diff --git a/lib/EAPBase/src/Credentials.cpp b/lib/EAPBase/src/Credentials.cpp
index 5d52390..0aa878f 100644
--- a/lib/EAPBase/src/Credentials.cpp
+++ b/lib/EAPBase/src/Credentials.cpp
@@ -660,13 +660,13 @@ void eap::credentials_connection::load(_In_ IXMLDOMNode *pConfigRoot)
             if (match(*cfg_prov)) {
                 // Matching provider found. Create matching blank credential set, then load.
                 if (cfg_prov->m_methods.empty())
-                    throw invalid_argument(string_printf(__FUNCTION__ " %ls provider has no methods.", cfg_prov->get_id().c_str()).c_str());
+                    throw invalid_argument(string_printf(__FUNCTION__ " %ls provider has no methods.", cfg_prov->get_id().c_str()));
                 m_cred.reset(cfg_prov->m_methods.front().get()->make_credentials());
                 m_cred->load(pXmlElClientSideCredential);
                 break;
             }
         } else
-            throw invalid_argument(string_printf(__FUNCTION__ " Credentials do not match to any provider within this connection configuration (provider: %ls).", get_id().c_str()).c_str());
+            throw invalid_argument(string_printf(__FUNCTION__ " Credentials do not match to any provider within this connection configuration (provider: %ls).", get_id().c_str()));
     }
 }
 
@@ -702,13 +702,13 @@ void eap::credentials_connection::operator>>(_Inout_ cursor_in &cursor)
             if (match(*cfg_prov)) {
                 // Matching provider found. Create matching blank credential set, then read.
                 if (cfg_prov->m_methods.empty())
-                    throw invalid_argument(string_printf(__FUNCTION__ " %ls provider has no methods.", cfg_prov->get_id().c_str()).c_str());
+                    throw invalid_argument(string_printf(__FUNCTION__ " %ls provider has no methods.", cfg_prov->get_id().c_str()));
                 m_cred.reset(cfg_prov->m_methods.front().get()->make_credentials());
                 cursor >> *m_cred;
                 break;
             }
         } else
-            throw invalid_argument(string_printf(__FUNCTION__ " Credentials do not match to any provider within this connection configuration (provider: %ls).", get_id().c_str()).c_str());
+            throw invalid_argument(string_printf(__FUNCTION__ " Credentials do not match to any provider within this connection configuration (provider: %ls).", get_id().c_str()));
     }
 }
 
diff --git a/lib/EAPBase/src/Method.cpp b/lib/EAPBase/src/Method.cpp
index 3d944b1..3a6a0c2 100644
--- a/lib/EAPBase/src/Method.cpp
+++ b/lib/EAPBase/src/Method.cpp
@@ -341,7 +341,7 @@ void eap::method_eap::get_response_packet(
         // Check packet size. We will suggest one EAP method alone, so we need one byte for data.
         size_t size_packet = sizeof(EapPacket) + 1;
         if (size_packet > size_max)
-            throw invalid_argument(string_printf(__FUNCTION__ " This method does not support packet fragmentation, but the data size is too big to fit in one packet (packet: %u, maximum: %u).", size_packet, size_max).c_str());
+            throw invalid_argument(string_printf(__FUNCTION__ " This method does not support packet fragmentation, but the data size is too big to fit in one packet (packet: %u, maximum: %u).", size_packet, size_max));
         packet.reserve(size_packet); // To avoid reallocation when inserting EAP packet header later.
 
