<?xml version="1.0"?> <rule version="1"> <pattern> if \( ([!] )*?(strlen) \( \w+? \) ([>] [0] )*?\) { </pattern> <message> <id>StrlenEmptyString</id> <severity>performance</severity> <summary>Using strlen() to check if a string is empty is not efficient.</summary> </message> </rule>