add UBSAN for debugging and fair-sched for test6

tests/Makefile

@@ -13,7 +13,7 @@
 CFLAGS=-pthread -Wall -O3 -Werror -Wmissing-prototypes -fopenmp -DNDEBUG
 LDFLAGS=-pthread
 # for debugging, you may use these
-#CFLAGS=-Wall -O0 -g -Werror -Wmissing-prototypes -fopenmp
+#CFLAGS=-Wall -O0 -g -Werror -Wmissing-prototypes -fopenmp -fsanitize=undefined
 
 OBJ=threadpool.o list.o threadpool_lib.o
 

tests/threadpool_test6.py

@@ -5,7 +5,7 @@
 
 import sys, subprocess, re, os
 
-valgrind_cmd = ["valgrind", "--leak-check=full", "--suppressions=sigaltstack.suppression", "./threadpool_test6"]
+valgrind_cmd = ["valgrind", "--fair-sched=yes", "--leak-check=full", "--suppressions=sigaltstack.suppression", "./threadpool_test6"]
 
 proc = subprocess.Popen(valgrind_cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
 stdout, stderr = proc.communicate()