diff --git a/hphp/runtime/base/builtin_functions.cpp b/hphp/runtime/base/builtin_functions.cpp
index 197e44c64..344c71c9e 100644
--- a/hphp/runtime/base/builtin_functions.cpp
+++ b/hphp/runtime/base/builtin_functions.cpp
@@ -685,7 +685,9 @@ void throw_unexpected_argument_type(int argNum, const char *fnName,
   case KindOfStaticString:
   case KindOfString:  otype = "string";      break;
   case KindOfArray:   otype = "array";       break;
-  case KindOfObject:  otype = val.getObjectData()->o_getClassName(); break;
+  case KindOfObject:
+    otype = val.getObjectData()->o_getClassName().c_str();
+    break;
   default:
     assert(false);
   }
diff --git a/hphp/runtime/base/class_info.cpp b/hphp/runtime/base/class_info.cpp
index 5e22bcbc9..b462498fa 100644
--- a/hphp/runtime/base/class_info.cpp
+++ b/hphp/runtime/base/class_info.cpp
@@ -654,17 +654,6 @@ bool ClassInfo::checkAccess(ClassInfo *defClass,
   return false;
 }
 
-const char *ClassInfo::getConstructor() const {
-  ClassInfo *defClass;
-  if (hasMethod("__construct", defClass)) {
-    return "__construct";
-  }
-  if (!(m_attribute & IsTrait) && hasMethod(m_name, defClass)) {
-    return m_name;
-  }
-  return nullptr;
-}
-
 void ClassInfo::getAllProperties(PropertyMap &props) const {
   const PropertyMap &properties = getProperties();
   props.insert(properties.begin(), properties.end());
diff --git a/hphp/runtime/base/class_info.h b/hphp/runtime/base/class_info.h
index b89a1ced3..608e5bdce 100644
--- a/hphp/runtime/base/class_info.h
+++ b/hphp/runtime/base/class_info.h
@@ -144,7 +144,7 @@ public:
 
   struct MethodInfo {
     MethodInfo() : docComment(nullptr) {}
-    MethodInfo(const char **&p);
+    explicit MethodInfo(const char **&p);
     ~MethodInfo();
     MethodInfo *getDeclared();
     Attribute attribute;
@@ -397,7 +397,6 @@ public:
                         bool staticCall, bool hasCallObject);
   static bool IsSubClass(CStrRef className1, CStrRef className2,
                          bool considerInterface);
-  const char *getConstructor() const;
 
   /**
    * Property functions.
@@ -457,7 +456,7 @@ public:
   /**
    * Read one class's information from specified map pointer and move it.
    */
-  ClassInfoUnique(const char **&p);
+  explicit ClassInfoUnique(const char **&p);
   virtual ~ClassInfoUnique();
 
   // implementing ClassInfo
diff --git a/hphp/runtime/base/execution_context.cpp b/hphp/runtime/base/execution_context.cpp
index d13f18f1d..f260ad53d 100644
--- a/hphp/runtime/base/execution_context.cpp
+++ b/hphp/runtime/base/execution_context.cpp
@@ -198,7 +198,7 @@ void BaseExecutionContext::setContentType(CStrRef mimetype, CStrRef charset) {
     contentType += "; ";
     contentType += "charset=";
     contentType += charset;
-    m_transport->addHeader("Content-Type", contentType);
+    m_transport->addHeader("Content-Type", contentType.c_str());
     m_transport->setDefaultContentType(false);
   }
 }
@@ -638,7 +638,7 @@ void BaseExecutionContext::handleError(const std::string &msg,
       if (!Eval::Debugger::InterruptException(String(msg))) return;
     } catch (const Eval::DebuggerClientExitException &e) {}
 
-    const char *file = nullptr;
+    String file = empty_string;
     int line = 0;
     if (RuntimeOption::InjectedStackTrace) {
       if (!bt.empty()) {
@@ -648,7 +648,7 @@ void BaseExecutionContext::handleError(const std::string &msg,
       }
     }
 
-    Logger::Log(Logger::LogError, prefix.c_str(), ee, file, line);
+    Logger::Log(Logger::LogError, prefix.c_str(), ee, file.c_str(), line);
   }
 }
 
@@ -702,7 +702,7 @@ void BaseExecutionContext::recordLastError(const Exception &e,
 
 bool BaseExecutionContext::onFatalError(const Exception &e) {
   recordLastError(e);
-  const char *file = nullptr;
+  String file = empty_string;
   int line = 0;
   if (RuntimeOption::InjectedStackTrace) {
     const ExtendedException *ee = dynamic_cast<const ExtendedException *>(&e);
@@ -716,7 +716,8 @@ bool BaseExecutionContext::onFatalError(const Exception &e) {
     }
   }
   if (RuntimeOption::AlwaysLogUnhandledExceptions) {
-    Logger::Log(Logger::LogError, "HipHop Fatal error: ", e, file, line);
+    Logger::Log(Logger::LogError, "HipHop Fatal error: ", e,
+                file.c_str(), line);
   }
   bool handled = false;
   if (RuntimeOption::CallUserHandlerOnFatals) {
@@ -724,7 +725,8 @@ bool BaseExecutionContext::onFatalError(const Exception &e) {
     handled = callUserErrorHandler(e, errnum, true);
   }
   if (!handled && !RuntimeOption::AlwaysLogUnhandledExceptions) {
-    Logger::Log(Logger::LogError, "HipHop Fatal error: ", e, file, line);
+    Logger::Log(Logger::LogError, "HipHop Fatal error: ", e,
+                file.c_str(), line);
   }
   return handled;
 }
diff --git a/hphp/runtime/base/execution_context.h b/hphp/runtime/base/execution_context.h
index 174bea88b..77999311f 100644
--- a/hphp/runtime/base/execution_context.h
+++ b/hphp/runtime/base/execution_context.h
@@ -311,7 +311,7 @@ public:
   int getErrorReportingLevel() const { return m_errorReportingLevel;}
   void setErrorReportingLevel(int level) { m_errorReportingLevel = level;}
   String getErrorPage() const { return m_errorPage;}
-  void setErrorPage(CStrRef page) { m_errorPage = page;}
+  void setErrorPage(CStrRef page) { m_errorPage = (std::string) page; }
   bool getLogErrors() const { return m_logErrors;}
   void setLogErrors(bool on);
   String getErrorLog() const { return m_errorLog;}
diff --git a/hphp/runtime/base/file/mem_file.cpp b/hphp/runtime/base/file/mem_file.cpp
index 8166d9ebf..517ea59cb 100644
--- a/hphp/runtime/base/file/mem_file.cpp
+++ b/hphp/runtime/base/file/mem_file.cpp
@@ -51,7 +51,8 @@ MemFile::~MemFile() {
 bool MemFile::open(CStrRef filename, CStrRef mode) {
   assert(m_len == -1);
   // mem files are read-only
-  if (strchr(mode, '+') || strchr(mode, 'a') || strchr(mode, 'w')) {
+  const char* mode_str = mode.c_str();
+  if (strchr(mode_str, '+') || strchr(mode_str, 'a') || strchr(mode_str, 'w')) {
     return false;
   }
   int len = INT_MIN;
@@ -72,7 +73,7 @@ bool MemFile::open(CStrRef filename, CStrRef mode) {
       m_len = len;
       return true;
     }
-    m_name = filename;
+    m_name = (std::string) filename;
     m_data = data;
     m_len = len;
     return true;
diff --git a/hphp/runtime/base/file/ssl_socket.cpp b/hphp/runtime/base/file/ssl_socket.cpp
index ff0be5795..bd314079e 100644
--- a/hphp/runtime/base/file/ssl_socket.cpp
+++ b/hphp/runtime/base/file/ssl_socket.cpp
@@ -487,19 +487,20 @@ bool SSLSocket::applyVerificationPolicy(X509 *peer) {
       return false;
     }
 
-    bool match = (strcmp(cnmatch, buf) == 0);
+    bool match = (strcmp(cnmatch.c_str(), buf) == 0);
     if (!match && strlen(buf) > 3 && buf[0] == '*' && buf[1] == '.') {
       /* Try wildcard */
       if (strchr(buf+2, '.')) {
-        const char *tmp = strstr(cnmatch, buf+1);
-        match = tmp && strcmp(tmp, buf+2) && tmp == strchr(cnmatch, '.');
+        const char* cnmatch_str = cnmatch.c_str();
+        const char *tmp = strstr(cnmatch_str, buf+1);
+        match = tmp && strcmp(tmp, buf+2) && tmp == strchr(cnmatch_str, '.');
       }
     }
 
     if (!match) {
       /* didn't match */
       raise_warning("Peer certificate CN=`%.*s' did not match expected CN=`%s'",
-                    name_len, buf, cnmatch.data());
+                    name_len, buf, cnmatch.c_str());
       return false;
     }
   }
diff --git a/hphp/runtime/base/file/url_file.cpp b/hphp/runtime/base/file/url_file.cpp
index 3c5cdcc6e..d0133ee64 100644
--- a/hphp/runtime/base/file/url_file.cpp
+++ b/hphp/runtime/base/file/url_file.cpp
@@ -41,7 +41,8 @@ UrlFile::UrlFile(const char *method /* = "GET" */,
 }
 
 bool UrlFile::open(CStrRef url, CStrRef mode) {
-  if (strchr(mode, '+') || strchr(mode, 'a') || strchr(mode, 'w')) {
+  const char* modestr = mode.c_str();
+  if (strchr(modestr, '+') || strchr(modestr, 'a') || strchr(modestr, 'w')) {
     std::string msg = "cannot open a url stream for write/append operation: ";
     msg += url.c_str();
     m_error = msg;
@@ -78,7 +79,7 @@ bool UrlFile::open(CStrRef url, CStrRef mode) {
   m_responseHeaders = r;
 
   if (code == 200) {
-    m_name = url;
+    m_name = (std::string) url;
     m_data = const_cast<char*>(m_response.data());
     m_len = m_response.size();
     return true;
diff --git a/hphp/runtime/base/file/zip_file.cpp b/hphp/runtime/base/file/zip_file.cpp
index 89eee6f6f..885c6a114 100644
--- a/hphp/runtime/base/file/zip_file.cpp
+++ b/hphp/runtime/base/file/zip_file.cpp
@@ -45,7 +45,7 @@ void ZipFile::sweep() {
 bool ZipFile::open(CStrRef filename, CStrRef mode) {
   assert(m_gzFile == nullptr);
 
-  if (strchr(mode, '+')) {
+  if (strchr(mode.c_str(), '+')) {
     raise_warning("cannot open a zlib stream for reading and writing "
                     "at the same time!");
     return false;
diff --git a/hphp/runtime/base/object_data.cpp b/hphp/runtime/base/object_data.cpp
index a1aa3da17..bdfaea640 100644
--- a/hphp/runtime/base/object_data.cpp
+++ b/hphp/runtime/base/object_data.cpp
@@ -123,7 +123,7 @@ bool ObjectData::o_instanceof(CStrRef s) const {
 }
 
 bool ObjectData::o_isClass(const char *s) const {
-  return strcasecmp(s, o_getClassName()) == 0;
+  return strcasecmp(s, o_getClassName().c_str()) == 0;
 }
 
 int64_t ObjectData::o_toInt64() const {
diff --git a/hphp/runtime/base/server/access_log.cpp b/hphp/runtime/base/server/access_log.cpp
index 001fa4998..fa7b5dc1f 100644
--- a/hphp/runtime/base/server/access_log.cpp
+++ b/hphp/runtime/base/server/access_log.cpp
@@ -381,7 +381,7 @@ bool AccessLog::genField(std::ostringstream &out, const char* &format,
     {
       String b, q;
       RequestURI::splitURL(transport->getUrl(), b, q);
-      out << b;
+      out << b.c_str();
     }
     break;
   case 'v':
diff --git a/hphp/runtime/base/server/http_protocol.cpp b/hphp/runtime/base/server/http_protocol.cpp
index bc9d772bd..a8c6ba175 100644
--- a/hphp/runtime/base/server/http_protocol.cpp
+++ b/hphp/runtime/base/server/http_protocol.cpp
@@ -282,10 +282,9 @@ void HttpProtocol::PrepareSystemVariables(Transport *transport,
   if (!transport->isSSL() && RuntimeOption::ServerPort != 80) {
     port_suffix = ":" + RuntimeOption::ServerPort;
   }
-  server.set("SCRIPT_URI", String(prefix +
-                                  (hostHeader.empty() ?
-                                    hostName + port_suffix : hostHeader)
-                                  + r.originalURL()));
+  server.set("SCRIPT_URI",
+             String(prefix + (hostHeader.empty() ? hostName + port_suffix :
+                              String(hostHeader)) + r.originalURL()));
 
