Fix for bug #31566: my_write(fd, 0x0, 0, flags) fails with EFAULT on some platforms
Fix for bug #31566: my_write(fd, 0x0, 0, flags) fails with EFAULT on
some platforms

Since the behavior of write(fd, buf, 0) is undefined, it may fail with
EFAULT on some architectures when buf == NULL. The error was propagated
up to a caller, since my_write() code did not handle it properly.

Fixed by checking the 'number of bytes' argument in my_write() and
returning before calling the write() system call when there is nothing
to write.


mysys/my_write.c:
  Return from my_write() before calling the write() system call when the
  number of bytes to be written is 0, since the behavior of write() in
  this case is not portable.

davidl-zend/zenddbi,ollie314/server,flynn1973/mariadb-aix,flynn1973/mariadb-aix,ollie314/server,natsys/mariadb_10.2,davidl-zend/zenddbi,flynn1973/mariadb-aix,natsys/mariadb_10.2,natsys/mariadb_10.2,ollie314/server,davidl-zend/zenddbi,flynn1973/mariadb-aix,ollie314/server,natsys/mariadb_10.2,ollie314/server,natsys/mariadb_10.2,flynn1973/mariadb-aix,davidl-zend/zenddbi,flynn1973/mariadb-aix,flynn1973/mariadb-aix,davidl-zend/zenddbi,davidl-zend/zenddbi,davidl-zend/zenddbi,ollie314/server,ollie314/server,flynn1973/mariadb-aix,ollie314/server,davidl-zend/zenddbi,flynn1973/mariadb-aix,flynn1973/mariadb-aix,natsys/mariadb_10.2,davidl-zend/zenddbi,slanterns/server,natsys/mariadb_10.2,ollie314/server,flynn1973/mariadb-aix,davidl-zend/zenddbi,ollie314/server,natsys/mariadb_10.2,davidl-zend/zenddbi,natsys/mariadb_10.2,ollie314/server,natsys/mariadb_10.2,natsys/mariadb_10.2