Normalize Ada ptype to use a single "?"

Sometimes -- notably with unchecked unions -- the Ada "ptype" code
will print a "?" or "??" to indicate something unknown.  The choice of
what was printed was somewhat arbitrary, and in one case, Ada would
print an empty string rather than "?".

This patch normalizes the Ada code to use "?" rather than an empty
string or "??".  My reasoning here is that a single question mark is
enough to convey unknown-ness.

gdb/ChangeLog
2019-12-10  Tom Tromey  <tromey@adacore.com>

	* ada-typeprint.c (print_choices): Use a single "?".
	(print_variant_part): Print "?" if the discriminant name
	is not known.

gdb/testsuite/ChangeLog
2019-12-10  Tom Tromey  <tromey@adacore.com>

	* gdb.ada/unchecked_union.exp: New file.
	* gdb.ada/unchecked_union/pck.adb: New file.
	* gdb.ada/unchecked_union/pck.ads: New file.
	* gdb.ada/unchecked_union/unchecked_union.adb: New file.
	* gdb-utils.exp (string_to_regexp): Also quote "?".

Change-Id: I3403040780a155ffa2c44c8e6a04ba86bc810e29

3 files changed, 91 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.ada/unchecked_union/pck.adb b/gdb/testsuite/gdb.ada/unchecked_union/pck.adb
new file mode 100644
index 00000000000..6535991a193
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/unchecked_union/pck.adb
@@ -0,0 +1,21 @@
+--  Copyright 2019 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/unchecked_union/pck.ads b/gdb/testsuite/gdb.ada/unchecked_union/pck.ads
new file mode 100644
index 00000000000..b8d00101753
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/unchecked_union/pck.ads
@@ -0,0 +1,19 @@
+--  Copyright 2019 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;
diff --git a/gdb/testsuite/gdb.ada/unchecked_union/unchecked_union.adb b/gdb/testsuite/gdb.ada/unchecked_union/unchecked_union.adb
new file mode 100644
index 00000000000..d6de66d86d9
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/unchecked_union/unchecked_union.adb
@@ -0,0 +1,51 @@
+--  Copyright 2019 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;
+with Pck; use Pck;
+
+procedure Foo is
+   type Key is (Alpha, Omega);
+
+   type Inner(Disc : Key := Omega) is record
+      case Disc is
+         when Alpha =>
+            Small : Integer range 0..255;
+         when others =>
+            Large : Integer range 255..510;
+      end case;
+   end record;
+   pragma Unchecked_Union (Inner);
+
+   type Outer(Disc : Key := Alpha) is record
+      case Disc is
+         when Alpha =>
+            Field_One : Integer range 0..255;
+         when others =>
+            Field_Two : Integer range 255..510;
+      end case;
+   end record;
+   pragma Unchecked_Union (Outer);
+
+   type Pair is record
+      Pone : Inner;
+      Ptwo : Outer;
+   end record;
+
+   Value : Pair;
+
+begin
+   Do_Nothing (Value'Address);          -- BREAK
+end Foo;