C++ dll 定义静态成员

C++ dll define static member

本文关键字：静态成员 定义 dll C++      更新时间：2023-10-16

我正在向DLL迈出第一步，我正在尝试为链表编写一个类并将其导出到.dll。当我尝试定义静态成员时，出现编译错误：

[错误] dllimport'd 类的静态数据成员 'dll：：Container：：IDcount' 的定义

这是我的代码：

容器.h

#ifndef _CONTAINER_H_
#define _CONTAINER_H_
#if BUILDING_DLL
#define DLLIMPORT __declspec(dllexport)
#else
#define DLLIMPORT __declspec(dllimport)
#endif
#define DEFAULT_SIZE 8
namespace dll{
typedef union{
char _c;
short _s;
int _i;
long _l;
float _f;
double _d;
}unit_t;
typedef unsigned long long size_t;
class DLLIMPORT Container{
private:
static size_t IDcount;
unit_t* data;
size_t size;
size_t bytes;
size_t memberID;
Container *next;
Container *prev;
public:
Container();
Container(size_t size);
Container(const Container &copy);
~Container();
}; 
}
#endif

容器.cpp

#include "container.h"
namespace dll{
size_t Container::IDcount = 0;
Container::Container(){
this->memberID = 0;
this->size = DEFAULT_SIZE;
this->bytes = DEFAULT_SIZE * sizeof(unit_t);
this->data = new unit_t[DEFAULT_SIZE];
for(size_t i = 0; i < DEFAULT_SIZE; i++)
this->data[i] = {0x0};
this->next = nullptr;
this->prev = nullptr;
}
Container::Container(size_t size)
: size(size){
this->memberID = 0;
this->bytes = this->size * sizeof(unit_t);
this->data = new unit_t[this->size];
for(size_t i = 0; i < this->size; i++)
this->data[i] = {0x0};
this->next = nullptr;
this->prev = nullptr;
}
Container::Container(const Container &copy){
this->memberID = copy.memberID;
this->size = copy.size;
this->bytes = copy.bytes;
this->data = new unit_t[this->size];
for(size_t i = 0; i < this->size; i++)
this->data[i] = copy.data[i];
this->next = copy.next;
this->prev = copy.prev;
}
Container::~Container(){
for(size_t i = 0; i < this->size; i++)
this->data[i]= {0x0};
delete[] this->data;
this->memberID = 0x0;
this->size = 0x0;
this->bytes = 0x0;
if(!(this->prev))
this->prev->next = this->next;      
if(!(this->next))
this->next->prev = this->prev;
this->next = nullptr;
this->prev = nullptr;
}
}

我错过了什么吗？

提前致谢

BUILDING_DLL宏定义不会进入编译器(即使由Dev-C++按照定义显示(。下面是一个小示例，它将文件(无需更改(从cmdline构建到.dll中(您可以忽略最后一部分，因为它是一个测试，以查看它是否也使用VStudio构建(。

输出：

e:WorkDevStackOverflowq050979671>set PATH=%PATH%;c:Installx64MinGW32MinGW327.2.0-posix-seh-rt_v5-rev1mingw64bin
e:WorkDevStackOverflowq050979671>dir /b
build.bat
container.cpp
container.h
e:WorkDevStackOverflowq050979671>g++ -shared -fPIC -DBUILDING_DLL=1 -std=c++11 -o container_g++.dll container.cpp
e:WorkDevStackOverflowq050979671>dir /b
build.bat
container.cpp
container.h
container_g++.dll
e:WorkDevStackOverflowq050979671>rem NOTE: "container_g++.dll" WAS CREATED
e:WorkDevStackOverflowq050979671>rem Building WITHOUT `-DBUILDING_DLL=1`
e:WorkDevStackOverflowq050979671>g++ -shared -fPIC -std=c++11 -o container_g++.dll container.cpp
container.cpp:5:20: warning: 'dll::Container::IDcount' redeclared without dllimport attribute: previous dllimport ignored [-Wattributes]
size_t Container::IDcount = 0;
^~~~~~~
container.cpp:7:2: warning: 'dll::Container::Container()' redeclared without dllimport attribute: previous dllimport ignored [-Wattributes]
Container::Container(){
^~~~~~~~~
container.cpp:18:2: warning: 'dll::Container::Container(dll::size_t)' redeclared without dllimport attribute: previous dllimport ignored [-Wattributes]
Container::Container(size_t size)
^~~~~~~~~
container.cpp:29:2: warning: 'dll::Container::Container(const dll::Container&)' redeclared without dllimport attribute: previous dllimport ignored [-Wattributes]
Container::Container(const Container &copy){
^~~~~~~~~
container.cpp:40:2: warning: 'dll::Container::~Container()' redeclared without dllimport attribute: previous dllimport ignored [-Wattributes]
Container::~Container(){
^~~~~~~~~
container.cpp:5:9: error: definition of static data member 'dll::Container::IDcount' of dllimport'd class
size_t Container::IDcount = 0;
^~~~~~~~~
e:WorkDevStackOverflowq050979671>"c:Installx86MicrosoftVisual Studio Community2015vcvcvarsall.bat" amd64
e:WorkDevStackOverflowq050979671>cl /DBUILDING_DLL=1 container.cpp /MD /Focontainer_msvc.obj /link /dll /out:container_msvc.dll
Microsoft (R) C/C++ Optimizing Compiler Version 19.00.24215.1 for x64
Copyright (C) Microsoft Corporation.  All rights reserved.
container.cpp
Microsoft (R) Incremental Linker Version 14.00.24215.1
Copyright (C) Microsoft Corporation.  All rights reserved.
/out:container_msvc.exe
/dll
/out:container_msvc.dll
container_msvc.obj
Creating library container_msvc.lib and object container_msvc.exp
e:WorkDevStackOverflowq050979671>dir /b
build.bat
container.cpp
container.h
container_g++.dll
container_msvc.dll
container_msvc.exp
container_msvc.lib
container_msvc.obj

如前所述，-DBUILDING_DLL=1：

  • 通过它时，.dll被构建
  • 不通过时，会弹出您遇到的错误

由于我没有Dev-C++，我不知道如何从其选项中设置它(尽管我认为这很简单，例如转到">工具 -> 编译器选项"并选择">C++编译器"，然后添加宏定义(，所以我将在代码级别启用它。
事情很简单，在容器中.cpp在包含container.h之前定义BUILDING_DLL，例如：

#define BUILDING_DLL 1
#include "container.h"

就个人而言，我更喜欢这种方法(而不是设置项目选项(，因为它只需要完成一次，无论使用多少个构建系统来构建代码。

运行失败的命令(如上(现在将生成.dll。

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