c++ - 为什么C++模板实例化失败？

在Linux / x86-64 (在Debian / Sid系统上)的 RefPerSys GPLv3 +项目中，git commit 37172c9af257865d，使用GCC 10编译，被调用为g++ -std=gnu++17 -Og -g3 -Wall -Wextra等...，我得到以下错误消息:

  refpersys.hh: In instantiation of ‘PaylClass* Rps_ObjectZone::put_new_arg3_payload(Arg1Class, Arg2Class, Arg3Class) [with PaylClass = Rps_PayloadWebex; Arg1Class = long unsigned int; Arg2Class = Onion::Request*; Arg3Class = Onion::Response*]’:
  httpweb_rps.cc:314:71:   required from here
  refpersys.hh:2162:76: error: no matching function for call to ‘Rps_ObjectZone::rps_allocate4<Rps_PayloadWebex, long unsigned int, Onion::Request*, Onion::Response*>(Rps_ObjectZone*, long unsigned int&, Onion::Request*&, Onion::Response*&)’
   2162 | Zone::rps_allocate4<PaylClass,Arg1Class,Arg2Class,Arg3Class>(this,arg1,arg2,arg3);
        | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~

  In file included from headweb_rps.hh:37,
                   from httpweb_rps.cc:34:
  refpersys.hh:1701:3: note: candidate: ‘template<class ZoneClass, class Arg1Class, class Arg2Class, class Arg3Class, class Arg4Class> static ZoneClass* Rps_QuasiZone::rps_allocate4(Arg1Class, Arg2Class, Arg3Class, Arg4Class)’
   1701 |   rps_allocate4(Arg1Class arg1, Arg2Class arg2, Arg3Class arg3, Arg4Class arg4)
        |   ^~~~~~~~~~~~~
  refpersys.hh:1701:3: note:   template argument deduction/substitution failed:
  In file included from headweb_rps.hh:37,
                   from httpweb_rps.cc:34:
  refpersys.hh:2162:76: note:   cannot convert ‘(Rps_ObjectZone*)this’ (type ‘Rps_ObjectZone*’) to type ‘long unsigned int’
   2162 | Zone::rps_allocate4<PaylClass,Arg1Class,Arg2Class,Arg3Class>(this,arg1,arg2,arg3);
        | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~

我不容易举一个小例子，但是我可以给出以下解释。它是关于通过多线程实现(和Web界面，以及我们的精确跟踪垃圾收集器)实现某种动态类型的语言(规则之类的专家系统，受Common Lisp启发)。
主头文件是 refpersys.hh ，到处都是#include d。伴随 header 文件 headweb_rps.hh 仅与使用libonion的Web相关代码相关，tagged union是一些HTTP服务器库(具有 namespace Onion::)，并且#include包含refpersys.hh header 。
在C++的意义上，不使用多重继承。
我们有一个枚举Rps_Type(在文件refpersys.hh行903中)定义了某种SBCL类型的标签。标记的联合类型是顶级类Rps_TypedZone(在refpersys.hh行1630中)，在Rps_TypedZone::Rps_TypedZone(const Rps_Type ty)第1637行中定义了一个明显的构造函数refpersys.hh。
我们有一个class Rps_QuasiZone的Rps_TypedZone子类(在refpersys.hh行1646中)。
我们有一个class Rps_ZoneValue的refpersys.hh:1755(在Rps_QuasiZone中)子类。class Rps_ObjectZone(在refpersys.hh:1964中)是Rps_ZoneValue的子类。让我们将RefPerSys对象称为Rps_ObjectZone的子类的任何C++实例。class Rps_ObjectRef(在refpersys.hh:694中)是我们通过GC编写的指向Rps_ObjectZone的智能指针。class Rps_Value(在refpersys.hh:967中)是一个单字智能指针(有点像Common Lisp中的ojit_a -value一样)。class Rps_Payload(在refpersys.hh:2264中)在Rps_ObjectZone内部携带一些可选的额外数据。每个此类有效负载都属于一个称为其所有者的RefPerSys对象(某些Rps_ObjectZone)。put_new_arg3_payload的Rps_ObjectZone模板成员函数很简单(在refpersys.hh:2157和以下几行中)，ob_payload是Rps_ObjectZone的成员字段，在std::atomic<Rps_Payload*> ob_payload;行中声明为refpersys.hh:1981:

  PaylClass* put_new_arg3_payload(Arg1Class arg1, Arg2Class arg2, Arg3Class arg3)
  {
    std::lock_guard<std::recursive_mutex> gu(ob_mtx);
    PaylClass*newpayl =
      Rps_QuasiZone::rps_allocate4<PaylClass,Arg1Class,Arg2Class,Arg3Class>(this,arg1,arg2,arg3);
    Rps_Payload*oldpayl = ob_payload.exchange(newpayl);
    if (oldpayl)
      delete oldpayl;
    return newpayl;
  };                // end put_new_arg3_payload

