[v3] Fix segfault when invoking -var-info-path-expression on a dynamic varobj

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 80626191c9..625c42af36 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@ 
+2018-06-04  Jan Vrany  <jan.vrany@fit.cvut.cz>
+
+	* varobj.c (varobj_get_path_expr_parent): Report an error if
+	parent is a dynamic varobj.
+
 2018-06-28  Petr Tesarik  <ptesarik@suse.cz>
 
 	* symfile.c (add_symbol_file_command, _initialize_symfile): Add
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index f93eb97d97..0d30ab2793 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,9 @@ 
+2018-06-04  Jan Vrany  <jan.vrany@fit.cvut.cz>
+
+	* gdb.python/py-mi-var-info-path-expression.c: New file.
+	* gdb.python/py-mi-var-info-path-expression.py: New file.
+	* gdb.python/py-mi-var-info-path-expression.exp: New file.
+
 2018-06-28  Richard Bunt  <richard.bunt@arm.com>
 
 	* gdb.base/watchpoint-hw-attach.c (main): Remove unneeded
diff --git a/gdb/testsuite/gdb.python/py-mi-var-info-path-expression.c b/gdb/testsuite/gdb.python/py-mi-var-info-path-expression.c
new file mode 100644
index 0000000000..9d6ff126dd
--- /dev/null
+++ b/gdb/testsuite/gdb.python/py-mi-var-info-path-expression.c
@@ -0,0 +1,62 @@ 
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright (C) 1999-2018 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/>.  */
+
+enum cons_type
+{
+  type_atom = 0,
+  type_cons = 1
+};
+
+struct atom
+{
+  int ival;
+};
+
+struct cons
+{
+  enum cons_type type;
+  union
+  {
+    struct atom atom;
+    struct cons *slots[2];
+  };
+};
+
+#define nil ((struct cons*)0);
+
+int
+main ()
+{
+  struct cons c1, c2, c3, c4;
+
+  c1.type = type_cons;
+  c1.slots[0] = &c4;
+  c1.slots[1] = &c2;
+
+  c2.type = type_cons;
+  c2.slots[0] = nil;
+  c2.slots[1] = &c3;
+
+  c3.type = type_cons;
+  c3.slots[0] = nil;
+  c3.slots[1] = nil;
+
+  c4.type = type_atom;
+  c4.atom.ival = 13;
+
+  return 0;			/* next line */
+}
diff --git a/gdb/testsuite/gdb.python/py-mi-var-info-path-expression.exp b/gdb/testsuite/gdb.python/py-mi-var-info-path-expression.exp
new file mode 100644
index 0000000000..ecebc2e761
--- /dev/null
+++ b/gdb/testsuite/gdb.python/py-mi-var-info-path-expression.exp
@@ -0,0 +1,91 @@ 
+# Copyright (C) 2008-2018 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/>.
+
+# Tests whether -var-info-path-expression fails as documented when
+# invoked on a dynamic varobj.
+
+load_lib mi-support.exp
+set MIFLAGS "-i=mi"
+
+gdb_exit
+if {[mi_gdb_start]} {
+    continue
+}
+
+#
+# Start here
+#
+standard_testfile
+
+if {[gdb_compile "$srcdir/$subdir/$srcfile" $binfile executable {debug}] != "" } {
+    return -1
+}
+
+mi_gdb_test "source ${srcdir}/${subdir}/${testfile}.py" \
+  ".*\\^done" \
+  "load python file"
+
+mi_gdb_test "-enable-pretty-printing" \
+  "\\^done" \
+  "-enable-pretty-printing"
+
+mi_gdb_test "set python print-stack full" \
+  ".*\\^done" \
+  "set python print-stack full"
+
+
+mi_run_to_main
+
+
+mi_continue_to_line [gdb_get_line_number "next line" ${srcfile}] \
+  "step to breakpoint"
+
+mi_gdb_test "-var-create c1 * &c1" \
+   "\\^done.*" \
+   "-var-create c1 * &c1"
+
+mi_gdb_test "-var-info-path-expression c1" \
+  "\\^done,path_expr=\"&c1\"" \
+  "-var-info-path-expression c1"
+
+mi_gdb_test "-var-list-children c1" \
+  "\\^done,numchild=\"2\",children=.child=\{name=\"c1.car\".*child=\{name=\"c1.cdr\".*" \
+  "-var-list-children c1"
+
+mi_gdb_test "-var-info-path-expression c1.cdr" \
+  "\\^error,msg=\".*\"" \
+  "-var-info-path-expression c1.cdr"
+
+mi_gdb_test "-var-list-children c1.cdr" \
+  "\\^done,numchild=\"2\",children=.child=\{name=\"c1.cdr.car\".*child=\{name=\"c1.cdr.cdr\".*" \
+  "-var-list-children c1.cdr"
+
+mi_gdb_test "-var-info-path-expression c1.cdr.cdr" \
+  "\\^error,msg=\".*\"" \
+  "-var-info-path-expression c1.cdr.cdr"
+
+mi_gdb_test "-var-list-children c1.car" \
+  "\\^done,numchild=\"1\",children=.child=\{name=\"c1.car.atom\".*" \
+  "-var-list-children c1.car"
+
+mi_gdb_test "-var-list-children c1.car.atom" \
+  "\\^done,numchild=\"1\",children=.child=\{name=\"c1.car.atom.ival\".*" \
+  "-var-list-children c1.car.atom"
+
+mi_gdb_test "-var-info-path-expression c1.car.atom.ival" \
+  "\\^error,msg=\".*\"" \
+  "-var-info-path-expression c1.car.atom.ival"
+
+
diff --git a/gdb/testsuite/gdb.python/py-mi-var-info-path-expression.py b/gdb/testsuite/gdb.python/py-mi-var-info-path-expression.py
new file mode 100644
index 0000000000..13f9742016
--- /dev/null
+++ b/gdb/testsuite/gdb.python/py-mi-var-info-path-expression.py
@@ -0,0 +1,51 @@ 
+# Copyright (C) 2008-2018 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/>.
+
+import gdb
+import gdb.types
+
+class cons_pp(object):
+  def __init__(self, val):
+    self._val = val
+
+  def to_string(self):
+    if int(self._val) == 0:
+      return "nil"
+    elif int(self._val['type']) == 0:
+      return "( . )"
+    else:
+      return "%d" % self._val['atom']['ival']
+
+  def children(self):
+    if int(self._val) == 0:
+      return []
+    elif int(self._val['type']) == 0:
+      return [
+        ('atom', self._val['atom'])
+      ]
+    else:
+      return [
+        ('car' ,  self._val["slots"][0]),
+        ('cdr' ,  self._val["slots"][1]),
+      ]
+
+def cons_pp_lookup(val):
+  if str(val.type) == 'struct cons *':
+    return cons_pp(val)
+  else:
+    return None
+
+del gdb.pretty_printers[1:]
+gdb.pretty_printers.append(cons_pp_lookup)
\ No newline at end of file
diff --git a/gdb/varobj.c b/gdb/varobj.c
index 02441410e8..af607963b4 100644
--- a/gdb/varobj.c
+++ b/gdb/varobj.c
@@ -948,6 +948,11 @@  varobj_get_path_expr_parent (const struct varobj *var)
   while (!is_root_p (parent) && !is_path_expr_parent (parent))
     parent = parent->parent;
 
+  /* Computation of full rooted expression for children of dynamic
+     varobjs is not supported.  */
+  if (varobj_is_dynamic_p (parent))
+    error (_("Invalid variable object (child of a dynamic varobj)"));
+
   return parent;
 }