malloc( )problem

To

the below code is in the memtest.c

data_written = (void*)alt_uncached_malloc(0x1000);

data_read = (void*)alt_uncached_malloc(0x1000);

/* Fill write buffer with known values */

for (pattern = 1, offset = 0; offset < sizeof(data_written); pattern++, offset+=4)

{

IOWR_32DIRECT((int)data_written, offset, pattern);

}

/* Fill write buffer with known values */

Fill the write buffer

But if the sizeof(data_written) is only 4 ,the for sentence do what?

and after malloc( ) the content in the location of memory is random number?