Internal error trying to print uninitialized string.

Trying to print the value of a string whose size is not known at
compile-time before it gets assigned a value can lead to the following
internal error:

    (gdb) p my_str
    $1 =
    /[...]/utils.c:1089: internal-error: virtual memory exhausted.

What happens is that my_str is described as a reference to an array
type whose bounds are dynamic. During the read of that variable's
value (in default_read_var_value), we end up resolving dynamic types
which, for reference types, makes us also resolve the target of that
reference type. This means we resolve our variable to a reference
to an array whose bounds are undefined, and unfortunately very far
appart.

So, when we pass that value to ada-valprint, and in particular to
da_val_print_ref, we eventually try to allocate too large of a buffer
corresponding to the (bogus) size of our array, hence the internal
error.

This patch fixes the problem by adding a size_check before trying
to print the dereferenced value. To perform this check, a function
that was previously specific to ada-lang.c (check_size) gets
exported, and renamed to something less prone to name collisions
(ada_ensure_varsize_limit).

gdb/ChangeLog:

        * ada-lang.h (ada_ensure_varsize_limit): Declare.
        * ada-lang.c (check_size): Remove advance declaration.
        (ada_ensure_varsize_limit): Renames check_size.
        Replace calls to check_size by calls to ada_ensure_varsize_limit
        throughout.
        * ada-valprint.c (ada_val_print_ref): Add call to
        ada_ensure_varsize_limit.  Add comment explaining why.

gdb/testsuite/ChangeLog:

        * gdb.ada/str_uninit: New testcase.

gdb/ChangeLog

@@ -1,3 +1,13 @@
+2014-12-13  Joel Brobecker  <brobecker@adacore.com>
+
+	* ada-lang.h (ada_ensure_varsize_limit): Declare.
+	* ada-lang.c (check_size): Remove advance declaration.
+	(ada_ensure_varsize_limit): Renames check_size.
+	Replace calls to check_size by calls to ada_ensure_varsize_limit
+	throughout.
+	* ada-valprint.c (ada_val_print_ref): Add call to
+	ada_ensure_varsize_limit.  Add comment explaining why.
+
 2014-12-13  Joel Brobecker  <brobecker@adacore.com>
 
 	* utils.c (make_hex_string): Replace use of sprintf by use of

gdb/ada-lang.c

@@ -232,8 +232,6 @@ static int ada_is_direct_array_type (struct type *);
 static void ada_language_arch_info (struct gdbarch *,
 				    struct language_arch_info *);
 
-static void check_size (const struct type *);
-
 static struct value *ada_index_struct_field (int, struct value *, int,
 					     struct type *);
 
@@ -678,7 +676,7 @@ coerce_unspec_val_to_type (struct value *val, struct type *type)
 
       /* Make sure that the object size is not unreasonable before
          trying to allocate some memory for it.  */
-      check_size (type);
+      ada_ensure_varsize_limit (type);
 
       if (value_lazy (val)
           || TYPE_LENGTH (type) > TYPE_LENGTH (value_type (val)))
@@ -740,8 +738,8 @@ lim_warning (const char *format, ...)
    i.e. if it would be a bad idea to allocate a value of this type in
    GDB.  */
 
-static void
-check_size (const struct type *type)
+void
+ada_ensure_varsize_limit (const struct type *type)
 {
   if (TYPE_LENGTH (type) > varsize_limit)
     error (_("object size is larger than varsize-limit"));
@@ -2052,7 +2050,7 @@ ada_coerce_to_simple_array (struct value *arr)
 
       if (arrVal == NULL)
         error (_("Bounds unavailable for null array pointer."));
-      check_size (TYPE_TARGET_TYPE (value_type (arrVal)));
+      ada_ensure_varsize_limit (TYPE_TARGET_TYPE (value_type (arrVal)));
       return value_ind (arrVal);
     }
   else if (ada_is_constrained_packed_array_type (value_type (arr)))
@@ -7917,7 +7915,7 @@ ada_template_to_fixed_record_type_1 (struct type *type,
 		 initialized, the type size may be completely bogus and
 		 GDB may fail to allocate a value for it.  So check the
 		 size first before creating the value.  */
-	      check_size (rtype);
+	      ada_ensure_varsize_limit (rtype);
 	      /* Using plain value_from_contents_and_address here
 		 causes problems because we will end up trying to
 		 resolve a type that is currently being
@@ -7965,7 +7963,7 @@ ada_template_to_fixed_record_type_1 (struct type *type,
 	     large (due to an uninitialized variable in the inferior)
 	     that it would cause an overflow when adding it to the
 	     record size.  */
-	  check_size (field_type);
+	  ada_ensure_varsize_limit (field_type);
 