许多Web交互(在C++中为HTTP请求，为Onion::Request，而在HTTP中为相应的HTTP答复，为C++一些Onion::Reply，其本身为C++ std::ostream的子类)被重新定义为class Rps_PayloadWebex在文件headweb_rps.hh第65行声明的C++实例，并且是Rps_Payload。
模板成员函数Rps_QuasiZone::rps_allocate4定义为(在refpersys.hh:1699行):

template <typename ZoneClass, typename Arg1Class, typename Arg2Class, typename Arg3Class, typename Arg4Class>
static ZoneClass*
rps_allocate4(Arg1Class arg1, Arg2Class arg2, Arg3Class arg3, Arg4Class arg4)
{
  return new(nullptr) ZoneClass(arg1, arg2, arg3, arg4);
};

我们的“解释器”的调用框架被重新编码为class Rps_ProtoCallFrame;，并且我们在refpersys.hh第691行中有一个typedef Rps_ProtoCallFrame Rps_CallFrame;class Rps_ProtoCallFrame是Rps_TypedZone中定义的refpersys.hh:2823的子类。
错误的行httpweb_rps.cc:314在里面:

 Rps_ObjectRef
 Rps_PayloadWebex::make_obwebex(Rps_CallFrame*callerframe, Onion::Request*req, Onion::Response*resp,
                                uint64_t reqnum)
 {
   RPS_ASSERT(callerframe != nullptr && callerframe->is_good_call_frame());
   RPS_ASSERT(req != nullptr);
   RPS_ASSERT(resp != nullptr);
   auto web_exchange_ob = RPS_ROOT_OB(_8zNtuRpzXUP013WG9S);
   RPS_DEBUG_LOG(WEB, "Rps_PayloadWebex::make_obwebex start reqnum#" << reqnum
                );
   RPS_LOCALFRAME(/*descr:*/ web_exchange_ob,
                             /*prev:*/callerframe,
                             /*locals:*/
                             Rps_ObjectRef obwebex);
   _f.obwebex = Rps_ObjectRef::make_object(&_, web_exchange_ob);
   auto paylwebex = ////////////////////////////////////// FAULTY LINE BELOW
     _f.obwebex->put_new_arg3_payload<Rps_PayloadWebex>(reqnum,req,resp);
   RPS_DEBUG_LOG(WEB, "Rps_PayloadWebex::make_obwebex end reqnum#" << reqnum
                 << " obwebex=" << _f.obwebex << " startim:" <<  paylwebex->webex_startim);
   RPS_ASSERT(paylwebex != nullptr);
   return _f.obwebex;
 } // end PayloadWebex::make_obwebex

在上面的代码中，RPS_ASSERT，RPS_ROOT_OB，RPS_LOCALFRAME，RPS_DEBUG_LOG是C++宏。上面的代码的宏扩展是:

Rps_ObjectRef
Rps_PayloadWebex::make_obwebex(Rps_CallFrame*callerframe, Onion::Request*req, Onion::Response*resp,
                               uint64_t reqnum)
{
  do { if (__builtin_expect(!!(!((callerframe != nullptr
                                  && callerframe->is_good_call_frame()))),0))
      { fprintf(
                //# 302 "httpweb_rps.cc" 3
                stderr
                //# 302 "httpweb_rps.cc"
                , "\n\n" "%s*** RefPerSys ASSERT failed: %s%s\n" "%s:%d: {%s}\n\n", (rps_stderr_istty?(rps_without_terminal_escape?"":"\033[1m"):""),
                "(callerframe != nullptr && callerframe->is_good_call_frame())",
                (rps_stderr_istty?(rps_without_terminal_escape?"":"\033[0m"):""),
                "httpweb_rps.cc",302,__PRETTY_FUNCTION__);
        rps_fatal_stop_at("httpweb_rps.cc",302); }}
  while(0);
  do
    { if (__builtin_expect(!!(!((req != nullptr))),0)) {
        fprintf(
                //# 303 "httpweb_rps.cc" 3
                stderr
                //# 303 "httpweb_rps.cc"
                , "\n\n" "%s*** RefPerSys ASSERT failed: %s%s\n" "%s:%d: {%s}\n\n",
                (rps_stderr_istty?(rps_without_terminal_escape?"":"\033[1m"):""), "(req != nullptr)",
                (rps_stderr_istty?(rps_without_terminal_escape?"":"\033[0m"):""), "httpweb_rps.cc",303,__PRETTY_FUNCTION__);
        rps_fatal_stop_at("httpweb_rps.cc",303); }} while(0);
  do { if (__builtin_expect(!!(!((resp != nullptr))),0)) {
      fprintf(
              //# 304 "httpweb_rps.cc" 3
              stderr
              //# 304 "httpweb_rps.cc"
              , "\n\n" "%s*** RefPerSys ASSERT failed: %s%s\n" "%s:%d: {%s}\n\n",
              (rps_stderr_istty?(rps_without_terminal_escape?"":"\033[1m"):""), "(resp != nullptr)",
              (rps_stderr_istty?(rps_without_terminal_escape?"":"\033[0m"):""), "httpweb_rps.cc",304,__PRETTY_FUNCTION__);
      rps_fatal_stop_at("httpweb_rps.cc",304); }} while(0);
  auto web_exchange_ob = rps_rootob_8zNtuRpzXUP013WG9S;
  do { if ((rps_debug_flags & (1 << RPS_DEBUG_WEB)))
      { std::ostringstream _logstream_306;
        _logstream_306 << "Rps_PayloadWebex::make_obwebex start reqnum#" << reqnum << std::flush;
        rps_debug_printf_at("httpweb_rps.cc", 306, RPS_DEBUG_WEB,
                            "%s", _logstream_306.str().c_str()); } } while (0)
    ;
  struct RpsFrameData308 {/*locals:*/ Rps_ObjectRef obwebex; };
  typedef Rps_FieldedCallFrame<RpsFrameData308> Rps_FldCallFrame308;
  class Rps_FrameAt308 : public Rps_FldCallFrame308
  { public:
    Rps_FrameAt308(Rps_ObjectRef obd308, Rps_CallFrame* prev308) :
      Rps_FldCallFrame308(obd308, prev308) { }; };
  Rps_FrameAt308 _((/*descr:*/ web_exchange_ob),(/*prev:*/callerframe));
  auto& _f = *_.fieldsptr();


