xcode 部署目标为 7.0 时架构错误的未定义符号
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Undefined symbols for architecture error when deployment target is 7.0
提问by Guven
I am using third party frameworks in my native iOS application (bunch of .a libraries). My application is developed with XCode 5 base SDK 7.0.
我在我的原生 iOS 应用程序（一堆 .a 库）中使用第三方框架。我的应用程序是使用 XCode 5 基础 SDK 7.0 开发的。
The libraries compile and link fine when the deployment target is 6.1 (library and header search paths are good). However, when I change the deployment target to be 7.0, I get the following linker error:
当部署目标为 6.1 时，库编译和链接正常（库和标头搜索路径良好）。但是，当我将部署目标更改为 7.0 时，出现以下链接器错误：
Undefined symbols for architecture i386:
"std::string::find_last_of(char const*, unsigned long) const", referenced from:
GetExecutionDir(ECTemplateString<char>&, char*, bool) in myLibrary.a(moPlatForm.o)
"std::string::find(char const*, unsigned long) const", referenced from:
ParseLog(std::string const&, unsigned int&, CmoDateTime&, int&, std::string&) in myLibrary.a(AppLog.o)
"std::string::size() const", referenced from:
mo::CmoParam::WriteToStream(void*, mo::STREAM_STATE*) in myLibrary.a(moParams.o)
"std::string::c_str() const", referenced from:
GetExecutionDir(ECTemplateString<char>&, char*, bool) in myLibrary.a(moPlatForm.o)
CMocaFileTransfer::UpdateParamsForGetTraceFiles(mo::CmoParamList&, long) in myLibrary.a(RobieFileTransfer.o)
CMocaFileTransfer::AddTraceFileForUpload(std::string const&, std::string const&) in myLibrary.a(RobieFileTransfer.o)
CMocaFileTransfer::CreateParamsForSendTraceFiles(mo::CmoObject&) in myLibrary.a(RobieFileTransfer.o)
mo::CmoParam::WriteToStream(void*, mo::STREAM_STATE*) in myLibrary.a(moParams.o)
ParseLog(std::string const&, unsigned int&, CmoDateTime&, int&, std::string&) in myLibrary.a(AppLog.o)
CAppLog::LogExists(unsigned int) in myLibrary.a(AppLog.o)
...
Libraries are a bit old, I am not sure if there is a compatibility issue. I am not planning to support iOS 6 so I need to set the deployment target as 7.0. Any kind of help/direction would be great.
库有点旧，我不确定是否存在兼容性问题。我不打算支持 iOS 6，所以我需要将部署目标设置为 7.0。任何形式的帮助/指导都会很棒。
回答by Denis
for me, including the 'stdc++.6.0.9.dylib' instead of 'stdc++.dylib' into the dependencies resolved the linker errors too
对我来说，在依赖项中包含“ stdc++.6.0.9.dylib”而不是“ stdc++.dylib”也解决了链接器错误
回答by Guven
It turns out that if XCode can't find any C++ files in the project, then it assumes that libstd++ is not required. So, you have to manually add a C++ file to the project (an empty .mm file would be enough). That is the solution.
事实证明，如果 XCode 在项目中找不到任何 C++ 文件，则它假定不需要 libstd++。因此，您必须手动将 C++ 文件添加到项目中（一个空的 .mm 文件就足够了）。这就是解决方案。
All the credits go to this answerin this Stackoverflow thread.
回答by Phillip Mills
It looks as if myLibrary.a was built with calls to C++ code and used libstdc++ as its C++ standard library. Your application project probably specifies libc++ instead, perhaps as the compiler default.
看起来 myLibrary.a 是通过调用 C++ 代码构建的，并使用 libstdc++ 作为其 C++ 标准库。您的应用程序项目可能会指定 libc++，也许作为编译器默认值。
Try switching back to libstdc++ and see if the errors go away (or change, at least). Your eventual solution is likely to be a library that's built against the new standard library.
尝试切换回 libstdc++ 并查看错误是否消失（或至少发生变化）。您最终的解决方案很可能是一个针对新标准库构建的库。
