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.

1 files changed, 40 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.ada/str_uninit.exp b/gdb/testsuite/gdb.ada/str_uninit.exp
new file mode 100644
index 00000000000..706d57d8eca
--- /dev/null
+++ b/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"