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[John Criswell <criswell AT illinois.edu>]

On 4/5/2011 7:56 PM, Matthew Wala wrote:
> Hi everyone:
>
> What's the purpose of the "complete" byte which is passed as an
> argument and the end of the pool_* string
> functions?

The Complete flag is a DSA flag set on a DSNode.  It indicates that the 
DSA information computed for the DSNode is as complete as it can be: 
everything that can be known about the memory object has been computed.

>   In what I've done so far I haven't used it at all, I just
> ignored it and it didn't seem to cause any
> issues until now. However I realized that whenever I try to pass a
> NULL pointer directly as an argument to a
> string function that has runtime checks, sometimes I get the following
> error, which happens during the computation
> of the complete flag, and I don't think any of my changes are causing this:
>
> sc: String.cpp:280: unsigned int
> safecode::StringTransform::getDSFlags(const llvm::Value*, const
> llvm::Function*): Assertion `DSN&&  "getDSFlags(): No DSNode for the
> specified value!\n"' failed.
>
> This is a problem because passing NULL pointers is legitimate for
> certain functions that should have their own
> runtime checks (eg., strtok). How do I fix this?

This is a problem unrelated to completeness.  In this case, DSA does not 
create a DSNode for the null pointer constant.  In this instance, you 
should create a NULL Pool handle and pass that in.  If the string 
function is supposed to handle NULL string pointers, then your run-time 
checks should be adjusted to take NULL pool handles and NULL pointers 
into account.

For a NULL constant pointer, you can consider it Complete since it is 
trivial to know everything about it that we care to know.

-- John T.

> Matt
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