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[Matthew Wala <wala1 AT illinois.edu>]

On Mon, Jul 11, 2011 at 11:10 AM, John Criswell 
<criswell AT illinois.edu>
 wrote:
> On 7/11/11 11:06 AM, Matthew Wala wrote:
>
> Hello everyone:
> When I compile the attached test case with SAFECode (tried on asha and
> bach) I get a large number of Out of Bounds / Load Store errors. The
> test calls gmtime() which returns static memory. These errors also
> occur if the function that is called is replaced with localtime().
>
> Check to see if gmtime() and localtime() are recognized by DSA's StdLib
> pass.  If so, then what is probably happening is that they are being marked
> complete, but since the memory objects aren't registered, you get an error.

I did check, and there are entries for those functions in StdLibPass.
There's also entries for ctime() and asctime(). It looks like all four
of those functions have the same flags in the StdLibPass table, but
despite that the error still occurs. Perhaps the flags are wrong.

I tested ctime() once more, and it looks that reading the output from
ctime() actually does cause a Load / Store error.
(The reason my previous testing didn't recognize this is that I did a
simple printf("%s\n", ctime(...)); call, and it looks like the C
frontend lowers such calls to puts(), which SAFECode doesn't currently
handle (I think I should probably add support for puts() in the
CStdLib pass for this reason). So the read of the value of ctime() was
being done in external code, which is why it didn't raise any errors.)

Matt

> If other functions aren't recognized by DSA's StdLib pass, then the pointer
> is being marked External, which means that SAFECode won't raise an error if
> the memory object isn't found in the pool.
>
> -- John T.
>
> However, other time-related functions that return static memory like
> ctime() (as well as the reentrant versions of gmtime() and
> localtime()) do not cause SAFECode to complain.
> Before filing a bug I'd like to know if there is a reason for this
> behavior or if this is already known.
>
> Thanks,
> Matt
>
>
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