   if (r.rewritten()) {
     // when URL is rewritten, PHP decided to put original URL as SCRIPT_NAME
diff --git a/hphp/runtime/base/server/http_request_handler.cpp b/hphp/runtime/base/server/http_request_handler.cpp
index a5b65645f..34885dd36 100644
--- a/hphp/runtime/base/server/http_request_handler.cpp
+++ b/hphp/runtime/base/server/http_request_handler.cpp
@@ -80,13 +80,13 @@ void HttpRequestHandler::sendStaticContent(Transport *transport,
     char age[20];
     snprintf(age, sizeof(age), "max-age=%d", RuntimeOption::ExpiresDefault);
     transport->addHeader("Cache-Control", age);
-    transport->addHeader
-      ("Expires", DateTime(expires, true).toString(DateTime::HttpHeader));
+    transport->addHeader("Expires",
+        DateTime(expires, true).toString(DateTime::HttpHeader).c_str());
   }
 
   if (mtime) {
-    transport->addHeader
-      ("Last-Modified", DateTime(mtime, true).toString(DateTime::HttpHeader));
+    transport->addHeader("Last-Modified",
+        DateTime(mtime, true).toString(DateTime::HttpHeader).c_str());
   }
   transport->addHeader("Accept-Ranges", "bytes");
 
diff --git a/hphp/runtime/base/server/pagelet_server.cpp b/hphp/runtime/base/server/pagelet_server.cpp
index b9f916d57..6043073dc 100644
--- a/hphp/runtime/base/server/pagelet_server.cpp
+++ b/hphp/runtime/base/server/pagelet_server.cpp
@@ -72,7 +72,7 @@ public:
 
     disableCompression(); // so we don't have to decompress during sendImpl()
     m_rfc1867UploadedFiles = rfc1867UploadedFiles;
-    m_files = f_serialize(files);
+    m_files = (std::string) f_serialize(files);
   }
 
   /**
diff --git a/hphp/runtime/base/server/request_uri.cpp b/hphp/runtime/base/server/request_uri.cpp
index 292ec05fa..394b17ee5 100644
--- a/hphp/runtime/base/server/request_uri.cpp
+++ b/hphp/runtime/base/server/request_uri.cpp
@@ -137,7 +137,7 @@ bool RequestURI::rewriteURL(const VirtualHost *vhost, Transport *transport,
           m_rewrittenURL.substr(0, 8) != "https://") {
         PrependSlash(m_rewrittenURL);
       }
-      transport->redirect(m_rewrittenURL, redirect, "rewriteURL");
+      transport->redirect(m_rewrittenURL.c_str(), redirect, "rewriteURL");
       return false;
     }
     splitURL(m_rewrittenURL, m_rewrittenURL, m_queryString);
@@ -168,7 +168,7 @@ bool RequestURI::rewriteURL(const VirtualHost *vhost, Transport *transport,
           m_rewrittenURL.substr(0, 8) != "https://") {
         PrependSlash(m_rewrittenURL);
       }
-      transport->redirect(m_rewrittenURL, 301, "rewriteURL");
+      transport->redirect(m_rewrittenURL.c_str(), 301, "rewriteURL");
       return false;
     }
   }
diff --git a/hphp/runtime/base/server/rpc_request_handler.cpp b/hphp/runtime/base/server/rpc_request_handler.cpp
index 65fc16ab8..7ec44b2a1 100644
--- a/hphp/runtime/base/server/rpc_request_handler.cpp
+++ b/hphp/runtime/base/server/rpc_request_handler.cpp
@@ -220,7 +220,9 @@ bool RPCRequestHandler::executePHPFunction(Transport *transport,
       reqInitDoc = m_serverInfo->getReqInitDoc();
     }
 
-    if (!reqInitDoc.empty()) reqInitDoc = canonicalize_path(reqInitDoc, "", 0);
+    if (!reqInitDoc.empty()) {
+      reqInitDoc = (std::string)canonicalize_path(reqInitDoc, "", 0);
+    }
     if (!reqInitDoc.empty()) {
       reqInitDoc = getSourceFilename(reqInitDoc, sourceRootInfo);
     }
@@ -248,7 +250,7 @@ bool RPCRequestHandler::executePHPFunction(Transport *transport,
         }
       }
       if (!forbidden) {
-        rpcFile = canonicalize_path(rpcFile, "", 0);
+        rpcFile = (std::string) canonicalize_path(rpcFile, "", 0);
         rpcFile = getSourceFilename(rpcFile, sourceRootInfo);
         ret = hphp_invoke(m_context, rpcFile, false, Array(), uninit_null(),
                           reqInitFunc, reqInitDoc, error, errorMsg, runOnce);
diff --git a/hphp/runtime/base/server/source_root_info.cpp b/hphp/runtime/base/server/source_root_info.cpp
index 98bb62e0d..87e33dfe0 100644
--- a/hphp/runtime/base/server/source_root_info.cpp
+++ b/hphp/runtime/base/server/source_root_info.cpp
@@ -224,8 +224,8 @@ string SourceRootInfo::parseSandboxServerVariable(const string &format) const {
           res.write(data, n);
           break;
         }
-      case 's': res << m_sandbox; break;
-      case 'u': res << m_user; break;
+      case 's': res << m_sandbox.c_str(); break;
+      case 'u': res << m_user.c_str(); break;
       default: res << c; break;
       }
       control = false;
diff --git a/hphp/runtime/base/server/transport.cpp b/hphp/runtime/base/server/transport.cpp
index 38b6f83ab..1f1dddb58 100644
--- a/hphp/runtime/base/server/transport.cpp
+++ b/hphp/runtime/base/server/transport.cpp
@@ -648,7 +648,7 @@ void Transport::prepareHeaders(bool compressed, const void *data, int size) {
         f_openssl_decrypt(encrypted, cipher, key, k_OPENSSL_RAW_DATA, iv);
       assert(decrypted->same(ip.get()));
     }
-    addHeaderImpl("X-FB-Debug", output);
+    addHeaderImpl("X-FB-Debug", output.c_str());
   }
 
   // shutting down servers, so need to terminate all Keep-Alive connections
diff --git a/hphp/runtime/base/string_data.cpp b/hphp/runtime/base/string_data.cpp
index 4f69bf3ae..295b9b7e2 100644
--- a/hphp/runtime/base/string_data.cpp
+++ b/hphp/runtime/base/string_data.cpp
@@ -91,6 +91,11 @@ StringData *StringData::GetStaticString(const StringData *str) {
   return const_cast<StringData*>(pair.first->first);
 }
 
+StringData* StringData::GetStaticString(const String& str) {
+  assert(!str.isNull());
+  return GetStaticString(str.get());
+}
+
 StringData* StringData::FindStaticString(const StringData* str) {
   if (UNLIKELY(!s_stringDataMap)) s_stringDataMap = new StringDataMap();
   StringDataMap::const_iterator it = s_stringDataMap->find(str);
diff --git a/hphp/runtime/base/string_data.h b/hphp/runtime/base/string_data.h
index bcb0108fe..94b1d592d 100644
--- a/hphp/runtime/base/string_data.h
+++ b/hphp/runtime/base/string_data.h
@@ -154,7 +154,7 @@ class StringData {
    * Different ways of constructing StringData. Default constructor at above
    * is actually only for SmartAllocator to pre-allocate the objects.
    */
-  StringData(const char* data) {
+  explicit StringData(const char* data) {
     initLiteral(data);
   }
   StringData(const char *data, AttachLiteralMode) {
@@ -208,9 +208,9 @@ class StringData {
    * Create a new empty string big enough to hold the requested size,
    * not counting the \0 terminator.
    */
-  StringData(int reserve);
+  explicit StringData(int reserve);
 
-  StringData(SharedVariant *shared);
+  explicit StringData(SharedVariant *shared);
 
 public:
   void append(StringSlice r) { append(r.ptr, r.len); }
@@ -360,10 +360,11 @@ public:
   std::string toCPPString() const;
   static void sweepAll();
 
-  static StringData *FindStaticString(const StringData *str);
-  static StringData *GetStaticString(const StringData *str);
-  static StringData *GetStaticString(const std::string &str);
-  static StringData *GetStaticString(const char *str);
+  static StringData *FindStaticString(const StringData* str);
+  static StringData *GetStaticString(const StringData* str);
+  static StringData *GetStaticString(const std::string& str);
+  static StringData *GetStaticString(const String& str);
+  static StringData *GetStaticString(const char* str);
   static StringData *GetStaticString(char c);
   static size_t GetStaticStringCount();
   static uint32_t GetCnsHandle(const StringData* cnsName);
@@ -440,7 +441,7 @@ public:
 class StackStringData : public StringData {
  public:
   StackStringData() { incRefCount(); }
-  StackStringData(const char* s) : StringData(s) { incRefCount(); }
+  explicit StackStringData(const char* s) : StringData(s) { incRefCount(); }
   template <class T>
   StackStringData(const char* s, T p) : StringData(s, p) { incRefCount(); }
   template <class T>
diff --git a/hphp/runtime/base/string_util.cpp b/hphp/runtime/base/string_util.cpp
index bd4fe6074..02535970c 100644
--- a/hphp/runtime/base/string_util.cpp
+++ b/hphp/runtime/base/string_util.cpp
@@ -288,8 +288,8 @@ Variant StringUtil::ChunkSplit(CStrRef body, int chunklen /* = 76 */,
     ret = body;
     ret += end;
   } else {
-    char *chunked = string_chunk_split(body.data(), len, end, end.size(),
-                                       chunklen);
+    char *chunked = string_chunk_split(body.data(), len, end.c_str(),
+                                       end.size(), chunklen);
     return String(chunked, len, AttachString);
   }
   return ret;
@@ -305,35 +305,36 @@ String StringUtil::CEncode(CStrRef input, CStrRef charlist) {
   }
   if (input.empty() || chars.empty()) return input;
   int len = input.size();
-  char *ret = string_addcslashes(input, len, chars.data(), chars.size());
+  char *ret = string_addcslashes(input.c_str(), len, chars.data(),
+                                 chars.size());
   return String(ret, len, AttachString);
 }
 
 String StringUtil::CDecode(CStrRef input) {
   if (input.empty()) return input;
   int len = input.size();
-  char *ret = string_stripcslashes(input, len);
+  char *ret = string_stripcslashes(input.c_str(), len);
   return String(ret, len, AttachString);
 }
 
 String StringUtil::SqlEncode(CStrRef input) {
   if (input.empty()) return input;
   int len = input.size();
-  char *ret = string_addslashes(input, len);
+  char *ret = string_addslashes(input.c_str(), len);
   return String(ret, len, AttachString);
 }
 
 String StringUtil::SqlDecode(CStrRef input) {
   if (input.empty()) return input;
   int len = input.size();
-  char *ret = string_stripslashes(input, len);
+  char *ret = string_stripslashes(input.c_str(), len);
   return String(ret, len, AttachString);
 }
 
 String StringUtil::RegExEncode(CStrRef input) {
   if (input.empty()) return input;
   int len = input.size();
-  char *ret = string_quotemeta(input, len);
+  char *ret = string_quotemeta(input.c_str(), len);
   return String(ret, len, AttachString);
 }
 
@@ -350,7 +351,7 @@ String StringUtil::HtmlEncode(CStrRef input, QuoteStyle quoteStyle,
   }
 
   int len = input.size();
-  char *ret = string_html_encode(input, len, quoteStyle != NoQuotes,
+  char *ret = string_html_encode(input.data(), len, quoteStyle != NoQuotes,
                                  quoteStyle == BothQuotes, utf8, nbsp);
   if (!ret) {
     raise_error("HtmlEncode called on too large input (%d)", len);
@@ -435,7 +436,7 @@ String StringUtil::HtmlEncodeExtra(CStrRef input, QuoteStyle quoteStyle,
   }
 
   int len = input.size();
-  char *ret = string_html_encode_extra(input, len,
+  char *ret = string_html_encode_extra(input.data(), len,
                                        (StringHtmlEncoding)flags, am);
   if (!ret) {
     raise_error("HtmlEncode called on too large input (%d)", len);
@@ -450,7 +451,7 @@ String StringUtil::HtmlDecode(CStrRef input, QuoteStyle quoteStyle,
   assert(charset);
 
   int len = input.size();
-  char *ret = string_html_decode(input, len, quoteStyle != NoQuotes,
+  char *ret = string_html_decode(input.data(), len, quoteStyle != NoQuotes,
                                  quoteStyle == BothQuotes, charset, all);
   if (!ret) {
     // null iff charset was not recognized
@@ -464,28 +465,28 @@ String StringUtil::HtmlDecode(CStrRef input, QuoteStyle quoteStyle,
 String StringUtil::QuotedPrintableEncode(CStrRef input) {
   if (input.empty()) return input;
   int len = input.size();
-  char *ret = string_quoted_printable_encode(input, len);
+  char *ret = string_quoted_printable_encode(input.data(), len);
   return String(ret, len, AttachString);
 }
 
