diff --git a/src/actions/accuracy.h b/src/actions/accuracy.h
index 6e78a422..a2af47af 100644
--- a/src/actions/accuracy.h
+++ b/src/actions/accuracy.h
@@ -29,7 +29,7 @@ namespace actions {
 
 class Accuracy : public Action {
  public:
-    explicit Accuracy(std::string action)
+    explicit Accuracy(const std::string &action) 
         : Action(action, ConfigurationKind),
         m_accuracy(0) { }
 
diff --git a/src/actions/audit_log.h b/src/actions/audit_log.h
index f63198f0..6e3ecbd0 100644
--- a/src/actions/audit_log.h
+++ b/src/actions/audit_log.h
@@ -32,7 +32,7 @@ namespace actions {
 
 class AuditLog : public Action {
  public:
-    explicit AuditLog(std::string action)
+    explicit AuditLog(const std::string &action) 
         : Action(action, RunTimeOnlyIfMatchKind) { }
 
     bool evaluate(Rule *rule, Transaction *transaction,
diff --git a/src/actions/block.h b/src/actions/block.h
index ecd73d8c..05f39f92 100644
--- a/src/actions/block.h
+++ b/src/actions/block.h
@@ -33,7 +33,7 @@ namespace actions {
 
 class Block : public Action {
  public:
-    explicit Block(std::string action) : Action(action) { }
+    explicit Block(const std::string &action) : Action(action) { }
 
     bool evaluate(Rule *rule, Transaction *transaction,
         std::shared_ptr<RuleMessage> rm) override;
diff --git a/src/actions/capture.h b/src/actions/capture.h
index be3cbae1..ae99543f 100644
--- a/src/actions/capture.h
+++ b/src/actions/capture.h
@@ -28,7 +28,7 @@ namespace actions {
 
 class Capture : public Action {
  public:
-    explicit Capture(std::string action)
+    explicit Capture(const std::string &action) 
         : Action(action, RunTimeOnlyIfMatchKind) { }
 
     bool evaluate(Rule *rule, Transaction *transaction) override;
diff --git a/src/actions/chain.h b/src/actions/chain.h
index 64962518..42af24fc 100644
--- a/src/actions/chain.h
+++ b/src/actions/chain.h
@@ -32,7 +32,7 @@ namespace actions {
 
 class Chain : public Action {
  public:
-    explicit Chain(std::string action)
+    explicit Chain(const std::string &action) 
         : Action(action, ConfigurationKind) { }
 
     bool evaluate(Rule *rule, Transaction *transaction) override;
diff --git a/src/actions/ctl/audit_log_parts.h b/src/actions/ctl/audit_log_parts.h
index e1d3546c..dae40191 100644
--- a/src/actions/ctl/audit_log_parts.h
+++ b/src/actions/ctl/audit_log_parts.h
@@ -28,7 +28,7 @@ namespace ctl {
 
 class AuditLogParts : public Action {
  public:
-    explicit AuditLogParts(std::string action)
+    explicit AuditLogParts(const std::string &action) 
         : Action(action, RunTimeOnlyIfMatchKind),
         mPartsAction(0),
         mParts("") { }
diff --git a/src/actions/ctl/request_body_access.h b/src/actions/ctl/request_body_access.h
index 8f2f05e9..aca57854 100644
--- a/src/actions/ctl/request_body_access.h
+++ b/src/actions/ctl/request_body_access.h
@@ -29,7 +29,7 @@ namespace ctl {
 
 class RequestBodyAccess : public Action {
  public:
-    explicit RequestBodyAccess(std::string action)
+    explicit RequestBodyAccess(const std::string &action) 
         : Action(action, RunTimeOnlyIfMatchKind),
         m_request_body_access(false) { }
 
diff --git a/src/actions/ctl/request_body_processor_json.h b/src/actions/ctl/request_body_processor_json.h
index dca4d608..4cd76dc4 100644
--- a/src/actions/ctl/request_body_processor_json.h
+++ b/src/actions/ctl/request_body_processor_json.h
@@ -28,7 +28,7 @@ namespace ctl {
 
 class RequestBodyProcessorJSON : public Action {
  public:
-    explicit RequestBodyProcessorJSON(std::string action)
+    explicit RequestBodyProcessorJSON(const std::string &action) 
         : Action(action, RunTimeOnlyIfMatchKind) { }
 
     bool evaluate(Rule *rule, Transaction *transaction) override;
diff --git a/src/actions/ctl/request_body_processor_urlencoded.h b/src/actions/ctl/request_body_processor_urlencoded.h
index 920b0553..a5a849ed 100644
--- a/src/actions/ctl/request_body_processor_urlencoded.h
+++ b/src/actions/ctl/request_body_processor_urlencoded.h
@@ -28,7 +28,7 @@ namespace ctl {
 
 class RequestBodyProcessorURLENCODED : public Action {
  public:
-    explicit RequestBodyProcessorURLENCODED(std::string action)
+    explicit RequestBodyProcessorURLENCODED(const std::string &action) 
         : Action(action, RunTimeOnlyIfMatchKind) { }
 
     bool evaluate(Rule *rule, Transaction *transaction) override;
diff --git a/src/actions/ctl/request_body_processor_xml.h b/src/actions/ctl/request_body_processor_xml.h
index 449eec12..bb8f00b5 100644
--- a/src/actions/ctl/request_body_processor_xml.h
+++ b/src/actions/ctl/request_body_processor_xml.h
@@ -28,7 +28,7 @@ namespace ctl {
 
 class RequestBodyProcessorXML : public Action {
  public:
-    explicit RequestBodyProcessorXML(std::string action)
+    explicit RequestBodyProcessorXML(const std::string &action) 
         : Action(action, RunTimeOnlyIfMatchKind) { }
 
     bool evaluate(Rule *rule, Transaction *transaction) override;
diff --git a/src/actions/ctl/rule_engine.h b/src/actions/ctl/rule_engine.h
index 93ef894c..e8a862d6 100644
--- a/src/actions/ctl/rule_engine.h
+++ b/src/actions/ctl/rule_engine.h
@@ -30,7 +30,7 @@ namespace ctl {
 
 class RuleEngine : public Action {
  public:
-    explicit RuleEngine(std::string action)
+    explicit RuleEngine(const std::string &action) 
         : Action(action, RunTimeOnlyIfMatchKind),
         m_ruleEngine(RulesProperties::PropertyNotSetRuleEngine) { }
 
diff --git a/src/actions/ctl/rule_remove_by_id.h b/src/actions/ctl/rule_remove_by_id.h
index efb0dc85..2347d4f3 100644
--- a/src/actions/ctl/rule_remove_by_id.h
+++ b/src/actions/ctl/rule_remove_by_id.h
@@ -29,7 +29,7 @@ namespace ctl {
 
 class RuleRemoveById : public Action {
  public:
-    explicit RuleRemoveById(std::string action)
+    explicit RuleRemoveById(const std::string &action) 
         : Action(action, RunTimeOnlyIfMatchKind) { }
 
     bool init(std::string *error) override;
diff --git a/src/actions/ctl/rule_remove_by_tag.h b/src/actions/ctl/rule_remove_by_tag.h
index 6f977883..1e5241a4 100644
--- a/src/actions/ctl/rule_remove_by_tag.h
+++ b/src/actions/ctl/rule_remove_by_tag.h
@@ -29,7 +29,7 @@ namespace ctl {
 
 class RuleRemoveByTag : public Action {
  public:
-    explicit RuleRemoveByTag(std::string action)
+    explicit RuleRemoveByTag(const std::string &action) 
         : Action(action, RunTimeOnlyIfMatchKind),
         m_tag("") { }
 
diff --git a/src/actions/ctl/rule_remove_target_by_id.h b/src/actions/ctl/rule_remove_target_by_id.h
index 03941f4a..489f8fcd 100644
--- a/src/actions/ctl/rule_remove_target_by_id.h
+++ b/src/actions/ctl/rule_remove_target_by_id.h
@@ -29,7 +29,7 @@ namespace ctl {
 
 class RuleRemoveTargetById : public Action {
  public:
-    explicit RuleRemoveTargetById(std::string action)
+    explicit RuleRemoveTargetById(const std::string &action) 
         : Action(action, RunTimeOnlyIfMatchKind),
         m_id(0),
         m_target("") { }
diff --git a/src/actions/ctl/rule_remove_target_by_tag.h b/src/actions/ctl/rule_remove_target_by_tag.h
index 3acf4c8b..97f65c0d 100644
--- a/src/actions/ctl/rule_remove_target_by_tag.h
+++ b/src/actions/ctl/rule_remove_target_by_tag.h
@@ -29,7 +29,7 @@ namespace ctl {
 
 class RuleRemoveTargetByTag : public Action {
  public:
-    explicit RuleRemoveTargetByTag(std::string action)
+    explicit RuleRemoveTargetByTag(const std::string &action) 
         : Action(action, RunTimeOnlyIfMatchKind) { }
 
     bool init(std::string *error) override;
diff --git a/src/actions/data/status.h b/src/actions/data/status.h
index 8a0232fd..7e14e1ff 100644
--- a/src/actions/data/status.h
+++ b/src/actions/data/status.h
@@ -33,7 +33,7 @@ namespace data {
 
 class Status : public Action {
  public:
-    explicit Status(std::string action) : Action(action, 2),
+    explicit Status(const std::string &action) : Action(action, 2),
     m_status(0) { }
 
     bool init(std::string *error) override;
diff --git a/src/actions/disruptive/allow.h b/src/actions/disruptive/allow.h
index 220f94fa..df5dd841 100644
--- a/src/actions/disruptive/allow.h
+++ b/src/actions/disruptive/allow.h
@@ -53,7 +53,7 @@ enum AllowType : int {
 
 class Allow : public Action {
  public:
-    explicit Allow(std::string action)
+    explicit Allow(const std::string &action) 
         : Action(action, RunTimeOnlyIfMatchKind),
         m_allowType(NoneAllowType) { }
 
diff --git a/src/actions/disruptive/deny.h b/src/actions/disruptive/deny.h
index 0d8871ec..9dadfe0f 100644
--- a/src/actions/disruptive/deny.h
+++ b/src/actions/disruptive/deny.h
@@ -31,7 +31,7 @@ namespace disruptive {
 
 class Deny : public Action {
  public:
-    explicit Deny(std::string action) : Action(action) { }
+    explicit Deny(const std::string &action) : Action(action) { }
 
     bool evaluate(Rule *rule, Transaction *transaction,
         std::shared_ptr<RuleMessage> rm) override;
diff --git a/src/actions/disruptive/drop.h b/src/actions/disruptive/drop.h
index fc96aeeb..530c3548 100644
--- a/src/actions/disruptive/drop.h
+++ b/src/actions/disruptive/drop.h
@@ -31,7 +31,7 @@ namespace disruptive {
 
 class Drop : public Action {
  public:
-    explicit Drop(std::string action) : Action(action) { }
+    explicit Drop(const std::string &action) : Action(action) { }
 
     bool evaluate(Rule *rule, Transaction *transaction,
         std::shared_ptr<RuleMessage> rm) override;
diff --git a/src/actions/disruptive/pass.h b/src/actions/disruptive/pass.h
index 50f8fd53..fe8fec92 100644
--- a/src/actions/disruptive/pass.h
+++ b/src/actions/disruptive/pass.h
@@ -29,7 +29,7 @@ namespace disruptive {
 
 class Pass : public Action {
  public:
-    explicit Pass(std::string action) : Action(action) { }
+    explicit Pass(const std::string &action) : Action(action) { }
 
     bool evaluate(Rule *rule, Transaction *transaction,
         std::shared_ptr<RuleMessage> rm) override;
diff --git a/src/actions/disruptive/redirect.h b/src/actions/disruptive/redirect.h
index b982a86b..b4973dff 100644
--- a/src/actions/disruptive/redirect.h
+++ b/src/actions/disruptive/redirect.h
@@ -38,10 +38,12 @@ class Redirect : public Action {
  public:
     explicit Redirect(const std::string &action)
         : Action(action, RunTimeOnlyIfMatchKind),
-        m_status(0) { }
+        m_status(0),
+        m_string(nullptr) { }
 
     explicit Redirect(std::unique_ptr<RunTimeString> z)
         : Action("redirert", RunTimeOnlyIfMatchKind),
+            m_status(0),
             m_string(std::move(z)) { }
 
     bool evaluate(Rule *rule, Transaction *transaction,
diff --git a/src/actions/exec.h b/src/actions/exec.h
index cffffb79..b337c9eb 100644
--- a/src/actions/exec.h
+++ b/src/actions/exec.h
@@ -30,7 +30,7 @@ namespace actions {
 
 class Exec : public Action {
  public:
-    explicit Exec(std::string action)
+    explicit Exec(const std::string &action) 
         : Action(action),
         m_script("") { }
 
diff --git a/src/actions/init_col.h b/src/actions/init_col.h
index bd06bf6f..e05186bb 100644
--- a/src/actions/init_col.h
+++ b/src/actions/init_col.h
@@ -32,9 +32,9 @@ namespace actions {
 
 class InitCol : public Action {
  public:
-    explicit InitCol(std::string action) : Action(action) { }
+    explicit InitCol(const std::string &action) : Action(action) { }
 
-    InitCol(std::string action, std::unique_ptr<RunTimeString> z)
+    InitCol(const std::string &action, std::unique_ptr<RunTimeString> z)
         : Action(action, RunTimeOnlyIfMatchKind),
             m_string(std::move(z)) { }
 
diff --git a/src/actions/log.h b/src/actions/log.h
index 1d7262f0..c917bc7a 100644
--- a/src/actions/log.h
+++ b/src/actions/log.h
@@ -30,7 +30,7 @@ namespace actions {
 
 class Log : public Action {
  public:
-    explicit Log(std::string action)
+    explicit Log(const std::string &action) 
         : Action(action, RunTimeOnlyIfMatchKind) { }
 
     bool evaluate(Rule *rule, Transaction *transaction,
diff --git a/src/actions/log_data.h b/src/actions/log_data.h
index 80056370..d0032cc8 100644
--- a/src/actions/log_data.h
+++ b/src/actions/log_data.h
@@ -32,7 +32,7 @@ namespace actions {
 
 class LogData : public Action {
  public:
-    explicit LogData(std::string action)
+    explicit LogData(const std::string &action) 
         : Action(action, RunTimeOnlyIfMatchKind) { }
 
     explicit LogData(std::unique_ptr<RunTimeString> z)
diff --git a/src/actions/maturity.h b/src/actions/maturity.h
index 6227fada..b6daac1f 100644
--- a/src/actions/maturity.h
+++ b/src/actions/maturity.h
@@ -29,7 +29,7 @@ namespace actions {
 
 class Maturity : public Action {
  public:
-    explicit Maturity(std::string action)
+    explicit Maturity(const std::string &action) 
         : Action(action, ConfigurationKind),
         m_maturity(0) { }
 
diff --git a/src/actions/msg.h b/src/actions/msg.h
index 6206ca17..16e4627c 100644
--- a/src/actions/msg.h
+++ b/src/actions/msg.h
@@ -33,7 +33,7 @@ namespace actions {
 
 class Msg : public Action {
  public:
-    explicit Msg(std::string action)
+    explicit Msg(const std::string &action) 
         : Action(action, RunTimeOnlyIfMatchKind) { }
 
     explicit Msg(std::unique_ptr<RunTimeString> z)
diff --git a/src/actions/multi_match.h b/src/actions/multi_match.h
index 6f74a414..1bcf77c1 100644
--- a/src/actions/multi_match.h
+++ b/src/actions/multi_match.h
@@ -32,7 +32,7 @@ namespace actions {
 
 class MultiMatch : public Action {
  public:
-    explicit MultiMatch(std::string action)
+    explicit MultiMatch(const std::string &action) 
         : Action(action, RunTimeOnlyIfMatchKind) { }
 
     bool evaluate(Rule *rule, Transaction *transaction) override;
diff --git a/src/actions/no_audit_log.h b/src/actions/no_audit_log.h
index d0543a9f..23de0598 100644
--- a/src/actions/no_audit_log.h
+++ b/src/actions/no_audit_log.h
@@ -32,7 +32,7 @@ namespace actions {
 
 class NoAuditLog : public Action {
  public:
-    explicit NoAuditLog(std::string action)
+    explicit NoAuditLog(const std::string &action) 
         : Action(action, RunTimeOnlyIfMatchKind) { }
 
     bool evaluate(Rule *rule, Transaction *transaction,
diff --git a/src/actions/no_log.h b/src/actions/no_log.h
index 9d4878be..f8ae51be 100644
--- a/src/actions/no_log.h
+++ b/src/actions/no_log.h
@@ -30,7 +30,7 @@ namespace actions {
 
 class NoLog : public Action {
  public:
-    explicit NoLog(std::string action)
+    explicit NoLog(const std::string &action) 
         : Action(action, RunTimeOnlyIfMatchKind) { }
 
     bool evaluate(Rule *rule, Transaction *transaction,
diff --git a/src/actions/phase.h b/src/actions/phase.h
index 99f0176f..81f6abf7 100644
--- a/src/actions/phase.h
+++ b/src/actions/phase.h
@@ -32,7 +32,7 @@ namespace actions {
 
 class Phase : public Action {
  public:
-    explicit Phase(std::string action) : Action(action, ConfigurationKind),
+    explicit Phase(const std::string &action) : Action(action, ConfigurationKind),
         m_phase(0),
         m_secRulesPhase(0) { }
 
diff --git a/src/actions/rev.h b/src/actions/rev.h
index 052085b0..64e57faf 100644
--- a/src/actions/rev.h
+++ b/src/actions/rev.h
@@ -29,7 +29,7 @@ namespace actions {
 
 class Rev : public Action {
  public:
-    explicit Rev(std::string action) : Action(action, ConfigurationKind) { }
+    explicit Rev(const std::string &action) : Action(action, ConfigurationKind) { }
 
     bool evaluate(Rule *rule, Transaction *transaction) override;
     bool init(std::string *error) override;
diff --git a/src/actions/rule_id.h b/src/actions/rule_id.h
index b327d2a2..d2ff0981 100644
--- a/src/actions/rule_id.h
+++ b/src/actions/rule_id.h
@@ -32,7 +32,7 @@ namespace actions {
 
 class RuleId : public Action {
  public:
-    explicit RuleId(std::string action)
+    explicit RuleId(const std::string &action) 
         : Action(action, ConfigurationKind),
         m_ruleId(0) { }
 
diff --git a/src/actions/set_env.h b/src/actions/set_env.h
index 194ee239..c9f971de 100644
--- a/src/actions/set_env.h
+++ b/src/actions/set_env.h
@@ -32,7 +32,7 @@ namespace actions {
 
 class SetENV : public Action {
  public:
-    explicit SetENV(std::string _action)
+    explicit SetENV(const std::string &_action)
         : Action(_action) { }
 
     explicit SetENV(std::unique_ptr<RunTimeString> z)
diff --git a/src/actions/set_rsc.h b/src/actions/set_rsc.h
index b3354002..e6cfabe0 100644
--- a/src/actions/set_rsc.h
+++ b/src/actions/set_rsc.h
@@ -32,7 +32,7 @@ namespace actions {
 
 class SetRSC : public Action {
  public:
-    explicit SetRSC(std::string _action)
+    explicit SetRSC(const std::string &_action)
         : Action(_action) { }
 
     explicit SetRSC(std::unique_ptr<RunTimeString> z)
diff --git a/src/actions/set_sid.h b/src/actions/set_sid.h
index 727745dd..f19fb9eb 100644
--- a/src/actions/set_sid.h
+++ b/src/actions/set_sid.h
@@ -32,7 +32,7 @@ namespace actions {
 
 class SetSID : public Action {
  public:
-    explicit SetSID(std::string _action)
+    explicit SetSID(const std::string &_action)
         : Action(_action) { }
 
     explicit SetSID(std::unique_ptr<RunTimeString> z)
diff --git a/src/actions/set_uid.h b/src/actions/set_uid.h
index 38c5aaa7..cd1bdd61 100644
--- a/src/actions/set_uid.h
+++ b/src/actions/set_uid.h
@@ -32,7 +32,7 @@ namespace actions {
 
 class SetUID : public Action {
  public:
-    explicit SetUID(std::string _action)
+    explicit SetUID(const std::string &_action)
         : Action(_action) { }
 
     explicit SetUID(std::unique_ptr<RunTimeString> z)
diff --git a/src/actions/severity.h b/src/actions/severity.h
index e67633d6..c0a85994 100644
--- a/src/actions/severity.h
+++ b/src/actions/severity.h
@@ -31,7 +31,7 @@ namespace actions {
 
 class Severity : public Action {
  public:
-    explicit Severity(std::string action)
+    explicit Severity(const std::string &action) 
         : Action(action),
         m_severity(0) { }
 
diff --git a/src/actions/skip.h b/src/actions/skip.h
index 0d7160ee..1c38202b 100644
--- a/src/actions/skip.h
+++ b/src/actions/skip.h
@@ -29,7 +29,7 @@ namespace actions {
 
 class Skip : public Action {
  public:
-    explicit Skip(std::string action)
+    explicit Skip(const std::string &action) 
         : Action(action, RunTimeOnlyIfMatchKind),
         m_skip_next(0) { }
 
diff --git a/src/actions/skip_after.h b/src/actions/skip_after.h
index a0017c09..5f29b9d8 100644
--- a/src/actions/skip_after.h
+++ b/src/actions/skip_after.h
@@ -29,7 +29,7 @@ namespace actions {
 
 class SkipAfter : public Action {
  public:
-    explicit SkipAfter(std::string action)
+    explicit SkipAfter(const std::string &action) 
         : Action(action, RunTimeOnlyIfMatchKind) { }
 
     bool evaluate(Rule *rule, Transaction *transaction) override;
diff --git a/src/actions/transformations/base64_decode.h b/src/actions/transformations/base64_decode.h
index e16c132f..7926f090 100644
--- a/src/actions/transformations/base64_decode.h
+++ b/src/actions/transformations/base64_decode.h
@@ -30,7 +30,7 @@ namespace transformations {
 
 class Base64Decode : public Transformation {
  public:
-    explicit Base64Decode(std::string action) : Transformation(action) { }
+    explicit Base64Decode(const std::string &action)  : Transformation(action) { }
 
     std::string evaluate(std::string exp,
         Transaction *transaction) override;
diff --git a/src/actions/transformations/base64_decode_ext.h b/src/actions/transformations/base64_decode_ext.h
index 903ccdd0..b959bbe4 100644
--- a/src/actions/transformations/base64_decode_ext.h
+++ b/src/actions/transformations/base64_decode_ext.h
@@ -30,7 +30,7 @@ namespace transformations {
 
 class Base64DecodeExt : public Transformation {
  public:
-    explicit Base64DecodeExt(std::string action) : Transformation(action) { }
+    explicit Base64DecodeExt(const std::string &action)  : Transformation(action) { }
 
     std::string evaluate(std::string exp,
         Transaction *transaction) override;
diff --git a/src/actions/transformations/base64_encode.h b/src/actions/transformations/base64_encode.h
index b04d6b65..1ba77bf4 100644
--- a/src/actions/transformations/base64_encode.h
+++ b/src/actions/transformations/base64_encode.h
@@ -30,7 +30,7 @@ namespace transformations {
 
 class Base64Encode : public Transformation {
  public:
-    explicit Base64Encode(std::string action) : Transformation(action) { }
+    explicit Base64Encode(const std::string &action)  : Transformation(action) { }
 
     std::string evaluate(std::string exp,
         Transaction *transaction) override;
diff --git a/src/actions/transformations/cmd_line.h b/src/actions/transformations/cmd_line.h
index 13843ad9..e70d752f 100644
--- a/src/actions/transformations/cmd_line.h
+++ b/src/actions/transformations/cmd_line.h
@@ -30,7 +30,7 @@ namespace transformations {
 
 class CmdLine : public Transformation {
  public:
-    explicit CmdLine(std::string action)
+    explicit CmdLine(const std::string &action) 
         : Transformation(action) { }
 
     std::string evaluate(std::string exp,
diff --git a/src/actions/transformations/compress_whitespace.cc b/src/actions/transformations/compress_whitespace.cc
index b51654aa..83d047ef 100644
--- a/src/actions/transformations/compress_whitespace.cc
+++ b/src/actions/transformations/compress_whitespace.cc
@@ -30,7 +30,7 @@ namespace modsecurity {
 namespace actions {
 namespace transformations {
 
-CompressWhitespace::CompressWhitespace(std::string action)
+CompressWhitespace::CompressWhitespace(const std::string &action) 
     : Transformation(action) {
     this->action_kind = 1;
 }
diff --git a/src/actions/transformations/compress_whitespace.h b/src/actions/transformations/compress_whitespace.h
index 3b569595..f4c490ee 100644
--- a/src/actions/transformations/compress_whitespace.h
+++ b/src/actions/transformations/compress_whitespace.h
@@ -30,7 +30,7 @@ namespace transformations {
 
 class CompressWhitespace : public Transformation {
  public:
-    explicit CompressWhitespace(std::string action);
+    explicit CompressWhitespace(const std::string &action) ;
     std::string evaluate(std::string exp,
         Transaction *transaction) override;
 };
diff --git a/src/actions/transformations/css_decode.h b/src/actions/transformations/css_decode.h
index 6861ea4b..f97d1979 100644
--- a/src/actions/transformations/css_decode.h
+++ b/src/actions/transformations/css_decode.h
@@ -31,7 +31,7 @@ namespace transformations {
 
 class CssDecode : public Transformation {
  public:
-    explicit CssDecode(std::string action)
+    explicit CssDecode(const std::string &action) 
         : Transformation(action) { }
     std::string evaluate(std::string exp,
         Transaction *transaction) override;
diff --git a/src/actions/transformations/escape_seq_decode.cc b/src/actions/transformations/escape_seq_decode.cc
index 2525e306..e9797ad2 100644
--- a/src/actions/transformations/escape_seq_decode.cc
+++ b/src/actions/transformations/escape_seq_decode.cc
@@ -31,7 +31,7 @@ namespace modsecurity {
 namespace actions {
 namespace transformations {
 
-EscapeSeqDecode::EscapeSeqDecode(std::string action)
+EscapeSeqDecode::EscapeSeqDecode(const std::string &action) 
     : Transformation(action) {
     this->action_kind = 1;
 }
diff --git a/src/actions/transformations/escape_seq_decode.h b/src/actions/transformations/escape_seq_decode.h
index 3ada2fbb..b046dace 100644
--- a/src/actions/transformations/escape_seq_decode.h
+++ b/src/actions/transformations/escape_seq_decode.h
@@ -30,7 +30,7 @@ namespace transformations {
 
 class EscapeSeqDecode : public Transformation {
  public:
-    explicit EscapeSeqDecode(std::string action);
+    explicit EscapeSeqDecode(const std::string &action) ;
     std::string evaluate(std::string exp,
         Transaction *transaction) override;
     int ansi_c_sequences_decode_inplace(unsigned char *input, int input_len);
diff --git a/src/actions/transformations/hex_decode.h b/src/actions/transformations/hex_decode.h
index fe951438..e0eb4fa0 100644
--- a/src/actions/transformations/hex_decode.h
+++ b/src/actions/transformations/hex_decode.h
@@ -30,7 +30,7 @@ namespace transformations {
 
 class HexDecode : public Transformation {
  public:
-    explicit HexDecode(std::string action) : Transformation(action) { }
+    explicit HexDecode(const std::string &action)  : Transformation(action) { }
 
     std::string evaluate(std::string exp,
         Transaction *transaction) override;
diff --git a/src/actions/transformations/hex_encode.cc b/src/actions/transformations/hex_encode.cc
index 4f55d1fe..a88d72fe 100644
--- a/src/actions/transformations/hex_encode.cc
+++ b/src/actions/transformations/hex_encode.cc
@@ -31,7 +31,7 @@ namespace modsecurity {
 namespace actions {
 namespace transformations {
 
-HexEncode::HexEncode(std::string action)
+HexEncode::HexEncode(const std::string &action) 
     : Transformation(action) {
     this->action_kind = 1;
 }
diff --git a/src/actions/transformations/hex_encode.h b/src/actions/transformations/hex_encode.h
index 74d12604..3862f72d 100644
--- a/src/actions/transformations/hex_encode.h
+++ b/src/actions/transformations/hex_encode.h
@@ -30,7 +30,7 @@ namespace transformations {
 
 class HexEncode : public Transformation {
  public:
-    explicit HexEncode(std::string action);
+    explicit HexEncode(const std::string &action) ;
     std::string evaluate(std::string exp,
         Transaction *transaction) override;
 };
diff --git a/src/actions/transformations/html_entity_decode.cc b/src/actions/transformations/html_entity_decode.cc
index ed119856..26a2915a 100644
--- a/src/actions/transformations/html_entity_decode.cc
+++ b/src/actions/transformations/html_entity_decode.cc
@@ -60,7 +60,7 @@ int HtmlEntityDecode::inplace(unsigned char *input, uint64_t input_len) {
     unsigned char *d = input;
     int i, count;
 
-    if ((input == NULL) || (input_len <= 0)) {
+    if ((input == NULL) || (input_len == 0)) {
         return 0;
     }
 
diff --git a/src/actions/transformations/html_entity_decode.h b/src/actions/transformations/html_entity_decode.h
index bd1b5250..06c535d4 100644
--- a/src/actions/transformations/html_entity_decode.h
+++ b/src/actions/transformations/html_entity_decode.h
@@ -33,7 +33,7 @@ namespace transformations {
 
 class HtmlEntityDecode : public Transformation {
  public:
-    explicit HtmlEntityDecode(std::string action)
+    explicit HtmlEntityDecode(const std::string &action) 
         : Transformation(action) { }
 
     std::string evaluate(std::string exp,
diff --git a/src/actions/transformations/js_decode.h b/src/actions/transformations/js_decode.h
index 86f6b330..fa26c838 100644
--- a/src/actions/transformations/js_decode.h
+++ b/src/actions/transformations/js_decode.h
@@ -30,7 +30,7 @@ namespace transformations {
 
 class JsDecode : public Transformation {
  public:
-    explicit JsDecode(std::string action)
+    explicit JsDecode(const std::string &action) 
         : Transformation(action) { }
 
     std::string evaluate(std::string exp,
diff --git a/src/actions/transformations/length.cc b/src/actions/transformations/length.cc
index 7c32f80f..8a6287a5 100644
--- a/src/actions/transformations/length.cc
+++ b/src/actions/transformations/length.cc
@@ -30,7 +30,7 @@ namespace modsecurity {
 namespace actions {
 namespace transformations {
 
-Length::Length(std::string action)
+Length::Length(const std::string &action) 
     : Transformation(action) {
     this->action_kind = 1;
 }
diff --git a/src/actions/transformations/length.h b/src/actions/transformations/length.h
index 0a2ef6bc..9a375423 100644
--- a/src/actions/transformations/length.h
+++ b/src/actions/transformations/length.h
@@ -30,7 +30,7 @@ namespace transformations {
 
 class Length : public Transformation {
  public:
-    explicit Length(std::string action);
+    explicit Length(const std::string &action) ;
     std::string evaluate(std::string exp,
         Transaction *transaction) override;
 };
diff --git a/src/actions/transformations/lower_case.cc b/src/actions/transformations/lower_case.cc
index 8dd0bcae..f02af7d3 100644
--- a/src/actions/transformations/lower_case.cc
+++ b/src/actions/transformations/lower_case.cc
@@ -27,7 +27,7 @@ namespace actions {
 namespace transformations {
 
 
-LowerCase::LowerCase(std::string a)
+LowerCase::LowerCase(const std::string &a)
     : Transformation(a) {
 }
 
diff --git a/src/actions/transformations/lower_case.h b/src/actions/transformations/lower_case.h
index 41e81761..223dad45 100644
--- a/src/actions/transformations/lower_case.h
+++ b/src/actions/transformations/lower_case.h
@@ -32,7 +32,7 @@ namespace transformations {
 
 class LowerCase : public Transformation {
  public:
-    explicit LowerCase(std::string action);
+    explicit LowerCase(const std::string &action) ;
     std::string evaluate(std::string exp,
         Transaction *transaction) override;
 };
diff --git a/src/actions/transformations/md5.h b/src/actions/transformations/md5.h
index b53b21fb..cc6e128b 100644
--- a/src/actions/transformations/md5.h
+++ b/src/actions/transformations/md5.h
@@ -30,7 +30,7 @@ namespace transformations {
 
 class Md5 : public Transformation {
  public:
-    explicit Md5(std::string action) : Transformation(action) { }
+    explicit Md5(const std::string &action)  : Transformation(action) { }
 
     std::string evaluate(std::string exp,
         Transaction *transaction) override;
diff --git a/src/actions/transformations/none.h b/src/actions/transformations/none.h
index 5d868d1f..af34d1e8 100644
--- a/src/actions/transformations/none.h
+++ b/src/actions/transformations/none.h
@@ -30,7 +30,7 @@ namespace transformations {
 
 class None : public Transformation {
  public:
-    explicit None(std::string action)
+    explicit None(const std::string &action) 
         : Transformation(action)
         { m_isNone = true; }
 
diff --git a/src/actions/transformations/normalise_path.cc b/src/actions/transformations/normalise_path.cc
index 5d17e0ed..d0be405f 100644
--- a/src/actions/transformations/normalise_path.cc
+++ b/src/actions/transformations/normalise_path.cc
@@ -32,7 +32,7 @@ namespace modsecurity {
 namespace actions {
 namespace transformations {
 
-NormalisePath::NormalisePath(std::string action)
+NormalisePath::NormalisePath(const std::string &action) 
     : Transformation(action) {
     this->action_kind = 1;
 }
diff --git a/src/actions/transformations/normalise_path.h b/src/actions/transformations/normalise_path.h
index 1df1ce55..58a28c31 100644
--- a/src/actions/transformations/normalise_path.h
+++ b/src/actions/transformations/normalise_path.h
@@ -30,7 +30,7 @@ namespace transformations {
 
 class NormalisePath : public Transformation {
  public:
-    explicit NormalisePath(std::string action);
+    explicit NormalisePath(const std::string &action) ;
     std::string evaluate(std::string exp,
         Transaction *transaction) override;
 
diff --git a/src/actions/transformations/normalise_path_win.h b/src/actions/transformations/normalise_path_win.h
index f0449529..f82e4b9f 100644
--- a/src/actions/transformations/normalise_path_win.h
+++ b/src/actions/transformations/normalise_path_win.h
@@ -30,7 +30,7 @@ namespace transformations {
 
 class NormalisePathWin : public Transformation {
  public:
-    explicit NormalisePathWin(std::string action)
+    explicit NormalisePathWin(const std::string &action) 
         : Transformation(action) { }
 
     std::string evaluate(std::string exp,
diff --git a/src/actions/transformations/parity_even_7bit.h b/src/actions/transformations/parity_even_7bit.h
index 672c406b..24e9a452 100644
--- a/src/actions/transformations/parity_even_7bit.h
+++ b/src/actions/transformations/parity_even_7bit.h
@@ -30,7 +30,7 @@ namespace transformations {
 
 class ParityEven7bit : public Transformation {
  public:
-    explicit ParityEven7bit(std::string action) : Transformation(action) { }
+    explicit ParityEven7bit(const std::string &action)  : Transformation(action) { }
 
     std::string evaluate(std::string exp, Transaction *transaction) override;
     static bool inplace(unsigned char *input, uint64_t input_len);
diff --git a/src/actions/transformations/parity_odd_7bit.h b/src/actions/transformations/parity_odd_7bit.h
index 14fa9ff8..dc936bf9 100644
--- a/src/actions/transformations/parity_odd_7bit.h
+++ b/src/actions/transformations/parity_odd_7bit.h
@@ -30,7 +30,7 @@ namespace transformations {
 
 class ParityOdd7bit : public Transformation {
  public:
-    explicit ParityOdd7bit(std::string action) : Transformation(action) { }
+    explicit ParityOdd7bit(const std::string &action)  : Transformation(action) { }
 
     std::string evaluate(std::string exp, Transaction *transaction) override;
     static bool inplace(unsigned char *input, uint64_t input_len);
diff --git a/src/actions/transformations/parity_zero_7bit.h b/src/actions/transformations/parity_zero_7bit.h
index 3904c3a4..7ef409e9 100644
--- a/src/actions/transformations/parity_zero_7bit.h
+++ b/src/actions/transformations/parity_zero_7bit.h
@@ -30,7 +30,7 @@ namespace transformations {
 
 class ParityZero7bit : public Transformation {
  public:
-    explicit ParityZero7bit(std::string action) : Transformation(action) { }
+    explicit ParityZero7bit(const std::string &action)  : Transformation(action) { }
 
     std::string evaluate(std::string exp, Transaction *transaction) override;
     static bool inplace(unsigned char *input, uint64_t input_len);
diff --git a/src/actions/transformations/remove_comments.h b/src/actions/transformations/remove_comments.h
index 481a1d14..e9b23966 100644
--- a/src/actions/transformations/remove_comments.h
+++ b/src/actions/transformations/remove_comments.h
@@ -31,7 +31,7 @@ namespace transformations {
 
 class RemoveComments : public Transformation {
  public:
-    explicit RemoveComments(std::string action) : Transformation(action) { }
+    explicit RemoveComments(const std::string &action)  : Transformation(action) { }
 
     std::string evaluate(std::string exp,
         Transaction *transaction) override;
diff --git a/src/actions/transformations/remove_comments_char.cc b/src/actions/transformations/remove_comments_char.cc
index 150235ba..1455b52f 100644
--- a/src/actions/transformations/remove_comments_char.cc
+++ b/src/actions/transformations/remove_comments_char.cc
@@ -30,7 +30,7 @@ namespace modsecurity {
 namespace actions {
 namespace transformations {
 
-RemoveCommentsChar::RemoveCommentsChar(std::string action)
+RemoveCommentsChar::RemoveCommentsChar(const std::string &action) 
     : Transformation(action) {
     this->action_kind = 1;
 }
diff --git a/src/actions/transformations/remove_comments_char.h b/src/actions/transformations/remove_comments_char.h
index adae0a07..33ba8e18 100644
--- a/src/actions/transformations/remove_comments_char.h
+++ b/src/actions/transformations/remove_comments_char.h
@@ -30,7 +30,7 @@ namespace transformations {
 
 class RemoveCommentsChar : public Transformation {
  public:
-    explicit RemoveCommentsChar(std::string action);
+    explicit RemoveCommentsChar(const std::string &action) ;
     std::string evaluate(std::string exp,
         Transaction *transaction) override;
 };
diff --git a/src/actions/transformations/remove_nulls.h b/src/actions/transformations/remove_nulls.h
index f09fddfc..ef4c28c0 100644
--- a/src/actions/transformations/remove_nulls.h
+++ b/src/actions/transformations/remove_nulls.h
@@ -30,7 +30,7 @@ namespace transformations {
 
 class RemoveNulls : public Transformation {
  public:
-    explicit RemoveNulls(std::string action)
+    explicit RemoveNulls(const std::string &action) 
         : Transformation(action) { }
 
     std::string evaluate(std::string exp,
diff --git a/src/actions/transformations/remove_whitespace.cc b/src/actions/transformations/remove_whitespace.cc
index 4297a3ee..973d5bad 100644
--- a/src/actions/transformations/remove_whitespace.cc
+++ b/src/actions/transformations/remove_whitespace.cc
@@ -31,7 +31,7 @@ namespace modsecurity {
 namespace actions {
 namespace transformations {
 
-RemoveWhitespace::RemoveWhitespace(std::string action)
+RemoveWhitespace::RemoveWhitespace(const std::string &action) 
     : Transformation(action) {
     this->action_kind = 1;
 }
diff --git a/src/actions/transformations/remove_whitespace.h b/src/actions/transformations/remove_whitespace.h
index ecafb34d..82336c05 100644
--- a/src/actions/transformations/remove_whitespace.h
+++ b/src/actions/transformations/remove_whitespace.h
@@ -30,7 +30,7 @@ namespace transformations {
 
 class RemoveWhitespace : public Transformation {
  public:
-    explicit RemoveWhitespace(std::string action);
+    explicit RemoveWhitespace(const std::string &action) ;
     std::string evaluate(std::string exp,
         Transaction *transaction) override;
 };
diff --git a/src/actions/transformations/replace_comments.cc b/src/actions/transformations/replace_comments.cc
index b2c61086..b64b1376 100644
--- a/src/actions/transformations/replace_comments.cc
+++ b/src/actions/transformations/replace_comments.cc
@@ -31,7 +31,7 @@ namespace modsecurity {
 namespace actions {
 namespace transformations {
 
-ReplaceComments::ReplaceComments(std::string action)
+ReplaceComments::ReplaceComments(const std::string &action) 
     : Transformation(action) {
     this->action_kind = 1;
 }
diff --git a/src/actions/transformations/replace_comments.h b/src/actions/transformations/replace_comments.h
index 1bbe735f..77cbaecc 100644
--- a/src/actions/transformations/replace_comments.h
+++ b/src/actions/transformations/replace_comments.h
@@ -30,7 +30,7 @@ namespace transformations {
 
 class ReplaceComments : public Transformation {
  public:
-    explicit ReplaceComments(std::string action);
+    explicit ReplaceComments(const std::string &action) ;
     std::string evaluate(std::string exp,
         Transaction *transaction) override;
 };
diff --git a/src/actions/transformations/replace_nulls.cc b/src/actions/transformations/replace_nulls.cc
index 01996cc3..32328a78 100644
--- a/src/actions/transformations/replace_nulls.cc
+++ b/src/actions/transformations/replace_nulls.cc
@@ -30,7 +30,7 @@ namespace modsecurity {
 namespace actions {
 namespace transformations {
 
-ReplaceNulls::ReplaceNulls(std::string action)
+ReplaceNulls::ReplaceNulls(const std::string &action) 
     : Transformation(action) {
     this->action_kind = 1;
 }
diff --git a/src/actions/transformations/replace_nulls.h b/src/actions/transformations/replace_nulls.h
index 353a4943..b96e3d27 100644
--- a/src/actions/transformations/replace_nulls.h
+++ b/src/actions/transformations/replace_nulls.h
@@ -30,7 +30,7 @@ namespace transformations {
 
 class ReplaceNulls : public Transformation {
  public:
-    explicit ReplaceNulls(std::string action);
+    explicit ReplaceNulls(const std::string &action) ;
     std::string evaluate(std::string exp,
         Transaction *transaction) override;
 };
diff --git a/src/actions/transformations/sha1.cc b/src/actions/transformations/sha1.cc
index 0e1f8bb2..9f6f1948 100644
--- a/src/actions/transformations/sha1.cc
+++ b/src/actions/transformations/sha1.cc
@@ -31,7 +31,7 @@ namespace modsecurity {
 namespace actions {
 namespace transformations {
 
-Sha1::Sha1(std::string action)
+Sha1::Sha1(const std::string &action) 
     : Transformation(action) {
     this->action_kind = 1;
 }
diff --git a/src/actions/transformations/sha1.h b/src/actions/transformations/sha1.h
index 61026dec..37df556c 100644
--- a/src/actions/transformations/sha1.h
+++ b/src/actions/transformations/sha1.h
@@ -30,7 +30,7 @@ namespace transformations {
 
 class Sha1 : public Transformation {
  public:
-    explicit Sha1(std::string action);
+    explicit Sha1(const std::string &action) ;
     std::string evaluate(std::string exp,
         Transaction *transaction) override;
 };
diff --git a/src/actions/transformations/sql_hex_decode.h b/src/actions/transformations/sql_hex_decode.h
index 6d05415d..81774ca2 100644
--- a/src/actions/transformations/sql_hex_decode.h
+++ b/src/actions/transformations/sql_hex_decode.h
@@ -30,7 +30,7 @@ namespace transformations {
 
 class SqlHexDecode : public Transformation {
  public:
-    explicit SqlHexDecode(std::string action) : Transformation(action) { }
+    explicit SqlHexDecode(const std::string &action)  : Transformation(action) { }
 
     std::string evaluate(std::string exp,
         Transaction *transaction) override;
diff --git a/src/actions/transformations/trim.cc b/src/actions/transformations/trim.cc
index cd70ac7d..b228b010 100644
--- a/src/actions/transformations/trim.cc
+++ b/src/actions/transformations/trim.cc
@@ -50,7 +50,7 @@ std::string *Trim::trim(std::string *s) {
 }
 
 
-Trim::Trim(std::string action)
+Trim::Trim(const std::string &action) 
     : Transformation(action) {
     this->action_kind = 1;
 }
diff --git a/src/actions/transformations/trim.h b/src/actions/transformations/trim.h
index 064e6083..c6862fba 100644
--- a/src/actions/transformations/trim.h
+++ b/src/actions/transformations/trim.h
@@ -30,7 +30,7 @@ namespace transformations {
 
 class Trim : public Transformation {
  public:
-    explicit Trim(std::string action);
+    explicit Trim(const std::string &action) ;
     std::string evaluate(std::string exp,
         Transaction *transaction) override;
 
diff --git a/src/actions/transformations/trim_left.cc b/src/actions/transformations/trim_left.cc
index b2ea6af5..aa8a18fe 100644
--- a/src/actions/transformations/trim_left.cc
+++ b/src/actions/transformations/trim_left.cc
@@ -33,7 +33,7 @@ namespace transformations {
 
 
 
-TrimLeft::TrimLeft(std::string action)
+TrimLeft::TrimLeft(const std::string &action) 
     : Trim(action) {
     this->action_kind = 1;
 }
diff --git a/src/actions/transformations/trim_left.h b/src/actions/transformations/trim_left.h
index f665cd63..048b8b00 100644
--- a/src/actions/transformations/trim_left.h
+++ b/src/actions/transformations/trim_left.h
@@ -31,7 +31,7 @@ namespace transformations {
 
 class TrimLeft : public Trim {
  public:
-    explicit TrimLeft(std::string action);
+    explicit TrimLeft(const std::string &action) ;
     std::string evaluate(std::string exp,
         Transaction *transaction) override;
 };
diff --git a/src/actions/transformations/trim_right.cc b/src/actions/transformations/trim_right.cc
index d543bd4b..4852aaed 100644
--- a/src/actions/transformations/trim_right.cc
+++ b/src/actions/transformations/trim_right.cc
@@ -31,7 +31,7 @@ namespace actions {
 namespace transformations {
 
 
-TrimRight::TrimRight(std::string action)
+TrimRight::TrimRight(const std::string &action) 
     : Trim(action) {
     this->action_kind = 1;
 }
diff --git a/src/actions/transformations/trim_right.h b/src/actions/transformations/trim_right.h
index d2b5e654..3113ae1a 100644
--- a/src/actions/transformations/trim_right.h
+++ b/src/actions/transformations/trim_right.h
@@ -31,7 +31,7 @@ namespace transformations {
 
 class TrimRight : public Trim {
  public:
-    explicit TrimRight(std::string action);
+    explicit TrimRight(const std::string &action) ;
     std::string evaluate(std::string exp,
         Transaction *transaction) override;
 };
diff --git a/src/actions/transformations/upper_case.cc b/src/actions/transformations/upper_case.cc
index ff082e8e..63325d6e 100644
--- a/src/actions/transformations/upper_case.cc
+++ b/src/actions/transformations/upper_case.cc
@@ -27,7 +27,7 @@ namespace actions {
 namespace transformations {
 
 
-UpperCase::UpperCase(std::string a)
+UpperCase::UpperCase(const std::string &a)
     : Transformation(a) {
 }
 
diff --git a/src/actions/transformations/upper_case.h b/src/actions/transformations/upper_case.h
index 6738cd17..f3ac1702 100644
--- a/src/actions/transformations/upper_case.h
+++ b/src/actions/transformations/upper_case.h
@@ -32,7 +32,7 @@ namespace transformations {
 
 class UpperCase : public Transformation {
  public:
-    explicit UpperCase(std::string action);
+    explicit UpperCase(const std::string &action) ;
     std::string evaluate(std::string exp,
         Transaction *transaction) override;
 };
diff --git a/src/actions/transformations/url_decode.cc b/src/actions/transformations/url_decode.cc
index 3c2e3e6d..a403f130 100644
--- a/src/actions/transformations/url_decode.cc
+++ b/src/actions/transformations/url_decode.cc
@@ -32,7 +32,7 @@ namespace actions {
 namespace transformations {
 
 
-UrlDecode::UrlDecode(std::string action)
+UrlDecode::UrlDecode(const std::string &action) 
     : Transformation(action) {
     this->action_kind = 1;
 }
diff --git a/src/actions/transformations/url_decode.h b/src/actions/transformations/url_decode.h
index 9777153b..9d644ae6 100644
--- a/src/actions/transformations/url_decode.h
+++ b/src/actions/transformations/url_decode.h
@@ -32,7 +32,7 @@ namespace transformations {
 
 class UrlDecode : public Transformation {
  public:
-    explicit UrlDecode(std::string action);
+    explicit UrlDecode(const std::string &action) ;
     std::string evaluate(std::string exp,
         Transaction *transaction) override;
 };
diff --git a/src/actions/transformations/url_decode_uni.h b/src/actions/transformations/url_decode_uni.h
index fc08f9a9..e4932be8 100644
--- a/src/actions/transformations/url_decode_uni.h
+++ b/src/actions/transformations/url_decode_uni.h
@@ -31,7 +31,7 @@ namespace transformations {
 
 class UrlDecodeUni : public Transformation {
  public:
-    explicit UrlDecodeUni(std::string action) : Transformation(action) { }
+    explicit UrlDecodeUni(const std::string &action)  : Transformation(action) { }
 
     std::string evaluate(std::string exp, Transaction *transaction) override;
     static int inplace(unsigned char *input, uint64_t input_len,
diff --git a/src/actions/transformations/url_encode.cc b/src/actions/transformations/url_encode.cc
index b3580a9f..004e57ec 100644
--- a/src/actions/transformations/url_encode.cc
+++ b/src/actions/transformations/url_encode.cc
@@ -31,7 +31,7 @@ namespace actions {
 namespace transformations {
 
 
-UrlEncode::UrlEncode(std::string action)
+UrlEncode::UrlEncode(const std::string &action) 
     : Transformation(action) {
     this->action_kind = 1;
 }
diff --git a/src/actions/transformations/url_encode.h b/src/actions/transformations/url_encode.h
index 4f1dcc13..e8656517 100644
--- a/src/actions/transformations/url_encode.h
+++ b/src/actions/transformations/url_encode.h
@@ -30,7 +30,7 @@ namespace transformations {
 
 class UrlEncode : public Transformation {
  public:
-    explicit UrlEncode(std::string action);
+    explicit UrlEncode(const std::string &action) ;
     std::string evaluate(std::string exp,
         Transaction *transaction) override;
 
diff --git a/src/actions/transformations/utf8_to_unicode.h b/src/actions/transformations/utf8_to_unicode.h
index 2a011517..d336bc11 100644
--- a/src/actions/transformations/utf8_to_unicode.h
+++ b/src/actions/transformations/utf8_to_unicode.h
@@ -35,7 +35,7 @@ namespace transformations {
 
 class Utf8ToUnicode : public Transformation {
  public:
-    explicit Utf8ToUnicode(std::string action) : Transformation(action) { }
+    explicit Utf8ToUnicode(const std::string &action)  : Transformation(action) { }
 
     std::string evaluate(std::string exp,
         Transaction *transaction) override;
diff --git a/src/actions/ver.h b/src/actions/ver.h
index 4d8e53f9..0ae7bb83 100644
--- a/src/actions/ver.h
+++ b/src/actions/ver.h
@@ -29,7 +29,7 @@ namespace actions {
 
 class Ver : public Action {
  public:
-    explicit Ver(std::string action) : Action(action, ConfigurationKind) { }
+    explicit Ver(const std::string &action) : Action(action, ConfigurationKind) { }
 
     bool evaluate(Rule *rule, Transaction *transaction) override;
 
diff --git a/src/actions/xmlns.h b/src/actions/xmlns.h
index 23dc8319..9dcd6d56 100644
--- a/src/actions/xmlns.h
+++ b/src/actions/xmlns.h
@@ -29,7 +29,7 @@ namespace actions {
 
 class XmlNS : public Action {
  public:
-    explicit XmlNS(std::string action) : Action(action) { }
+    explicit XmlNS(const std::string &action) : Action(action) { }
 
     bool evaluate(Rule *rule, Transaction *transaction) override {
         return true;