diff --git a/src/AuthConfig.cc b/src/AuthConfig.cc
index ec80b99f..470aa0b9 100644
--- a/src/AuthConfig.cc
+++ b/src/AuthConfig.cc
@@ -51,7 +51,10 @@ AuthConfig::~AuthConfig() {}
 
 std::string AuthConfig::getAuthText() const
 {
-  return strconcat(user_, ":", password_);
+  std::string s = user_;
+  s += ":";
+  s += password_;
+  return s;
 }
 
 std::ostream& operator<<(std::ostream& o, const AuthConfigHandle& authConfig)
diff --git a/src/BtBitfieldMessage.cc b/src/BtBitfieldMessage.cc
index de4cece0..6992d281 100644
--- a/src/BtBitfieldMessage.cc
+++ b/src/BtBitfieldMessage.cc
@@ -119,7 +119,10 @@ size_t BtBitfieldMessage::getMessageLength() {
 }
 
 std::string BtBitfieldMessage::toString() const {
-  return strconcat(NAME, " ", util::toHex(bitfield_, bitfieldLength_));
+  std::string s = NAME;
+  s += " ";
+  s += util::toHex(bitfield_, bitfieldLength_);
+  return s;
 }
 
 } // namespace aria2
diff --git a/src/BtExtendedMessage.cc b/src/BtExtendedMessage.cc
index 12128394..103bd64e 100644
--- a/src/BtExtendedMessage.cc
+++ b/src/BtExtendedMessage.cc
@@ -90,7 +90,10 @@ bool BtExtendedMessage::sendPredicate() const
 }
 
 std::string BtExtendedMessage::toString() const {
-  return strconcat(NAME, " ", extensionMessage_->toString());
+  std::string s = NAME;
+  s += " ";
+  s += extensionMessage_->toString();
+  return s;
 }
 
 BtExtendedMessageHandle
diff --git a/src/BtHandshakeMessage.cc b/src/BtHandshakeMessage.cc
index d30601d9..bd441fee 100644
--- a/src/BtHandshakeMessage.cc
+++ b/src/BtHandshakeMessage.cc
@@ -103,10 +103,13 @@ size_t BtHandshakeMessage::getMessageLength() {
 }
 
 std::string BtHandshakeMessage::toString() const {
-  return strconcat(NAME, " peerId=",
-                   util::percentEncode(peerId_, PEER_ID_LENGTH),
-                   ", reserved=",
-                   util::toHex(reserved_, RESERVED_LENGTH));
+  char buf[256];
+  snprintf(buf, sizeof(buf),
+           "%s peerId=%s, reserved=%s",
+           NAME.c_str(),
+           util::percentEncode(peerId_, PEER_ID_LENGTH).c_str(),
+           util::toHex(reserved_, RESERVED_LENGTH).c_str());
+  return buf;
 }
 
 bool BtHandshakeMessage::isFastExtensionSupported() const {
diff --git a/src/BtPieceMessage.cc b/src/BtPieceMessage.cc
index b58ab647..7b563699 100644
--- a/src/BtPieceMessage.cc
+++ b/src/BtPieceMessage.cc
@@ -213,8 +213,13 @@ void BtPieceMessage::pushPieceData(off_t offset, size_t length) const
 
 std::string BtPieceMessage::toString() const
 {
-  return strconcat(NAME, " index=", util::itos(index_), ", begin=",
-                   util::itos(begin_), ", length=", util::itos(blockLength_));
+  char buf[256];
+  snprintf(buf, sizeof(buf), "%s index=%lu, begin=%u, length=%lu",
+           NAME.c_str(),
+           static_cast<unsigned long>(index_),
+           begin_,
+           static_cast<unsigned long>(blockLength_));
+  return buf;
 }
 
 bool BtPieceMessage::checkPieceHash(const SharedHandle<Piece>& piece)
diff --git a/src/BtPortMessage.cc b/src/BtPortMessage.cc
index 0e13b061..4f904245 100644
--- a/src/BtPortMessage.cc
+++ b/src/BtPortMessage.cc
@@ -118,7 +118,9 @@ size_t BtPortMessage::getMessageLength() {
 }
 