         // Data of Legacy Nak packet is a list of supported EAP types: our method alone.
diff --git a/lib/EapHost/include/Method.h b/lib/EapHost/include/Method.h
index 392d23c..a2d324f 100644
--- a/lib/EapHost/include/Method.h
+++ b/lib/EapHost/include/Method.h
@@ -142,7 +142,7 @@ namespace eap
                 case EapHostPeerResponseRespond            : return EapPeerMethodResponseActionRespond ;
                 case EapHostPeerResponseStartAuthentication: return EapPeerMethodResponseActionDiscard ; // The session could not be found. So the supplicant either needs to start session again with the same packet or discard the packet.
                 case EapHostPeerResponseNone               : return EapPeerMethodResponseActionNone    ;
-                default                                    : throw std::invalid_argument(winstd::string_printf(__FUNCTION__ " Unknown action (%u).", action).c_str());
+                default                                    : throw std::invalid_argument(winstd::string_printf(__FUNCTION__ " Unknown action (%u).", action));
             }
         }
 
diff --git a/lib/MSCHAPv2/src/Method.cpp b/lib/MSCHAPv2/src/Method.cpp
index 2519ad0..76f9d9c 100644
--- a/lib/MSCHAPv2/src/Method.cpp
+++ b/lib/MSCHAPv2/src/Method.cpp
@@ -96,7 +96,7 @@ void eap::method_mschapv2_base::get_response_packet(
     _In_opt_ DWORD           size_max)
 {
     if (m_packet_res.size() > size_max)
-        throw invalid_argument(string_printf(__FUNCTION__ " This method does not support packet fragmentation, but the data size is too big to fit in one packet (packet: %u, maximum: %u).", m_packet_res.size(), size_max).c_str());
+        throw invalid_argument(string_printf(__FUNCTION__ " This method does not support packet fragmentation, but the data size is too big to fit in one packet (packet: %u, maximum: %u).", m_packet_res.size(), size_max));
 
     packet.assign(m_packet_res.begin(), m_packet_res.end());
 }
@@ -173,7 +173,7 @@ void eap::method_mschapv2_base::process_error(_In_ const list<string> &argv)
             bool is_last;
             dec.decode(resp, is_last, val.data() + 2, (size_t)-1);
             if (resp.size() != sizeof(m_challenge_server))
-                throw invalid_argument(string_printf(__FUNCTION__ " Incorrect MSCHAPv2 challenge length (expected: %uB, received: %uB).", sizeof(m_challenge_server), resp.size()).c_str());
+                throw invalid_argument(string_printf(__FUNCTION__ " Incorrect MSCHAPv2 challenge length (expected: %uB, received: %uB).", sizeof(m_challenge_server), resp.size()));
             memcpy(&m_challenge_server, resp.data(), sizeof(m_challenge_server));
         } else if ((val[0] == 'M' || val[0] == 'm') && val[1] == '=') {
             MultiByteToWideChar(CP_UTF8, 0, val.data() + 2, -1, m_cfg.m_last_msg);
@@ -423,7 +423,7 @@ EapPeerMethodResponseAction eap::method_mschapv2_diameter::process_request_packe
         return EapPeerMethodResponseActionNone;
 
     default:
-        throw invalid_argument(string_printf(__FUNCTION__ " Unknown phase (phase %u).", m_phase).c_str());
+        throw invalid_argument(string_printf(__FUNCTION__ " Unknown phase (phase %u).", m_phase));
     }
 }
 
@@ -457,7 +457,7 @@ void eap::method_mschapv2_diameter::process_packet(_In_bytecount_(size_pck) cons
         if (code == 26 && vendor == 311) {
             // MS-CHAP2-Success
             if (msg[0] != m_ident)
-                throw invalid_argument(string_printf(__FUNCTION__ " Wrong MSCHAPv2 ident (expected: %u, received: %u).", m_ident, msg[0]).c_str());
+                throw invalid_argument(string_printf(__FUNCTION__ " Wrong MSCHAPv2 ident (expected: %u, received: %u).", m_ident, msg[0]));
             const char *str = reinterpret_cast<const char*>(msg + 1);
             process_success(parse_response(str, (reinterpret_cast<const char*>(msg_end) - str)));
         } else if (code == 2 && vendor == 311) {
@@ -466,7 +466,7 @@ void eap::method_mschapv2_diameter::process_packet(_In_bytecount_(size_pck) cons
             const char *str = reinterpret_cast<const char*>(msg + 1);
             process_error(parse_response(str, (reinterpret_cast<const char*>(msg_end) - str)));
         } else if (hdr->flags & diameter_avp_flag_mandatory)
-            throw win_runtime_error(ERROR_NOT_SUPPORTED, string_printf(__FUNCTION__ " Server sent mandatory Diameter AVP we do not support (code: %u, vendor: %u).", code, vendor).c_str());
+            throw win_runtime_error(ERROR_NOT_SUPPORTED, string_printf(__FUNCTION__ " Server sent mandatory Diameter AVP we do not support (code: %u, vendor: %u).", code, vendor));
 