 String StringUtil::QuotedPrintableDecode(CStrRef input) {
   if (input.empty()) return input;
   int len = input.size();
-  char *ret = string_quoted_printable_decode(input, len, false);
+  char *ret = string_quoted_printable_decode(input.data(), len, false);
   return String(ret, len, AttachString);
 }
 
 String StringUtil::HexEncode(CStrRef input) {
   if (input.empty()) return input;
   int len = input.size();
-  char *ret = string_bin2hex(input, len);
+  char *ret = string_bin2hex(input.data(), len);
   return String(ret, len, AttachString);
 }
 
 String StringUtil::HexDecode(CStrRef input) {
   if (input.empty()) return input;
   int len = input.size();
-  char *ret = string_hex2bin(input, len);
+  char *ret = string_hex2bin(input.data(), len);
   return String(ret, len, AttachString);
 }
 
@@ -493,7 +494,7 @@ String StringUtil::UUEncode(CStrRef input) {
   if (input.empty()) return input;
 
   int len;
-  char *encoded = string_uuencode(input, input.size(), len);
+  char *encoded = string_uuencode(input.data(), input.size(), len);
   return String(encoded, len, AttachString);
 }
 
@@ -558,38 +559,37 @@ String StringUtil::Translate(CStrRef input, CStrRef from, CStrRef to) {
   if (input.empty()) return input;
 
   int len = input.size();
-  char *ret = (char *)malloc(len + 1);
-  memcpy(ret, input, len);
-  ret[len] = '\0';
-  int fromSize = from.size();
-  int toSize = to.size();
-  int trlen = (fromSize < toSize) ? fromSize : toSize;
-  string_translate(ret, len, from, to, trlen);
-  return String(ret, len, AttachString);
+  String retstr(len, ReserveString);
+  char *ret = retstr.mutableSlice().ptr;
+  memcpy(ret, input.data(), len);
+  auto trlen = std::min(from.size(), to.size());
+  string_translate(ret, len, from.data(), to.data(), trlen);
+  return retstr.setSize(len);
 }
 
 String StringUtil::ROT13(CStrRef input) {
   if (input.empty()) return input;
-  return String(string_rot13(input, input.size()), input.size(), AttachString);
+  return String(string_rot13(input.data(), input.size()),
+                input.size(), AttachString);
 }
 
 int64_t StringUtil::CRC32(CStrRef input) {
-  return string_crc32(input, input.size());
+  return string_crc32(input.data(), input.size());
 }
 
 String StringUtil::Crypt(CStrRef input, const char *salt /* = "" */) {
-  return String(string_crypt(input, salt), AttachString);
+  return String(string_crypt(input.c_str(), salt), AttachString);
 }
 
 String StringUtil::MD5(CStrRef input, bool raw /* = false */) {
   int len;
-  char *ret = string_md5(input, input.size(), raw, len);
+  char *ret = string_md5(input.data(), input.size(), raw, len);
   return String(ret, len, AttachString);
 }
 
 String StringUtil::SHA1(CStrRef input, bool raw /* = false */) {
   int len;
-  char *ret = string_sha1(input, input.size(), raw, len);
+  char *ret = string_sha1(input.data(), input.size(), raw, len);
   return String(ret, len, AttachString);
 }
 
diff --git a/hphp/runtime/base/type_object.cpp b/hphp/runtime/base/type_object.cpp
index ec2f5fb00..b1ca149d3 100644
--- a/hphp/runtime/base/type_object.cpp
+++ b/hphp/runtime/base/type_object.cpp
@@ -82,7 +82,7 @@ bool Object::equal(CObjRef v2) const {
   if (isResource() || v2.isResource()) {
     return false;
   }
-  if (!v2.get()->o_isClass(m_px->o_getClassName())) {
+  if (!v2.get()->o_isClass(m_px->o_getClassName().c_str())) {
     return false;
   }
   if (m_px->isCollection()) {
diff --git a/hphp/runtime/base/type_object.h b/hphp/runtime/base/type_object.h
index f1a09b010..c9c4df70a 100644
--- a/hphp/runtime/base/type_object.h
+++ b/hphp/runtime/base/type_object.h
@@ -14,14 +14,14 @@
    +----------------------------------------------------------------------+
 */
 
+#ifndef incl_HPHP_OBJECT_H_
+#define incl_HPHP_OBJECT_H_
+
 #ifndef incl_HPHP_INSIDE_HPHP_COMPLEX_TYPES_H_
 #error Directly including 'type_object.h' is prohibited. \
        Include 'complex_types.h' instead.
 #endif
 
-#ifndef incl_HPHP_OBJECT_H_
-#define incl_HPHP_OBJECT_H_
-
 #include <runtime/base/util/smart_ptr.h>
 #include <runtime/base/object_data.h>
 #include <runtime/base/type_string.h>
@@ -57,8 +57,8 @@ public:
   /**
    * Constructors
    */
-  Object(ObjectData *data) : ObjectBase(data) { }
-  Object(CObjRef src) : ObjectBase(src.m_px) { }
+  /* implicit */ Object(ObjectData *data) : ObjectBase(data) { }
+  /* implicit */ Object(CObjRef src) : ObjectBase(src.m_px) { }
 
   // Move ctor
   Object(Object&& src) : ObjectBase(std::move(src)) {
@@ -125,7 +125,7 @@ public:
     T *px = dynamic_cast<T*>(cur);
     if (!px) {
       if (!badTypeOkay) {
-        throw InvalidObjectTypeException(m_px->o_getClassName());
+        throw InvalidObjectTypeException(m_px->o_getClassName().c_str());
       }
       return nullptr;
     }
diff --git a/hphp/runtime/base/type_string.h b/hphp/runtime/base/type_string.h
index c5724e8a0..358fa186c 100644
--- a/hphp/runtime/base/type_string.h
+++ b/hphp/runtime/base/type_string.h
@@ -14,14 +14,14 @@
    +----------------------------------------------------------------------+
 */
 
+#ifndef incl_HPHP_STRING_H_
+#define incl_HPHP_STRING_H_
+
 #ifndef incl_HPHP_INSIDE_HPHP_COMPLEX_TYPES_H_
 #error Directly including 'type_string.h' is prohibited. \
        Include 'complex_types.h' instead.
 #endif
 
-#ifndef incl_HPHP_STRING_H_
-#define incl_HPHP_STRING_H_
-
 #include <util/assertions.h>
 #include <runtime/base/util/smart_ptr.h>
 #include <runtime/base/string_data.h>
@@ -119,21 +119,21 @@ public:
   /**
    * Constructors
    */
-  String(StringData *data) : StringBase(data) { }
-  String(int     n);
-  String(int64_t   n);
-  String(double  n);
-  String(litstr  s) {
+  /* implicit */ String(StringData *data) : StringBase(data) { }
+  /* implicit */ String(int     n);
+  /* implicit */ String(int64_t   n);
+  /* implicit */ String(double  n);
+  /* implicit */ String(litstr  s) {
     if (s) {
       m_px = buildStringData(s);
       m_px->setRefCount(1);
     }
   }
-  String(CStrRef str) : StringBase(str.m_px) { }
+  String(const String& str) : StringBase(str.m_px) { }
 
   // Move ctor
-  String(String&& str) : StringBase(std::move(str)) {}
-  String(Variant&& src);
+  /* implicit */ String(String&& str) : StringBase(std::move(str)) {}
+  /* implicit */ String(Variant&& src);
   // Move assign
   String& operator=(String&& src) {
     static_assert(sizeof(String) == sizeof(StringBase),"Fix this.");
@@ -144,7 +144,7 @@ public:
   // Move assign from Variant
   String& operator=(Variant&& src);
 
-  String(const std::string &s) { // always make a copy
+  /* implicit */ String(const std::string &s) { // always make a copy
     m_px = NEW(StringData)(s.data(), s.size(), CopyString);
     m_px->setRefCount(1);
   }
@@ -190,6 +190,13 @@ public:
       m_px->setRefCount(1);
     }
   }
+  // force a copy of a String
+  String(const String& s, CopyStringMode mode) {
+    if (s.m_px) {
+      m_px = NEW(StringData)(s.c_str(), s.size(), mode);
+      m_px->setRefCount(1);
+    }
+  }
   // make an empty string with cap reserve bytes, plus 1 for '\0'
   String(int cap, ReserveStringMode mode) {
     m_px = NEW(StringData)(cap);
@@ -203,9 +210,6 @@ public:
   /**
    * Informational
    */
-  operator const char *() const {
-    return m_px ? m_px->data() : "";
-  }
   const char *data() const {
     return m_px ? m_px->data() : "";
   }
@@ -326,6 +330,12 @@ public:
   String &operator &= (CStrRef v);
   String &operator ^= (CStrRef v);
   String  operator ~  () const;
+  explicit operator std::string () const {
+    return std::string(c_str(), size());
+  }
+  explicit operator bool() const {
+    return m_px != nullptr;
+  }
 
   /**
    * These are convenient functions for writing extensions, since code
@@ -600,9 +610,9 @@ class StaticString : public String {
 public:
   friend class StringUtil;
 
-  StaticString(litstr s);
+  explicit StaticString(litstr s);
   StaticString(litstr s, int length); // binary string
-  StaticString(std::string s);
+  explicit StaticString(std::string s);
   StaticString(const StaticString &str);
   ~StaticString() {
     // prevent ~SmartPtr from calling decRefCount after data is released
diff --git a/hphp/runtime/base/type_variant.cpp b/hphp/runtime/base/type_variant.cpp
index 17a5a3179..487c245e4 100644
--- a/hphp/runtime/base/type_variant.cpp
+++ b/hphp/runtime/base/type_variant.cpp
@@ -2404,7 +2404,7 @@ Variant Variant::o_invoke(CStrRef s, CArrRef params, int64_t hash /* = -1 */) {
   } else if (m_type == KindOfRef) {
     return m_data.pref->var()->o_invoke(s, params, hash);
   } else {
-    throw_call_non_object(s);
+    throw_call_non_object(s.c_str());
   }
 }
 
@@ -2417,7 +2417,7 @@ Variant Variant::o_invoke_few_args(CStrRef s, int64_t hash, int count,
     return m_data.pref->var()->o_invoke_few_args(s, hash, count,
                                                  INVOKE_FEW_ARGS_PASS_ARGS);
   } else {
-    throw_call_non_object(s);
+    throw_call_non_object(s.c_str());
   }
 }
 
@@ -3041,7 +3041,7 @@ void Variant::unserialize(VariableUnserializer *uns,
       Object obj;
       if (RuntimeOption::UnserializationWhitelistCheck &&
           !uns->isWhitelistedClass(clsName)) {
-        String err_msg =
+        const char* err_msg =
           "The object being unserialized with class name '%s' "
           "is not in the given whitelist. "
           "See http://fburl.com/SafeSerializable for more detail";
diff --git a/hphp/runtime/base/zend/zend_pack.cpp b/hphp/runtime/base/zend/zend_pack.cpp
index 39370edad..7d93893c4 100644
--- a/hphp/runtime/base/zend/zend_pack.cpp
+++ b/hphp/runtime/base/zend/zend_pack.cpp
@@ -111,7 +111,7 @@ Variant ZendPack::pack(CStrRef fmt, CArrRef argv) {
   vector<int> formatargs;
   int argc = argv.size();
 
-  const char *format = fmt;
+  const char *format = fmt.c_str();
   int formatlen = fmt.size();
   int currentarg = 0;
   for (int i = 0; i < formatlen; ) {
@@ -288,7 +288,7 @@ Variant ZendPack::pack(CStrRef fmt, CArrRef argv) {
     case 'A':
       memset(&output[outputpos], (code == 'a') ? '\0' : ' ', arg);
       val = argv[currentarg++].toString();
-      s = (const char *)val;
+      s = val.c_str();
       slen = val.size();
       memcpy(&output[outputpos], s, (slen < arg) ? slen : arg);
       outputpos += arg;
@@ -454,9 +454,9 @@ int32_t ZendPack::unpack(const char *data, int size, int issigned, int *map) {
 }
 
 Variant ZendPack::unpack(CStrRef fmt, CStrRef data) {
-  const char *format = fmt;
+  const char *format = fmt.c_str();
   int formatlen = fmt.size();
-  const char *input = data;
+  const char *input = data.c_str();
   int inputlen = data.size();
   int inputpos = 0;
 
diff --git a/hphp/runtime/base/zend/zend_printf.cpp b/hphp/runtime/base/zend/zend_printf.cpp
index e7c07ab39..f11c2a3bb 100644
--- a/hphp/runtime/base/zend/zend_printf.cpp
+++ b/hphp/runtime/base/zend/zend_printf.cpp
@@ -926,7 +926,7 @@ char *string_printf(const char *format, int len, CArrRef args, int *outlen) {
     switch (ch) {
     case 's': {
       String s = tmp.toString();
-      appendstring(&result, &outpos, &size, s,
+      appendstring(&result, &outpos, &size, s.c_str(),
                    width, precision, padding, alignment, s.size(),
                    0, expprec, 0);
       break;
diff --git a/hphp/runtime/eval/debugger/cmd/cmd_instrument.cpp b/hphp/runtime/eval/debugger/cmd/cmd_instrument.cpp
index f43d81f5d..44305a08e 100644
--- a/hphp/runtime/eval/debugger/cmd/cmd_instrument.cpp
+++ b/hphp/runtime/eval/debugger/cmd/cmd_instrument.cpp
@@ -85,13 +85,13 @@ bool CmdInstrument::onClient(DebuggerClient *client) {
   if (loc == "here") {
     InstPointInfoPtr ipi(new InstPointInfo());
     ipi->setLocHere();
-    ipi->m_code = code.toString();
+    ipi->m_code = (std::string) code.toString();
     ipi->m_desc = desc;
     m_instPoints->push_back(ipi);
   } else if (loc.rfind("()") == loc.size() - 2){
     InstPointInfoPtr ipi(new InstPointInfo());
     ipi->setLocFuncEntry(loc.substr(0, loc.size() - 2));
-    ipi->m_code = code.toString();
+    ipi->m_code = (std::string) code.toString();
     ipi->m_desc = desc;
     m_instPoints->push_back(ipi);
   } else {
diff --git a/hphp/runtime/eval/debugger/debugger_client.cpp b/hphp/runtime/eval/debugger/debugger_client.cpp
index 0d799d746..fb4d223de 100644
--- a/hphp/runtime/eval/debugger/debugger_client.cpp
+++ b/hphp/runtime/eval/debugger/debugger_client.cpp
@@ -529,7 +529,7 @@ bool DebuggerClient::connectRemote(const std::string &host, int port) {
   }
   info("Connecting to %s:%d...", host.c_str(), port);
   Socket *sock = new Socket(socket(PF_INET, SOCK_STREAM, 0), PF_INET,
-                            String(host), port);
+                            host.c_str(), port);
   // Ensure the socket is not swept---it is cached across requests in
   // API mode, and in client mode we expect to destruct it ourselves
   // when ~DebuggerClient runs.
@@ -556,7 +556,7 @@ bool DebuggerClient::reconnect() {
   if (port) {
     info("Re-connecting to %s:%d...", host.c_str(), port);
     Socket *sock = new Socket(socket(PF_INET, SOCK_STREAM, 0), PF_INET,
-                              String(host), port);
+                              host.c_str(), port);
     sock->unregister();
     Object obj(sock);
     if (f_socket_connect(sock, String(host), port)) {
diff --git a/hphp/runtime/ext/ext_domdocument.cpp b/hphp/runtime/ext/ext_domdocument.cpp
index d7ae08515..5cf43c3a9 100644
--- a/hphp/runtime/ext/ext_domdocument.cpp
+++ b/hphp/runtime/ext/ext_domdocument.cpp
@@ -400,7 +400,7 @@ static Variant dom_canonicalization(xmlNodePtr nodep, CStrRef file,
     }
   }
   if (mode == 1) {
-    buf = xmlOutputBufferCreateFilename(file, NULL, 0);
+    buf = xmlOutputBufferCreateFilename(file.c_str(), nullptr, 0);
   } else {
     buf = xmlAllocOutputBuffer(NULL);
   }
@@ -1499,8 +1499,8 @@ struct PropertyAccessor {
 
 class PropertyAccessorMap : private hphp_const_char_imap<PropertyAccessor*> {
 public:
-  PropertyAccessorMap(PropertyAccessor* props,
-                      PropertyAccessorMap *base = NULL) {
+  explicit PropertyAccessorMap(PropertyAccessor* props,
+                               PropertyAccessorMap *base = nullptr) {
     if (base) {
       *this = *base;
     }
@@ -5434,17 +5434,17 @@ Variant c_DOMNodeIterator::t_valid() {
 ///////////////////////////////////////////////////////////////////////////////
 // function-style wrappers
 
-#define DOM_GET_OBJ(name)					\
+#define DOM_GET_OBJ(name)                                       \
   c_DOM ##name *pobj = NULL;                                    \
   if (obj.isObject()) {                                         \
     pobj = obj.toObject().getTyped<c_DOM ##name>(true, true);   \
     if (pobj == NULL) {                                         \
       raise_warning("Expecting dom " #name " object");          \
-      return uninit_null();                                              \
+      return uninit_null();                                     \
     }                                                           \
   } else {                                                      \
     raise_warning("Expecting dom objects in parameters");       \
-    return uninit_null();                                                \
+    return uninit_null();                                       \
   }
 
 Variant f_dom_document_create_element(CVarRef obj, CStrRef name,
diff --git a/hphp/runtime/ext/ext_fb.cpp b/hphp/runtime/ext/ext_fb.cpp
index 8a15df65a..83654b6fa 100644
--- a/hphp/runtime/ext/ext_fb.cpp
+++ b/hphp/runtime/ext/ext_fb.cpp
@@ -1159,7 +1159,7 @@ Array f_fb_crossall_query(CStrRef sql, int max_thread /* = 50 */,
 
   Array ret;
   // parameter checking
-  if (!sql || !*sql) {
+  if (sql.empty()) {
     static const StaticString s_errstr("empty SQL");
     ret.set(s_error, s_errstr);
     return ret;
diff --git a/hphp/runtime/ext/ext_file.cpp b/hphp/runtime/ext/ext_file.cpp
index 5d9fbb43d..8203791ca 100644
--- a/hphp/runtime/ext/ext_file.cpp
+++ b/hphp/runtime/ext/ext_file.cpp
@@ -407,7 +407,7 @@ Variant f_file_put_contents(CStrRef filename, CVarRef data,
       String value = data.toString();
       if (!value.empty()) {
         numbytes += value.size();
-        int written = f->writeImpl(value, value.size());
+        int written = f->writeImpl(value.data(), value.size());
         if (written != value.size()) {
           numbytes = -1;
         }
@@ -821,9 +821,9 @@ Variant f_realpath(CStrRef path) {
       StaticContentCache::TheFileCache->exists(translated.data(), false)) {
     return translated;
   }
-  if (access(translated.data(), F_OK) == 0) {
+  if (access(translated.c_str(), F_OK) == 0) {
     char resolved_path[PATH_MAX];
-    if (!realpath(translated, resolved_path)) {
+    if (!realpath(translated.c_str(), resolved_path)) {
       return false;
     }
     return String(resolved_path, CopyString);
@@ -891,7 +891,8 @@ Variant f_pathinfo(CStrRef path, int opt /* = 15 */) {
 
 Variant f_disk_free_space(CStrRef directory) {
   struct statfs buf;
-  CHECK_SYSTEM(statfs(File::TranslatePath(directory), &buf));
+  String translated = File::TranslatePath(directory);
+  CHECK_SYSTEM(statfs(translated.c_str(), &buf));
   return (double)buf.f_bsize * (double)buf.f_bavail;
 }
 
@@ -901,7 +902,8 @@ Variant f_diskfreespace(CStrRef directory) {
 
 Variant f_disk_total_space(CStrRef directory) {
   struct statfs buf;
-  CHECK_SYSTEM(statfs(File::TranslatePath(directory), &buf));
+  String translated = File::TranslatePath(directory);
+  CHECK_SYSTEM(statfs(translated.c_str(), &buf));
   return (double)buf.f_bsize * (double)buf.f_blocks;
 }
 
@@ -909,7 +911,8 @@ Variant f_disk_total_space(CStrRef directory) {
 // system wrappers
 
 bool f_chmod(CStrRef filename, int64_t mode) {
-  CHECK_SYSTEM(chmod(File::TranslatePath(filename).data(), mode));
+  String translated = File::TranslatePath(filename);
+  CHECK_SYSTEM(chmod(translated.c_str(), mode));
   return true;
 }
 
diff --git a/hphp/runtime/ext/ext_hash.cpp b/hphp/runtime/ext/ext_hash.cpp
index b9da84b9e..5cc81ae55 100644
--- a/hphp/runtime/ext/ext_hash.cpp
+++ b/hphp/runtime/ext/ext_hash.cpp
@@ -381,7 +381,7 @@ String f_hash_final(CObjRef context, bool raw_output /* = false */) {
 
 int64_t f_furchash_hphp_ext(CStrRef key, int len, int nPart) {
   len = std::max(std::min(len, key.size()), 0);
-  return furc_hash(key, len, nPart);
+  return furc_hash(key.data(), len, nPart);
 }
 
 bool f_furchash_hphp_ext_supported() {
@@ -390,7 +390,7 @@ bool f_furchash_hphp_ext_supported() {
 
 int64_t f_hphp_murmurhash(CStrRef key, int len, int seed) {
   len = std::max(std::min(len, key.size()), 0);
-  return murmur_hash_64A(key, len, seed);
+  return murmur_hash_64A(key.data(), len, seed);
 }
 
 ///////////////////////////////////////////////////////////////////////////////
diff --git a/hphp/runtime/ext/ext_iconv.cpp b/hphp/runtime/ext/ext_iconv.cpp
index 9b8743b6c..5bf407a3d 100644
--- a/hphp/runtime/ext/ext_iconv.cpp
+++ b/hphp/runtime/ext/ext_iconv.cpp
@@ -1827,11 +1827,11 @@ String f_ob_iconv_handler(CStrRef contents, int status) {
     char *out_buffer;
     size_t out_len;
     php_iconv_err_t err =
-      php_iconv_string(contents.data(), contents.size(),
-                       &out_buffer, &out_len,
-                       ICONVG(output_encoding), ICONVG(internal_encoding));
-    _php_iconv_show_error(err, ICONVG(output_encoding),
-                          ICONVG(internal_encoding));
+      php_iconv_string(contents.data(), contents.size(), &out_buffer, &out_len,
+                       ICONVG(output_encoding).c_str(),
+                       ICONVG(internal_encoding).c_str());
+    _php_iconv_show_error(err, ICONVG(output_encoding).c_str(),
+                          ICONVG(internal_encoding).c_str());
     if (out_buffer != NULL) {
       g_context->setContentType(mimetype, ICONVG(output_encoding));
       return String(out_buffer, out_len, AttachString);
diff --git a/hphp/runtime/ext/ext_icu_ucnv.cpp b/hphp/runtime/ext/ext_icu_ucnv.cpp
index 3e21c2f0a..6c69e5a41 100644
--- a/hphp/runtime/ext/ext_icu_ucnv.cpp
+++ b/hphp/runtime/ext/ext_icu_ucnv.cpp
@@ -546,7 +546,7 @@ Array c_UConverter::ti_getaliases(const char* cls , CStrRef encoding) {
   Array ret = Array::Create();
   for(i = 0; i < count; ++i) {
     error = U_ZERO_ERROR;
-    const char *alias = ucnv_getAlias(encoding, i, &error);
+    const char *alias = ucnv_getAlias(encoding.c_str(), i, &error);
     if (U_FAILURE(error)) {
       THROW_UFAILURE(ucnv_getAlias, error, s_intl_error->m_error);
       return uninit_null();
diff --git a/hphp/runtime/ext/ext_ipc.cpp b/hphp/runtime/ext/ext_ipc.cpp
index 613bc3001..7fef422e6 100644
--- a/hphp/runtime/ext/ext_ipc.cpp
+++ b/hphp/runtime/ext/ext_ipc.cpp
@@ -57,10 +57,10 @@ int64_t f_ftok(CStrRef pathname, CStrRef proj) {
   }
   if (proj.length() != 1) {
     raise_warning("Project identifier has to be one character int64: %s",
-                    (const char *)proj);
+                  proj.c_str());
     return -1;
   }
-  return ftok((const char *)pathname, (int)(*((const char *)proj)));
+  return ftok(pathname.c_str(), (int)proj[0]);
 }
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -193,7 +193,7 @@ bool f_msg_send(CObjRef queue, int64_t msgtype, CVarRef message,
   buffer = (struct msgbuf *)calloc(len + sizeof(struct msgbuf), 1);
   ScopedMem deleter(buffer);
   MSGBUF_MTYPE(buffer) = msgtype;
-  memcpy(MSGBUF_MTEXT(buffer), (const char *)data, len + 1);
+  memcpy(MSGBUF_MTEXT(buffer), data.c_str(), len + 1);
 
