kstrto*: accept "-0" for signed conversion

strtol(3) et al accept "-0", so should we.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: Alexey Dobriyan

lib/kstrtox.c

@@ -152,7 +152,7 @@ int kstrtoll(const char *s, unsigned int base, long long *res)
 		rv = _kstrtoull(s + 1, base, &tmp);
 		if (rv < 0)
 			return rv;
-		if ((long long)(-tmp) >= 0)
+		if ((long long)-tmp > 0)
 			return -ERANGE;
 		*res = -tmp;
 	} else {

lib/test-kstrtox.c

@@ -260,6 +260,7 @@ static void __init test_kstrtoll_ok(void)
 		{"4294967297",	10,	4294967297LL},
 		{"9223372036854775807",	10,	9223372036854775807LL},
 
+		{"-0",	10,	0LL},
 		{"-1",	10,	-1LL},
 		{"-2",	10,	-2LL},
 		{"-9223372036854775808",	10,	LLONG_MIN},
@@ -277,11 +278,6 @@ static void __init test_kstrtoll_fail(void)
 		{"-9223372036854775809",	10},
 		{"-18446744073709551614",	10},
 		{"-18446744073709551615",	10},
-		/* negative zero isn't an integer in Linux */
-		{"-0",	0},
-		{"-0",	8},
-		{"-0",	10},
-		{"-0",	16},
 		/* sign is first character if any */
 		{"-+1", 0},
 		{"-+1", 8},