Initialize variable in if statement to avoid doing dynamic_cast twice

- Refactored duplicate code in RuleWithOperator::getVariablesExceptions
- Leveraged auto to simplify declaration of dynamic_cast pointers.

headers/modsecurity/rule_with_operator.h

@@ -50,7 +50,7 @@ class RuleWithOperator : public RuleWithActions {
     bool evaluate(Transaction *transaction,
         std::shared_ptr<RuleMessage> rm) override;
 
-    void getVariablesExceptions(Transaction *t,
+    void getVariablesExceptions(Transaction &t,
         variables::Variables *exclusion, variables::Variables *addition);
     inline void getFinalVars(variables::Variables *vars,
         variables::Variables *eclusion, Transaction *trans);

src/actions/set_var.cc

@@ -51,18 +51,12 @@ bool SetVar::evaluate(RuleWithActions *rule, Transaction *t) {
     std::string m_variableNameExpanded;
 
     auto *v = m_variable.get();
-    variables::Tx_DynamicElement *tx = dynamic_cast<
-        variables::Tx_DynamicElement *> (v);
-    variables::Session_DynamicElement *session = dynamic_cast<
-        variables::Session_DynamicElement *> (v);
-    variables::Ip_DynamicElement *ip = dynamic_cast<
-        variables::Ip_DynamicElement *> (v);
-    variables::Resource_DynamicElement *resource = dynamic_cast<
-        variables::Resource_DynamicElement *> (v);
-    variables::Global_DynamicElement *global = dynamic_cast<
-        variables::Global_DynamicElement *> (v);
-    variables::User_DynamicElement *user = dynamic_cast<
-        variables::User_DynamicElement *> (v);
+    auto tx = dynamic_cast<variables::Tx_DynamicElement *> (v);
+    auto session = dynamic_cast<variables::Session_DynamicElement *> (v);
+    auto ip = dynamic_cast<variables::Ip_DynamicElement *> (v);
+    auto resource = dynamic_cast<variables::Resource_DynamicElement *> (v);
+    auto global = dynamic_cast<variables::Global_DynamicElement *> (v);
+    auto user = dynamic_cast<variables::User_DynamicElement *> (v);
     if (tx) {
         m_variableNameExpanded = tx->m_string->evaluate(t, rule);
     } else if (session) {