[commit] off-by-one max exponent computation in convert_doublest_to_floatformat

[Joel Brobecker <brobecker@adacore.com>]

Hello,

This is a followup on a patch I checked in a while ago.

Assuming the following variable definition:

    long double inp = 2.0;

On platforms where "long double" is a double precision IEEE floating
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.

Tested on x86_64-linux. Checked in.

---
 gdb/ChangeLog                        |    5 +++++
 gdb/doublest.c                       |    2 +-
 gdb/testsuite/ChangeLog              |    4 ++++
 gdb/testsuite/gdb.base/ldbl_e308.c   |   26 ++++++++++++++++++++++++++
 gdb/testsuite/gdb.base/ldbl_e308.exp |   31 +++++++++++++++++++++++++++++++
 5 files changed, 67 insertions(+), 1 deletion(-)
 create mode 100644 gdb/testsuite/gdb.base/ldbl_e308.c
 create mode 100644 gdb/testsuite/gdb.base/ldbl_e308.exp

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 4d3c3ec..20ab7a9 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,10 @@
 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
 	"unwind-seh.c".
 
diff --git a/gdb/doublest.c b/gdb/doublest.c
index f683002..0308dac 100644
--- a/gdb/doublest.c
+++ b/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.  */
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index a7a1180..633c0ab 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,5 +1,9 @@
 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.
 
 2012-10-24  Mark Kettenis  <kettenis@gnu.org>
diff --git a/gdb/testsuite/gdb.base/ldbl_e308.c b/gdb/testsuite/gdb.base/ldbl_e308.c
new file mode 100644
index 0000000..8bbe01b
--- /dev/null
+++ b/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;
+}
diff --git a/gdb/testsuite/gdb.base/ldbl_e308.exp b/gdb/testsuite/gdb.base/ldbl_e308.exp
new file mode 100644
index 0000000..89c54b5
--- /dev/null
+++ b/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)"
+
-- 
1.7.9.5