 std::string BtPortMessage::toString() const {
-  return strconcat(NAME, " port=", util::uitos(port_));
+  char buf[256];
+  snprintf(buf, sizeof(buf), "%s port=%u", NAME.c_str(), port_);
+  return buf;
 }
 
 void BtPortMessage::setLocalNode(DHTNode* localNode)
diff --git a/src/Cookie.cc b/src/Cookie.cc
index 40cb36f2..5dc8db54 100644
--- a/src/Cookie.cc
+++ b/src/Cookie.cc
@@ -110,7 +110,10 @@ Cookie& Cookie::operator=(const Cookie& c)
 
 std::string Cookie::toString() const
 {
-  return strconcat(name_, '=', value_);
+  std::string s = name_;
+  s += "=";
+  s += value_;
+  return s;
 }
 
 bool Cookie::match
diff --git a/src/DHTAnnouncePeerMessage.cc b/src/DHTAnnouncePeerMessage.cc
index da4fb533..85c381a5 100644
--- a/src/DHTAnnouncePeerMessage.cc
+++ b/src/DHTAnnouncePeerMessage.cc
@@ -129,9 +129,13 @@ void DHTAnnouncePeerMessage::setTokenTracker(DHTTokenTracker* tokenTracker)
 
 std::string DHTAnnouncePeerMessage::toStringOptional() const
 {
-  return strconcat("token=", util::toHex(token_),
-                   ", info_hash=", util::toHex(infoHash_, INFO_HASH_LENGTH),
-                   ", tcpPort=", util::uitos(tcpPort_));
+  char buf[256];
+  snprintf(buf, sizeof(buf),
+           "token=%s, info_hash=%s, tcpPort=%u",
+           util::toHex(token_).c_str(),
+           util::toHex(infoHash_, INFO_HASH_LENGTH).c_str(),
+           tcpPort_);
+  return buf;
 }
 
 } // namespace aria2
diff --git a/src/DHTGetPeersReplyMessage.cc b/src/DHTGetPeersReplyMessage.cc
index 76c525c7..7564df56 100644
--- a/src/DHTGetPeersReplyMessage.cc
+++ b/src/DHTGetPeersReplyMessage.cc
@@ -158,9 +158,13 @@ void DHTGetPeersReplyMessage::accept(DHTMessageCallback* callback)
 
 std::string DHTGetPeersReplyMessage::toStringOptional() const
 {
-  return strconcat("token=", util::toHex(token_),
-                   ", values=", util::uitos(values_.size()),
-                   ", nodes=", util::uitos(closestKNodes_.size()));
+  char buf[256];
+  snprintf(buf, sizeof(buf),
+           "token=%s, values=%lu, nodes=%lu",
+           util::toHex(token_).c_str(),
+           static_cast<unsigned long>(values_.size()),
+           static_cast<unsigned long>(closestKNodes_.size()));
+  return buf;
 }
 
 } // namespace aria2
diff --git a/src/DHTNode.cc b/src/DHTNode.cc
index b04959ae..967bd9a8 100644
--- a/src/DHTNode.cc
+++ b/src/DHTNode.cc
@@ -117,10 +117,15 @@ void DHTNode::timeout()
 
 std::string DHTNode::toString() const
 {
-  return strconcat("DHTNode ID=", util::toHex(id_, DHT_ID_LENGTH),
-                   ", Host=", ipaddr_, ":", util::uitos(port_),
-                   ", Condition=", util::uitos(condition_),
-                   ", RTT=", util::uitos(rtt_));
+  char buf[256];
+  snprintf(buf, sizeof(buf),
+           "DHTNode ID=%s, Host=%s(%u), Condition=%u, RTT=%u",
+           util::toHex(id_, DHT_ID_LENGTH).c_str(),
+           ipaddr_.c_str(),
+           port_,
+           condition_,
+           rtt_);
+  return buf;
 }
 
