Bug#15583: BIN()/OCT()/CONV() do not work with BIT values

Converting BIT to a string (an intermediate step in conversion) does 
not yield an ASCII numeric string, so we skip that step for BIT and
get the integer value directly from the item.

This site in sql/item_strfunc.cc may be ripe for refactoring for
other types as well, where converting to a string is a waste of time.

mysql-test/r/type_bit.result

@@ -572,4 +572,34 @@ def	test	t1	t1	a	a	16	7	1	Y	0	0	63
 a
 `
 drop table t1;
+create table bug15583(b BIT(8), n INT);
+insert into bug15583 values(128, 128);
+insert into bug15583 values(null, null);
+insert into bug15583 values(0, 0);
+insert into bug15583 values(255, 255);
+select hex(b), bin(b), oct(b), hex(n), bin(n), oct(n) from bug15583;
+hex(b)	bin(b)	oct(b)	hex(n)	bin(n)	oct(n)
+80	10000000	200	80	10000000	200
+NULL	NULL	NULL	NULL	NULL	NULL
+0	0	0	0	0	0
+FF	11111111	377	FF	11111111	377
+select hex(b)=hex(n) as should_be_onetrue, bin(b)=bin(n) as should_be_onetrue, oct(b)=oct(n) as should_be_onetrue from bug15583;
+should_be_onetrue	should_be_onetrue	should_be_onetrue
+1	1	1
+NULL	NULL	NULL
+1	1	1
+1	1	1
+select hex(b + 0), bin(b + 0), oct(b + 0), hex(n), bin(n), oct(n) from bug15583;
+hex(b + 0)	bin(b + 0)	oct(b + 0)	hex(n)	bin(n)	oct(n)
+80	10000000	200	80	10000000	200
+NULL	NULL	NULL	NULL	NULL	NULL
+0	0	0	0	0	0
+FF	11111111	377	FF	11111111	377
+select conv(b, 10, 2), conv(b + 0, 10, 2) from bug15583;
+conv(b, 10, 2)	conv(b + 0, 10, 2)
+10000000	10000000
+NULL	NULL
+0	0
+11111111	11111111
+drop table bug15583;
 End of 5.0 tests

mysql-test/t/type_bit.test

@@ -238,4 +238,19 @@ select * from t1;
 --disable_metadata
 drop table t1;
 
+#
+# Bug#15583: BIN()/OCT()/CONV() do not work with BIT values
+#
+create table bug15583(b BIT(8), n INT);
+insert into bug15583 values(128, 128);
+insert into bug15583 values(null, null);
+insert into bug15583 values(0, 0);
+insert into bug15583 values(255, 255);
+select hex(b), bin(b), oct(b), hex(n), bin(n), oct(n) from bug15583;
+select hex(b)=hex(n) as should_be_onetrue, bin(b)=bin(n) as should_be_onetrue, oct(b)=oct(n) as should_be_onetrue from bug15583;
+select hex(b + 0), bin(b + 0), oct(b + 0), hex(n), bin(n), oct(n) from bug15583; 
+select conv(b, 10, 2), conv(b + 0, 10, 2) from bug15583;
+drop table bug15583;
+
+
 --echo End of 5.0 tests

sql/item_strfunc.cc

@@ -2359,17 +2359,33 @@ String *Item_func_conv::val_str(String *str)
       abs(to_base) > 36 || abs(to_base) < 2 ||
       abs(from_base) > 36 || abs(from_base) < 2 || !(res->length()))
   {
-    null_value=1;
-    return 0;
+    null_value= 1;
+    return NULL;
   }
-  null_value=0;
+  null_value= 0;
   unsigned_flag= !(from_base < 0);
+
+  if (args[0]->field_type() == MYSQL_TYPE_BIT) 
+  {
+    /* 
+     Special case: The string representation of BIT doesn't resemble the
+     decimal representation, so we shouldn't change it to string and then to
+     decimal. 
+    */
+    dec= args[0]->val_int();
+  }
+  else
+  {
     if (from_base < 0)
-    dec= my_strntoll(res->charset(),res->ptr(),res->length(),-from_base,&endptr,&err);
+      dec= my_strntoll(res->charset(), res->ptr(), res->length(),
+                       -from_base, &endptr, &err);
     else
-    dec= (longlong) my_strntoull(res->charset(),res->ptr(),res->length(),from_base,&endptr,&err);
-  ptr= longlong2str(dec,ans,to_base);
-  if (str->copy(ans,(uint32) (ptr-ans), default_charset()))
+      dec= (longlong) my_strntoull(res->charset(), res->ptr(), res->length(),
+                                   from_base, &endptr, &err);
+  }
+
+  ptr= longlong2str(dec, ans, to_base);
+  if (str->copy(ans, (uint32) (ptr-ans), default_charset()))
     return &my_empty_string;
   return str;
 }