无法编译具有 snappy 支持的 leveldb

Question

我正在尝试在 mac os x high sierra 上构建 https://github.com/google/leveldb with support for https://github.com/google/snappy 压缩以供以后在 XCode 项目中使用，我正在完成标准编译过程两个项目的自述文件中都有描述。这包括通过 cmake 为两个项目构建项目。在 snappy 项目的情况下，过程很顺利，一切都可以完美地构建和安装。但是在 leveldb 的情况下，我无法让 cmake 找到我之前通过 make install 安装的 snappy 库。我不明白如何调试 cmake 并找到它查找库的位置。

感谢任何帮助。

以下是两个构建的结果：

编辑

这是一个输出，似乎 /usr/local/lib 在列表中

另一个编辑

我已经按照 sel-fish 提供的解决方案尝试了运行 cc -DCHECK_FUNCTION_EXISTS=snappy_compress -Wl,-search_paths_first -Wl,-headerpad_max_install_names -o check_snappy_exist CheckFunctionExists.c -lsnappy。但如果失败并显示以下输出：

Undefined symbols for architecture x86_64:
  "std::__1::__vector_base_common<true>::__throw_length_error() const", referenced from:
      void std::__1::vector<snappy::SnappySinkAllocator::Datablock, std::__1::allocator<snappy::SnappySinkAllocator::Datablock> >::__push_back_slow_path<snappy::SnappySinkAllocator::Datablock const>(snappy::SnappySinkAllocator::Datablock const&) in libsnappy.a(snappy.cc.o)
      void std::__1::vector<char*, std::__1::allocator<char*> >::__push_back_slow_path<char* const>(char* const&) in libsnappy.a(snappy.cc.o)
  "std::logic_error::logic_error(char const*)", referenced from:
      void std::__1::vector<snappy::SnappySinkAllocator::Datablock, std::__1::allocator<snappy::SnappySinkAllocator::Datablock> >::__push_back_slow_path<snappy::SnappySinkAllocator::Datablock const>(snappy::SnappySinkAllocator::Datablock const&) in libsnappy.a(snappy.cc.o)
      void std::__1::vector<char*, std::__1::allocator<char*> >::__push_back_slow_path<char* const>(char* const&) in libsnappy.a(snappy.cc.o)
  "std::length_error::~length_error()", referenced from:
      void std::__1::vector<snappy::SnappySinkAllocator::Datablock, std::__1::allocator<snappy::SnappySinkAllocator::Datablock> >::__push_back_slow_path<snappy::SnappySinkAllocator::Datablock const>(snappy::SnappySinkAllocator::Datablock const&) in libsnappy.a(snappy.cc.o)
      void std::__1::vector<char*, std::__1::allocator<char*> >::__push_back_slow_path<char* const>(char* const&) in libsnappy.a(snappy.cc.o)
  "std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::resize(unsigned long, char)", referenced from:
      snappy::Uncompress(char const*, unsigned long, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >*) in libsnappy.a(snappy.cc.o)
      snappy::Compress(char const*, unsigned long, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >*) in libsnappy.a(snappy.cc.o)
  "std::terminate()", referenced from:
      ___clang_call_terminate in libsnappy.a(snappy.cc.o)
  "typeinfo for std::length_error", referenced from:
      void std::__1::vector<snappy::SnappySinkAllocator::Datablock, std::__1::allocator<snappy::SnappySinkAllocator::Datablock> >::__push_back_slow_path<snappy::SnappySinkAllocator::Datablock const>(snappy::SnappySinkAllocator::Datablock const&) in libsnappy.a(snappy.cc.o)
      void std::__1::vector<char*, std::__1::allocator<char*> >::__push_back_slow_path<char* const>(char* const&) in libsnappy.a(snappy.cc.o)
  "vtable for __cxxabiv1::__class_type_info", referenced from:
      typeinfo for snappy::Sink in libsnappy.a(snappy-sinksource.cc.o)
      typeinfo for snappy::Source in libsnappy.a(snappy-sinksource.cc.o)
  NOTE: a missing vtable usually means the first non-inline virtual member function has no definition.
  "vtable for __cxxabiv1::__si_class_type_info", referenced from:
      typeinfo for snappy::ByteArraySource in libsnappy.a(snappy-sinksource.cc.o)
      typeinfo for snappy::UncheckedByteArraySink in libsnappy.a(snappy-sinksource.cc.o)
  NOTE: a missing vtable usually means the first non-inline virtual member function has no definition.
  "vtable for std::length_error", referenced from:
      void std::__1::vector<snappy::SnappySinkAllocator::Datablock, std::__1::allocator<snappy::SnappySinkAllocator::Datablock> >::__push_back_slow_path<snappy::SnappySinkAllocator::Datablock const>(snappy::SnappySinkAllocator::Datablock const&) in libsnappy.a(snappy.cc.o)
      void std::__1::vector<char*, std::__1::allocator<char*> >::__push_back_slow_path<char* const>(char* const&) in libsnappy.a(snappy.cc.o)
  NOTE: a missing vtable usually means the first non-inline virtual member function has no definition.
  "operator delete[](void*)", referenced from:
      snappy::Compress(snappy::Source*, snappy::Sink*) in libsnappy.a(snappy.cc.o)
      snappy::SnappySinkAllocator::Deleter(void*, char const*, unsigned long) in libsnappy.a(snappy.cc.o)
  "operator delete(void*)", referenced from:
      snappy::UncompressAsMuchAsPossible(snappy::Source*, snappy::Sink*) in libsnappy.a(snappy.cc.o)
      snappy::Uncompress(snappy::Source*, snappy::Sink*) in libsnappy.a(snappy.cc.o)
