sort: use long doubles for general numeric mode

* src/sort.c (general_numcompare): Use long doubles unconditionally,
and strtold when available, to convert numbers with greater range and
precision.  Performance was seen to be on par with standard doubles.
* doc/coreutils.texi (sort invocation): Amend the -g description to
mention long double rather than double, and strtold rather than strtod.
* src/getlimits.c (main): Output floating point limits for use in tests.
* tests/misc/sort-float: A new test to ensure sort is using long
doubles when possible, and that locale specific floats are handled.
* tests/Makefile.am: Reference the new test.
* tests/test-lib.sh (getlimits_): Normalize indenting.
* NEWS: Mention the new behaviour.
Reported by Nelson Beebe.

tests/Makefile.am

@@ -224,6 +224,7 @@ TESTS =						\
   misc/sort-compress				\
   misc/sort-continue				\
   misc/sort-files0-from				\
+  misc/sort-float				\
   misc/sort-merge				\
   misc/sort-merge-fdlimit			\
   misc/sort-month				\

tests/misc/sort-float

@@ -0,0 +1,56 @@
+#!/bin/sh
+# Ensure sort -g sorts floating point limits correctly
+
+# Copyright (C) 2010 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/>.
+
+if test "$VERBOSE" = yes; then
+  set -x
+  sort --version
+fi
+
+. $srcdir/test-lib.sh
+
+for LOC in C $LOCALE_FR; do
+
+  LC_ALL=$LOC getlimits_
+
+  # See if sort should be using long doubles
+  grep '^#define HAVE_C99_STRTOLD 1' $CONFIG_HEADER > /dev/null ||
+    { LDBL_MAX="$DBL_MAX"; LDBL_MIN="$DBL_MIN"; }
+
+  printf -- "\
+-$LDBL_MAX
+-$DBL_MAX
+-$FLT_MAX
+-$FLT_MIN
+-$DBL_MIN
+-$LDBL_MIN
+0
+$LDBL_MIN
+$DBL_MIN
+$FLT_MIN
+$FLT_MAX
+$DBL_MAX
+$LDBL_MAX
+" |
+  grep '^[0-9.,e+-]*$' > exp # restrict to numeric just in case
+
+  tac exp | LC_ALL=$LOC sort -sg > out || fail=1
+
+  compare out exp || fail=1
+done
+
+Exit $fail

tests/test-lib.sh

@@ -57,8 +57,8 @@ skip_test_()
 
 getlimits_()
 {
-    eval $(getlimits)
-    test "$INT_MAX" ||
+  eval $(getlimits)
+  test "$INT_MAX" ||
     error_ "Error running getlimits"
 }