Apple Mach-O链接器和使用OpenCV的多个"未定义符号"错误

Question

我目前是Objective C的真正初学者,我正在使用框架OpenCV开发一个应用程序.

我正在学习一个教程,但在构建项目时,我遇到了几个错误:

Undefined symbols for architecture i386:
  "std::__1::basic_ostream<char, std::__1::char_traits<char> >::flush()", referenced from:
      cv::gpu::error(char const*, char const*, int, char const*) in opencv2(gpumat.o)
  "std::__1::basic_ostream<char, std::__1::char_traits<char> >::sentry::sentry(std::__1::basic_ostream<char, std::__1::char_traits<char> >&)", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::operator<< <std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*) in opencv2(gpumat.o)
  "std::__1::basic_ostream<char, std::__1::char_traits<char> >::sentry::~sentry()", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::operator<< <std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*) in opencv2(gpumat.o)
  "std::__1::basic_ostream<char, std::__1::char_traits<char> >::operator<<(int)", referenced from:
      cv::gpu::error(char const*, char const*, int, char const*) in opencv2(gpumat.o)
  "std::__1::cerr", referenced from:
      cv::gpu::error(char const*, char const*, int, char const*) in opencv2(gpumat.o)
  "std::__1::ios_base::__set_badbit_and_consider_rethrow()", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::operator<< <std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*) in opencv2(gpumat.o)
  "std::__1::ios_base::clear(unsigned int)", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::operator<< <std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*) in opencv2(gpumat.o)
  "std::__1::__vector_base_common<true>::__throw_length_error() const", referenced from:
      __ZNSt3__16vectorImNS_9allocatorImEEE6assignIPmEENS_9enable_ifIXsr21__is_forward_iteratorIT_EE5valueEvE4typeES7_S7_ in opencv2(matrix.o)
      std::__1::vector<unsigned long, std::__1::allocator<unsigned long> >::vector(unsigned long) in opencv2(matrix.o)
      std::__1::vector<unsigned long, std::__1::allocator<unsigned long> >::__append(unsigned long) in opencv2(matrix.o)
      std::__1::vector<cv::Vec<float, 2>, std::__1::allocator<cv::Vec<float, 2> > >::vector(unsigned long) in opencv2(matrix.o)
      std::__1::vector<int, std::__1::allocator<int> >::vector(unsigned long) in opencv2(matrix.o)
      std::__1::vector<cv::Vec<int, 128>, std::__1::allocator<cv::Vec<int, 128> > >::__append(unsigned long) in opencv2(matrix.o)
      std::__1::vector<cv::Vec<int, 64>, std::__1::allocator<cv::Vec<int, 64> > >::__append(unsigned long) in opencv2(matrix.o)
      ...
  "std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::__init(char const*, unsigned long)", referenced from:
      cv::Mat::create(int, int const*, int) in opencv2(matrix.o)
      __ZN2cvL7setSizeERNS_3MatEiPKiPKmb in opencv2(matrix.o)
      cv::Mat::Mat(cv::Mat const&, cv::Range const&, cv::Range const&) in opencv2(matrix.o)
      cv::Mat::Mat(cv::Mat const&, cv::Rect_<int> const&) in opencv2(matrix.o)
      cv::Mat::Mat(cv::Mat const&, cv::Range const*) in opencv2(matrix.o)
      cv::Mat::diag(int) const in opencv2(matrix.o)
      cv::Mat::Mat(_IplImage const*, bool) in opencv2(matrix.o)
      ...
  "std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::~basic_string()", referenced from:
      cv::Mat::create(int, int const*, int) in opencv2(matrix.o)
      __ZN2cvL7setSizeERNS_3MatEiPKiPKmb in opencv2(matrix.o)
      cv::Mat::Mat(cv::Mat const&, cv::Range const&, cv::Range const&) in opencv2(matrix.o)
      cv::Mat::Mat(cv::Mat const&, cv::Rect_<int> const&) in opencv2(matrix.o)
      cv::Mat::Mat(cv::Mat const&, cv::Range const*) in opencv2(matrix.o)
      cv::Mat::diag(int) const in opencv2(matrix.o)
      cv::Mat::Mat(_IplImage const*, bool) in opencv2(matrix.o)
      ...
  "std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::resize(unsigned long, char)", referenced from:
      __ZL8icvCloseP13CvFileStoragePNSt3__112basic_stringIcNS1_11char_traitsIcEENS1_9allocatorIcEEEE in opencv2(persistence.o)
  "std::__1::basic_string<wchar_t, std::__1::char_traits<wchar_t>, std::__1::allocator<wchar_t> >::__init(wchar_t const*, unsigned long)", referenced from:
      cv::toUtf16(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in opencv2(persistence.o)
  "std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::__init(char const*, unsigned long, unsigned long)", referenced from:
      std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > std::__1::operator+<char, std::__1::char_traits<char>, std::__1::allocator<char> >(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, char const*) in opencv2(system.o)
  "std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::append(char const*)", referenced from:
      cv::tempfile(char const*) in opencv2(system.o)
  "std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::append(char const*, unsigned long)", referenced from:
      std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > std::__1::operator+<char, std::__1::char_traits<char>, std::__1::allocator<char> >(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, char const*) in opencv2(system.o)
  "std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::assign(char const*)", referenced from:
      cv::tempfile(char const*) in opencv2(system.o)
  "std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::basic_string(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&)", referenced from:
      cv::Exception::Exception(int, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, int) in opencv2(system.o)
      cv::tempfile(char const*) in opencv2(system.o)
      cv::Exception::Exception(cv::Exception const&) in opencv2(system.o)
      cv::operator<<(cv::FileStorage&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in opencv2(persistence.o)
  "std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::operator=(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&)", referenced from:
      cv::Exception::formatMessage() in opencv2(system.o)
      cv::tempfile(char const*) in opencv2(system.o)
      cv::operator<<(cv::FileStorage&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in opencv2(persistence.o)
ld: symbol(s) not found for architecture i386

