Please describe the problem:
The xmlNewTextWriterFilename function rejects some uris that have a scheme but no authority, such as file:/home/sthomas/file.xml. If you insert an empty authority component, as in file:///home/sthomas/file.xml, it works. The xmlReaderForFile function has no problem with authority-less uris.

Steps to reproduce:
// Here's a program that demonstrates the problem

#include <string>
#include <iostream>
#include <libxml/xmlreader.h>
#include <libxml/xmlwriter.h>

using namespace std;

void attemptReadFile(string uri) {
	xmlTextReaderPtr reader = xmlReaderForFile(uri.c_str(), NULL, 0);
	cout << "read " << uri << " " << (reader ? "succeeded" : "failed") << endl;
	xmlFreeTextReader(reader);
}

void attemptWriteFile(string uri) {
	xmlTextWriterPtr writer = xmlNewTextWriterFilename(uri.c_str(), 0);
	cout << "write " << uri << " " << (writer ? "succeeded" : "failed") << endl;
	xmlFreeTextWriter(writer);
}

int main() {
	// Creating an xmlTextWriter without an authority component in the uri
	// fails. It works for xmlTextReaders...
	attemptReadFile("/home/sthomas/file.xml");        // Works
	attemptReadFile("file:/home/sthomas/file.xml");   // Works
	attemptReadFile("file:///home/sthomas/file.xml"); // Works

	// ... but not xmlTextWriters
	attemptWriteFile("/home/sthomas/file2.xml");        // Works
	attemptWriteFile("file:/home/sthomas/file2.xml");   // Fails!
	attemptWriteFile("file:///home/sthomas/file2.xml"); // Works

	return 0;
}


Actual results:
Writing to the uri "file:/home/sthomas/file2.xml" fails.

Expected results:
Writing to that uri should work fine.

Does this happen every time?
Yes

Other information: