Issue 5216 - [emscripten] Use a more reliable way of retrieving mangled function name

compiled/bindings/generator.cpp

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2017 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 39 matching lines @@
     for (const auto& method : methods)
       if (!instanceOnly || method.call.instance_function)
         printf("%s: %s,\n", method.name.c_str(), wrapCall(method.call).c_str());
   }
 }
 
 namespace bindings_internal
 {
   FunctionInfo::FunctionInfo()
   {
-    name[0] = '\0';
   }
 
   FunctionInfo::FunctionInfo(TypeCategory returnType, TYPEID pointerType,
       std::initializer_list<TypeCategory> argTypes, bool instance_function,
       void* function)
       : returnType(returnType), pointerType(pointerType),
         instance_function(instance_function)
   {
-    name[0] = '\0';
-
     // The function parameter is a pointer to the function pointer.
     // Emscripten's "function pointers" are actually integers indicating the
     // position in the call table. 0 represents nullptr.
     if (!*reinterpret_cast<int*>(function))
       return;
 
     std::string signature;
 
     // Add return type to the signature. Similar logic in Emscripten:
     // https://github.com/kripken/emscripten/blob/1.37.3/src/modules.js#L46
@@ skipping 52 matching lines @@
           break;
         case TypeCategory::DOUBLE:
           signature += 'd';
           break;
         default:
           throw std::runtime_error("Unexpected function argument type");
       }
       args.push_back(type);
     }
 
-    GetFunctionName(name, function, signature.c_str());
+    int nameLength = GetFunctionName(nullptr, function, signature.c_str());
+    name.resize(nameLength);
+    GetFunctionName(name.data(), function, signature.c_str());
   }
 
   bool FunctionInfo::empty() const
   {
-    return name[0] == '\0';
+    return name.empty();
   }
 
   ClassInfo* find_class(TYPEID classID)
   {
     for (auto& classInfo : classes)
       if (classInfo.id == classID)
         return &classInfo;
     return nullptr;
   }
 
@@ skipping 151 matching lines @@
         return "  var result = readString(" + call_str + ");\n";
       case TypeCategory::CLASS_PTR:
       {
         std::string result;
         result += "  var result = " + call_str + ";\n";
         result += "  if (result)\n";
         result += "  {\n";
 
         const ClassInfo* cls = find_class(call.pointerType);
         if (!cls)
-          throw std::runtime_error("Function " + std::string(call.name) + " returns pointer to unknown class");
+          throw std::runtime_error("Function " + call.name + " returns pointer to unknown class");
 
         auto offset = cls->subclass_differentiator.offset;
         if (offset == SIZE_MAX)
           result += "    result = exports." + cls->name + "(result);\n";
         else
           result += "    result = exports." + cls->name + ".fromPointer(result);\n";
 
         result += "  }\n";
         result += "  else\n";
         result += "    result = null;\n";
         return result;
       }
       default:
-        throw std::runtime_error("Unexpected return type for " + std::string(call.name));
+        throw std::runtime_error("Unexpected return type for " + call.name);
     }
   }
 
   std::string wrapCall(const FunctionInfo& call, bool isFunction)
   {
     bool hasStringArgs = false;
     std::vector<std::string> params;
     std::string prefix;
 
     if (isFunction)
@@ skipping 155 matching lines @@
 
 void printBindings()
 {
   bindings_internal::printHelpers();
 
   for (const auto& item : classes)
     bindings_internal::printClass(item);
   for (const auto& item : namespaces)
     bindings_internal::printNamespace(item);
 }