clang: error: linker command failed with exit code 1 (use -v to see invocation)

我确信问题来自框架,但不是框架本身,而是它是如何在项目中链接,或者......

我确切地说,我已经在.pch文件中以这种方式链接了它

 #import <Availability.h>

#ifndef __IPHONE_5_0
#warning "This project uses features only available in iOS SDK 5.0 and later."
#endif

#ifdef __cplusplus
#import <opencv2/opencv.hpp>
#endif

#ifdef __OBJC__
    #import <UIKit/UIKit.h>
    #import <Foundation/Foundation.h>
#endif

真的不知道该怎么办..

编辑:忘了告诉我我将.m文件重命名为.mm和我的.h文件为.hh我们还需要做些什么才能获得客观的C++项目吗？

Answer 1

在Cthutu的回答基础上,将libc ++.dylib添加到您的项目中:

1. 在项目导航器中选择项目(蓝色文件)(如果隐藏了命令1)
2. 选择目标
3. 转到构建阶段
4. 展开"链接二进制文件库"
5. 点击"+"
6. 在搜索栏中键入libc ++.dylib.
7. 选择libc ++.dylib文件并按"添加"

Answer 2

你错过了标准的C++库.您需要链接它以获取您遇到错误的STL类的所有实现.

将libc ++.dylib添加到项目中.

Answer 3

这实际上似乎隐藏了实际问题:您的LLVM编译器默认情况下可能不会选择适当的标准C++库进行编译.你应该去

Project (or your Target) -> Build Settings -> Apple LLVM 6.0 - Language - C++ -> C++ Standard Library

并确保libc++您选择,而不仅仅是Compiler Default,因为现代OpenCV库与libc ++链接.这将解决您的问题,而无需添加额外的libc ++.dylib.如果您Compiler Default实际上没有选择libc ++库,那么包含libc ++.dylib框架作为一种解决方法并不总是有效!

要检查"编译器默认值"是什么,您可以执行类似的操作.我某种程度上选择c ++ 98作为默认值.