   int result = msgsnd(q->id, buffer, len, blocking ? 0 : IPC_NOWAIT);
   if (result < 0) {
diff --git a/hphp/runtime/ext/ext_iterator.cpp b/hphp/runtime/ext/ext_iterator.cpp
index 83c15df46..dddb962fc 100644
--- a/hphp/runtime/ext/ext_iterator.cpp
+++ b/hphp/runtime/ext/ext_iterator.cpp
@@ -42,7 +42,7 @@ StaticString
 static RecursiveIteratorIterator *
 get_recursiveiteratoriterator(CObjRef obj) {
   if (!obj->instanceof(SystemLib::s_RecursiveIteratorIteratorClass)) {
-    throw InvalidObjectTypeException(obj->o_getClassName());
+    throw InvalidObjectTypeException(obj->o_getClassName().c_str());
   }
   CObjRef rsrc = obj->o_get("rsrc", true, "RecursiveIteratorIterator");
   return rsrc.getTyped<RecursiveIteratorIterator>();
@@ -51,7 +51,7 @@ get_recursiveiteratoriterator(CObjRef obj) {
 static RecursiveDirectoryIterator *
 get_recursivedirectoryiterator(CObjRef obj) {
   if (!obj->instanceof(SystemLib::s_RecursiveDirectoryIteratorClass)) {
-    throw InvalidObjectTypeException(obj->o_getClassName());
+    throw InvalidObjectTypeException(obj->o_getClassName().c_str());
   }
   // SplFileInfo as context -- rsrc is a private property
   CObjRef rsrc = obj->o_get("rsrc", true, "SplFileInfo");
@@ -61,7 +61,7 @@ get_recursivedirectoryiterator(CObjRef obj) {
 static DirectoryIterator *
 get_directoryiterator(CObjRef obj) {
   if (!obj->instanceof(SystemLib::s_DirectoryIteratorClass)) {
-    throw InvalidObjectTypeException(obj->o_getClassName());
+    throw InvalidObjectTypeException(obj->o_getClassName().c_str());
   }
   // SplFileInfo as context -- rsrc is a private property
   CObjRef rsrc = obj->o_get("rsrc", true, "SplFileInfo");
diff --git a/hphp/runtime/ext/ext_ldap.cpp b/hphp/runtime/ext/ext_ldap.cpp
index 9f66d7cc1..fdfb9d818 100644
--- a/hphp/runtime/ext/ext_ldap.cpp
+++ b/hphp/runtime/ext/ext_ldap.cpp
@@ -510,7 +510,7 @@ static void get_attributes(Array &ret, LDAP *ldap,
     ldap_value_free_len(ldap_value);
 
     String sAttribute(attribute, CopyString);
-    ret.set(to_lower ? Util::toLower(attribute) : sAttribute, tmp);
+    ret.set(to_lower ? String(Util::toLower(attribute)) : sAttribute, tmp);
     ret.set(num_attrib, sAttribute);
 
     num_attrib++;
diff --git a/hphp/runtime/ext/ext_mailparse.cpp b/hphp/runtime/ext/ext_mailparse.cpp
index 79083142f..eab1d3de8 100644
--- a/hphp/runtime/ext/ext_mailparse.cpp
+++ b/hphp/runtime/ext/ext_mailparse.cpp
@@ -183,7 +183,7 @@ Array f_mailparse_msg_get_part_data(CObjRef mimemail) {
 }
 
 Variant f_mailparse_msg_get_part(CObjRef mimemail, CStrRef mimesection) {
-  Object part = mimemail.getTyped<MimePart>()->findByName(mimesection);
+  Object part = mimemail.getTyped<MimePart>()->findByName(mimesection.c_str());
   if (part.isNull()) {
     raise_warning("cannot find section %s in message", mimesection.data());
     return false;
diff --git a/hphp/runtime/ext/ext_mcrypt.cpp b/hphp/runtime/ext/ext_mcrypt.cpp
index 09d95d211..8808d3f67 100644
--- a/hphp/runtime/ext/ext_mcrypt.cpp
+++ b/hphp/runtime/ext/ext_mcrypt.cpp
@@ -31,7 +31,7 @@ IMPLEMENT_DEFAULT_EXTENSION(mcrypt);
 
 class MCrypt : public SweepableResourceData {
 public:
-  MCrypt(MCRYPT td) : m_td(td), m_init(false) {
+  explicit MCrypt(MCRYPT td) : m_td(td), m_init(false) {
   }
 
   ~MCrypt() {
@@ -241,7 +241,7 @@ bool f_mcrypt_module_close(CObjRef td) {
 }
 
 Array f_mcrypt_list_algorithms(CStrRef lib_dir /* = null_string */) {
-  String dir = lib_dir.empty() ? MCG(algorithms_dir) : lib_dir;
+  String dir = lib_dir.empty() ? String(MCG(algorithms_dir)) : lib_dir;
 
   int count = 0;
   char **modules = mcrypt_list_algorithms((char*)dir.data(), &count);
@@ -257,7 +257,7 @@ Array f_mcrypt_list_algorithms(CStrRef lib_dir /* = null_string */) {
 }
 
 Array f_mcrypt_list_modes(CStrRef lib_dir /* = null_string */) {
-  String dir = lib_dir.empty() ? MCG(modes_dir) : lib_dir;
+  String dir = lib_dir.empty() ? String(MCG(modes_dir)) : lib_dir;
 
   int count = 0;
   char **modules = mcrypt_list_modes((char*)dir.data(), &count);
@@ -274,21 +274,21 @@ Array f_mcrypt_list_modes(CStrRef lib_dir /* = null_string */) {
 
 int64_t f_mcrypt_module_get_algo_block_size(CStrRef algorithm,
                                         CStrRef lib_dir /* = null_string */) {
-  String dir = lib_dir.empty() ? MCG(algorithms_dir) : lib_dir;
+  String dir = lib_dir.empty() ? String(MCG(algorithms_dir)) : lib_dir;
   return mcrypt_module_get_algo_block_size((char*)algorithm.data(),
                                            (char*)dir.data());
 }
 
 int64_t f_mcrypt_module_get_algo_key_size(CStrRef algorithm,
                                       CStrRef lib_dir /* = null_string */) {
-  String dir = lib_dir.empty() ? MCG(algorithms_dir) : lib_dir;
+  String dir = lib_dir.empty() ? String(MCG(algorithms_dir)) : lib_dir;
   return mcrypt_module_get_algo_key_size((char*)algorithm.data(),
                                          (char*)dir.data());
 }
 
 Array f_mcrypt_module_get_supported_key_sizes(CStrRef algorithm,
                                               CStrRef lib_dir /* = null_string */) {
-  String dir = lib_dir.empty() ? MCG(algorithms_dir) : lib_dir;
+  String dir = lib_dir.empty() ? String(MCG(algorithms_dir)) : lib_dir;
 
   int count = 0;
   int *key_sizes = mcrypt_module_get_algo_supported_key_sizes
@@ -304,28 +304,28 @@ Array f_mcrypt_module_get_supported_key_sizes(CStrRef algorithm,
 
 bool f_mcrypt_module_is_block_algorithm_mode(CStrRef mode,
                                              CStrRef lib_dir /* = null_string */) {
-  String dir = lib_dir.empty() ? MCG(modes_dir) : lib_dir;
+  String dir = lib_dir.empty() ? String(MCG(modes_dir)) : lib_dir;
   return mcrypt_module_is_block_algorithm_mode((char*)mode.data(),
                                                (char*)dir.data()) == 1;
 }
 
 bool f_mcrypt_module_is_block_algorithm(CStrRef algorithm,
                                         CStrRef lib_dir /* = null_string */) {
-  String dir = lib_dir.empty() ? MCG(algorithms_dir) : lib_dir;
+  String dir = lib_dir.empty() ? String(MCG(algorithms_dir)) : lib_dir;
   return mcrypt_module_is_block_algorithm((char*)algorithm.data(),
                                           (char*)dir.data()) == 1;
 }
 
 bool f_mcrypt_module_is_block_mode(CStrRef mode,
                                    CStrRef lib_dir /* = null_string */) {
-  String dir = lib_dir.empty() ? MCG(modes_dir) : lib_dir;
+  String dir = lib_dir.empty() ? String(MCG(modes_dir)) : lib_dir;
   return mcrypt_module_is_block_mode((char*)mode.data(),
                                      (char*)dir.data()) == 1;
 }
 
 bool f_mcrypt_module_self_test(CStrRef algorithm,
                                CStrRef lib_dir /* = null_string */) {
-  String dir = lib_dir.empty() ? MCG(algorithms_dir) : lib_dir;
+  String dir = lib_dir.empty() ? String(MCG(algorithms_dir)) : lib_dir;
   return mcrypt_module_self_test((char*)algorithm.data(),
                                  (char*)dir.data()) == 0;
 }
diff --git a/hphp/runtime/ext/ext_memcached.cpp b/hphp/runtime/ext/ext_memcached.cpp
index b60faa436..39dc741be 100644
--- a/hphp/runtime/ext/ext_memcached.cpp
+++ b/hphp/runtime/ext/ext_memcached.cpp
@@ -169,7 +169,7 @@ namespace {
 class MemcachedResultWrapper {
 public:
   memcached_result_st value;
-  MemcachedResultWrapper(memcached_st *memcached) {
+  explicit MemcachedResultWrapper(memcached_st *memcached) {
     memcached_result_create(memcached, &value);
   }
   ~MemcachedResultWrapper() {
@@ -630,7 +630,7 @@ Variant c_Memcached::t_getserverbykey(CStrRef server_key) {
 
   memcached_return_t error;
   const memcached_server_st *server = memcached_server_by_key(
-      &m_impl->memcached, server_key, server_key.length(), &error);
+      &m_impl->memcached, server_key.c_str(), server_key.size(), &error);
   if (!server) {
     handleError(error);
     return false;
diff --git a/hphp/runtime/ext/ext_misc.cpp b/hphp/runtime/ext/ext_misc.cpp
index b68dc25a5..f0ca89783 100644
--- a/hphp/runtime/ext/ext_misc.cpp
+++ b/hphp/runtime/ext/ext_misc.cpp
@@ -282,10 +282,10 @@ String f_uniqid(CStrRef prefix /* = null_string */,
   char uniqid[256];
   if (more_entropy) {
     snprintf(uniqid, sizeof(uniqid), "%s%08x%05x%.8F",
-             (const char *)prefix, sec, usec, math_combined_lcg() * 10);
+             prefix.c_str(), sec, usec, math_combined_lcg() * 10);
   } else {
     snprintf(uniqid, sizeof(uniqid), "%s%08x%05x",
-             (const char *)prefix, sec, usec);
+             prefix.c_str(), sec, usec);
   }
   return String(uniqid, CopyString);
 }
diff --git a/hphp/runtime/ext/ext_mysql.cpp b/hphp/runtime/ext/ext_mysql.cpp
index aed19c9f3..b63281890 100644
--- a/hphp/runtime/ext/ext_mysql.cpp
+++ b/hphp/runtime/ext/ext_mysql.cpp
@@ -561,7 +561,8 @@ static Variant php_mysql_do_connect(String server, String username,
   }
 
   if (mySQL == NULL) {
-    mySQL = new MySQL(host, port, username, password, database);
+    mySQL = new MySQL(host.c_str(), port, username.c_str(), password.c_str(),
+                      database.c_str());
     ret = mySQL;
     if (async) {
 #ifdef FACEBOOK
diff --git a/hphp/runtime/ext/ext_openssl.cpp b/hphp/runtime/ext/ext_openssl.cpp
index 8764dfb31..8eb53e726 100644
--- a/hphp/runtime/ext/ext_openssl.cpp
+++ b/hphp/runtime/ext/ext_openssl.cpp
@@ -1379,7 +1379,7 @@ bool f_openssl_pkcs7_encrypt(CStrRef infilename, CStrRef outfilename,
     raise_warning("error opening the file, %s", infilename.data());
     goto clean_exit;
   }
-  outfile = BIO_new_file(outfilename, "w");
+  outfile = BIO_new_file(outfilename.data(), "w");
   if (outfile == NULL) {
     raise_warning("error opening the file, %s", outfilename.data());
     goto clean_exit;
@@ -2352,7 +2352,7 @@ static String php_openssl_validate_iv(String piv, int iv_required_len) {
 Variant f_openssl_encrypt(CStrRef data, CStrRef method, CStrRef password,
                           int options /* = 0 */,
                           CStrRef iv /* = null_string */) {
-  const EVP_CIPHER *cipher_type = EVP_get_cipherbyname(method);
+  const EVP_CIPHER *cipher_type = EVP_get_cipherbyname(method.c_str());
   if (!cipher_type) {
     raise_warning("Unknown cipher algorithm");
     return false;
@@ -2426,7 +2426,7 @@ Variant f_openssl_encrypt(CStrRef data, CStrRef method, CStrRef password,
 Variant f_openssl_decrypt(CStrRef data, CStrRef method, CStrRef password,
                           int options /* = 0 */,
                           CStrRef iv /* = null_string */) {
-  const EVP_CIPHER *cipher_type = EVP_get_cipherbyname(method);
+  const EVP_CIPHER *cipher_type = EVP_get_cipherbyname(method.c_str());
   if (!cipher_type) {
     raise_warning("Unknown cipher algorithm");
     return false;
@@ -2489,7 +2489,7 @@ Variant f_openssl_decrypt(CStrRef data, CStrRef method, CStrRef password,
 
 Variant f_openssl_digest(CStrRef data, CStrRef method,
                          bool raw_output /* = false */) {
-  const EVP_MD *mdtype = EVP_get_digestbyname(method);
+  const EVP_MD *mdtype = EVP_get_digestbyname(method.c_str());
 
   if (!mdtype) {
     raise_warning("Unknown signature algorithm");
diff --git a/hphp/runtime/ext/ext_output.cpp b/hphp/runtime/ext/ext_output.cpp
index b21dd69e8..187a4f2fc 100644
--- a/hphp/runtime/ext/ext_output.cpp
+++ b/hphp/runtime/ext/ext_output.cpp
@@ -107,7 +107,7 @@ Array f_hphp_get_iostatus() {
   return ServerStats::GetThreadIOStatuses();
 }
 void f_hphp_set_iostatus_address(CStrRef name) {
-  return ServerStats::SetThreadIOStatusAddress(name);
+  return ServerStats::SetThreadIOStatusAddress(name.c_str());
 }
 
 
diff --git a/hphp/runtime/ext/ext_pdo.cpp b/hphp/runtime/ext/ext_pdo.cpp
index b685c0a2b..e460340e0 100644
--- a/hphp/runtime/ext/ext_pdo.cpp
+++ b/hphp/runtime/ext/ext_pdo.cpp
@@ -2548,7 +2548,8 @@ rewrite:
       String name(plc->pos, plc->len, AttachLiteral);
 
       /* check if bound parameter is already available */
-      if (!strcmp(name, "?") || !stmt->bound_param_map.exists(name)) {
+      if (!strcmp(name.c_str(), "?") ||
+          !stmt->bound_param_map.exists(name.c_str())) {
         idxbuf.printf(tmpl, bind_no++);
       } else {
         idxbuf.clear();
diff --git a/hphp/runtime/ext/ext_process.cpp b/hphp/runtime/ext/ext_process.cpp
index 8bb8788ce..b2766d190 100644
--- a/hphp/runtime/ext/ext_process.cpp
+++ b/hphp/runtime/ext/ext_process.cpp
@@ -138,7 +138,7 @@ void f_pcntl_exec(CStrRef path, CArrRef args /* = null_array */,
   // build environment pair list
   std::vector<String> senvs; // holding those char *
   char **envp = build_envp(envs, senvs);
-  if (execve(path, argv, envp) == -1) {
+  if (execve(path.c_str(), argv, envp) == -1) {
     raise_warning("Error has occured: (errno %d) %s",
                     errno, Util::safe_strerror(errno).c_str());
   }
@@ -418,7 +418,7 @@ private:
 
 String f_shell_exec(CStrRef cmd) {
   ShellExecContext ctx;
-  FILE *fp = ctx.exec(cmd);
+  FILE *fp = ctx.exec(cmd.c_str());
   if (!fp) return "";
   StringBuffer sbuf;
   sbuf.read(fp);
@@ -428,7 +428,7 @@ String f_shell_exec(CStrRef cmd) {
 String f_exec(CStrRef command, VRefParam output /* = null */,
               VRefParam return_var /* = null */) {
   ShellExecContext ctx;
-  FILE *fp = ctx.exec(command);
+  FILE *fp = ctx.exec(command.c_str());
   if (!fp) return "";
   StringBuffer sbuf;
   sbuf.read(fp);
@@ -457,7 +457,7 @@ String f_exec(CStrRef command, VRefParam output /* = null */,
 
 void f_passthru(CStrRef command, VRefParam return_var /* = null */) {
   ShellExecContext ctx;
-  FILE *fp = ctx.exec(command);
+  FILE *fp = ctx.exec(command.c_str());
   if (!fp) return;
 
   char buffer[1024];
@@ -475,7 +475,7 @@ void f_passthru(CStrRef command, VRefParam return_var /* = null */) {
 
 String f_system(CStrRef command, VRefParam return_var /* = null */) {
   ShellExecContext ctx;
-  FILE *fp = ctx.exec(command);
+  FILE *fp = ctx.exec(command.c_str());
   if (!fp) return "";
   StringBuffer sbuf;
   if (fp) {
@@ -612,7 +612,7 @@ public:
   bool openFile(CStrRef zfile, CStrRef zmode) {
     mode = DESC_FILE;
     /* try a wrapper */
-    FILE *file = fopen(zfile, zmode);
+    FILE *file = fopen(zfile.c_str(), zmode.c_str());
     if (!file) {
       raise_warning("Unable to open specified file: %s (mode %s)",
                       zfile.data(), zmode.data());
@@ -894,7 +894,7 @@ bool f_proc_nice(int increment) {
 
 String f_escapeshellarg(CStrRef arg) {
   if (!arg.empty()) {
-    char *ret = string_escape_shell_arg(arg);
+    char *ret = string_escape_shell_arg(arg.c_str());
     return String(ret, AttachString);
   }
   return arg;
@@ -902,7 +902,7 @@ String f_escapeshellarg(CStrRef arg) {
 
 String f_escapeshellcmd(CStrRef command) {
   if (!command.empty()) {
-    char *ret = string_escape_shell_cmd(command);
+    char *ret = string_escape_shell_cmd(command.c_str());
     return String(ret, AttachString);
   }
   return command;
diff --git a/hphp/runtime/ext/ext_soap.cpp b/hphp/runtime/ext/ext_soap.cpp
index 7a6f47745..d897c28f4 100644
--- a/hphp/runtime/ext/ext_soap.cpp
+++ b/hphp/runtime/ext/ext_soap.cpp
@@ -68,7 +68,7 @@ private:
 
 class SoapServerScope : public SoapScope {
 public:
-  SoapServerScope(c_SoapServer *server) {
+  explicit SoapServerScope(c_SoapServer *server) {
     USE_SOAP_GLOBAL;
     SOAP_GLOBAL(error_code) = "Server";
     SOAP_GLOBAL(error_object) = Object(server);
@@ -77,7 +77,7 @@ public:
 
 class SoapClientScope : public SoapScope {
 public:
-  SoapClientScope(c_SoapClient *client) {
+  explicit SoapClientScope(c_SoapClient *client) {
     USE_SOAP_GLOBAL;
     SOAP_GLOBAL(error_code) = "Client";
     SOAP_GLOBAL(error_object) = Object(client);
@@ -86,7 +86,7 @@ public:
 
 class SoapServiceScope {
 public:
-  SoapServiceScope(c_SoapServer *server) {
+  explicit SoapServiceScope(c_SoapServer *server) {
     save();
     USE_SOAP_GLOBAL;
     SOAP_GLOBAL(soap_version) = server->m_version;
@@ -97,7 +97,7 @@ public:
     SOAP_GLOBAL(features) = server->m_features;
   }
 
-  SoapServiceScope(c_SoapClient *client) {
+  explicit SoapServiceScope(c_SoapClient *client) {
     save();
     USE_SOAP_GLOBAL;
     SOAP_GLOBAL(soap_version) = client->m_soap_version;
@@ -1009,7 +1009,7 @@ static sdlFunctionPtr deserialize_function_call
               key += (char*)hdr_func->ns->href;
               key += ':';
             }
-            key += h->function_name;
+            key += (std::string)h->function_name;
             sdlSoapBindingFunctionHeaderMap::iterator iter =
               fnb->input.headers.find(key);
             if (iter != fnb->input.headers.end()) {
@@ -1132,7 +1132,7 @@ static int serialize_response_call2(xmlNodePtr body, sdlFunction *function,
         param_index = key.toInt64();
       }
 
-      parameter = get_param(function, param_name, param_index, true);
+      parameter = get_param(function, param_name.c_str(), param_index, true);
       if (style == SOAP_RPC) {
         param = serialize_parameter(parameter, data, i, param_name.data(),
                                     use, method);
@@ -2131,9 +2131,9 @@ void c_SoapServer::t_handle(CStrRef request /* = null_string */) {
   int soap_version = 0;
   sdlFunctionPtr function;
   try {
-    function = deserialize_function_call
-      (m_sdl, doc_request, m_actor, function_name, params, soap_version,
-       m_soap_headers);
+    function = deserialize_function_call(m_sdl, doc_request, m_actor.c_str(),
+                                         function_name, params, soap_version,
+                                         m_soap_headers);
   } catch (Exception &e) {
     xmlFreeDoc(doc_request);
     send_soap_server_fault(function, e, NULL);
@@ -2560,11 +2560,11 @@ Variant c_SoapClient::t___soapcall(CStrRef name, CArrRef args,
         action += '#';
         action += name.data();
       } else {
-        action += soap_action;
+        action += (std::string) soap_action;
       }
       Variant response;
       try {
-        ret = do_request(this, request, location, action.c_str(),
+        ret = do_request(this, request, location.c_str(), action.c_str(),
                          m_soap_version, 0, response);
       } catch (Exception &e) {
         xmlFreeDoc(request);
diff --git a/hphp/runtime/ext/ext_socket.cpp b/hphp/runtime/ext/ext_socket.cpp
index 9aa22f9ae..4630192d9 100644
--- a/hphp/runtime/ext/ext_socket.cpp
+++ b/hphp/runtime/ext/ext_socket.cpp
@@ -773,7 +773,7 @@ Variant f_socket_sendto(CObjRef socket, CStrRef buf, int len, int flags,
       s_un.sun_family = AF_UNIX;
       snprintf(s_un.sun_path, 108, "%s", addr.data());
 
-      retval = sendto(sock->fd(), buf, len, flags,
+      retval = sendto(sock->fd(), buf.data(), len, flags,
                       (struct sockaddr *)&s_un, SUN_LEN(&s_un));
     }
     break;
@@ -783,11 +783,11 @@ Variant f_socket_sendto(CObjRef socket, CStrRef buf, int len, int flags,
       memset(&sin, 0, sizeof(sin));
       sin.sin_family = AF_INET;
       sin.sin_port = htons((unsigned short) port);
-      if (!php_set_inet_addr(&sin, addr, sock)) {
+      if (!php_set_inet_addr(&sin, addr.c_str(), sock)) {
         return false;
       }
 
-      retval = sendto(sock->fd(), buf, len, flags,
+      retval = sendto(sock->fd(), buf.data(), len, flags,
                       (struct sockaddr *)&sin, sizeof(sin));
     }
     break;
@@ -798,11 +798,11 @@ Variant f_socket_sendto(CObjRef socket, CStrRef buf, int len, int flags,
       sin6.sin6_family = AF_INET6;
       sin6.sin6_port = htons((unsigned short) port);
 