         pck = msg_next;
     }
diff --git a/lib/PAP/src/Method.cpp b/lib/PAP/src/Method.cpp
index 9c7b41f..94a9849 100644
--- a/lib/PAP/src/Method.cpp
+++ b/lib/PAP/src/Method.cpp
@@ -112,7 +112,7 @@ EapPeerMethodResponseAction eap::method_pap_diameter::process_request_packet(
         return EapPeerMethodResponseActionNone;
 
     default:
-        throw invalid_argument(string_printf(__FUNCTION__ " Unknown phase (phase %u).", m_phase).c_str());
+        throw invalid_argument(string_printf(__FUNCTION__ " Unknown phase (phase %u).", m_phase));
     }
 }
 
@@ -122,7 +122,7 @@ void eap::method_pap_diameter::get_response_packet(
     _In_opt_ DWORD           size_max)
 {
     if (m_packet_res.size() > size_max)
-        throw invalid_argument(string_printf(__FUNCTION__ " This method does not support packet fragmentation, but the data size is too big to fit in one packet (packet: %u, maximum: %u).", m_packet_res.size(), size_max).c_str());
+        throw invalid_argument(string_printf(__FUNCTION__ " This method does not support packet fragmentation, but the data size is too big to fit in one packet (packet: %u, maximum: %u).", m_packet_res.size(), size_max));
 
     packet.assign(m_packet_res.begin(), m_packet_res.end());
 }
diff --git a/lib/TTLS/src/Method.cpp b/lib/TTLS/src/Method.cpp
index d725e6c..1642754 100644
--- a/lib/TTLS/src/Method.cpp
+++ b/lib/TTLS/src/Method.cpp
@@ -293,7 +293,7 @@ EapPeerMethodResponseAction eap::method_eapmsg::process_request_packet(
     }
 
     default:
-        throw invalid_argument(string_printf(__FUNCTION__ " Unknown phase (phase %u).", m_phase).c_str());
+        throw invalid_argument(string_printf(__FUNCTION__ " Unknown phase (phase %u).", m_phase));
     }
 }
 
@@ -325,7 +325,7 @@ void eap::method_eapmsg::get_response_packet(
         packet.insert(packet.end(), (unsigned int)((4 - size_packet) % 4), 0);
     } else {
         if (m_packet_res.size() > size_max)
-            throw invalid_argument(string_printf(__FUNCTION__ " This method does not support packet fragmentation, but the data size is too big to fit in one packet (packet: %u, maximum: %u).", m_packet_res.size(), size_max).c_str());
+            throw invalid_argument(string_printf(__FUNCTION__ " This method does not support packet fragmentation, but the data size is too big to fit in one packet (packet: %u, maximum: %u).", m_packet_res.size(), size_max));
 
         packet.assign(m_packet_res.begin(), m_packet_res.end());
     }
@@ -653,7 +653,7 @@ EapPeerMethodResponseAction eap::method_ttls::process_request_packet(
                 switch (action) {
                 case EapPeerMethodResponseActionSend: m_packet_res_inner = true ; break;
                 case EapPeerMethodResponseActionNone: m_packet_res_inner = false; break;
-                default                             : throw invalid_argument(string_printf(__FUNCTION__ " Inner method returned an unsupported action (action %u).", action).c_str());
+                default                             : throw invalid_argument(string_printf(__FUNCTION__ " Inner method returned an unsupported action (action %u).", action));
                 }
             }
             return EapPeerMethodResponseActionSend;
@@ -717,7 +717,7 @@ EapPeerMethodResponseAction eap::method_ttls::process_request_packet(
     }
 
