Prevent exception from being thrown

[Mike Giancola <mi...@gmail.com>]

Hi,

If a user calls XMLScanner::setExternalNoNamespaceSchemaLocation or
setExternalNoNamespaceSchemaLocation with an emptry string (not null) we
throw a c++ exception.

The fix: inside IGXMLScanner.cpp ::scanStartTagNS we check if the char*
pointers are null, but not empty. I suggest we add a gate for empty
strings. For example:

current gate:
if (isRoot && fDoSchema && (fExternalSchemaLocation ||
fExternalNoNamespaceSchemaLocation))  {

// proposed change:
if (XMLString::stringLen(fExternalSchemaLocation) > 0)
   parseSchemaLocation(fExternalSchemaLocation, true);

if (XMLString::stringLen(fExternalNoNamespaceLocation) > 0)
    resolveSchemaGrammer(fExternalNoNamespaceSchemaLocation,
XMLUni::fgZeroLenString, true);
}

*** reasons **
when we call scanDocument, it calls scanContent, scanContent calls
scanStartTagNS - if fExternalNoNamespaceSchemlaLocation = "" ....

we call resolveSchemaGrammer, which calls, parse, which calls scanDocument,
which calls scanReset, which calls createReader which calls
LocalFileInputSource::makeStream - which calls BinFileInputStream with an
empty file name.

The call to MakeStream fails since we can't open filename "". This causes
an error code to be returned to IGXMLScannner::scanReset - (newReader is
null). This causes us to attempt to throw an XML exception of
XMLExcepts::Scan_CouldNotOpenSource_Warning.

When we attempt to call this ThrowXMLwithMemMgr1 - we run into trouble. I
haven't traced this yet, but in debugger i get "First chance exception at
... in ... Microsoft C++ exception: xercesc_3_1::RuntimeException at memory
location .."

There appears to be something naughty going on with a free - but as i say,
i haven't traced this yet.

To repro this, just set the fExternalNoNamespaceLocation = "".

Thanks,
Mike