 	  TYPE_FIELD_TYPE (rtype, f) = field_type;
           TYPE_FIELD_NAME (rtype, f) = TYPE_FIELD_NAME (type, f);
@@ -10907,7 +10905,7 @@ ada_evaluate_subexp (struct type *expect_type, struct expression *exp,
 		    (ada_aligned_type
 		     (ada_check_typedef (TYPE_TARGET_TYPE (type))));
 		}
-	      check_size (type);
+	      ada_ensure_varsize_limit (type);
               return value_zero (type, lval_memory);
             }
           else if (TYPE_CODE (type) == TYPE_CODE_INT)

gdb/ada-lang.h

@@ -162,6 +162,8 @@ struct ada_task_info
 
 extern void *grow_vect (void *, size_t *, size_t, int);
 
+extern void ada_ensure_varsize_limit (const struct type *type);
+
 extern int ada_get_field_index (const struct type *type,
                                 const char *field_name,
                                 int maybe_missing);

gdb/ada-valprint.c

@@ -1055,6 +1055,12 @@ ada_val_print_ref (struct type *type, const gdb_byte *valaddr,
   if (ada_is_tagged_type (value_type (deref_val), 1))
     deref_val = ada_tag_value_at_base_address (deref_val);
 
+  /* Make sure that the object does not have an unreasonable size
+     before trying to print it.  This can happen for instance with
+     references to dynamic objects whose contents is uninitialized
+     (Eg: an array whose bounds are not set yet).  */
+  ada_ensure_varsize_limit (value_type (deref_val));
+
   val_print (value_type (deref_val),
 	     value_contents_for_printing (deref_val),
 	     value_embedded_offset (deref_val),

gdb/testsuite/ChangeLog

@@ -1,3 +1,7 @@
+2014-12-13  Joel Brobecker  <brobecker@adacore.com>
+
+	* gdb.ada/str_uninit: New testcase.
+
 2014-12-13  Jan Kratochvil  <jan.kratochvil@redhat.com>
 
 	PR symtab/17642

gdb/testsuite/gdb.ada/str_uninit.exp

@@ -0,0 +1,40 @@
+# Copyright 2014 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 parse
+
+if {[gdb_compile_ada "${srcfile}" "${binfile}" executable [list debug ]] != "" } {
+  return -1
+}
+
+clean_restart ${testfile}
+
+set bp_location [gdb_get_line_number "START" ${testdir}/parse.adb]
+if ![runto "parse.adb:$bp_location" ] then {
+  perror "Couldn't run ${testfile}"
+  return
+}
+
+# Print MY_STR.  Since the string has not been initialized, including
+# its bounds, anything can happen, including an error.  The purpose
+# of this test is just to verify that we do not get an _internal_
+# error.
+gdb_test "print my_str" " = .*"
+
+# Just to be certain that the debugger is really still alive,
+# try printing something really simple.
+gdb_test "print 1235813" " = 1235813"

gdb/testsuite/gdb.ada/str_uninit/parse.adb

@@ -0,0 +1,22 @@
+--  Copyright 2014 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 Parse is
+   My_Str : String := Foos;  -- START
+begin
+   Do_Nothing (My_Str'Address);
+end Parse;

gdb/testsuite/gdb.ada/str_uninit/pck.adb

@@ -0,0 +1,28 @@
+--  Copyright 2011-2014 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;
+
+   function Foos return String is
+   begin
+      return "string";
+   end Foos;
+
+end Pck;

gdb/testsuite/gdb.ada/str_uninit/pck.ads

@@ -0,0 +1,24 @@
+--  Copyright 2011-2014 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);
+
+   function Foos return String;
+
+end Pck;