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[John Criswell <criswell AT illinois.edu>]

On 6/14/12 3:06 AM, Baozeng wrote:
> 2012/6/14 John 
> Criswell<criswell AT illinois.edu>:
> > On 6/13/12 8:37 AM, Baozeng wrote:
> > > Hello,
> > > I use current BBC implementation to test an example (buffer.c):
> > >
> > > #include<stdio.h>
> > > #include<stdlib.h>
> > >
> > > int main (int argc, char ** argv) {
> > >    char array[17];
> > >    return array[17];
> > > }
> > >
> > > $ clang -g -fmemsafety -bbc buffer.c -o mytest
> > > -L/home/sploving/llvm/projects/safecode/Debug/lib
> > > $ ./mytest
> > >
> > > It output this:
> > > 0xbfd00b9b, 0xbfd00b80, 17 Not aligned
> > >
> > > This related code is in the function __internal_register in
> > > BaggyBoundsCheck.cpp:
> > >
> > > if(Source1 != Source) {
> > >      printf("%p, %p, %u Not aligned\n", (void*)Source, (void*)Source1,
> > > NumBytes);
> > >      assert(0&&    "Memory objects not aligned");
> > >    }
> >
> > I think the problem is that the stack object being registered isn't aligned
> > on a power-of-two boundary like it should be.
> yep.
> I debugged and found that the function adjustAlloca is not called.
> I inserted some printf statement in the following function:
>
> void
> InsertBaggyBoundsChecks::adjustAllocasFor (Function * F) {
>    //
>    // If there is no such function, do nothing.
>    //
>    if (!F) return;
>    printf("test1\n");     // It output!
>    //
>    // Scan through all uses of the function and process any allocas used by 
> it.
>    //
>    for (Value::use_iterator FU = F->use_begin(); FU != F->use_end(); ++FU) {
>      printf("test2\n");   // It does not ouput!
>      if (CallInst * CI = dyn_cast<CallInst>(*FU)) {
> printf("test3\n");   // It does not ouput!
>        Value * Ptr = CI->getArgOperand(2)->stripPointerCasts();
>        if (AllocaInst * AI = dyn_cast<AllocaInst>(Ptr)){
>          adjustAlloca (AI);
>     printf("test4\n");    // It does not ouput!
>        }
>      }
>    }
>
>    return;
> }
>
> Only test1 was printed out. So the statements in the for loop are not
> executed. why?

I'm not sure, but it looks like a bug in the code.  You should add more 
debugging to see what Ptr is (you can use CI->dump() and Ptr->dump() to 
print them to stderr).  It's possible that the code is looking at the 
wrong argument of the call to pool_register_stack().

-- John T.