pattern mode cannot detect access to un-allocated memory

_From [zhao...@google.com](https://code.google.com/u/106321947286816917100/) on February 27, 2012 16:16:34_

Using pattern mode, it is difficult to detect any unaddr access from memory that was not allocated before.
for example, wincrt test:

oob_read_test(void)
{
char _pre = (char_) calloc(1,64);
char _foo = (char_) malloc(8);
use(foo+48);
...
}

the foo+48 cannot be detected.

_Original issue: http://code.google.com/p/drmemory/issues/detail?id=803_