c++ - 在 iOS : "Undefined symbols" and "ld: warning: ignoring file" 中为 C++ 编译 Protobuf 时出错

Question

我有一些 iOS 项目使用的 C++ 代码。因此，我需要在 iOS 中为 C++ 代码提供 protobuf 支持。

我试过这个链接:https://developers.google.com/cardboard/develop/ios/protobuf ，还有这个要点:https://gist.github.com/eyeplum/ff0b76f70ca5b8d192cac0b52496433d .但是，它们都给出了以下错误:

...
  CXX      google/protobuf/compiler/csharp/csharp_reflection_class.lo
  CXX      google/protobuf/compiler/csharp/csharp_repeated_enum_field.lo
  CXX      google/protobuf/compiler/csharp/csharp_repeated_message_field.lo
  CXX      google/protobuf/compiler/csharp/csharp_repeated_primitive_field.lo
  CXX      google/protobuf/compiler/csharp/csharp_source_generator_base.lo
In file included from google/protobuf/compiler/csharp/csharp_source_generator_base.cc:39:
./google/protobuf/compiler/csharp/csharp_source_generator_base.h:62:25: warning: private field 'descriptor_' is not used [-Wunused-private-field]
  const FileDescriptor* descriptor_;
                        ^
1 warning generated.
  CXX      google/protobuf/compiler/csharp/csharp_wrapper_field.lo
  CXXLD    libprotoc.la
ar: `u' modifier ignored since `D' is the default (see `U')
  CXXLD    protoc
ld: warning: ignoring file ./.libs/libprotobuf.a, building for iOS-armv7 but attempting to link with file built for iOS-armv7
ld: warning: ignoring file /Users/tom/RefCode/protobuf/src/.libs/libprotobuf.a, building for iOS-armv7 but attempting to link with file built for iOS-armv7
ld: warning: ignoring file ./.libs/libprotoc.a, building for iOS-armv7 but attempting to link with file built for unknown-unsupported file format ( 0x21 0x3C 0x61 0x72 0x63 0x68 0x3E 0x0A 0x2F 0x20 0x20 0x20 0x20 0x20 0x20 0x20 )
Undefined symbols for architecture armv7:
  "google::protobuf::compiler::objectivec::ObjectiveCGenerator::ObjectiveCGenerator()", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "google::protobuf::compiler::objectivec::ObjectiveCGenerator::~ObjectiveCGenerator()", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "google::protobuf::compiler::CodeGenerator::~CodeGenerator()", referenced from:
      google::protobuf::compiler::js::Generator::~Generator() in main.o
      google::protobuf::compiler::ruby::Generator::~Generator() in main.o
      google::protobuf::compiler::php::Generator::~Generator() in main.o
  "google::protobuf::compiler::CommandLineInterface::AllowPlugins(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&)", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "google::protobuf::compiler::CommandLineInterface::RegisterGenerator(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&, google::protobuf::compiler::CodeGenerator*, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&)", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "google::protobuf::compiler::CommandLineInterface::Run(int, char const* const*)", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "google::protobuf::compiler::CommandLineInterface::CommandLineInterface()", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "google::protobuf::compiler::CommandLineInterface::~CommandLineInterface()", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "google::protobuf::compiler::cpp::CppGenerator::CppGenerator()", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "google::protobuf::compiler::cpp::CppGenerator::~CppGenerator()", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "google::protobuf::compiler::java::JavaGenerator::JavaGenerator()", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "google::protobuf::compiler::java::JavaGenerator::~JavaGenerator()", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "google::protobuf::compiler::csharp::Generator::Generator()", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "google::protobuf::compiler::csharp::Generator::~Generator()", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "google::protobuf::compiler::python::Generator::Generator()", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "google::protobuf::compiler::python::Generator::~Generator()", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "vtable for google::protobuf::compiler::CodeGenerator", referenced from:
      google::protobuf::compiler::CodeGenerator::CodeGenerator() in main.o
  NOTE: a missing vtable usually means the first non-inline virtual member function has no definition.
  "vtable for google::protobuf::compiler::js::Generator", referenced from:
      google::protobuf::compiler::js::Generator::Generator() in main.o
  NOTE: a missing vtable usually means the first non-inline virtual member function has no definition.
  "vtable for google::protobuf::compiler::php::Generator", referenced from:
      google::protobuf::compiler::php::Generator::Generator() in main.o
  NOTE: a missing vtable usually means the first non-inline virtual member function has no definition.
  "vtable for google::protobuf::compiler::ruby::Generator", referenced from:
      google::protobuf::compiler::ruby::Generator::Generator() in main.o
  NOTE: a missing vtable usually means the first non-inline virtual member function has no definition.
ld: symbol(s) not found for architecture armv7
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[2]: *** [protoc] Error 1
make[1]: *** [all-recursive] Error 1
make: *** [all] Error 2

我已经尝试解决了，没有任何进展。感谢您的帮助!

