[Ada] Fix the evaluation of access to packed array subscript

This change is relevant only for standard DWARF (as opposed to the GNAT
encodings extensions): at the time of writing it only makes a difference
with GCC patches that are to be integrated: see in particular
<https://gcc.gnu.org/ml/gcc-patches/2015-07/msg01364.html>.

Given the following Ada declarations:

    type Small is mod 2 ** 6;
    type Array_Type is array (0 .. 9) of Small
       with Pack;
    type Array_Access is access all Array_Type;

    A  : aliased Array_Type := (1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
    AA : constant Array_Type := A'Access;

Before this change, we would get the following GDB session:

    (gdb) print aa.all(2)
    $1 = 3
    (gdb) print aa(2)
    $2 = 16

This is wrong: both expression should yield the same value: 3.  The
problem is simply that the routine which handles accesses to arrays lack
general handling for packed arrays.  After this patch, we have the
expected output:

    (gdb) print aa.all(2)
    $1 = 3
    (gdb) print aa(2)
    $2 = 3

gdb/ChangeLog:

	* ada-lang.c (ada_value_ptr_subscript): Update the heading
	comment.  Handle packed arrays.

gdb/testsuite/ChangeLog:

	* gdb.ada/access_to_packed_array.exp: New testcase.
	* gdb.ada/access_to_packed_array/foo.adb: New file.
	* gdb.ada/access_to_packed_array/pack.adb: New file.
	* gdb.ada/access_to_packed_array/pack.ads: New file.

Tested on x86_64-linux, no regression.

4 files changed, 106 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.ada/access_to_packed_array.exp b/gdb/testsuite/gdb.ada/access_to_packed_array.exp
new file mode 100644
index 0000000..0dca780
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/access_to_packed_array.exp
@@ -0,0 +1,33 @@
+# Copyright 2015 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 foo
+
+if {[gdb_compile_ada "${srcfile}" "${binfile}" executable [list debug]] != "" } {
+  return -1
+}
+
+clean_restart ${testfile}
+
+set bp_location [gdb_get_line_number "BREAK" ${testdir}/foo.adb]
+runto "foo.adb:$bp_location"
+
+gdb_test "print pack.a" "\\(0 => 1, 2, 3, 4, 5, 6, 7, 8, 9, 10\\)")
+gdb_test "pack.aa"      "\\(access pack\\.array_type\\) 0x.* <pack\\.a>")
+
+gdb_test "pack.a(2)"   "3"
+gdb_test "pack.aa(2)"  "3"
diff --git a/gdb/testsuite/gdb.ada/access_to_packed_array/foo.adb b/gdb/testsuite/gdb.ada/access_to_packed_array/foo.adb
new file mode 100644
index 0000000..71ae5bf
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/access_to_packed_array/foo.adb
@@ -0,0 +1,21 @@
+--  Copyright 2015 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 Pack;
+
+procedure Foo is
+begin
+   Pack.Do_Nothing (Pack.AA); --  BREAK
+end Foo;
diff --git a/gdb/testsuite/gdb.ada/access_to_packed_array/pack.adb b/gdb/testsuite/gdb.ada/access_to_packed_array/pack.adb
new file mode 100644
index 0000000..60d752d
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/access_to_packed_array/pack.adb
@@ -0,0 +1,23 @@
+--  Copyright 2015 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 body Pack is
+
+   procedure Do_Nothing (A : Array_Access) is
+   begin
+      null;
+   end Do_Nothing;
+
+end Pack;
diff --git a/gdb/testsuite/gdb.ada/access_to_packed_array/pack.ads b/gdb/testsuite/gdb.ada/access_to_packed_array/pack.ads
new file mode 100644
index 0000000..bb08742
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/access_to_packed_array/pack.ads
@@ -0,0 +1,29 @@
+--  Copyright 2015 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 Pack is
+
+   type Small is mod 2 ** 6;
+   type Array_Type is array (0 .. 9) of Small
+      with Pack;
+   type Array_Access is access all Array_Type;
+
+   A  : aliased Array_Type :=
+     (1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
+   AA : constant Array_Access := A'Access;
+
+   procedure Do_Nothing (A : Array_Access);
+
+end Pack;