(Ada) Fix -var-list-children MI command for union type

Using this Ada code:

   type Union_Type (A : Boolean := False) is record
      case A is
         when True  => B : Integer;
         when False => C : Float;
      end case;
   end record;
   pragma Unchecked_Union (Union_Type);
   Ut : Union_Type := (A => True, B => 3);

In GDB/MI mode, once creating a varobj from variable "Ut" as follow:

(gdb) -var-create var1 * ut
^done,name="var1",numchild="2",value="{...}",type="foo.union_type",thread-id="1",has_more="0"

Printing the list of its children displays:

(gdb) -var-list-children 1 var1
^error,msg="Duplicate variable object name"

Whereas it should be

(gdb) -var-list-children 1 var1
^done,numchild="2",children=[child={name="var1.b",exp="b",numchild="0",value="3",type="integer",thread-id="1"},child={name="var1.c",exp="c",numchild="0",value="4.20389539e-45",type="float",thread-id="1"}],has_more="0"

The problem occurs because ada_varobj_describe_struct_child wasn't
handling unions.  This patch fixes this.

gdb/ChangeLog:

        * ada-varobj.c (ada_varobj_describe_struct_child)
        (ada_varobj_describe_child): Handle union case like struct one.

testsuite/ChangeLog

        * gdb.ada/mi_var_union.exp: New testcase.
        * gdb.ada/mi_var_union/bar.adb: New file.
        * gdb.ada/mi_var_union/pck.adb: New file.
        * gdb.ada/mi_var_union/pck.asd: New file.

Tested on x86_64-linux.

7 files changed, 139 insertions, 2 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 7adb11f..ca678dd 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2018-09-10  Xavier Roirand  <roirand@adacore.com>
+
+	* ada-varobj.c (ada_varobj_describe_struct_child)
+	(ada_varobj_describe_child): Handle union case like struct one.
+
 2018-09-10  Tom Tromey  <tom@tromey.com>
 
 	PR python/18380:
diff --git a/gdb/ada-varobj.c b/gdb/ada-varobj.c
index 6dafe47..5baefd9 100644
--- a/gdb/ada-varobj.c
+++ b/gdb/ada-varobj.c
@@ -419,7 +419,8 @@ ada_varobj_describe_struct_child (struct value *parent_value,
   int fieldno;
   int childno = 0;
 
-  gdb_assert (TYPE_CODE (parent_type) == TYPE_CODE_STRUCT);
+  gdb_assert (TYPE_CODE (parent_type) == TYPE_CODE_STRUCT
+	      || TYPE_CODE (parent_type) == TYPE_CODE_UNION);
 
   for (fieldno = 0; fieldno < TYPE_NFIELDS (parent_type); fieldno++)
     {
@@ -699,7 +700,8 @@ ada_varobj_describe_child (struct value *parent_value,
       return;
     }
 
-  if (TYPE_CODE (parent_type) == TYPE_CODE_STRUCT)
+  if (TYPE_CODE (parent_type) == TYPE_CODE_STRUCT
+      || TYPE_CODE (parent_type) == TYPE_CODE_UNION)
     {
       ada_varobj_describe_struct_child (parent_value, parent_type,
 					parent_name, parent_path_expr,
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index a360c22..3911b8c 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,10 @@
+2018-09-10  Xavier Roirand  <roirand@adacore.com>
+
+	* gdb.ada/mi_var_union.exp: New testcase.
+	* gdb.ada/mi_var_union/bar.adb: New file.
+	* gdb.ada/mi_var_union/pck.adb: New file.
+	* gdb.ada/mi_var_union/pck.asd: New file.
+
 2018-09-08  Tom Tromey  <tom@tromey.com>
 
 	* gdb.python/py-prettyprint.exp: Use with_test_prefix.
diff --git a/gdb/testsuite/gdb.ada/mi_var_union.exp b/gdb/testsuite/gdb.ada/mi_var_union.exp
new file mode 100644
index 0000000..26a7ed0
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/mi_var_union.exp
@@ -0,0 +1,54 @@
+# 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 bar
+
+if {[gdb_compile_ada "${srcfile}" "${binfile}" executable [list debug]] != "" } {
+  return -1
+}
+
+load_lib mi-support.exp
+set MIFLAGS "-i=mi"
+
+gdb_exit
+if [mi_gdb_start] {
+    continue
+}
+
+set float "\\-?((\[0-9\]+(\\.\[0-9\]+)?(e\[-+\]\[0-9\]+)?)|(nan\\($hex\\)))"
+
+mi_delete_breakpoints
+mi_gdb_reinitialize_dir $srcdir/$subdir
+mi_gdb_load ${binfile}
+
+if ![mi_run_to_main] then {
+   fail "Cannot run to main, testcase aborted"
+   return 0
+}
+
+set bp_location [gdb_get_line_number "STOP" ${testdir}/bar.adb]
+mi_continue_to_line \
+    "bar.adb:$bp_location" \
+    "stop at start of main Ada procedure"
+
+mi_gdb_test "-var-create var1 * Ut" \
+    "\\^done,name=\"var1\",numchild=\"2\",.*" \
+    "Create var1 varobj"
+
+mi_gdb_test "-var-list-children 1 var1" \
+    "\\^done,numchild=\"2\",children=\\\[child={name=\"var1.b\",exp=\"b\",numchild=\"0\",value=\"3\",type=\"integer\",thread-id=\"$decimal\"},child={name=\"var1.c\",exp=\"c\",numchild=\"0\",value=\"$float\",type=\"float\",thread-id=\"$decimal\"}\\\],has_more=\"0\"" \
+    "list var1's children"
diff --git a/gdb/testsuite/gdb.ada/mi_var_union/bar.adb b/gdb/testsuite/gdb.ada/mi_var_union/bar.adb
new file mode 100644
index 0000000..9563f34
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/mi_var_union/bar.adb
@@ -0,0 +1,29 @@
+--  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;
+
+procedure Bar is
+   type Union_Type (A : Boolean := False) is record
+      case A is
+         when True  => B : Integer;
+         when False => C : Float;
+      end case;
+   end record;
+   pragma Unchecked_Union (Union_Type);
+   Ut : Union_Type := (A => True, B => 3);
+begin
+   Do_Nothing (Ut'Address);  -- STOP
+end Bar;
diff --git a/gdb/testsuite/gdb.ada/mi_var_union/pck.adb b/gdb/testsuite/gdb.ada/mi_var_union/pck.adb
new file mode 100644
index 0000000..dcfb306
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/mi_var_union/pck.adb
@@ -0,0 +1,21 @@
+--  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;
diff --git a/gdb/testsuite/gdb.ada/mi_var_union/pck.ads b/gdb/testsuite/gdb.ada/mi_var_union/pck.ads
new file mode 100644
index 0000000..33e369e
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/mi_var_union/pck.ads
@@ -0,0 +1,19 @@
+--  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;