Question

我们定义了一些方法，以在需要时允许临时控制台输入。这些方法包含在名称空间中，并定义并使用一个类来执行实际工作。

为简洁起见，对这些定义进行了简化：

ConsoleInput.h

#include <cstddef>
#include <map>
#include <memory>
#include <vector>

namespace MyNameSpc
{

typedef std::vector<char> buffer_t;

class ConsoleInput
{
// Methods for windows and linux console input
}

int GetString(buffer_t &buffer, ...);

}

RequestInput.h

#include "ConsoleInput.h"
#include <cstddef>
#include <string>

namespace MyNameSpc
{

const std::string empty = std::string();

class RequestInputParam
{
// Methods
}

int RequestInput(buffer_t &buffer);
int RequestInput(buffer_t &buffer, const RequestInputParam &param);
// and other overloads
}

ConsoleInput.cpp

#include "ConsoleInput.h"
#include "RequestInput.h"
#include <cstddef>
#include <iostream>
#include <memory>
#include <string>
#include <fcntl.h>
#include <stdio.h>
// and other headers.

namespace MyNameSpc
{
// implements class ConsoleInput methods.
// Implements GetString()
}

RequestInput.cpp

#include "ConsoleInput.h"
#include "RequestInput.h"
#include <cstddef>
#include <iostream>
#include <memory>
#include <string>

namespace MyNameSpc
{
// implements the overloaded methods.
}

然后我们用#include RequestInput.h来调用它们，然后再调用int retVal = MyNameSpc::RequestInput(...)。当所有代码都是C ++时，这一切都很好。现在，我必须从最近放入我们的存储库的C代码中引用此代码。我不认为我可以（嗯，我可以，但是我认为它会破坏其他东西）只是将C代码编译为C ++，所以我确实确实需要以某种方式将其引入C。

当我尝试构建时，由于没有找到iostream标头，我遇到了一些初始错误。但是，在阅读了关于extern“ C”的信息后，当我将这些C ++标头包含在其中时，我不清楚如何继续进行操作。代码，类（我可能需要引用的唯一一个是参数类）和名称空间。

更新

我已查看了提供的链接，并试图利用来自here和here的信息。我没有成功。

RequestInputWrapper.h

#ifndef REQUEST_WRAPPER_H
#define REQUEST_WRAPPER_H

#include <stddef.h>
#include "RequestInput.h"

#ifdef __cplusplus
extern "C" {
#endif

typedef struct RequestInputParam RequestInputParam; // line 29

RequestInputParam* CreateRequestInputParam();
void DisposeRequestInputParam( RequestInputParam* pObject );

void C_AddMainPrompt(RequestInputParam *param, char *msg);

int C_RequestInputAllocPtr(char * * const ppInput,
                           unsigned int * const pInputLen);

int C_RequestInput(char * const pInput,
                   unsigned int * const pInputLen);

#ifdef __cplusplus
}
#endif

#endif   /* REQUEST_WRAPPER_H */

RequestInputWrapper.cpp

#include "RequestInput.h"
#include "RequestInputWrapper.h" // line 13

#ifdef __cplusplus
extern "C" {
#endif

RequestInputParam* CreateRequestInputParam()
{
    return new RequestInputParam();   // line 25
}

void DisposeRequestInputParam( RequestInputParam* pObject ) // line 28
{
    if ( pObject != NULL )
    {
        delete pObject; // line 32
        pObject = NULL;
    }
}

void C_AddMainPrompt(RequestInputParam *param, char *msg)          { param->AddMainPrompt( msg ); }

int C_RequestInputAllocPtr(char * * const ppInput,
                           unsigned int * const pInputLen)
{
    return RequestInput(ppInput, pInputLen);
}

int C_RequestInput(char * const pInput,
                   unsigned int * const pInputLen)
{
    return RequestInput(pInput, pInputLen);
}

