c++ - cppunit 和 xcode 项目的 vtable 问题

Question

我正在尝试构建 zxing iphone 项目并运行用 cppunit-1.12.1 编写的测试套件。我在项目中复制了 cppunit-1.12.1 代码，并将事件 SDK 更改为 10.5，我能够构建 cppunit 和 zxingcore 目标，但是当我尝试构建 zxingcore-tests 目标时，出现以下错误，这似乎与 vtables 有关，还有一个与库的体系结构类型有关的奇怪警告:

有没有一种格式化它的好方法，基本上是转义格式化而不必在每一行的前面插入一个>。我用了<pre>在预览中效果很好但在最终渲染中效果不佳的标签 - 不遵守格式并切断文本。一旦有人给我建议，我会尽快修改格式。

Ld build/Debug/zxingcore-tests normal i386
cd /Users/andres/src/zxing/iphone
setenv MACOSX_DEPLOYMENT_TARGET 10.5
/Developer/usr/bin/g++-4.2 -arch i386 -isysroot /Developer/SDKs/MacOSX10.5.sdk -L/Users/andres/src/zxing/iphone/build/Debug -F/Users/andres/src/zxing/iphone/build/Debug -filelist /Users/andres/src/zxing/iphone/build/ZXing.build/Debug/zxingcore-tests.build/Objects-normal/i386/zxingcore-tests.LinkFileList -mmacosx-version-min=10.5 -lzxingcore -lCppUnit -o /Users/andres/src/zxing/iphone/build/Debug/zxingcore-tests

ld: warning: in /Developer/SDKs/MacOSX10.5.sdk/usr/local/lib/libCppUnit.dylib, file is not of required architecture
ld: warning: common::Counted::Counted()has different visibility (default) in /Users/andres/src/zxing/iphone/build/Debug/libzxingcore.a(GF256.o) and (hidden) in /Users/andres/src/zxing/iphone/build/ZXing.build/Debug/zxingcore-tests.build/Objects-normal/i386/BitSourceTest.o
ld: warning: common::Counted::retain()    has different visibility (default) in /Users/andres/src/zxing/iphone/build/Debug/libzxingcore.a(GF256.o) and (hidden) in /Users/andres/src/zxing/iphone/build/ZXing.build/Debug/zxingcore-tests.build/Objects-normal/i386/BitSourceTest.o
ld: warning: common::ArrayRef::~ArrayRef()has different visibility (default) in /Users/andres/src/zxing/iphone/build/Debug/libzxingcore.a(GF256.o) and (hidden) in /Users/andres/src/zxing/iphone/build/ZXing.build/Debug/zxingcore-tests.build/Objects-normal/i386/ReedSolomonTest.o
ld: warning: std::valarray::operator[](unsigned long)has different visibility (default) in /Users/andres/src/zxing/iphone/build/Debug/libzxingcore.a(GF256.o) and (hidden) in /Users/andres/src/zxing/iphone/build/ZXing.build/Debug/zxingcore-tests.build/Objects-normal/i386/ReedSolomonTest.o
ld: warning: common::ArrayRef::reset(common::Array*)has different visibility (default) in /Users/andres/src/zxing/iphone/build/Debug/libzxingcore.a(GF256.o) and (hidden) in /Users/andres/src/zxing/iphone/build/ZXing.build/Debug/zxingcore-tests.build/Objects-normal/i386/ReedSolomonTest.o
ld: warning: common::ArrayRef::ArrayRef(common::Array*)has different visibility (default) in /Users/andres/src/zxing/iphone/build/Debug/libzxingcore.a(GF256.o) and (hidden) in /Users/andres/src/zxing/iphone/build/ZXing.build/Debug/zxingcore-tests.build/Objects-normal/i386/ReedSolomonTest.o
ld: warning: common::ArrayRef::ArrayRef(common::ArrayRef const&)has different visibility (default) in /Users/andres/src/zxing/iphone/build/Debug/libzxingcore.a(GF256.o) and (hidden) in /Users/andres/src/zxing/iphone/build/ZXing.build/Debug/zxingcore-tests.build/Objects-normal/i386/ReedSolomonTest.o

....many more of these warnings...