     default:
-        throw invalid_argument(string_printf(__FUNCTION__ " Unknown phase (phase %u).", m_phase).c_str());
+        throw invalid_argument(string_printf(__FUNCTION__ " Unknown phase (phase %u).", m_phase));
     }
 }
 
@@ -733,7 +733,7 @@ void eap::method_ttls::get_response_packet(
         if (FAILED(status))
             throw sec_runtime_error(status, __FUNCTION__ " Error getting Schannel required encryption sizes.");
         if (m_packet_res.size() + sizes.cbHeader + sizes.cbTrailer > size_max)
-            throw invalid_argument(string_printf(__FUNCTION__ " This method does not support packet fragmentation, but the data size is too big to fit in one packet (packet: %u, maximum: %u).", m_packet_res.size(), size_max).c_str());
+            throw invalid_argument(string_printf(__FUNCTION__ " This method does not support packet fragmentation, but the data size is too big to fit in one packet (packet: %u, maximum: %u).", m_packet_res.size(), size_max));
         sizes.cbMaximumMessage = std::min<unsigned long>(sizes.cbMaximumMessage, size_max - (unsigned long)(m_packet_res.size() + sizes.cbHeader + sizes.cbTrailer));
 
         // Get inner response packet.
@@ -762,7 +762,7 @@ void eap::method_ttls::get_response_packet(
             m_packet_res.insert(m_packet_res.end(), reinterpret_cast<const unsigned char*>(buf[0].pvBuffer), reinterpret_cast<const unsigned char*>(buf[0].pvBuffer) + buf[0].cbBuffer + buf[1].cbBuffer + buf[2].cbBuffer);
         }
     } else if (m_packet_res.size() > size_max)
-        throw invalid_argument(string_printf(__FUNCTION__ " This method does not support packet fragmentation, but the data size is too big to fit in one packet (packet: %u, maximum: %u).", m_packet_res.size(), size_max).c_str());
+        throw invalid_argument(string_printf(__FUNCTION__ " This method does not support packet fragmentation, but the data size is too big to fit in one packet (packet: %u, maximum: %u).", m_packet_res.size(), size_max));
 
     packet.assign(m_packet_res.begin(), m_packet_res.end());
 }
diff --git a/lib/TTLS/src/Module.cpp b/lib/TTLS/src/Module.cpp
index 019c1af..a3a36d7 100644
--- a/lib/TTLS/src/Module.cpp
+++ b/lib/TTLS/src/Module.cpp
@@ -218,12 +218,12 @@ EAP_SESSION_HANDLE eap::peer_ttls::begin_session(
             if (s->m_cred.match(*cfg_prov)) {
                 // Matching provider found.
                 if (cfg_prov->m_methods.empty())
-                    throw invalid_argument(string_printf(__FUNCTION__ " %ls provider has no methods.", cfg_prov->get_id().c_str()).c_str());
+                    throw invalid_argument(string_printf(__FUNCTION__ " %ls provider has no methods.", cfg_prov->get_id().c_str()));
                 cfg_method = dynamic_cast<config_method_ttls*>(cfg_prov->m_methods.front().get());
                 break;
             }
         } else
-            throw invalid_argument(string_printf(__FUNCTION__ " Credentials do not match to any provider within this connection configuration (provider: %ls).", s->m_cred.get_id().c_str()).c_str());
+            throw invalid_argument(string_printf(__FUNCTION__ " Credentials do not match to any provider within this connection configuration (provider: %ls).", s->m_cred.get_id().c_str()));
     }
 
     // We have configuration, we have credentials, create method.