-      if (!php_set_inet6_addr(&sin6, addr, sock)) {
+      if (!php_set_inet6_addr(&sin6, addr.c_str(), sock)) {
         return false;
       }
 
-      retval = sendto(sock->fd(), buf, len, flags,
+      retval = sendto(sock->fd(), buf.data(), len, flags,
                       (struct sockaddr *)&sin6, sizeof(sin6));
     }
     break;
diff --git a/hphp/runtime/ext/ext_splfile.cpp b/hphp/runtime/ext/ext_splfile.cpp
index 67f2648b8..0e00c8547 100644
--- a/hphp/runtime/ext/ext_splfile.cpp
+++ b/hphp/runtime/ext/ext_splfile.cpp
@@ -34,7 +34,7 @@ IMPLEMENT_OBJECT_ALLOCATION(SplFileObject)
 
 static SplFileInfo *get_splfileinfo(CObjRef obj) {
   if (!obj->o_instanceof("SplFileInfo")) {
-    throw InvalidObjectTypeException(obj->o_getClassName());
+    throw InvalidObjectTypeException(obj->o_getClassName().c_str());
   }
   CObjRef rsrc = obj->o_get("rsrc", true, "SplFileInfo");
   return rsrc.getTyped<SplFileInfo>();
@@ -42,7 +42,7 @@ static SplFileInfo *get_splfileinfo(CObjRef obj) {
 
 static SplFileObject *get_splfileobject(CObjRef obj) {
   if (!obj->o_instanceof("SplFileObject")) {
-    throw InvalidObjectTypeException(obj->o_getClassName());
+    throw InvalidObjectTypeException(obj->o_getClassName().c_str());
   }
   // "SplFileInfo" as context -- rsrc is a private property
   CObjRef rsrc = obj->o_get("rsrc", true, "SplFileInfo");
diff --git a/hphp/runtime/ext/ext_string.cpp b/hphp/runtime/ext/ext_string.cpp
index 11378e6a0..65afb9ad6 100644
--- a/hphp/runtime/ext/ext_string.cpp
+++ b/hphp/runtime/ext/ext_string.cpp
@@ -372,7 +372,7 @@ Variant f_vsprintf(CStrRef format, CArrRef args) {
 Variant f_sscanf(int _argc, CStrRef str, CStrRef format, CArrRef _argv /* = null_array */) {
   Variant ret;
   int result;
-  result = string_sscanf(str, format, _argv.size(), ret);
+  result = string_sscanf(str.c_str(), format.c_str(), _argv.size(), ret);
   if (SCAN_ERROR_WRONG_PARAM_COUNT == result) return uninit_null();
   if (_argv.empty()) return ret;
 
@@ -391,11 +391,13 @@ String f_chr(int64_t ascii) {
   char buf[2]; buf[0] = ascii; buf[1] = 0;
   return String(buf, 1, CopyString);
 }
+
 int64_t f_ord(CStrRef str) {
-  return (int64_t)(unsigned char)(*((const char *)str));
+  return (int64_t)(unsigned char)str[0];
 }
+
 Variant f_money_format(CStrRef format, double number) {
-  String s = StringUtil::MoneyFormat(format, number);
+  String s = StringUtil::MoneyFormat(format.c_str(), number);
   if (s.isNull()) return false;
   return s;
 }
@@ -406,7 +408,7 @@ String f_number_format(double number, int decimals /* = 0 */,
   char ch_dec_point = '.';
   if (!dec_point.isNull()) {
     if (dec_point.size() >= 1) {
-      ch_dec_point = ((const char *)dec_point)[0];
+      ch_dec_point = dec_point[0];
     } else {
       ch_dec_point = 0;
     }
@@ -414,7 +416,7 @@ String f_number_format(double number, int decimals /* = 0 */,
   char ch_thousands_sep = ',';
   if (!thousands_sep.isNull()) {
     if (thousands_sep.size() >= 1) {
-      ch_thousands_sep = ((const char *)thousands_sep)[0];
+      ch_thousands_sep = thousands_sep[0];
     } else {
       ch_thousands_sep = 0;
     }
@@ -439,9 +441,11 @@ int64_t f_strnatcmp(CStrRef str1, CStrRef str2) {
   return string_natural_cmp(str1.data(), str1.size(), str2.data(), str2.size(),
                             false);
 }
+
 int64_t f_strcasecmp(CStrRef str1, CStrRef str2) {
   return bstrcasecmp(str1.data(), str1.size(), str2.data(), str2.size());
 }
+
 Variant f_strncasecmp(CStrRef str1, CStrRef str2, int len) {
   if (len < 0) {
     raise_warning("Length must be greater than or equal to 0");
@@ -450,12 +454,14 @@ Variant f_strncasecmp(CStrRef str1, CStrRef str2, int len) {
   return string_strncasecmp(str1.data(), str1.size(), str2.data(), str2.size(),
                             len);
 }
+
 int64_t f_strnatcasecmp(CStrRef str1, CStrRef str2) {
   return string_natural_cmp(str1.data(), str1.size(), str2.data(), str2.size(),
                             true);
 }
+
 int64_t f_strcoll(CStrRef str1, CStrRef str2) {
-  return strcoll(str1, str2);
+  return strcoll(str1.c_str(), str2.c_str());
 }
 
 Variant f_substr_compare(CStrRef main_str, CStrRef str, int offset,
@@ -478,9 +484,9 @@ Variant f_substr_compare(CStrRef main_str, CStrRef str, int offset,
 
   const char *s1 = main_str.data();
   if (case_insensitivity) {
-    return bstrcasecmp(s1 + offset, cmp_len, str, cmp_len);
+    return bstrcasecmp(s1 + offset, cmp_len, str.data(), cmp_len);
   }
-  return string_ncmp(s1 + offset, str, cmp_len);
+  return string_ncmp(s1 + offset, str.data(), cmp_len);
 }
 
 Variant f_strrchr(CStrRef haystack, CVarRef needle) {
@@ -517,7 +523,7 @@ Variant f_strpbrk(CStrRef haystack, CStrRef char_list) {
     throw_invalid_argument("char_list: (empty)");
     return false;
   }
-  const char *p = strpbrk(haystack, char_list);
+  const char *p = strpbrk(haystack.c_str(), char_list.c_str());
   if (p) {
     return String(p, CopyString);
   }
@@ -624,8 +630,8 @@ Variant f_substr_count(CStrRef haystack, CStrRef needle, int offset /* = 0 */,
 
 Variant f_strspn(CStrRef str1, CStrRef str2, int start /* = 0 */,
                  int length /* = 0x7FFFFFFF */) {
-  const char *s1 = str1;
-  const char *s2 = str2;
+  const char *s1 = str1.data();
+  const char *s2 = str2.data();
   int s1_len = str1.size();
   int s2_len = str2.size();
 
@@ -643,8 +649,8 @@ Variant f_strspn(CStrRef str1, CStrRef str2, int start /* = 0 */,
 
 Variant f_strcspn(CStrRef str1, CStrRef str2, int start /* = 0 */,
                   int length /* = 0x7FFFFFFF */) {
-  const char *s1 = str1;
-  const char *s2 = str2;
+  const char *s1 = str1.data();
+  const char *s2 = str2.data();
   int s1_len = str1.size();
   int s2_len = str2.size();
 
@@ -683,7 +689,7 @@ Variant f_strlen(CVarRef vstr) {
 Variant f_count_chars(CStrRef str, int64_t mode /* = 0 */) {
   int chars[256];
   memset((void*)chars, 0, sizeof(chars));
-  const unsigned char *buf = (const unsigned char *)(const char *)str;
+  const unsigned char *buf = (const unsigned char *)str.data();
   for (int len = str.size(); len > 0; len--) {
     chars[*buf++]++;
   }
@@ -763,15 +769,15 @@ Variant f_str_word_count(CStrRef str, int64_t format /* = 0 */,
   }
 
   char ch[256];
-  const char *char_list = charlist;
+  const char *char_list = charlist.data();
   if (*char_list) {
-    string_charmask(charlist, charlist.size(), ch);
+    string_charmask(char_list, charlist.size(), ch);
   } else {
     char_list = NULL;
   }
 
   int word_count = 0;
-  const char *s0 = str;
+  const char *s0 = str.data();
   const char *p = s0;
   const char *e = p + str_len;
 
@@ -818,23 +824,26 @@ Variant f_str_word_count(CStrRef str, int64_t format /* = 0 */,
 
 int64_t f_levenshtein(CStrRef str1, CStrRef str2, int cost_ins /* = 1 */,
                          int cost_rep /* = 1 */, int cost_del /* = 1 */) {
-  return string_levenshtein(str1, str1.size(), str2, str2.size(),
+  return string_levenshtein(str1.data(), str1.size(), str2.data(), str2.size(),
                             cost_ins, cost_rep, cost_del);
 }
+
 int64_t f_similar_text(CStrRef first, CStrRef second,
                        VRefParam percent /* = uninit_null() */) {
   float p;
-  int ret = string_similar_text(first, first.size(), second, second.size(),
-                                &p);
+  int ret = string_similar_text(first.data(), first.size(),
+                                second.data(), second.size(), &p);
   percent = p;
   return ret;
 }
+
 Variant f_soundex(CStrRef str) {
   if (str.empty()) return false;
-  return String(string_soundex(str), AttachString);
+  return String(string_soundex(str.c_str()), AttachString);
 }
+
 Variant f_metaphone(CStrRef str, int phones /* = 0 */) {
-  char *ret = string_metaphone(str, str.size(), 0, 1);
+  char *ret = string_metaphone(str.data(), str.size(), 0, 1);
   if (ret) {
     return String(ret, AttachString);
   }
@@ -848,6 +857,7 @@ String f_html_entity_decode(CStrRef str, int quote_style /* = k_ENT_COMPAT */,
   return StringUtil::HtmlDecode(str, (StringUtil::QuoteStyle)quote_style,
                                 scharset, true);
 }
+
 String f_htmlentities(CStrRef str, int quote_style /* = k_ENT_COMPAT */,
                       CStrRef charset /* = "ISO-8859-1" */,
                       bool double_encode /* = true */) {
@@ -901,7 +911,7 @@ int64_t f_crc32(CStrRef str) {
   return (uint32_t)StringUtil::CRC32(str);
 }
 String f_crypt(CStrRef str, CStrRef salt /* = "" */) {
-  return StringUtil::Crypt(str, salt);
+  return StringUtil::Crypt(str, salt.c_str());
 }
 String f_md5(CStrRef str, bool raw_output /* = false */) {
   return StringUtil::MD5(str, raw_output);
@@ -992,7 +1002,7 @@ Variant f_setlocale(int _argc, int category, CVarRef locale, CArrRef _argv /* =
       slocale = argv[i].toString();
     }
 
-    const char *loc = slocale;
+    const char *loc = slocale.c_str();
     if (slocale.size() >= 255) {
       throw_invalid_argument("locale name is too long: %s", loc);
       return false;
@@ -1082,8 +1092,8 @@ String f_nl_langinfo(int item) {
 }
 
 String f_convert_cyr_string(CStrRef str, CStrRef from, CStrRef to) {
-  char ch_from = ((const char *)from)[0];
-  char ch_to = ((const char *)to)[0];
+  char ch_from = from[0];
+  char ch_to = to[0];
   char *ret = string_convert_cyrillic_string(str.data(), str.size(),
                                              ch_from, ch_to);
   return String(ret, str.size(), AttachString);
diff --git a/hphp/runtime/ext/ext_xmlreader.cpp b/hphp/runtime/ext/ext_xmlreader.cpp
index 60e35e07a..cfa2c2a87 100644
--- a/hphp/runtime/ext/ext_xmlreader.cpp
+++ b/hphp/runtime/ext/ext_xmlreader.cpp
@@ -439,7 +439,7 @@ bool c_XMLReader::t_setschema(CStrRef source) {
   }
 
   if (m_ptr) {
-    int ret = xmlTextReaderSchemaValidate(m_ptr, source);
+    int ret = xmlTextReaderSchemaValidate(m_ptr, source.c_str());
     if (ret == 0) {
       return true;
     }
@@ -510,8 +510,8 @@ struct PropertyAccessor {
 
 class PropertyAccessorMap : private hphp_const_char_imap<PropertyAccessor*> {
 public:
-  PropertyAccessorMap(PropertyAccessor* props,
-                      PropertyAccessorMap *base = NULL) {
+  explicit PropertyAccessorMap(PropertyAccessor* props,
+                               PropertyAccessorMap *base = nullptr) {
     if (base) {
       *this = *base;
     }
@@ -554,7 +554,7 @@ static PropertyAccessorMap xmlreader_properties_map
 
