Issue 5610 - Deal with a '/' base path

src/DefaultFileSystem.cpp

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 53 matching lines @@
   std::string NormalizePath(const std::string& path)
   {
     return path;
   }
 #endif
 }
 
 DefaultFileSystemSync::DefaultFileSystemSync(const std::string& path)
   : basePath(path)
 {
-  if (!basePath.empty() && *basePath.rbegin() == PATH_SEPARATOR)
+  if (basePath.size() > 1 && *basePath.rbegin() == PATH_SEPARATOR)
   {
     basePath.resize(basePath.size() - 1);
   }
 }
 
 IFileSystem::IOBuffer
 DefaultFileSystemSync::Read(const std::string& path) const
 {
   std::ifstream file(NormalizePath(path).c_str(), std::ios_base::binary);
   if (file.fail())
@@ skipping 91 matching lines @@
     return path;
   }
   else
   {
 #ifdef _WIN32
   if (PathIsRelative(NormalizePath(path).c_str()))
 #else
   if (path.length() && *path.begin() != PATH_SEPARATOR)
 #endif
     {
-      return basePath + PATH_SEPARATOR + path;
+      if (*basePath.rbegin() != PATH_SEPARATOR)
+        return basePath + PATH_SEPARATOR + path;
+      else
+        return basePath + path;
     }
     else
     {
       return path;
     }
   }
 }
 
 DefaultFileSystem::DefaultFileSystem(const Scheduler& scheduler, std::unique_ptr<DefaultFileSystemSync> syncImpl)
   : scheduler(scheduler), syncImpl(std::move(syncImpl))
@@ skipping 113 matching lines @@
       error = "Unknown error while calling stat on " + fileName + " as " + Resolve(fileName);
     }
     callback(StatResult(), error);
   });
 }
 
 std::string DefaultFileSystem::Resolve(const std::string& fileName) const
 {
   return syncImpl->Resolve(fileName);
 }