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[Alex Miller <mille151 AT illinois.edu>]

2012/5/24 Baozeng <sploving1 AT gmail.com>

Hello,
I cannot understand the following code in function _barebone_boundscheck defined in BaggyBoundsCheck.cpp:

if (val) {
  
    if (Source & SET_MASK) {  // If I understand correctly, this means that Source is OOB pointer.

      Source = Source & UNSET_MASK;
      if (Source & 0x8) {//  Could you explain me why add or sub 16?
        Source += 16;
      } else {
        Source -= 16;
      }
      Dest = Dest & UNSET_MASK;

`Source & SET_MASK` does indeed test to see if `Source` is an OOB pointer.

As for the additions/subtraction, I stared at this code before, and couldn't figure out any explanation for it. Hopefully someone else can shed some light on it?

2012/5/24 Baozeng <sploving1 AT gmail.com>

Another thing, I change BBRuntime.h as the following:
#if defined(i386) || defined(__i386__)
  #define UNSET_MASK 0xbfffffff
  #define SET_MASK 0xc0000000
#else
  #define UNSET_MASK 0x7fffffffffff
  #define SET_MASK 0xffff800000000000
#endif
Then
 Dest = (Dest | SET_MASK); should works like this:
if Dest = 0x891234; then after the above statement it should be 0xc0891234. But it does not work. The result is not changed, 0x891234, why?
I use printf("SET_MASK is %d", SET_MASK); It prints
SET_MASK is 0. any suggestion?

I would guess that neither i386 nor __i386__ are defined. I also don't recall seeing those as preprocessor defines. You might want to throw a #warning into both parts of your #if to see which one is being selected.