Fixed Bug #2338 Trigonometric arithmetic problem

by fixing optimizer bug with help of 'volatile' keyword

mysql-test/r/func_math.result

@@ -20,3 +20,15 @@ PI()	sin(pi()/2)	cos(pi()/2)	abs(tan(pi()))	cot(1)	asin(1)	acos(0)	atan(1)
 3.141593	1.000000	0.000000	0.000000	0.64209262	1.570796	1.570796	0.785398
 degrees(pi())	radians(360)
 180	6.2831853071796
+ACOS(1.0)
+0.000000
+ASIN(1.0)
+1.570796
+ACOS(0.2*5.0)
+0.000000
+ACOS(0.5*2.0)
+0.000000
+ASIN(0.8+0.2)
+1.570796
+ASIN(1.2-0.2)
+1.570796

mysql-test/t/func_math.test

@@ -13,3 +13,14 @@ select pow(10,log10(10)),power(2,4);
 select rand(999999),rand();
 select pi(),sin(pi()/2),cos(pi()/2),abs(tan(pi())),cot(1),asin(1),acos(0),atan(1);
 select degrees(pi()),radians(360);
+
+#
+# Bug #2338 Trignometric arithmatic problems 
+#
+
+SELECT ACOS(1.0);
+SELECT ASIN(1.0);
+SELECT ACOS(0.2*5.0);
+SELECT ACOS(0.5*2.0);
+SELECT ASIN(0.8+0.2);
+SELECT ASIN(1.2-0.2);

sql/item_func.cc

@@ -456,7 +456,8 @@ double Item_func_pow::val()
 
 double Item_func_acos::val()
 {
-  double value=args[0]->val();
+  // this 'volatile' was added as a fix for BUG #2338 to calm optimizer down
+  volatile double value=args[0]->val();
   if ((null_value=(args[0]->null_value || (value < -1.0 || value > 1.0))))
     return 0.0;
   return fix_result(acos(value));
@@ -464,7 +465,8 @@ double Item_func_acos::val()
 
 double Item_func_asin::val()
 {
-  double value=args[0]->val();
+  // this 'volatile' was added as a fix for BUG #2338 to calm optimizer down
+  volatile double value=args[0]->val();
   if ((null_value=(args[0]->null_value || (value < -1.0 || value > 1.0))))
     return 0.0;
   return fix_result(asin(value));