从不兼容的类型分配给 DWORD nullptr_t

Question

尽管阅读了几个互联网和论坛 questions/answers 我还不明白为什么以下代码会生成“来自不兼容指针类型的赋值”错误。

void ITEM_MANAGER::FindItemMonster(LPCHARACTER ch, std::string name_item){
    DWORD iGasite = 1;
    int iIndex = 0;
    itertype(m_map_pkDropItemGroup) it;

    for (std::map<DWORD, CDropItemGroup*>::iterator it = m_map_pkDropItemGroup.begin(); it != m_map_pkDropItemGroup.end(); it++)
    {
        if (it != m_map_pkDropItemGroup.end())
        {
            __typeof(it->second->GetVector()) v = it->second->GetVector();

            for (DWORD i = 0; i < v.size(); ++i)
            {
                TItemTable* Titem = ITEM_MANAGER::instance().GetTable(v[i].dwVnum);
                bool nume = (name_item.length() ? strstr(Titem->szLocaleName, name_item.c_str()) != NULL : true);
                const CMob* pMob = CMobManager::instance().Get(it->first);
                std::string name_monster(pMob->m_table.szLocaleName);
                if (nume)
                {
                    DWORD mob_vnum = pMob->m_table.dwVnum;
                    int iFounded = SECTREE_MANAGER::instance().GetMonsterCountSpawned(mob_vnum);
                    std::string nume_item(Titem->szLocaleName);
                    boost::algorithm::replace_all(nume_item, " ", "_");
                    std::string nume_mob(name_monster.c_str());
                    boost::algorithm::replace_all(nume_mob, " ", "_");
                    ch->ChatPacket(CHAT_TYPE_COMMAND, "searched_item %d %s %s %d %d %d %d %d", iIndex, nume_item.c_str(), nume_mob.c_str(), v[i].dwVnum, v[i].iCount, v[i].iProcent, iFounded, mob_vnum);
                    iIndex = iIndex + 1;
                    iGasite = iGasite + 1;

                }

            }
        }
    }

    ch->ChatPacket(CHAT_TYPE_COMMAND, "searched_item_count %d", iGasite);

    iGasite = iGasite = NULL;
    iIndex = iIndex = NULL;
}

编译器错误：

item_manager.cpp:1136:22: error: assigning to 'DWORD' (aka 'unsigned int') from incompatible type 
  'nullptr_t'
    iGasite = iGasite = NULL;
                        ^~~~
/usr/include/sys/_null.h:35:14: note: expanded from macro 'NULL'
#define NULL    nullptr
            ^~~~~~~
item_manager.cpp:1137:20: error: assigning to 'int' from incompatible type 'nullptr_t'
    iIndex = iIndex = NULL;
                      ^~~~
/usr/include/sys/_null.h:35:14: note: expanded from macro 'NULL'
#define NULL    nullptr
            ^~~~~~~
2 errors generated.

Answer 1

您正在使用 NULL 作为零的常量，而它被定义为：

// in /usr/include/sys/_null.h:35:14
#define NULL nullptr

从 C++11 开始，这是标准定义。

nullptr的类型是std::nullptr_t，不是整数，所以不能赋值给DWORD iGasite，unsigned int.

简单地删除所有使用 NULL 的地方，并适当地用 0 或 nullptr 替换它。

从不兼容的类型分配给 DWORD nullptr_t

Assigning to DWORD from incompatible type nullptr_t

c++

type-conversion

nullptr