 void DHTNode::setID(const unsigned char* id)
diff --git a/src/DHTQueryMessage.cc b/src/DHTQueryMessage.cc
index 61e3fba6..3f03fa97 100644
--- a/src/DHTQueryMessage.cc
+++ b/src/DHTQueryMessage.cc
@@ -68,20 +68,17 @@ bool DHTQueryMessage::isReply() const
 
 std::string DHTQueryMessage::toString() const
 {
-  std::string s = strconcat
-    ("dht query ", getMessageType(),
-     " TransactionID=", util::toHex(getTransactionID()),
-     " Remote:", getRemoteNode()->getIPAddress(),
-     ":", util::uitos(getRemoteNode()->getPort()),
-     ", id=", util::toHex(getRemoteNode()->getID(), DHT_ID_LENGTH),
-     ", ");
-  if(!getVersion().empty()) {
-    s += "v=";
-    s += util::torrentPercentEncode(getVersion());
-    s += ", ";
-  }
-  s += toStringOptional();
-  return s;
+  char buf[256];
+  snprintf(buf, sizeof(buf),
+           "dht query %s TransactionID=%s Remote:%s(%u), id=%s, v=%s, %s",
+           getMessageType().c_str(),
+           util::toHex(getTransactionID()).c_str(),
+           getRemoteNode()->getIPAddress().c_str(),
+           getRemoteNode()->getPort(),
+           util::toHex(getRemoteNode()->getID(), DHT_ID_LENGTH).c_str(),
+           util::torrentPercentEncode(getVersion()).c_str(),
+           toStringOptional().c_str());
+  return buf;
 }
 
 } // namespace aria2
diff --git a/src/DHTResponseMessage.cc b/src/DHTResponseMessage.cc
index 03fcbde7..906eef7d 100644
--- a/src/DHTResponseMessage.cc
+++ b/src/DHTResponseMessage.cc
@@ -65,20 +65,17 @@ bool DHTResponseMessage::isReply() const
 
 std::string DHTResponseMessage::toString() const
 {
-  std::string s = strconcat
-    ("dht response ", getMessageType(),
-     " TransactionID=", util::toHex(getTransactionID()),
-     " Remote:", getRemoteNode()->getIPAddress(),
-     ":", util::uitos(getRemoteNode()->getPort()),
-     ", id=", util::toHex(getRemoteNode()->getID(), DHT_ID_LENGTH),
-     ", ");
-  if(!getVersion().empty()) {
-    s += "v=";
-    s += util::torrentPercentEncode(getVersion());
-    s += ", ";
-  }
-  s += toStringOptional();
-  return s;
+  char buf[256];
+  snprintf(buf, sizeof(buf),
+           "dht response %s TransactionID=%s Remote:%s(%u), id=%s, v=%s, %s",
+           getMessageType().c_str(),
+           util::toHex(getTransactionID()).c_str(),
+           getRemoteNode()->getIPAddress().c_str(),
+           getRemoteNode()->getPort(),
+           util::toHex(getRemoteNode()->getID(), DHT_ID_LENGTH).c_str(),
+           util::torrentPercentEncode(getVersion()).c_str(),
+           toStringOptional().c_str());
+  return buf;
 }
 
 } // namespace aria2
diff --git a/src/DHTUnknownMessage.cc b/src/DHTUnknownMessage.cc
index b5facb43..365f78d3 100644
--- a/src/DHTUnknownMessage.cc
+++ b/src/DHTUnknownMessage.cc
@@ -89,10 +89,13 @@ std::string DHTUnknownMessage::toString() const
     sampleLength = length_;
   }
   std::string sample(&data_[0], &data_[sampleLength]);
-
-  return strconcat("dht unknown Remote:", ipaddr_, ":", util::uitos(port_),
-                   " length=", util::uitos(length_),
-                   ", first 8 bytes(hex)=", util::toHex(sample));
+  char buf[256];
+  snprintf(buf, sizeof(buf),
+           "dht unknown Remote:%s(%u) length=%lu, first 8 bytes(hex)=%s",
+           ipaddr_.c_str(), port_,
+           static_cast<unsigned long>(length_),
+           util::toHex(data_, sampleLength).c_str());
+  return buf;
 }
 
