Disable ptype/o for dynamic types

A user pointed out that "ptype/o" of a certain Ada type -- while in C
mode -- caused gdb to crash.

The bug here is that dynamic types can't really be printed this way.
This patch avoids the bug by disabling the "/o" feature in this case.

Note that using "ptype/o" in this way makes sense for the time being,
because the Ada code doesn't support the "/o" feature (yet); and in
any case gdb should not crash.

3 files changed, 82 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.ada/ptype-o.exp b/gdb/testsuite/gdb.ada/ptype-o.exp
new file mode 100644
index 0000000..987c6e7
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/ptype-o.exp
@@ -0,0 +1,47 @@
+# Copyright 2023 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/>.
+
+# Test that ptype/o of a dynamic type does not crash.
+
+load_lib "ada.exp"
+
+if { [skip_ada_tests] } { return -1 }
+
+standard_ada_testfile prog
+
+foreach_with_prefix scenario {all minimal} {
+    set flags [list debug additional_flags=-fgnat-encodings=$scenario]
+
+    if {[gdb_compile_ada "${srcfile}" "${binfile}-${scenario}" executable $flags] != ""} {
+	return -1
+    }
+
+    clean_restart ${testfile}-${scenario}
+
+    set bp_location [gdb_get_line_number "BREAK" ${testdir}/prog.adb]
+    runto "prog.adb:$bp_location"
+
+    gdb_test "set lang c" \
+	"Warning: the current language does not match this frame."
+
+    if {$scenario == "minimal"} {
+	set exp "ptype/o does not work with dynamic types.*"
+    } else {
+	# In "all" mode this prints nonsense, but at least does not
+	# crash.
+	set exp ".*"
+    }
+    gdb_test "ptype/o struct prog__rec" $exp
+}
diff --git a/gdb/testsuite/gdb.ada/ptype-o/prog.adb b/gdb/testsuite/gdb.ada/ptype-o/prog.adb
new file mode 100644
index 0000000..1a3caad
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/ptype-o/prog.adb
@@ -0,0 +1,29 @@
+--  Copyright 2023 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/>.
+
+procedure Prog is
+  type Index is range 0 .. 31;
+  type Char_Array is array ( Index range <>) of Character;
+
+  type Rec (Length : Index) is
+    record
+      TV_Description        : Char_Array (1 .. Length);
+      Note                  : Char_Array (1 .. Length);
+    end record;
+
+  X : Rec (7);
+begin
+  null; -- BREAK
+end Prog;
diff --git a/gdb/typeprint.c b/gdb/typeprint.c
index 87df7f2..41b5735 100644
--- a/gdb/typeprint.c
+++ b/gdb/typeprint.c
@@ -539,6 +539,12 @@ whatis_exp (const char *exp, int show)
       type = value_type (val);
     }
 
+  if (flags.print_offsets && is_dynamic_type (type))
+    {
+      warning (_("ptype/o does not work with dynamic types; disabling '/o'"));
+      flags.print_offsets = 0;
+    }
+
   get_user_print_options (&opts);
   if (val != NULL && opts.objectprint)
     {