TYPE_CODE_ARRAY)
+  if (TYPE_CODE (lhs_type) == TYPE_CODE_ARRAY)
     {
       struct type *index_type = builtin_type (exp->gdbarch)->builtin_int;
       struct value *index_val = value_from_longest (index_type, index);
@@ -10020,11 +10021,11 @@ assign_aggregate (struct value *container,
   if (!deprecated_value_modifiable (lhs))
     error (_("Left operand of assignment is not a modifiable lvalue."));
 
-  lhs_type = value_type (lhs);
+  lhs_type = check_typedef (value_type (lhs));
   if (ada_is_direct_array_type (lhs_type))
     {
       lhs = ada_coerce_to_simple_array (lhs);
-      lhs_type = value_type (lhs);
+      lhs_type = check_typedef (value_type (lhs));
       low_index = TYPE_ARRAY_LOWER_BOUND_VALUE (lhs_type);
       high_index = TYPE_ARRAY_UPPER_BOUND_VALUE (lhs_type);
     }

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 3075686..c074186 100644 (file)
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2017-12-18  Joel Brobecker  <brobecker@adacore.com>
+
+       * gdb.ada/assign_arr: New testcase.
+
 2017-12-18  Xavier Roirand  <roirand@adacore.com>
 
        * gdb.ada/funcall_ptr: New testcase.

diff --git a/gdb/testsuite/gdb.ada/assign_arr.exp b/gdb/testsuite/gdb.ada/assign_arr.exp
new file mode 100644 (file)
index 0000000..7129f22
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/assign_arr.exp
@@ -0,0 +1,30 @@
+# Copyright 2016-2017 Free Software Foundation, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+load_lib "ada.exp"
+
+standard_ada_testfile main_p324_051
+
+if {[gdb_compile_ada "${srcfile}" "${binfile}" executable [list debug]] != "" } {
+  return -1
+}
+
+clean_restart ${testfile}
+
+set bp_location [gdb_get_line_number "STOP" ${testdir}/main_p324_051.adb]
+runto "main_p324_051.adb:$bp_location"
+
+gdb_test "print input.u2 := (0.25,0.5,0.75)" \
+         " = \\(0\\.25, 0\\.5, 0\\.75\\)"

diff --git a/gdb/testsuite/gdb.ada/assign_arr/main_p324_051.adb b/gdb/testsuite/gdb.ada/assign_arr/main_p324_051.adb
new file mode 100644 (file)
index 0000000..519c7b5
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/assign_arr/main_p324_051.adb
@@ -0,0 +1,21 @@
+--  Copyright 2016-2017 Free Software Foundation, Inc.
+--
+--  This program is free software; you can redistribute it and/or modify
+--  it under the terms of the GNU General Public License as published by
+--  the Free Software Foundation; either version 3 of the License, or
+--  (at your option) any later version.
+--
+--  This program is distributed in the hope that it will be useful,
+--  but WITHOUT ANY WARRANTY; without even the implied warranty of
+--  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+--  GNU General Public License for more details.
+--
+--  You should have received a copy of the GNU General Public License
+--  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+with target_wrapper; use target_wrapper;
+
+procedure Main_P324_051 is
+begin
+   input.u2 := (0.2,0.3,0.4);  -- STOP
+end Main_P324_051;

diff --git a/gdb/testsuite/gdb.ada/assign_arr/target_wrapper.ads b/gdb/testsuite/gdb.ada/assign_arr/target_wrapper.ads
new file mode 100644 (file)
index 0000000..d4a0417
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/assign_arr/target_wrapper.ads
@@ -0,0 +1,26 @@
+--  Copyright 2016-2017 Free Software Foundation, Inc.
+--
+--  This program is free software; you can redistribute it and/or modify
+--  it under the terms of the GNU General Public License as published by
+--  the Free Software Foundation; either version 3 of the License, or
+--  (at your option) any later version.
+--
+--  This program is distributed in the hope that it will be useful,
+--  but WITHOUT ANY WARRANTY; without even the implied warranty of
+--  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+--  GNU General Public License for more details.
+--
+--  You should have received a copy of the GNU General Public License
+--  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package target_wrapper is
+
+   type Float_Array_3 is array (1 .. 3) of Float;
+
+   type parameters is record
+      u2 : Float_Array_3;
+   end record;
+
+   input : parameters;
+
+end target_wrapper;