Question

我在使这个COMPARE宏工作时遇到问题。关于如何解决的任何想法？

它是一个人造样本 - 我想尽可能小。

#include <iostream>
#include <string.h>

enum rqtypes {Unknown, Monitor, Query, Snapshot };

class base {
public:
   base() : type(Unknown) {}
   rqtypes type;
};

class CBMonitorDeviceRequest : public base
{
public:
   CBMonitorDeviceRequest() : dn(0) {}
   char* dn;
};


//I want the equivalent of:
//        case MonitorDeviceRequestID:
//           CBMonitorDeviceRequest* pthis = static_cast<CBMonitorDeviceRequest*>(thisrq);
//           if(pthis && strcmp(pthis->dn1, "1234") == 0)
//              return 0;
//           else
//              return -1;
//           break;


int main(int argc, char* argv[])
{
   CBMonitorDeviceRequest* ptr = new CBMonitorDeviceRequest;
   ptr->type = Monitor;
   ptr->dn = new char(strlen("1234") + 1);
   strcpy(ptr->dn, "1234");

#define COMPARE(id, thismsg) case id##ID: { \
   CB##id * pthis = static_cast<CB##id *>(thismsg); \
   if(pthis && strcmp(pthis->dn, "1234") == 0) \
      std::cout << "found"; \
   else \
      std::cout << "not found"; \
     break;  } \

   switch(ptr->type){
      COMPARE(Monitor, ptr);
   }

#undef COMPARE

    return 0;
}

我得到例如：

(46) : error C2065: 'MonitorID' : undeclared identifier
(46) : error C2051: case expression not constant
(46) : error C2065: 'CBMonitor' : undeclared identifier
(46) : error C2065: 'pthis' : undeclared identifier
(46) : error C2061: syntax error : identifier 'CBMonitor'
(46) : error C2065: 'pthis' : undeclared identifier
(46) : error C2065: 'pthis' : undeclared identifier
(46) : error C2227: left of '->dn' must point to class/struct/union/generic type

使用gcc -E我得到：＃30＆＃34; macro_fun2.cpp＆＃34; int main（int argc，char * argv []） { CBMonitorDeviceRequest * ptr = new CBMonitorDeviceRequest; ptr-＆gt; type = Monitor; ptr-> dn = new char（strlen（＆＃34; 1234＆＃34;）+ 1）; strcpy（ptr-> dn，＆＃34; 1234＆＃34;）; ＃45＆＃34; macro_fun2.cpp＆＃34; 开关（ptr-＆GT;类型）{ case MonitorID：{CBMonitor * pthis = static_cast（ptr）; if（pthis＆amp;＆amp; strcmp（pthis-＆gt; dn，＆＃34; 1234＆＃34;）== 0）Monitor = Query; else Monitor = Snapshot; 打破; }; }

返回0; }

*** By the way I changed code to to avoid the massive printing of iostream by preprocessor - otherwise -E printing would have been huge.

#define COMPARE(id, thismsg) case id##ID: { \
   CB##id * pthis = static_cast<CB##id *>(thismsg); \
   if(pthis && strcmp(pthis->dn, "1234") == 0) \
      id = Query; \
   else \
      id =  Snapshot; \
     break;  } \

Answer 1

我认为您需要CB##id，而不是CBid##。

Answer 2

id##ID将扩展为MonitorID，未定义。您要么在Monitor的定义中将MonitorID重命名为rqtypes，要么将其更改为id。

CB##id将扩展为CBMonitor，这也未定义。您要么将class CBMonitorDeviceRequest重命名为class CBMonitor，要么将其更改为CB##id##DeviceRequest。

除此之外，我看不出任何明显的问题。当然，除了内存泄漏。为什么不使用std::string作为字符串？

预处理器字符串化宏不起作用

2 个答案: