libxml2 issues a segmentation fault when creating xsd pattern regular expression that contains a specific pattern of () parenthesis and | pipes. You will notice I did this on OSX, however I experience the same issue on Ubuntu as well.

=text.xsd=
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema attributeFormDefault="unqualified"
	elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema">
		
	<xs:element name="data">
		<xs:complexType>
			<xs:all>
				<xs:element name="phone1">
					<xs:simpleType>
						<xs:restriction base="xs:string">
							<xs:pattern value="([0-9]{10})|"></xs:pattern>
						</xs:restriction>
					</xs:simpleType>
				</xs:element>
			</xs:all>
		</xs:complexType>
	</xs:element>
</xs:schema>

=test.xml=
<?xml version="1.0" encoding="utf-8"?>
<data>
  <phone1>2484718566</phone1>
</data>

=GDB=
gdb --args xmllint --noout --schema test.xsd test.xml 
GNU gdb 6.3.50-20050815 (Apple version gdb-1820) (Sat Jun 16 02:40:11 UTC 2012)
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "x86_64-apple-darwin"...Reading symbols for shared libraries ... done

(gdb) run  
Starting program: /usr/bin/xmllint --noout --schema test.xsd test.xml
Reading symbols for shared libraries ++................................ done

Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_INVALID_ADDRESS at address: 0x0000000000000014
0x00007fff8f082e3e in xmlRegexpExec ()
(gdb) bt

+ Trace 231648

=Regular expressions that work (Possible work arounds)=
([0-9]{10})|()
[0-9]{10}|
[0-9]{10}|()

=Regular expressions that do not work=
([0-9]{10})|

=How it should work=
Fail gracefully and let me know I have written a bad regular expression.