Cleanup: remove some unneeded c_str() calls

src/game/game_text.cpp

@@ -231,7 +231,7 @@ GameStrings *LoadTranslations()
 	basename.erase(e + 1);
 
 	std::string filename = basename + "lang" PATHSEP "english.txt";
-	if (!FioCheckFileExists(filename.c_str() , GAME_DIR)) return nullptr;
+	if (!FioCheckFileExists(filename, GAME_DIR)) return nullptr;
 
 	auto ls = ReadRawLanguageStrings(filename);
 	if (!ls.IsValid()) return nullptr;

src/script/script_scanner.cpp

@@ -182,7 +182,7 @@ struct ScriptFileChecksumCreator : FileScanner {
 		byte tmp_md5sum[16];
 
 		/* Open the file ... */
-		FILE *f = FioFOpenFile(filename.c_str(), "rb", this->dir, &size);
+		FILE *f = FioFOpenFile(filename, "rb", this->dir, &size);
 		if (f == nullptr) return false;
 
 		/* ... calculate md5sum... */

src/settings.cpp

@@ -708,7 +708,7 @@ static void IniSaveSettingList(IniFile *ini, const char *grpname, StringList &li
 	group->Clear();
 
 	for (const auto &iter : list) {
-		group->GetItem(iter.c_str(), true)->SetValue("");
+		group->GetItem(iter, true)->SetValue("");
 	}
 }
 
@@ -1272,7 +1272,7 @@ static void AILoadConfig(IniFile *ini, const char *grpname)
 				continue;
 			}
 		}
-		if (item->value.has_value()) config->StringToSettings(item->value->c_str());
+		if (item->value.has_value()) config->StringToSettings(*item->value);
 	}
 }
 
@@ -1299,7 +1299,7 @@ static void GameLoadConfig(IniFile *ini, const char *grpname)
 			return;
 		}
 	}
-	if (item->value.has_value()) config->StringToSettings(item->value->c_str());
+	if (item->value.has_value()) config->StringToSettings(*item->value);
 }
 
 /**

src/vehicle_cmd.cpp

@@ -804,7 +804,7 @@ static void CloneVehicleName(const Vehicle *src, Vehicle *dst)
 
 		/* Check the name is unique. */
 		auto new_name = oss.str();
-		if (IsUniqueVehicleName(new_name.c_str())) {
+		if (IsUniqueVehicleName(new_name)) {
 			dst->name = new_name;
 			break;
 		}