 Variant c_XMLReader::t___get(Variant name) {
   const xmlChar *retchar = NULL;
-	int retint = 0;
+  int retint = 0;
 
   PropertyAccessor *propertyMap = xmlreader_properties_map.get(name);
   if (m_ptr) {
diff --git a/hphp/runtime/ext/pdo_sqlite.cpp b/hphp/runtime/ext/pdo_sqlite.cpp
index 28fea5777..bdbf1e3f3 100644
--- a/hphp/runtime/ext/pdo_sqlite.cpp
+++ b/hphp/runtime/ext/pdo_sqlite.cpp
@@ -120,8 +120,8 @@ PDOSqliteConnection::~PDOSqliteConnection() {
 }
 
 bool PDOSqliteConnection::create(CArrRef options) {
-  String filename = data_source.substr(0,1) == ":" ? data_source :
-    File::TranslatePath(data_source);
+  String filename = data_source.substr(0,1) == ":" ? String(data_source) :
+                    File::TranslatePath(data_source);
   if (filename.empty()) {
     throw_pdo_exception(0, Array(),
                         "safe_mode/open_basedir prohibits opening %s",
@@ -467,7 +467,8 @@ bool PDOSqliteStatement::paramHook(PDOBoundParam *param,
 
     if (param->is_param) {
       if (param->paramno == -1) {
-        param->paramno = sqlite3_bind_parameter_index(m_stmt, param->name) - 1;
+        param->paramno = sqlite3_bind_parameter_index(m_stmt,
+                                                      param->name.c_str()) - 1;
       }
 
       switch (PDO_PARAM_TYPE(param->param_type)) {
diff --git a/hphp/runtime/ext/soap/encoding.cpp b/hphp/runtime/ext/soap/encoding.cpp
index a5dc35d9f..dfe0e14a3 100644
--- a/hphp/runtime/ext/soap/encoding.cpp
+++ b/hphp/runtime/ext/soap/encoding.cpp
@@ -552,7 +552,7 @@ static xmlNodePtr master_to_xml_int(encodePtr encode, CVarRef data, int style,
 
     if (style == SOAP_ENCODED || (SOAP_GLOBAL(sdl) && encode != enc)) {
       if (!p->m_stype.empty()) {
-        set_ns_and_type_ex(node, p->m_ns, p->m_stype);
+        set_ns_and_type_ex(node, p->m_ns.c_str(), p->m_stype.c_str());
       }
     }
 
diff --git a/hphp/runtime/ext/thrift/binary.cpp b/hphp/runtime/ext/thrift/binary.cpp
index 6b5b0cb03..0615cb940 100644
--- a/hphp/runtime/ext/thrift/binary.cpp
+++ b/hphp/runtime/ext/thrift/binary.cpp
@@ -369,7 +369,7 @@ void binary_serialize(int8_t thrift_typeID, PHPOutputTransport& transport,
     case T_UTF16:
     case T_STRING: {
         String sv = value.toString();
-        transport.writeString(sv, sv.size());
+        transport.writeString(sv.data(), sv.size());
     } return;
     case T_MAP: {
       Array ht = value.toArray();
@@ -460,10 +460,10 @@ void f_thrift_protocol_write_binary(CObjRef transportobj, CStrRef method_name,
   if (strict_write) {
     int32_t version = VERSION_1 | msgtype;
     transport.writeI32(version);
-    transport.writeString(method_name, method_name.size());
+    transport.writeString(method_name.data(), method_name.size());
     transport.writeI32(seqid);
   } else {
-    transport.writeString(method_name, method_name.size());
+    transport.writeString(method_name.data(), method_name.size());
     transport.writeI8(msgtype);
     transport.writeI32(seqid);
   }
diff --git a/hphp/runtime/ext/thrift/compact.cpp b/hphp/runtime/ext/thrift/compact.cpp
index 6b3af3fd0..d900c0979 100644
--- a/hphp/runtime/ext/thrift/compact.cpp
+++ b/hphp/runtime/ext/thrift/compact.cpp
@@ -164,7 +164,7 @@ static void thrift_error(CStrRef what, TError why) {
 
 class CompactWriter {
   public:
-    CompactWriter(CObjRef _transportobj) :
+    explicit CompactWriter(CObjRef _transportobj) :
       transport(_transportobj),
       version(VERSION),
       state(STATE_CLEAR),
@@ -336,9 +336,9 @@ class CompactWriter {
         case T_UTF16:
         case T_STRING: {
             String s = value.toString();
-            uint32_t len = s.size();
-            writeVarint(len);
-            transport.write(s, len);
+            auto slice = s.slice();
+            writeVarint(slice.len);
+            transport.write(slice.ptr, slice.len);
             break;
           }
 
@@ -458,9 +458,9 @@ class CompactWriter {
     }
 
     void writeString(CStrRef s) {
-      uint32_t len = s.size();
-      writeVarint(len);
-      transport.write(s, len);
+      auto slice = s.slice();
+      writeVarint(slice.len);
+      transport.write(slice.ptr, slice.len);
     }
 
     uint64_t i64ToZigzag(int64_t n) {
@@ -470,7 +470,7 @@ class CompactWriter {
 
 class CompactReader {
   public:
-    CompactReader(CObjRef _transportobj) :
+    explicit CompactReader(CObjRef _transportobj) :
       transport(_transportobj),
       version(VERSION),
       state(STATE_CLEAR),
diff --git a/hphp/test/test_cpp_base.cpp b/hphp/test/test_cpp_base.cpp
index cbd8ab9d1..9a9a93872 100644
--- a/hphp/test/test_cpp_base.cpp
+++ b/hphp/test/test_cpp_base.cpp
@@ -53,7 +53,7 @@ bool TestCppBase::RunTests(const std::string &which) {
 
 class Timer {
 public:
-  Timer(const char *name = nullptr) {
+  explicit Timer(const char *name = nullptr) {
     if (name) m_name = name;
     gettimeofday(&m_start, 0);
   }
@@ -126,13 +126,13 @@ bool TestCppBase::TestSmartAllocator() {
 bool TestCppBase::TestString() {
   // constructors
   {
-    VS((const char *)String(15), "15");
-    VS((const char *)String(-15), "-15");
-    VS((const char *)String(int64_t(12345678912345678LL)), "12345678912345678");
-    VS((const char *)String(int64_t(-12345678912345678LL)), "-12345678912345678");
-    VS((const char *)String(5.603), "5.603");
-    VS((const char *)String("test"), "test");
-    VS((const char *)String(String("test")), "test");
+    VS(String(15).c_str(), "15");
+    VS(String(-15).c_str(), "-15");
+    VS(String(int64_t(12345678912345678LL)).c_str(), "12345678912345678");
+    VS(String(int64_t(-12345678912345678LL)).c_str(), "-12345678912345678");
+    VS(String(5.603).c_str(), "5.603");
+    VS(String("test").c_str(), "test");
+    VS(String(String("test")).c_str(), "test");
   }
 
   // informational
@@ -163,27 +163,27 @@ bool TestCppBase::TestString() {
   // operators
   {
     String s;
-    s = "test1";                   VS((const char *)s, "test1");
-    s = String("test2");           VS((const char *)s, "test2");
-    s = Variant("test3");          VS((const char *)s, "test3");
-    s = String("a") + "b";         VS((const char *)s, "ab");
-    s = String("c") + String("d"); VS((const char *)s, "cd");
-    s += "efg";                    VS((const char *)s, "cdefg");
-    s += String("hij");            VS((const char *)s, "cdefghij");
+    s = "test1";                   VS(s.c_str(), "test1");
+    s = String("test2");           VS(s.c_str(), "test2");
+    s = Variant("test3");          VS(s.c_str(), "test3");
+    s = String("a") + "b";         VS(s.c_str(), "ab");
+    s = String("c") + String("d"); VS(s.c_str(), "cd");
+    s += "efg";                    VS(s.c_str(), "cdefg");
+    s += String("hij");            VS(s.c_str(), "cdefghij");
 
-    s = String("\x50\x51") | "\x51\x51"; VS((const char *)s, "\x51\x51");
-    s = String("\x50\x51") & "\x51\x51"; VS((const char *)s, "\x50\x51");
-    s = String("\x50\x51") ^ "\x51\x51"; VS((const char *)s, "\x01");
-    s = "\x50\x51"; s |= "\x51\x51";     VS((const char *)s, "\x51\x51");
-    s = "\x50\x51"; s &= "\x51\x51";     VS((const char *)s, "\x50\x51");
-    s = "\x50\x51"; s ^= "\x51\x51";     VS((const char *)s, "\x01");
-    s = "\x50\x51"; s = ~s;              VS((const char *)s, "\xAF\xAE");
+    s = String("\x50\x51") | "\x51\x51"; VS(s.c_str(), "\x51\x51");
+    s = String("\x50\x51") & "\x51\x51"; VS(s.c_str(), "\x50\x51");
+    s = String("\x50\x51") ^ "\x51\x51"; VS(s.c_str(), "\x01");
+    s = "\x50\x51"; s |= "\x51\x51";     VS(s.c_str(), "\x51\x51");
+    s = "\x50\x51"; s &= "\x51\x51";     VS(s.c_str(), "\x50\x51");
+    s = "\x50\x51"; s ^= "\x51\x51";     VS(s.c_str(), "\x01");
+    s = "\x50\x51"; s = ~s;              VS(s.c_str(), "\xAF\xAE");
   }
 
   // manipulations
   {
     String s = StringUtil::ToLower("Test");
-    VS((const char *)s, "test");
+    VS(s.c_str(), "test");
   }
 
   // conversions
@@ -199,7 +199,7 @@ bool TestCppBase::TestString() {
 
   // offset
   {
-    VS((const char *)String("test").rvalAt(2), "s");
+    VS(String("test").rvalAt(2).c_str(), "s");
     String s = "test";
     s.lvalAt(2) = "";
     VS(s, String("te\0t", 4, AttachLiteral));
diff --git a/hphp/test/test_debugger.cpp b/hphp/test/test_debugger.cpp
index 6ef18991d..92f45feb3 100644
--- a/hphp/test/test_debugger.cpp
+++ b/hphp/test/test_debugger.cpp
@@ -93,7 +93,7 @@ bool TestDebugger::getResponse(const string& path, string& result,
     printf("  Request failed\n");
     return false;
   }
-  result = res.toString();
+  result = (std::string) res.toString();
   printf("  Request succeeded, returning '%s'\n", result.c_str());
   return true;
 }
diff --git a/hphp/test/test_ext_curl.cpp b/hphp/test/test_ext_curl.cpp
index e398be574..a16d5d4c4 100644
--- a/hphp/test/test_ext_curl.cpp
+++ b/hphp/test/test_ext_curl.cpp
@@ -36,7 +36,7 @@ public:
       const void *data = transport->getPostData(len);
       String res = "POST: ";
       res += String((char*)data, len, CopyString);
-      transport->sendString(res);
+      transport->sendString(res.c_str());
     } else {
       transport->sendString("OK");
     }
diff --git a/hphp/test/test_ext_icu.cpp b/hphp/test/test_ext_icu.cpp
index 2f23f2eca..b956a1d55 100644
--- a/hphp/test/test_ext_icu.cpp
+++ b/hphp/test/test_ext_icu.cpp
@@ -174,7 +174,7 @@ bool TestExtIcu::test_icu_transliterate() {
   VERIFY(output_de == "Ich mochte uberzeugend oder ahnliche sein");
 
   // Verify that keeping accents works.
-  VERIFY(f_icu_transliterate(input_de, false) == (const char*)input_de);
+  VERIFY(f_icu_transliterate(input_de, false) == input_de.c_str());
 
   // Check an non-Latin language.
   String input_zh = String("\xe5\x9b\x9b"
diff --git a/hphp/test/test_server.cpp b/hphp/test/test_server.cpp
index 7eebb22d8..cf6280588 100644
--- a/hphp/test/test_server.cpp
+++ b/hphp/test/test_server.cpp
@@ -98,7 +98,7 @@ bool TestServer::VerifyServerResponse(const char *input, const char **outputs,
 
       Variant res = f_curl_exec(c);
       if (!same(res, false)) {
-        actual = res.toString();
+        actual = (std::string) res.toString();
         break;
       }
       sleep(1); // wait until HTTP server is up and running