off-by-one max exponent computation in convert_doublest_to_floatformat

Assuming the following variable definition:

    long double inp = 2.0;

On platforms where "long double" is a double precision IEEE flaoting
point, GDB currently behaves as follow:

    (gdb) set variable inp = 1.6e+308l
    (gdb) p inp
    $2 = inf   <<<<---- !!!!

Instead, the value of "inp" should be printed as:

    (gdb) p inp
    $1 = 1.6e+308

The problem is due to a small error in the comparison of the exponent
versus the maximum value this exponent can take, causing us to think
that the value was too big to fit. But it isn't.

gdb/ChangeLog:

        * doublest.c (convert_doublest_to_floatformat): Fix comparison
        against maximum exponent value.

gdb/testsuite/ChangeLog:

        * gdb.base/ldbl_e308.c, gdb.base/ldbl_e308.exp: New files.

gdb/ChangeLog

@@ -1,3 +1,8 @@
+2012-10-24  Joel Brobecker  <brobecker@adacore.com>
+
+	* doublest.c (convert_doublest_to_floatformat): Fix comparison
+	against maximum exponent value.
+
 2012-10-24  Joel Brobecker  <brobecker@adacore.com>
 
 	* ada-lang.h (ADA_KNOWN_RUNTIME_FILE_NAME_PATTERNS): Add entry for

gdb/doublest.c

@@ -483,7 +483,7 @@ convert_doublest_to_floatformat (CONST struct floatformat *fmt,
       goto finalize_byteorder;
     }
 
-  if (exponent + fmt->exp_bias >= (1 << fmt->exp_len) - 1)
+  if (exponent + fmt->exp_bias >= (1 << fmt->exp_len))
     {
       /* The value is too large to fit into the destination.
 	 Treat as infinity.  */

gdb/testsuite/ChangeLog

@@ -1,3 +1,7 @@
+2012-10-24  Joel Brobecker  <brobecker@adacore.com>
+
+	* gdb.base/ldbl_e308.c, gdb.base/ldbl_e308.exp: New files.
+
 2012-10-24  Joel Brobecker  <brobecker@adacore.com>
 
 	* gdb.ada/unc_arr_ptr_in_var_rec: New testcase.

gdb/testsuite/gdb.base/ldbl_e308.c

@@ -0,0 +1,26 @@
+/* Copyright (C) 2012 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   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/>.  */
+
+long double ldbl_308 = 2.0;
+
+int
+main (void)
+{
+  ldbl_308 = ldbl_308 / 2;
+
+  return 0;
+}

gdb/testsuite/gdb.base/ldbl_e308.exp

@@ -0,0 +1,31 @@
+# Copyright (C) 2012 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/>.
+
+set testfile ldbl_e308
+set srcfile ${testfile}.c
+if { [prepare_for_testing ${testfile}.exp ${testfile} ${srcfile}] } {
+    return -1
+}
+
+if ![runto_main] {
+    untested ${testfile}.exp
+    return -1
+}
+
+gdb_test_no_output "set variable ldbl_308 = 1.6e+308l"
+
+gdb_test "print ldbl_308" \
+         "= (1\..*e\\+308|inf)"
+