radix tree test suite: Enable ubsan

Add support for the undefined behaviour sanitizer and fix the bugs
that ubsan pointed out.  Nothing major, and all in the test suite,
not the code.
Signed-off-by: Matthew Wilcox <willy@infradead.org>

tools/testing/radix-tree/Makefile

 # SPDX-License-Identifier: GPL-2.0
 
-CFLAGS += -I. -I../../include -g -O2 -Wall -D_LGPL_SOURCE -fsanitize=address
-LDFLAGS += -fsanitize=address
+CFLAGS += -I. -I../../include -g -Og -Wall -D_LGPL_SOURCE -fsanitize=address \
+	  -fsanitize=undefined
+LDFLAGS += -fsanitize=address -fsanitize=undefined
 LDLIBS+= -lpthread -lurcu
 TARGETS = main idr-test multiorder
 CORE_OFILES := radix-tree.o idr.o linux.o test.o find_bit.o

tools/testing/radix-tree/main.c

@@ -27,20 +27,22 @@ void __gang_check(unsigned long middle, long down, long up, int chunk, int hop)
 		item_check_present(&tree, middle + idx);
 	item_check_absent(&tree, middle + up);
 
-	item_gang_check_present(&tree, middle - down,
-			up + down, chunk, hop);
+	if (chunk > 0) {
+		item_gang_check_present(&tree, middle - down, up + down,
+				chunk, hop);
 		item_full_scan(&tree, middle - down, down + up, chunk);
+	}
 	item_kill_tree(&tree);
 }
 
 void gang_check(void)
 {
-	__gang_check(1 << 30, 128, 128, 35, 2);
-	__gang_check(1 << 31, 128, 128, 32, 32);
-	__gang_check(1 << 31, 128, 128, 32, 100);
-	__gang_check(1 << 31, 128, 128, 17, 7);
-	__gang_check(0xffff0000, 0, 65536, 17, 7);
-	__gang_check(0xfffffffe, 1, 1, 17, 7);
+	__gang_check(1UL << 30, 128, 128, 35, 2);
+	__gang_check(1UL << 31, 128, 128, 32, 32);
+	__gang_check(1UL << 31, 128, 128, 32, 100);
+	__gang_check(1UL << 31, 128, 128, 17, 7);
+	__gang_check(0xffff0000UL, 0, 65536, 17, 7);
+	__gang_check(0xfffffffeUL, 1, 1, 17, 7);
 }
 
 void __big_gang_check(void)