使用 #include <string> 编译错误在可可应用程序中 [英] Compile errors with #include <string> in Cocoa App
问题描述
我正在尝试在 xcode 4.0 中编译 Cocoa 应用程序，但出现此错误...
I am trying to compile a Cocoa app in xcode 4.0 and I'm getting this error...
fatal error: 'string' file not found
...当试图在这一行编译为 .pch 文件时:
...when trying to compile to .pch file on this line:
#include <string>
我有另一个 xcode 项目做同样的事情，但没有得到错误.我已经搜索了一些不同的构建设置，但我找不到一个.唯一不同的是，编译OK的项目是作为命令行项目启动的，不是Cocoa项目，但是构建设置是一样的.
I have another xcode project that does the same thing, but does not get the error. I have scoured the build settings for some different, but I can't find one. The only difference is that the project that compiles OK was started as a command line project, not a Cocoa project, but the build setting are the same.
目标操作系统是 Mac OS X 10.6
The target OS is Mac OS X 10.6
该错误发生在编译预编译头文件时，并且没有到达任何其他文件.编译版本唯一的框架是Foundation.framework，非编译版本也有.
The error happens when compiling the precompiled header and doesn't get to any of the other files. The only framework that the compiling version has is Foundation.framework and the non-compiling one has it as well.
为什么在一个项目中找不到，而在另一个项目中找不到?有什么建议吗?
Why is it not finding in one project and not the other? Any advice?
推荐答案
你的源文件的扩展名是什么?如果是.m"，请尝试将其更改为obj-cpp.mm"，以便Xcode 推断出正确的语言.或者只是将特定于 c++ 的头文件放在#ifdef __cplusplus"块中
What is the extension of your source files? If it is ".m", try to change it to obj-cpp ".mm", so that Xcode will deduce correct language. Or just put c++-specific headers inside "#ifdef __cplusplus" block
更新
项目中编译的每种语言都必须存在保护，因为这个特定的包含在 pch 中.IOW，如果都是 c++ 和/或 objc++，就不会有错误.显然，至少有一个文件不能识别 C++(例如，C 或 ObjC 源也在目标中编译).因此，您只需像这样保护它:
The guard must exist for each language compiled in the project because this specific include is in the pch. IOW, if it were all c++ and/or objc++ there would be no error. Evidently, there is at least one file that does not recognize C++ (e.g. C or ObjC sources are also compiled in the target). Therefore, you simply guard it like so:
// MONPrefix.pch
#ifdef __cplusplus
#include <string>
#endif
// same for objc, so your C and C++ sources compile with no error:
#ifdef __OBJC__
#include <Foundation/Foundation.h>
#endif
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