#ifdef __cplusplus
}
#endif

当前正在引发以下错误（我仅对C＆P的第一部分进行重复，开始重复；行号与上面的代码不匹配，该代码已删除所有注释，因此我在注释中添加了注释行号）：

cli/RequestInputWrapper.cpp: In function ‘RequestInputParam* CreateRequestInputParam()’:
cli/RequestInputWrapper.cpp:25:35: error: invalid use of incomplete type ‘RequestInputParam {aka struct RequestInputParam}’
     return new RequestInputParam();
                                   ^
In file included from cli/RequestInputWrapper.cpp:13:0:
./Include/RequestInputWrapper.h:29:16: error: forward declaration of ‘RequestInputParam {aka struct RequestInputParam}’
 typedef struct RequestInputParam RequestInputParam;
                ^
cli/RequestInputWrapper.cpp: In function ‘void DisposeRequestInputParam(RequestInputParam*)’:
cli/RequestInputWrapper.cpp:32:16: error: possible problem detected in invocation of delete operator: [-Werror]
         delete pObject;
                ^
cli/RequestInputWrapper.cpp:28:6: error: ‘pObject’ has incomplete type [-Werror]
 void DisposeRequestInputParam( RequestInputParam* pObject )
      ^
In file included from cli/RequestInputWrapper.cpp:13:0:
./Include/RequestInputWrapper.h:29:16: error: forward declaration of ‘struct RequestInputParam’ [-Werror]
 typedef struct RequestInputParam RequestInputParam;
                ^
cli/RequestInputWrapper.cpp:32:16: note: neither the destructor nor the class-specific operator delete will be called, even if they are declared when the class is defined
         delete pObject;
                ^

Answer 1

我怀疑文章中被建议为“重复项”的答案仅是书面形式，未经测试。经过更多搜索之后，我最终偶然发现了this answer，它提供了构建此文件所需的指导。

简而言之，我在我的C ++包装代码（facepalm）中缺少名称空间，并且我不得不添加reinterpret_cast调用。我还在typedef中更改了类型的名称...我以为它是在引用C ++类型（因为这至少是一个示例似乎显示的内容），但是，不……它必须是它自己的struct类型。

RequestInputWrapper.h

#ifndef REQUEST_WRAPPER_H
#define REQUEST_WRAPPER_H

#ifdef __cplusplus
extern "C" {
#endif

#include <stddef.h>

typedef struct C_RequestInputParam C_RequestInputParam;

C_RequestInputParam * CreateRequestInputParam();
void DisposeRequestInputParam( C_RequestInputParam *pObject );

void C_AddMainPrompt( C_RequestInputParam *param, char *msg);

int C_RequestInputAllocPtr( char * * const ppInput,
                           unsigned int * const pInputLen );

int C_RequestInput( char * const pInput,
                    unsigned int * const pInputLen );

#ifdef __cplusplus
}
#endif

#endif   /* REQUEST_WRAPPER_H */

RequestInputWrapper.cpp

#include "RequestInput.h"
#include "RequestInputWrapper.h"

extern "C" {

C_RequestInputParam * CreateRequestInputParam()
{
    return reinterpret_cast< C_RequestInputParam * >( new RequestInputParam() );
}

void DisposeRequestInputParam( C_RequestInputParam *pObject )
{
    if ( pObject != NULL )
    {
        delete reinterpret_cast< MyNameSpc::RequestInputParam * >( pObject );
        pObject = NULL;
    }
}

void C_AddMainPrompt( C_RequestInputParam *param, char *msg )
{
    reinterpret_cast< MyNameSpc::RequestInputParam * >( param )->AddMainPrompt( msg );
}

int C_RequestInputAllocPtr( char * * const ppInput,
                            unsigned int * const pInputLen )
{
    return MyNameSpc::RequestInput( ppInput, pInputLen );
}

int C_RequestInput( char * const pInput,
                    unsigned int * const pInputLen )
{
    return MyNameSpc::RequestInput( pInput, pInputLen );
}

}

不确定如何装饰我的C ++库代码以在C中使用

1 个答案: