Fix string_view C++17 compatibility

string_view was implicitly convertible to std::string, but
std::string_view is only explicitly convertible.  This makes the
`operator std::string` explicit to be more compatible, and re-adds a
bunch of explicit string casts to the code where needed.

(This also fixes the build if changing the standard to c++17)

llarp/config/config.cpp

@@ -106,14 +106,14 @@ namespace llarp
     }
     if(key == "default-protocol")
     {
-      m_DefaultLinkProto = val;
+      m_DefaultLinkProto = str(val);
       LogInfo("overriding default link protocol to '", val, "'");
     }
     if(key == "netid")
     {
       if(val.size() <= NetID::size())
       {
-        m_netId = val;
+        m_netId = str(val);
         LogInfo("setting netid to '", val, "'");
       }
       else
@@ -141,29 +141,29 @@ namespace llarp
     }
     if(key == "nickname")
     {
-      m_nickname = val;
+      m_nickname = str(val);
       // set logger name here
       LogContext::Instance().nodeName = nickname();
       LogInfo("nickname set");
     }
     if(key == "encryption-privkey")
     {
-      m_encryptionKeyfile = val;
+      m_encryptionKeyfile = str(val);
       LogDebug("encryption key set to ", m_encryptionKeyfile);
     }
     if(key == "contact-file")
     {
-      m_ourRcFile = val;
+      m_ourRcFile = str(val);
       LogDebug("rc file set to ", m_ourRcFile);
     }
     if(key == "transport-privkey")
     {
-      m_transportKeyfile = val;
+      m_transportKeyfile = str(val);
       LogDebug("transport key set to ", m_transportKeyfile);
     }
     if((key == "identity-privkey" || key == "ident-privkey"))
     {
-      m_identKeyfile = val;
+      m_identKeyfile = str(val);
       LogDebug("identity key set to ", m_identKeyfile);
     }
     if(key == "public-address" || key == "public-ip")
@@ -229,12 +229,12 @@ namespace llarp
     }
     else if(key == "profiles")
     {
-      m_routerProfilesFile = val;
+      m_routerProfilesFile = str(val);
       llarp::LogInfo("setting profiles to ", routerProfilesFile());
     }
     else if(key == "strict-connect")
     {
-      m_strictConnect = val;
+      m_strictConnect = str(val);
     }
     else
     {
@@ -247,7 +247,7 @@ namespace llarp
   {
     if(key == "dir")
     {
-      m_nodedbDir = val;
+      m_nodedbDir = str(val);
     }
   }
 
@@ -279,12 +279,12 @@ namespace llarp
       idx = val.find_first_of(delimiter);
       if(idx != string_view::npos)
       {
-        parsed_opts.insert(TrimWhitespace(val.substr(0, idx)));
+        parsed_opts.emplace(TrimWhitespace(val.substr(0, idx)));
         val.remove_prefix(idx + 1);
       }
       else
       {
-        parsed_opts.insert(TrimWhitespace(val));
+        parsed_opts.emplace(TrimWhitespace(val));
       }
     } while(idx != string_view::npos);
     std::unordered_set< std::string > opts;
@@ -335,7 +335,7 @@ namespace llarp
   {
     if(key == "pidfile")
     {
-      pidfile = val;
+      pidfile = str(val);
     }
   }
 
@@ -348,7 +348,7 @@ namespace llarp
     }
     if(key == "bind")
     {
-      m_rpcBindAddr = val;
+      m_rpcBindAddr = str(val);
     }
     if(key == "authkey")
     {
@@ -370,15 +370,15 @@ namespace llarp
     }
     if(key == "jsonrpc" || key == "addr")
     {
-      lokidRPCAddr = val;
+      lokidRPCAddr = str(val);
     }
     if(key == "username")
     {
-      lokidRPCUser = val;
+      lokidRPCUser = str(val);
     }
     if(key == "password")
     {
-      lokidRPCPassword = val;
+      lokidRPCPassword = str(val);
     }
   }
 