现在是错误

Undefined symbols:
  "vtable for CppUnit::TestSuiteBuilderContextBase", referenced from:
      __ZTVN7CppUnit27TestSuiteBuilderContextBaseE$non_lazy_ptr in BitArrayTest.o
      __ZTVN7CppUnit27TestSuiteBuilderContextBaseE$non_lazy_ptr in BitMatrixTest.o
      __ZTVN7CppUnit27TestSuiteBuilderContextBaseE$non_lazy_ptr in BitSourceTest.o
      __ZTVN7CppUnit27TestSuiteBuilderContextBaseE$non_lazy_ptr in BlackPointEstimatorTest.o
      __ZTVN7CppUnit27TestSuiteBuilderContextBaseE$non_lazy_ptr in PerspectiveTransformTest.o
      __ZTVN7CppUnit27TestSuiteBuilderContextBaseE$non_lazy_ptr in ReedSolomonTest.o
      __ZTVN7CppUnit27TestSuiteBuilderContextBaseE$non_lazy_ptr in DataMaskTest.o
      __ZTVN7CppUnit27TestSuiteBuilderContextBaseE$non_lazy_ptr in ErrorCorrectionLevelTest.o
      __ZTVN7CppUnit27TestSuiteBuilderContextBaseE$non_lazy_ptr in FormatInformationTest.o
      __ZTVN7CppUnit27TestSuiteBuilderContextBaseE$non_lazy_ptr in ModeTest.o
      __ZTVN7CppUnit27TestSuiteBuilderContextBaseE$non_lazy_ptr in VersionTest.o
  "CppUnit::TestLeaf::doGetChildTestAt(int) const", referenced from:
      vtable for CppUnit::TestCaller in BitArrayTest.o
      vtable for CppUnit::TestCaller in BitMatrixTest.o
      vtable for CppUnit::TestCaller in BitSourceTest.o
      vtable for CppUnit::TestCaller in BlackPointEstimatorTest.o
      vtable for CppUnit::TestCaller in PerspectiveTransformTest.o
      vtable for CppUnit::TestCaller  in ReedSolomonTest.o
      vtable for CppUnit::TestCallerin DataMaskTest.o
      vtable for CppUnit::TestCallerin ErrorCorrectionLevelTest.o
      vtable for CppUnit::TestCallerin FormatInformationTest.o
      vtable for CppUnit::TestCallerin ModeTest.o
      vtable for CppUnit::TestCallerin VersionTest.o
  "typeinfo for CppUnit::TestCase", referenced from:
      typeinfo for CppUnit::TestCallerin BitArrayTest.o
      typeinfo for CppUnit::TestCallerin BitMatrixTest.o
      typeinfo for CppUnit::TestCallerin BitSourceTest.o
      typeinfo for CppUnit::TestCallerin BlackPointEstimatorTest.o
      typeinfo for CppUnit::TestCallerin PerspectiveTransformTest.o
      typeinfo for CppUnit::TestCallerin ReedSolomonTest.o
      typeinfo for CppUnit::TestCallerin DataMaskTest.o
      typeinfo for CppUnit::TestCallerin ErrorCorrectionLevelTest.o
      typeinfo for CppUnit::TestCallerin FormatInformationTest.o
      typeinfo for CppUnit::TestCallerin ModeTest.o
      typeinfo for CppUnit::TestCallerin VersionTest.o
  "CppUnit::TestLeaf::countTestCases() const", referenced from:
      vtable for CppUnit::TestCaller in BitArrayTest.o
      vtable for CppUnit::TestCaller in BitMatrixTest.o
      vtable for CppUnit::TestCaller in BitSourceTest.o
      vtable for CppUnit::TestCaller in BlackPointEstimatorTest.o
      vtable for CppUnit::TestCaller in 
`... lots of these errors ... `
CppUnit::assertEquals(qrcode::decoder::FormatInformation const&, qrcode::decoder::FormatInformation const&, CppUnit::SourceLine, std::basic_string, std::allocator > const&)in FormatInformationTest.o
      void CppUnit::assertEquals(int const&, int const&, CppUnit::SourceLine, std::basic_string, std::allocator > const&)in ModeTest.o
      void CppUnit::assertEquals(qrcode::decoder::Mode* const&, qrcode::decoder::Mode* const&, CppUnit::SourceLine, std::basic_string, std::allocator > const&)in ModeTest.o
      void CppUnit::assertEquals(int const&, int const&, CppUnit::SourceLine, std::basic_string, std::allocator > const&)in VersionTest.o
      void CppUnit::assertEquals(bool const&, bool const&, CppUnit::SourceLine, std::basic_string, std::allocator > const&)in VersionTest.o
ld: symbol(s) not found
collect2: ld returned 1 exit status
 

Answer 1

好的，这就是我认为的问题所在，但不要在这方面引用我的话；)

cppunit 代码使用 CPPUNIT_API要结束的宏

__declspec(dllexport)

和

__declspec(dllimport)

在 Win32 上构建时。它不使用等价物

__attribute__ ((visibility("default")))

gcc .当在确实使用 gcc 中的可见性属性的项目中包含该代码时，这可能会导致问题，最值得注意的是当项目使用 gcc命令行标志

-fvisibility=hidden

默认将所有符号设为库私有(private)，然后使用

__attribute__((visibility("default")))

代替__declspec(dllexport/import)在适当情况下。如果一个符号(例如 vtable)仅在一个库中被标记为隐藏，即使它在所有其他库中被标记为公开，那么显然(请参阅下面的链接)它被标记为隐藏并且您会收到链接器错误。

在您的情况下，您最初收到的链接器警告表明 zxingcore-tests正在构建时默认隐藏符号(在构建时检查 -f 选项)，而 xzingcore本身将它们公开。 cppunit vtable 的符号将存在于 cppunit 中, zxingcore和 zxingcore-tests但在 zxingcore-test 中标记为隐藏所以他们被隐藏了。

我认为您需要尝试找出 zxingcore-tests 的原因build 正在隐藏符号并阻止它这样做。

要进一步阅读，请尝试 gcc wiki visibility page ，特别是关于“C++ 异常问题”的部分(并遵循其中关于模糊链接的链接，这也表明它也适用于 vtables)。因为被dynamic_cast咬过，所以对这玩意隐约有些熟悉跨库失败，在这种情况下，是由 typeinfo 引起的错误地隐藏了对象。