windows DLL 和静态库的相同头文件
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Same Header File for both DLL and Static Library
提问by DeusAduro
So the common (at least VS 2005 states) way to define exports/imports for a DLL is:
因此，为 DLL 定义导出/导入的常见（至少 VS 2005 状态）方法是：
#ifdef MY_EXPORTS
#define MY_API __declspec(dllexport)
#else
#define MY_API __declspec(dllimport)
#endif
class MY_API MyClass {
...
};
This works great if I'm just building my code as a DLL. However, I want to have the option of using a static library OR a DLL. Now one obvious (but terrible) solution, is to copy all the code, removing the DLL 'MY_API' defines. Now what would seem a much better approach is a command line switch to either define, or not define the DLL stuff. However in the case of a static library what should 'MY_API' be?
如果我只是将我的代码构建为 DLL，这非常有效。但是，我希望可以选择使用静态库或 DLL。现在一个明显（但可怕）的解决方案是复制所有代码，删除 DLL 'MY_API' 定义。现在看起来更好的方法是使用命令行开关来定义或不定义 DLL 内容。但是，在静态库的情况下，“MY_API”应该是什么？
#ifdef DLL_CONFIG
#ifdef MY_EXPORTS
#define MY_API __declspec(dllexport)
#else
#define MY_API __declspec(dllimport)
#endif
#else
#define MY_API // What goes here?
#endif
class MY_API MyClass {
...
};
Now assuming that this can be done will there be issues when a user of the library includes the header files (ie. will they have to define 'DLL_CONFIG')?
现在假设可以这样做，当库的用户包含头文件时会出现问题（即，他们是否必须定义“DLL_CONFIG”）？
回答by GManNickG
Nothing.
没有。
Leave it as #define MY_APIand all instances of MY_API will simply vanish.
保持原样#define MY_API，MY_API 的所有实例都会消失。
You can add new build configurations, such as Debug - DLL and Release - DLL that mimic the others except they #define DLL_CONFIG.
您可以添加新的构建配置，例如 Debug-DLL 和 Release-DLL，它们模仿除它们之外的其他配置#define DLL_CONFIG。
To clone a configuration, get to the configuration manager (like the drop down of the Debug/Release list box), then under 'Active solution configuration' select new. You can now name it "Debug - DLL" and set Copy Settingsto Debugand now that's left to do is define DLL_CONFIG.
要克隆配置，请访问配置管理器（如调试/发布列表框的下拉菜单），然后在“活动解决方案配置”下选择新的。您现在可以将其命名为“Debug-DLL”并设置Copy Settings为Debug，现在剩下要做的就是定义DLL_CONFIG.
To do this, go to project properties->configuration properties->C/C++->Preprocessor, and type DLL_CONFIGin there. You will also see that's where things like NDEBUGand WIN32are defined.
为此，请转到项目属性->配置属性->C/C++->预处理器，然后DLL_CONFIG在其中键入。您还将看到这就是定义likeNDEBUG和的地方WIN32。
Like haffax said, use project specific names. I would recommend something like:
就像haffax 说的那样，使用项目特定的名称。我会推荐类似的东西：
#ifdef THEPROJECT_USE_DLL
#ifdef THEPROJECT_BUILDING_PROJECT
#define THEPROJECT_API __declspec(dllexport)
#else
#define THEPROJECT_API __declspec(dllimport)
#endif
#else
#define THEPROJECT_API
#endif
Now users of your DLL just #define THEPROJECT_USE_DLLif they are using the DLL version, just like your "- DLL" configurations have.
现在你的 DLL 的用户#define THEPROJECT_USE_DLL只要他们使用的是 DLL 版本，就像你的“- DLL”配置一样。
回答by haffax
Just define MY_API as empty. Like this:
只需将 MY_API 定义为空。像这样：
#ifdef DLL_CONFIG
#ifdef MY_EXPORTS
#define MY_API __declspec(dllexport)
#else
#define MY_API __declspec(dllimport)
#endif
#else
#define MY_API
#endif
In case of static linking no declspec is necessary.
在静态链接的情况下，不需要 declspec。
Users of your library will have to define DLL_CONFIGif they want to use it as a dll or not define it if they want to use it as a static library.
There won't be any issues as is. This kind of configuration is done in many libraries.
您的库的用户必须定义DLL_CONFIG他们是否要将其用作 dll，或者如果他们想将其用作静态库，则不定义它。不会有任何问题。这种配置在许多库中都有完成。
Edit: Of course you shouldn't use the names MY_EXPORTSand DLL_CONFIGas such. Use project specific prefixes for all of your macros, so that there are no name clashes.
编辑：当然，你不应该使用的名字MY_EXPORTS和DLL_CONFIG这样。为所有宏使用项目特定的前缀，以免发生名称冲突。
回答by ralphtheninja
Do nothing. No special calling convention is needed to link against a static library. The only thing you need to do, is to make sure that the linker links with your.lib.
没做什么。链接静态库不需要特殊的调用约定。您唯一需要做的就是确保链接器与 your.lib 链接。
