Fix for BUG#14703 "Valgrind error when inserting 0 into a BIT column (like in type_bit.test)":

test "length" first (otherwise when "length" is 0, the *from invalid access still triggers a Valgrind warning).
I wrote to the Valgrind authors in case this is something fixable in Valgrind (normally the
decision to issue a warning is based on the simulated CPU condition code, which should not be undefined here).

BUILD/compile-pentium64-valgrind-max

@@ -3,13 +3,13 @@
 path=`dirname $0`
 . "$path/SETUP.sh"
 
-extra_flags="$pentium64_cflags $debug_cflags -USAFEMALLOC -UFORCE_INIT_OF_VARS -DHAVE_purify -DMYSQL_SERVER_SUFFIX=-valgrind-max"
+extra_flags="$pentium64_cflags $debug_cflags $max_cflags -USAFEMALLOC -UFORCE_INIT_OF_VARS -DHAVE_purify -DMYSQL_SERVER_SUFFIX=-valgrind-max"
 c_warnings="$c_warnings $debug_extra_warnings"
 cxx_warnings="$cxx_warnings $debug_extra_warnings"
 extra_configs="$pentium_configs $debug_configs"
 
 # We want to test isam when building with valgrind
-extra_configs="$extra_configs --with-berkeley-db --with-innodb --with-isam --with-embedded-server --with-openssl --with-raid --with-ndbcluster"
+extra_configs="$extra_configs $max_leave_isam_configs --with-isam"
 
 . "$path/FINISH.sh"
 

mysql-test/r/read_only.result

@@ -14,6 +14,8 @@ create table t3 (a int);
 ERROR HY000: The MySQL server is running with the --read-only option so it cannot execute this statement
 insert into t1 values(1);
 ERROR HY000: The MySQL server is running with the --read-only option so it cannot execute this statement
+update t1 set a=1 where 1=0;
+ERROR HY000: The MySQL server is running with the --read-only option so it cannot execute this statement
 update t1,t2 set t1.a=t2.a+1 where t1.a=t2.a;
 ERROR HY000: The MySQL server is running with the --read-only option so it cannot execute this statement
 delete t1,t2 from t1,t2 where t1.a=t2.a;

sql/field.cc

@@ -7931,7 +7931,7 @@ int Field_bit::store(const char *from, uint length, CHARSET_INFO *cs)
 {
   int delta;
 
-  for (; !*from && length; from++, length--);          // skip left 0's
+  for (; length && !*from; from++, length--);          // skip left 0's
   delta= field_length - length;
 
   if (delta < -1 ||
@@ -8151,7 +8151,7 @@ int Field_bit_as_char::store(const char *from, uint length, CHARSET_INFO *cs)
   int delta;
   uchar bits= create_length & 7;
 
-  for (; !*from && length; from++, length--);          // skip left 0's
+  for (; length && !*from; from++, length--);          // skip left 0's
   delta= field_length - length;
 
   if (delta < 0 ||