  ;
  _f.obwebex = Rps_ObjectRef::make_object(&_, web_exchange_ob);
  auto paylwebex =
    _f.obwebex->put_new_arg3_payload<Rps_PayloadWebex>(reqnum,req,resp);
  do { if ((rps_debug_flags & (1 << RPS_DEBUG_WEB)))
      { std::ostringstream _logstream_315;
        _logstream_315 << "Rps_PayloadWebex::make_obwebex end reqnum#"
                       << reqnum << " obwebex=" << _f.obwebex << " startim:"
                       << paylwebex->webex_startim << std::flush; rps_debug_printf_at("httpweb_rps.cc",
                                                                                      315, RPS_DEBUG_WEB, "%s",
                                                                                      _logstream_315.str().c_str()); } } while (0)
    ;
  do { if (__builtin_expect(!!(!((paylwebex != nullptr))),0)) {
      fprintf(
              //# 317 "httpweb_rps.cc" 3
              stderr
              //# 317 "httpweb_rps.cc"
              , "\n\n" "%s*** RefPerSys ASSERT failed: %s%s\n" "%s:%d: {%s}\n\n",
              (rps_stderr_istty?(rps_without_terminal_escape?"":"\033[1m"):""), "(paylwebex != nullptr)",
              (rps_stderr_istty?(rps_without_terminal_escape?"":"\033[0m"):""), "httpweb_rps.cc",317,__PRETTY_FUNCTION__);
      rps_fatal_stop_at("httpweb_rps.cc",317); }} while(0);
  return _f.obwebex;
} // end PayloadWebex::make_obwebex

我究竟做错了什么？

最佳答案

错误消息末尾的这一行很清楚，表明long unsigned int应该在寻找...

cannot convert ‘(Rps_ObjectZone*)this’ (type ‘Rps_ObjectZone*’) to type ‘long unsigned int’

这与错误消息开头的这一行相关:

refpersys.hh:2162:76: error: no matching function for call to Rps_ObjectZone::rps_allocate4<Rps_PayloadWebex, long unsigned int, Onion::Request*, Onion::Response*>(Rps_ObjectZone*, long unsigned int&, Onion::Request*&, Onion::Response*&)’

这是第一行错误:

refpersys.hh: In instantiation of ‘PaylClass* Rps_ObjectZone::put_new_arg3_payload(Arg1Class, Arg2Class, Arg3Class) [with PaylClass = Rps_PayloadWebex; Arg1Class = long unsigned int; Arg2Class = Onion::Request*; Arg3Class = Onion::Response*

重要的部分是Arg1Class = long unsigned int;所有这一切都意味着long unsigned int(变量reqnum的类型对于您调用时第一个参数不是有效类型_f.obwebex->put_new_arg3_payload<Rps_PayloadWebex>();似乎ArgClass1应该至少是某种指针，甚至更有可能是指向从Rps_ObjectZone派生的类型的指针。
我没有使用这个特定的库，但这就是错误消息的含义。
我认为最可能的错误是您混合了此函数调用的前两个参数的顺序。

   Rps_QuasiZone::rps_allocate4<PaylClass,Arg1Class,Arg2Class,Arg3Class> (this,arg1,arg2,arg3);

在那里，或者在对ZoneClass类的构造函数的调用中。
参数的混合顺序只是一个假设，我还没有看到您的ZoneClass类的构造函数。
顺便提一句:如果Arg1Class必须可转换为ZoneClass*，这意味着所讨论的代码正在声明模板参数类型，而不应该在其中声明。