---

已编辑:64 位版本也有错误。我也遵循谷歌的指南(https://developers.google.com/cardboard/develop/ios/protobuf)

...
  CXXLD    protoc
ld: warning: ignoring file /Users/tom/RefCode/protobuf/src/.libs/libprotobuf.a, building for iOS-arm64 but attempting to link with file built for unknown-unsupported file format ( 0x21 0x3C 0x61 0x72 0x63 0x68 0x3E 0x0A 0x2F 0x20 0x20 0x20 0x20 0x20 0x20 0x20 )
ld: warning: ignoring file ./.libs/libprotobuf.a, building for iOS-arm64 but attempting to link with file built for unknown-unsupported file format ( 0x21 0x3C 0x61 0x72 0x63 0x68 0x3E 0x0A 0x2F 0x20 0x20 0x20 0x20 0x20 0x20 0x20 )
ld: warning: ignoring file ./.libs/libprotoc.a, building for iOS-arm64 but attempting to link with file built for unknown-unsupported file format ( 0x21 0x3C 0x61 0x72 0x63 0x68 0x3E 0x0A 0x2F 0x20 0x20 0x20 0x20 0x20 0x20 0x20 )
Undefined symbols for architecture arm64:
  "google::protobuf::compiler::objectivec::ObjectiveCGenerator::ObjectiveCGenerator()", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "google::protobuf::compiler::objectivec::ObjectiveCGenerator::~ObjectiveCGenerator()", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "google::protobuf::compiler::CodeGenerator::~CodeGenerator()", referenced from:
      google::protobuf::compiler::js::Generator::~Generator() in main.o
      google::protobuf::compiler::ruby::Generator::~Generator() in main.o
      google::protobuf::compiler::php::Generator::~Generator() in main.o
  "google::protobuf::compiler::CommandLineInterface::AllowPlugins(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&)", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "google::protobuf::compiler::CommandLineInterface::RegisterGenerator(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&, google::protobuf::compiler::CodeGenerator*, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&)", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "google::protobuf::compiler::CommandLineInterface::Run(int, char const* const*)", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "google::protobuf::compiler::CommandLineInterface::CommandLineInterface()", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "google::protobuf::compiler::CommandLineInterface::~CommandLineInterface()", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "google::protobuf::compiler::cpp::CppGenerator::CppGenerator()", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "google::protobuf::compiler::cpp::CppGenerator::~CppGenerator()", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "google::protobuf::compiler::java::JavaGenerator::JavaGenerator()", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "google::protobuf::compiler::java::JavaGenerator::~JavaGenerator()", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "google::protobuf::compiler::csharp::Generator::Generator()", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "google::protobuf::compiler::csharp::Generator::~Generator()", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "google::protobuf::compiler::python::Generator::Generator()", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "google::protobuf::compiler::python::Generator::~Generator()", referenced from:
      google::protobuf::compiler::ProtobufMain(int, char**) in main.o
  "vtable for google::protobuf::compiler::CodeGenerator", referenced from:
      google::protobuf::compiler::CodeGenerator::CodeGenerator() in main.o
  NOTE: a missing vtable usually means the first non-inline virtual member function has no definition.
  "vtable for google::protobuf::compiler::js::Generator", referenced from:
      google::protobuf::compiler::js::Generator::Generator() in main.o
  NOTE: a missing vtable usually means the first non-inline virtual member function has no definition.
  "vtable for google::protobuf::compiler::php::Generator", referenced from:
      google::protobuf::compiler::php::Generator::Generator() in main.o
  NOTE: a missing vtable usually means the first non-inline virtual member function has no definition.
  "vtable for google::protobuf::compiler::ruby::Generator", referenced from:
      google::protobuf::compiler::ruby::Generator::Generator() in main.o
  NOTE: a missing vtable usually means the first non-inline virtual member function has no definition.
ld: symbol(s) not found for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[2]: *** [protoc] Error 1
make[1]: *** [all-recursive] Error 1
make: *** [all] Error 2

Answer 1

哦，我找到答案了!

看https://github.com/openssl/openssl/issues/10709#issuecomment-589430851和 https://github.com/bitcoin/bitcoin/issues/20825#issuecomment-753444519 ，解决方案非常简单:

brew uninstall binutils

非常有趣的错误信息和解决方案...