 } // namespace aria2
diff --git a/src/FtpNegotiationCommand.cc b/src/FtpNegotiationCommand.cc
index 4d2bc719..0fc22d4c 100644
--- a/src/FtpNegotiationCommand.cc
+++ b/src/FtpNegotiationCommand.cc
@@ -723,8 +723,11 @@ bool FtpNegotiationCommand::sendTunnelRequest()
     httpRequest->setUserAgent(getOption()->get(PREF_USER_AGENT));
     SharedHandle<Request> req(new Request());
     // Construct fake URI in order to use HttpRequest
-    req->setUri(strconcat("ftp://", dataConnAddr_.first,
-                          A2STR::COLON_C, util::uitos(dataConnAddr_.second)));
+    // TODO Handle IPv6 address; it must be enclosed with [].
+    char fakeUriBuf[1024];
+    snprintf(fakeUriBuf, sizeof(fakeUriBuf), "ftp://%s:%u",
+             dataConnAddr_.first.c_str(), dataConnAddr_.second);
+    req->setUri(fakeUriBuf);
     httpRequest->setRequest(req);
     httpRequest->setProxyRequest(createProxyRequest());
     http_->sendProxyRequest(httpRequest);
diff --git a/src/HttpRequest.cc b/src/HttpRequest.cc
index 7f8191fb..8d3c5937 100644
--- a/src/HttpRequest.cc
+++ b/src/HttpRequest.cc
@@ -229,14 +229,17 @@ std::string HttpRequest::createRequest()
   }
   if(cookieStorage_) {
     std::string cookiesValue;
+    std::string path = getDir();
+    if(getDir() == "/") {
+      path += getFile();
+    } else {
+      path += "/";
+      path += getFile();
+    }
     std::vector<Cookie> cookies =
-      cookieStorage_->criteriaFind
-      (getHost(),
-       getDir() == A2STR::SLASH_C?
-       getDir()+getFile():strconcat(getDir(), A2STR::SLASH_C, getFile()),
-       Time().getTime(),
-       getProtocol() == Request::PROTO_HTTPS ?
-       true : false);
+      cookieStorage_->criteriaFind(getHost(), path,
+                                   Time().getTime(),
+                                   getProtocol() == Request::PROTO_HTTPS);
     for(std::vector<Cookie>::const_iterator itr = cookies.begin(),
           eoi = cookies.end(); itr != eoi; ++itr) {
       strappend(cookiesValue, (*itr).toString(), ";");
diff --git a/src/IndexBtMessage.cc b/src/IndexBtMessage.cc
index 2480975b..108d5840 100644
--- a/src/IndexBtMessage.cc
+++ b/src/IndexBtMessage.cc
@@ -60,7 +60,11 @@ size_t IndexBtMessage::getMessageLength()
 
 std::string IndexBtMessage::toString() const
 {
-  return strconcat(getName(), " index=", util::itos(index_));
+  char buf[256];
+  snprintf(buf, sizeof(buf), "%s index=%lu",
+           getName().c_str(),
+           static_cast<unsigned long>(index_));
+  return buf;
 }
 
 } // namespace aria2
diff --git a/src/Piece.cc b/src/Piece.cc
index a0698c3e..29b4cade 100644
--- a/src/Piece.cc
+++ b/src/Piece.cc
@@ -167,8 +167,11 @@ bool Piece::getAllMissingBlockIndexes
 }
 
 std::string Piece::toString() const {
-  return strconcat("piece: index=", util::itos(index_),
-                   ", length=", util::itos(length_));
+  char buf[256];
+  snprintf(buf, sizeof(buf), "piece: index=%lu, length=%lu",
+           static_cast<unsigned long>(index_),
+           static_cast<unsigned long>(length_));
+  return buf;
 }
 
 void Piece::reconfigure(size_t length)
diff --git a/src/RangeBtMessage.cc b/src/RangeBtMessage.cc
index b5318810..51c75c2e 100644
--- a/src/RangeBtMessage.cc
+++ b/src/RangeBtMessage.cc
@@ -72,9 +72,14 @@ size_t RangeBtMessage::getMessageLength()
 
 std::string RangeBtMessage::toString() const
 {
-  return strconcat(getName(), " index=", util::uitos(index_),
-                   ", begin=", util::uitos(begin_),
-                   ", length=", util::uitos(length_));
+  char buf[256];
+  snprintf(buf, sizeof(buf),
+           "%s index=%lu, begin=%u, length=%lu",
+           getName().c_str(),
+           static_cast<unsigned long>(index_),
+           begin_,
+           static_cast<unsigned long>(length_));
+  return buf;
 }
 
 } // namespace aria2
diff --git a/src/Request.cc b/src/Request.cc
index 7c80aa18..5732f391 100644
--- a/src/Request.cc
+++ b/src/Request.cc
@@ -163,7 +163,10 @@ const SharedHandle<PeerStat>& Request::initPeerStat()
 std::string Request::getURIHost() const
 {
   if(isIPv6LiteralAddress()) {
-    return strconcat("[", getHost(), "]");
+    std::string s = "[";
+    s += getHost();
+    s += "]";
+    return s;
   } else {
     return getHost();
   }
diff --git a/src/RequestGroup.cc b/src/RequestGroup.cc
index a622d8a5..35cbb737 100644
--- a/src/RequestGroup.cc
+++ b/src/RequestGroup.cc
@@ -793,7 +793,10 @@ bool RequestGroup::tryAutoFileRenaming()
     return false;
   }
   for(unsigned int i = 1; i < 10000; ++i) {
-    File newfile(strconcat(filepath, A2STR::DOT_C, util::uitos(i)));
+    std::string newfilename = filepath;
+    newfilename += ".";
+    newfilename += util::uitos(i);
+    File newfile(newfilename);
     File ctrlfile(newfile.getPath()+DefaultBtProgressInfoFile::getSuffix());
     if(!newfile.exists() || (newfile.exists() && ctrlfile.exists())) {
       downloadContext_->getFirstFileEntry()->setPath(newfile.getPath());
diff --git a/src/UTMetadataDataExtensionMessage.cc b/src/UTMetadataDataExtensionMessage.cc
index b5d63043..e63264a3 100644
--- a/src/UTMetadataDataExtensionMessage.cc
+++ b/src/UTMetadataDataExtensionMessage.cc
@@ -71,7 +71,10 @@ std::string UTMetadataDataExtensionMessage::getPayload()
 
 std::string UTMetadataDataExtensionMessage::toString() const
 {
-  return strconcat("ut_metadata data piece=", util::uitos(getIndex()));
+  char buf[256];
+  snprintf(buf, sizeof(buf), "ut_metadata data piece=%lu",
+           static_cast<unsigned long>(getIndex()));
+  return buf;
 }
 
 void UTMetadataDataExtensionMessage::doReceivedAction()
diff --git a/src/UTMetadataRejectExtensionMessage.cc b/src/UTMetadataRejectExtensionMessage.cc
index 4221b794..8f65708a 100644
--- a/src/UTMetadataRejectExtensionMessage.cc
+++ b/src/UTMetadataRejectExtensionMessage.cc
@@ -54,7 +54,10 @@ std::string UTMetadataRejectExtensionMessage::getPayload()
 
 std::string UTMetadataRejectExtensionMessage::toString() const
 {
-  return strconcat("ut_metadata reject piece=", util::uitos(getIndex()));
+  char buf[256];
+  snprintf(buf, sizeof(buf), "ut_metadata reject piece=%lu",
+           static_cast<unsigned long>(getIndex()));
+  return buf;
 }
 
 void UTMetadataRejectExtensionMessage::doReceivedAction()
diff --git a/src/UTMetadataRequestExtensionMessage.cc b/src/UTMetadataRequestExtensionMessage.cc
index 18315444..8a2fd496 100644
--- a/src/UTMetadataRequestExtensionMessage.cc
+++ b/src/UTMetadataRequestExtensionMessage.cc
@@ -69,7 +69,10 @@ std::string UTMetadataRequestExtensionMessage::getPayload()
 
 std::string UTMetadataRequestExtensionMessage::toString() const
 {
-  return strconcat("ut_metadata request piece=", util::uitos(getIndex()));
+  char buf[256];
+  snprintf(buf, sizeof(buf), "ut_metadata request piece=%lu",
+           static_cast<unsigned long>(getIndex()));
+  return buf;
 }
 
 void UTMetadataRequestExtensionMessage::doReceivedAction()
diff --git a/src/UTPexExtensionMessage.cc b/src/UTPexExtensionMessage.cc
index fe0e99c6..f4cb0018 100644
--- a/src/UTPexExtensionMessage.cc
+++ b/src/UTPexExtensionMessage.cc
@@ -121,8 +121,11 @@ UTPexExtensionMessage::createCompactPeerListAndFlag
 
 std::string UTPexExtensionMessage::toString() const
 {
-  return strconcat("ut_pex added=", util::uitos(freshPeers_.size()),
-                   ", dropped=", util::uitos(droppedPeers_.size()));
+  char buf[256];
+  snprintf(buf, sizeof(buf), "ut_pex added=%lu, dropped=%lu",
+           static_cast<unsigned long>(freshPeers_.size()),
+           static_cast<unsigned long>(droppedPeers_.size()));
+  return buf;
 }
 
 void UTPexExtensionMessage::doReceivedAction()
diff --git a/src/a2functional.h b/src/a2functional.h
index 065afbb6..28b32ec6 100644
--- a/src/a2functional.h
+++ b/src/a2functional.h
@@ -283,109 +283,6 @@ std::string strjoin(InputIterator first, InputIterator last,
   return result;
 }
 
-template<typename T1, typename T2>
-inline std::string strconcat(const T1& a1, const T2& a2)
-{
-  std::string s(a1); s += a2; return s;
-}
-
-template<typename T1, typename T2, typename T3>
-inline std::string strconcat(const T1& a1, const T2& a2, const T3& a3)
-{
-  std::string s(a1); s += a2; s += a3; return s;
-}
-
-template<typename T1, typename T2, typename T3, typename T4>
-inline std::string
-strconcat(const T1& a1, const T2& a2, const T3& a3, const T4& a4)
-{
-  std::string s(a1); s += a2; s += a3; s += a4; return s;
-}
-
-template<typename T1, typename T2, typename T3, typename T4, typename T5>
-inline std::string
-strconcat(const T1& a1, const T2& a2, const T3& a3, const T4& a4,
-          const T5& a5)
-{
-  std::string s(a1); s += a2; s += a3; s += a4; s += a5; return s;
-}
-
-template<typename T1, typename T2, typename T3, typename T4, typename T5,
-         typename T6>
-inline std::string
-strconcat(const T1& a1, const T2& a2, const T3& a3, const T4& a4,
-          const T5& a5, const T6& a6)
-{
-  std::string s(a1); s += a2; s += a3; s += a4; s += a5; s += a6; return s;
-}
-
-template<typename T1, typename T2, typename T3, typename T4, typename T5,
-         typename T6, typename T7>
-inline std::string
-strconcat(const T1& a1, const T2& a2, const T3& a3, const T4& a4,
-          const T5& a5, const T6& a6, const T7& a7)
-{
-  std::string s(a1); s += a2; s += a3; s += a4; s += a5; s += a6; s += a7;
-  return s;
-}
-
-template<typename T1, typename T2, typename T3, typename T4, typename T5,
-         typename T6, typename T7, typename T8>
-inline std::string
-strconcat(const T1& a1, const T2& a2, const T3& a3, const T4& a4,
-          const T5& a5, const T6& a6, const T7& a7, const T8& a8)
-{
-  std::string s(a1); s += a2; s += a3; s += a4; s += a5; s += a6; s += a7;
-  s += a8; return s;
-}
-
-template<typename T1, typename T2, typename T3, typename T4, typename T5,
-         typename T6, typename T7, typename T8, typename T9>
-inline std::string
-strconcat(const T1& a1, const T2& a2, const T3& a3, const T4& a4,
-          const T5& a5, const T6& a6, const T7& a7, const T8& a8,
-          const T9& a9)
-{
-  std::string s(a1); s += a2; s += a3; s += a4; s += a5; s += a6; s += a7;
-  s += a8; s += a9; return s;
-}
-
-template<typename T1, typename T2, typename T3, typename T4, typename T5,
-         typename T6, typename T7, typename T8, typename T9, typename T10>
-inline std::string
-strconcat(const T1& a1, const T2& a2, const T3& a3, const T4& a4,
-          const T5& a5, const T6& a6, const T7& a7, const T8& a8,
-          const T9& a9, const T10& a10)
-{
-  std::string s(a1); s += a2; s += a3; s += a4; s += a5; s += a6; s += a7;
-  s += a8; s += a9; s += a10; return s;
-}
-
-template<typename T1, typename T2, typename T3, typename T4, typename T5,
-         typename T6, typename T7, typename T8, typename T9, typename T10,
-         typename T11>
-inline std::string
-strconcat(const T1& a1, const T2& a2, const T3& a3, const T4& a4,
-          const T5& a5, const T6& a6, const T7& a7, const T8& a8,
-          const T9& a9, const T10& a10, const T11& a11)
-{
-  std::string s(a1); s += a2; s += a3; s += a4; s += a5; s += a6; s += a7;
-  s += a8; s += a9; s += a10; s += a11; return s;
-}
-
-template<typename T1, typename T2, typename T3, typename T4, typename T5,
-         typename T6, typename T7, typename T8, typename T9, typename T10,
-         typename T11, typename T12>
-inline std::string
-strconcat(const T1& a1, const T2& a2, const T3& a3, const T4& a4,
-          const T5& a5, const T6& a6, const T7& a7, const T8& a8,
-          const T9& a9, const T10& a10, const T11& a11,
-          const T12& a12)
-{
-  std::string s(a1); s += a2; s += a3; s += a4; s += a5; s += a6; s += a7;
-  s += a8; s += a9; s += a10; s += a11; s += a12; return s;
-}
-
 template<typename T1, typename T2>
 inline void strappend(std::string& base, const T1& a1, const T2& a2)
 {
diff --git a/src/bittorrent_helper.cc b/src/bittorrent_helper.cc
index 4c859f0a..0997270c 100644
--- a/src/bittorrent_helper.cc
+++ b/src/bittorrent_helper.cc
@@ -220,7 +220,8 @@ void extractFileEntries
            error_code::BITTORRENT_PARSE_ERROR);
       }
     } else {
-      utf8Name = strconcat(File(defaultName).getBasename(), ".file");
+      utf8Name = File(defaultName).getBasename();
+      utf8Name += ".file";
     }
   } else {
     utf8Name = overrideName;
@@ -951,8 +952,9 @@ std::string metadata2Torrent
     torrent += "13:announce-list";
     torrent += bencode2::encode(&announceList);
   }
-  torrent +=
-    strconcat("4:info", metadata, "e");
+  torrent += "4:info";
+  torrent += metadata;
+  torrent += "e";
   return torrent;
 }
 
diff --git a/src/util.cc b/src/util.cc
index c9b64758..d923a20b 100644
--- a/src/util.cc
+++ b/src/util.cc
@@ -1367,11 +1367,16 @@ std::string applyDir(const std::string& dir, const std::string& relPath)
 {
   std::string s;
   if(dir.empty()) {
-    s = strconcat(A2STR::DOT_C, A2STR::SLASH_C, relPath);
-  } else if(dir == A2STR::SLASH_C) {
-    s = strconcat(A2STR::SLASH_C, relPath);
+    s = "./";
+    s += relPath;
   } else {
-    s = strconcat(dir, A2STR::SLASH_C, relPath);
+    s = dir;
+    if(dir == "/") {
+      s += relPath;
+    } else {
+      s += "/";
+      s += relPath;
+    }
   }
 #ifdef __MINGW32__
   for(std::string::iterator i = s.begin(), eoi = s.end(); i != eoi; ++i) {
diff --git a/test/DHTUnknownMessageTest.cc b/test/DHTUnknownMessageTest.cc
index ea1e31de..4e399ec0 100644
--- a/test/DHTUnknownMessageTest.cc
+++ b/test/DHTUnknownMessageTest.cc
@@ -35,7 +35,7 @@ void DHTUnknownMessageTest::testToString()
                           data.size(),
                           ipaddr, port);
 
-    CPPUNIT_ASSERT_EQUAL(std::string("dht unknown Remote:192.168.0.1:6881 length=9, first 8 bytes(hex)=63686f636f6c6174"), msg.toString());
+    CPPUNIT_ASSERT_EQUAL(std::string("dht unknown Remote:192.168.0.1(6881) length=9, first 8 bytes(hex)=63686f636f6c6174"), msg.toString());
   }
   {
     // data.size() == 3
@@ -45,7 +45,7 @@ void DHTUnknownMessageTest::testToString()
                           data.size(),
                           ipaddr, port);
 
-    CPPUNIT_ASSERT_EQUAL(std::string("dht unknown Remote:192.168.0.1:6881 length=3, first 8 bytes(hex)=666f6f"), msg.toString());
+    CPPUNIT_ASSERT_EQUAL(std::string("dht unknown Remote:192.168.0.1(6881) length=3, first 8 bytes(hex)=666f6f"), msg.toString());
   }
 }
 
diff --git a/test/SessionSerializerTest.cc b/test/SessionSerializerTest.cc
index 883991c9..84f298a5 100644
--- a/test/SessionSerializerTest.cc
+++ b/test/SessionSerializerTest.cc
@@ -77,7 +77,7 @@ void SessionSerializerTest::testSave()
   std::getline(ss, line);
   CPPUNIT_ASSERT_EQUAL(std::string("http://error\t"), line);
   std::getline(ss, line);
-  CPPUNIT_ASSERT_EQUAL(strconcat(uris[0], "\t", uris[1], "\t"), line);
+  CPPUNIT_ASSERT_EQUAL(uris[0]+"\t"+uris[1]+"\t", line);
   std::getline(ss, line);
   CPPUNIT_ASSERT_EQUAL(std::string(" dir=/tmp"), line);
   std::getline(ss, line);
diff --git a/test/a2functionalTest.cc b/test/a2functionalTest.cc
index 0e9a816e..d4c77e07 100644
--- a/test/a2functionalTest.cc
+++ b/test/a2functionalTest.cc
@@ -14,7 +14,6 @@ class a2functionalTest:public CppUnit::TestFixture {
   CPPUNIT_TEST(testMemFunSh);
   CPPUNIT_TEST(testAdopt2nd);
   CPPUNIT_TEST(testStrjoin);
-  CPPUNIT_TEST(testStrconcat);
   CPPUNIT_TEST(testStrappend);
   CPPUNIT_TEST(testLeastRecentAccess);
   CPPUNIT_TEST_SUITE_END();
@@ -22,7 +21,6 @@ public:
   void testMemFunSh();
   void testAdopt2nd();
   void testStrjoin();
-  void testStrconcat();
   void testStrappend();
   void testLeastRecentAccess();
 
@@ -100,11 +98,6 @@ void a2functionalTest::testStrjoin()
                        strjoin(v.begin(), v.end(), " "));
 }
 
-void a2functionalTest::testStrconcat()
-{
-  CPPUNIT_ASSERT_EQUAL(std::string("X=3"), strconcat("X=", "3"));
-}
-
 void a2functionalTest::testStrappend()
 {
   std::string str = "X=";