@@ -406,7 +406,7 @@ namespace llarp
     }
     if(key == "level")
     {
-      const auto maybe = LogLevelFromString(val);
+      const auto maybe = LogLevelFromString(str(val));
       if(not maybe.has_value())
       {
         LogError("bad log level: ", val);
@@ -423,7 +423,7 @@ namespace llarp
     if(key == "file")
     {
       LogInfo("open log file: ", val);
-      std::string fname   = val;
+      std::string fname{val};
       FILE *const logfile = ::fopen(fname.c_str(), "a");
       if(logfile)
       {

llarp/config/ini.cpp

@@ -129,7 +129,7 @@ namespace llarp
           LogError(m_FileName, " invalid line (", lineno, "): '", line, "'");
           return false;
         }
-        Section_t& sect = m_Config[sectName];
+        Section_t& sect = m_Config[str(sectName)];
         LogDebug(m_FileName, ": ", sectName, ".", k, "=", v);
         sect.emplace(k, v);
       }

llarp/handlers/tun.cpp

@@ -191,7 +191,7 @@ namespace llarp
         {
           routerStr = v;
         }
-        routerStr = TrimWhitespace(routerStr);
+        routerStr = str(TrimWhitespace(routerStr));
         if(!(exitRouter.FromString(routerStr)
              || HexDecode(routerStr.c_str(), exitRouter.begin(),
                           exitRouter.size())))

llarp/util/string_view.hpp

@@ -53,7 +53,7 @@ public:
     constexpr size_t length() const noexcept { return size_; }
     constexpr size_t max_size() const noexcept { return std::numeric_limits<size_t>::max(); }
     constexpr bool empty() const noexcept { return size_ == 0; }
-    operator std::string() const { return {data_, size_}; }
+    explicit operator std::string() const { return {data_, size_}; }
     constexpr const char* begin() const noexcept { return data_; }
     constexpr const char* cbegin() const noexcept { return data_; }
     constexpr const char* end() const noexcept { return data_ + size_; }
@@ -218,4 +218,14 @@ using string_view = simple_string_view;
 
 #endif
 
+namespace llarp {
+
+// Shortcut for explicitly casting a string_view to a string.  Saves 8
+// characters compared to `std::string(view)`.
+inline std::string str(string_view s) {
+    return std::string{s};
+}
+
+}
+
 #endif

test/config/test_llarp_config_ini.cpp

@@ -32,11 +32,7 @@ TEST_F(TestINIParser, TestParseOneSection)
   ASSERT_EQ(itr, sect.end());
   itr = sect.find("key");
   ASSERT_NE(itr, sect.end());
-#if __cplusplus >= 201703L
-  ASSERT_STREQ(llarp::string_view_string(itr->second).c_str(), "val");
-#else
   ASSERT_EQ(itr->second, "val");
-#endif
 }
 
 TEST_F(TestINIParser, TestParseSectionDuplicateKeys)

test/util/test_llarp_util_str.cpp

@@ -11,7 +11,7 @@ TEST_CASE("TrimWhitespace -- positive tests", "[str][trim]")
   auto fo = "\fthe   "s;
   auto fum = " \t\r\n\v\f Beanstalk\n\n\n\t\r\f\v   \n\n\r\f\f\f\f\v"s;
   for (auto* s: {&fee, &fi, &fo, &fum})
-    *s = llarp::TrimWhitespace(*s);
+    *s = llarp::str(llarp::TrimWhitespace(*s));
 
   REQUIRE( fee == "J a c k" );
   REQUIRE( fi == "a\nd" );
@@ -24,7 +24,7 @@ TEST_CASE("TrimWhitespace -- negative tests", "[str][trim]")
   // Test that things that shouldn't be trimmed don't get trimmed
   auto c = GENERATE(range(std::numeric_limits<char>::min(), std::numeric_limits<char>::max()));
   std::string plant = c + "bean"s + c;
-  plant = llarp::TrimWhitespace(plant);
+  plant = llarp::str(llarp::TrimWhitespace(plant));
   if (c == ' ' || c == '\t' || c == '\r' || c == '\n' || c == '\f' || c == '\v')
     REQUIRE( plant == "bean" );
   else