(Ada) assigning packed array aggregate with variable as component

Consider a variable "PRA" defined as a packed array of packed
records as follow:

   subtype Int is Integer range 0 .. 7;
   type Packed_Rec is record
      X, Y : Int;
      W    : Integer;
   end record;
   pragma Pack (Packed_Rec);
   type Packed_RecArr is array (Integer range <>) of Packed_Rec;
   pragma Pack (Packed_RecArr);

   PRA : Packed_RecArr (1 .. 3);

Consider also a variable "PR", which is a Packed_Rec record,
declared as follow:

   PR : Packed_Rec := (2, 2, 2);

Trying to assign a new value to PRA using an aggregate expression
where one of the components is our variable PR yields the wrong
result on big-endian machines (e.g. on ppc-linux):

    (gdb) p pra := (pr, (2,2,2), (2,2,2))
    $6 = ((x => 1, y => 0, w => 8), [...]

On the other hand, replacing "pr" by "(2,2,2)" does work.

I tracked the issue down to the bit offset we use to extract
the value of "PR" and copy it inside PRA. in value_assign_to_component,
we have:

  if (gdbarch_bits_big_endian (get_type_arch (value_type (container))))
    move_bits ([target buffer], [bit offset in target buffer],
               [source buffer where PR is stored],
               TYPE_LENGTH (value_type (component)) * TARGET_CHAR_BIT - bits,
               bits, 1);

The issue is with the third-to-last argument, which provides the bit
offset where the value of PR is stored relative to its start address,
and therefore the bit offset relative to the start of the source
buffer passed as the previous argument.

In our case, component is a 38bit packed record whose TYPE_LENGTH
is 5 bytes, so the bit-offset that gets calculated is 2 (bits).
However, that formula only really applies to scalars, whereas
in our case, we have a record (struct). The offset in the non-scalar
case should be zero.

gdb/ChangeLog:

        * ada-lang.c (value_assign_to_component): In the case of
        big-endian targets, extract the bits of the given VAL
        using an src_offset of zero if container is not a scalar.

gdb/testsuite/ChangeLog:

        * gdb.ada/packed_array_assign: New testcase.

gdb/ChangeLog

@@ -1,3 +1,9 @@
+2018-09-08  Joel Brobecker  <brobecker@adacore.com>
+
+	* ada-lang.c (value_assign_to_component): In the case of
+	big-endian targets, extract the bits of the given VAL
+	using an src_offset of zero if container is not a scalar.
+
 2018-09-06  Simon Ser  <contact@emersion.fr>
 
 	PR gdb/23105

gdb/ada-lang.c

@@ -2809,11 +2809,18 @@ value_assign_to_component (struct value *container, struct value *component,
     bits = value_bitsize (component);
 
   if (gdbarch_bits_big_endian (get_type_arch (value_type (container))))
-    move_bits (value_contents_writeable (container) + offset_in_container,
-	       value_bitpos (container) + bit_offset_in_container,
-	       value_contents (val),
-	       TYPE_LENGTH (value_type (component)) * TARGET_CHAR_BIT - bits,
-	       bits, 1);
+    {
+      int src_offset;
+
+      if (is_scalar_type (check_typedef (value_type (component))))
+        src_offset
+	  = TYPE_LENGTH (value_type (component)) * TARGET_CHAR_BIT - bits;
+      else
+	src_offset = 0;
+      move_bits (value_contents_writeable (container) + offset_in_container,
+		 value_bitpos (container) + bit_offset_in_container,
+		 value_contents (val), src_offset, bits, 1);
+    }
   else
     move_bits (value_contents_writeable (container) + offset_in_container,
 	       value_bitpos (container) + bit_offset_in_container,

gdb/testsuite/ChangeLog

@@ -1,3 +1,7 @@
+2018-09-08  Joel Brobecker  <brobecker@adacore.com>
+
+	* gdb.ada/packed_array_assign: New testcase.
+
 2018-09-07  Andrew Burgess  <andrew.burgess@embecosm.com>
 
 	* gdb.base/watchpoint.exp (test_complex_watchpoint): Extend test

gdb/testsuite/gdb.ada/packed_array_assign.exp

@@ -0,0 +1,30 @@
+# Copyright 2018 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 tester
+
+if {[gdb_compile_ada "${srcfile}" "${binfile}" executable [list debug]] != "" } {
+  return -1
+}
+
+clean_restart ${testfile}
+
+runto "aggregates.run_test"
+
+gdb_test \
+    "print pra := ((x => 2, y => 0, w => 17), pr, (x => 7, y => 1, w => 23))" \
+    " = \\(\\(w => 17, x => 2, y => 0\\), \\(w => 104, x => 2, y => 3\\), \\(w => 23, x => 7, y => 1\\)\\)"

gdb/testsuite/gdb.ada/packed_array_assign/aggregates.adb

@@ -0,0 +1,25 @@
+--  Copyright 2018 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 Pck; use Pck;
+
+package body Aggregates is
+   procedure Run_Test is
+   begin
+      --  Fake the use of PRA to prevent the AIX linker from optimizing
+      --  the following symbols away.
+      Do_Nothing (PRA'Address);
+   end;
+end Aggregates;

gdb/testsuite/gdb.ada/packed_array_assign/aggregates.ads

@@ -0,0 +1,33 @@
+--  Copyright 2018 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 Aggregates is
+   subtype Int is Integer range 0 .. 7;
+
+   type Packed_Rec is record
+      X, Y : Int;
+      W    : Integer;
+   end record;
+   pragma Pack (Packed_Rec);
+
+   type Packed_RecArr is array (Integer range <>) of Packed_Rec;
+   pragma Pack (Packed_RecArr);
+
+   procedure Run_Test;
+
+private
+   PR : Packed_Rec := (y => 3, w => 104, x => 2);
+   PRA : Packed_RecArr (1 .. 3);
+end Aggregates;

gdb/testsuite/gdb.ada/packed_array_assign/pck.adb

@@ -0,0 +1,23 @@
+--  Copyright 2018 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 Pck is
+
+   procedure Do_Nothing (A : System.Address) is
+   begin
+      null;
+   end Do_Nothing;
+
+end Pck;

gdb/testsuite/gdb.ada/packed_array_assign/pck.ads

@@ -0,0 +1,22 @@
+--  Copyright 2018 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 System;
+
+package Pck is
+
+   procedure Do_Nothing (A : System.Address);
+
+end Pck;

gdb/testsuite/gdb.ada/packed_array_assign/tester.adb

@@ -0,0 +1,20 @@
+--  Copyright 2018 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 Aggregates;
+procedure Tester is
+begin
+   Aggregates.Run_Test;
+end Tester;