      void std::__1::vector<snappy::SnappySinkAllocator::Datablock, std::__1::allocator<snappy::SnappySinkAllocator::Datablock> >::__push_back_slow_path<snappy::SnappySinkAllocator::Datablock const>(snappy::SnappySinkAllocator::Datablock const&) in libsnappy.a(snappy.cc.o)
      void std::__1::vector<char*, std::__1::allocator<char*> >::__push_back_slow_path<char* const>(char* const&) in libsnappy.a(snappy.cc.o)
      snappy::ByteArraySource::~ByteArraySource() in libsnappy.a(snappy-sinksource.cc.o)
      snappy::UncheckedByteArraySink::~UncheckedByteArraySink() in libsnappy.a(snappy-sinksource.cc.o)
  "operator new[](unsigned long)", referenced from:
      snappy::internal::WorkingMemory::GetHashTable(unsigned long, int*) in libsnappy.a(snappy.cc.o)
      snappy::Compress(snappy::Source*, snappy::Sink*) in libsnappy.a(snappy.cc.o)
      snappy::SnappyScatteredWriter<snappy::SnappySinkAllocator>::SlowAppend(char const*, unsigned long) in libsnappy.a(snappy.cc.o)
  "operator new(unsigned long)", referenced from:
      void std::__1::vector<snappy::SnappySinkAllocator::Datablock, std::__1::allocator<snappy::SnappySinkAllocator::Datablock> >::__push_back_slow_path<snappy::SnappySinkAllocator::Datablock const>(snappy::SnappySinkAllocator::Datablock const&) in libsnappy.a(snappy.cc.o)
      void std::__1::vector<char*, std::__1::allocator<char*> >::__push_back_slow_path<char* const>(char* const&) in libsnappy.a(snappy.cc.o)
  "___cxa_allocate_exception", referenced from:
      void std::__1::vector<snappy::SnappySinkAllocator::Datablock, std::__1::allocator<snappy::SnappySinkAllocator::Datablock> >::__push_back_slow_path<snappy::SnappySinkAllocator::Datablock const>(snappy::SnappySinkAllocator::Datablock const&) in libsnappy.a(snappy.cc.o)
      void std::__1::vector<char*, std::__1::allocator<char*> >::__push_back_slow_path<char* const>(char* const&) in libsnappy.a(snappy.cc.o)
  "___cxa_begin_catch", referenced from:
      ___clang_call_terminate in libsnappy.a(snappy.cc.o)
  "___cxa_free_exception", referenced from:
      void std::__1::vector<snappy::SnappySinkAllocator::Datablock, std::__1::allocator<snappy::SnappySinkAllocator::Datablock> >::__push_back_slow_path<snappy::SnappySinkAllocator::Datablock const>(snappy::SnappySinkAllocator::Datablock const&) in libsnappy.a(snappy.cc.o)
      void std::__1::vector<char*, std::__1::allocator<char*> >::__push_back_slow_path<char* const>(char* const&) in libsnappy.a(snappy.cc.o)
  "___cxa_pure_virtual", referenced from:
      vtable for snappy::Sink in libsnappy.a(snappy-sinksource.cc.o)
      vtable for snappy::Source in libsnappy.a(snappy-sinksource.cc.o)
  "___cxa_throw", referenced from:
      void std::__1::vector<snappy::SnappySinkAllocator::Datablock, std::__1::allocator<snappy::SnappySinkAllocator::Datablock> >::__push_back_slow_path<snappy::SnappySinkAllocator::Datablock const>(snappy::SnappySinkAllocator::Datablock const&) in libsnappy.a(snappy.cc.o)
      void std::__1::vector<char*, std::__1::allocator<char*> >::__push_back_slow_path<char* const>(char* const&) in libsnappy.a(snappy.cc.o)
  "___gxx_personality_v0", referenced from:
      snappy::GetUncompressedLength(snappy::Source*, unsigned int*) in libsnappy.a(snappy.cc.o)
      snappy::Compress(snappy::Source*, snappy::Sink*) in libsnappy.a(snappy.cc.o)
      snappy::RawUncompressToIOVec(char const*, unsigned long, iovec const*, unsigned long) in libsnappy.a(snappy.cc.o)
      snappy::RawUncompressToIOVec(snappy::Source*, iovec const*, unsigned long) in libsnappy.a(snappy.cc.o)
      snappy::RawUncompress(char const*, unsigned long, char*) in libsnappy.a(snappy.cc.o)
      snappy::RawUncompress(snappy::Source*, char*) in libsnappy.a(snappy.cc.o)
      snappy::Uncompress(char const*, unsigned long, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >*) in libsnappy.a(snappy.cc.o)
      ...
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Answer 1

您的 link 人似乎找不到 /usr/local/lib/libsnappy.a。

尝试运行clang -Xlinker -v，确保/usr/local/lib存在于Library search paths:

clang -Xlinker -v

@(#)PROGRAM:ld  PROJECT:ld64-278.4
configured to support archs: armv6 armv7 armv7s arm64 i386 x86_64 x86_64h armv6m armv7k armv7m armv7em (tvOS)
Library search paths:
    /usr/lib
    /usr/local/lib

通常，它会存在。然后尝试 sudo update_dyld_shared_cache。

谈到调试 cmake，您可以使用像 --debug-output:

这样的标志

cmake --debug-output --trace --debug-trycompile ..

更新:

check_library_exists(snappy snappy_compress "" HAVE_SNAPPY)

实际执行如下操作，它将尝试link snappy 并查找函数是否存在：

cc  -DCHECK_FUNCTION_EXISTS=snappy_compress -Wl,-search_paths_first -Wl,-headerpad_max_install_names -o check_snappy_exist CheckFunctionExists.c -lsnappy

CheckFunctionExists.c的来源你可以找到here。
我认为这会简化问题。

Answer 2

我已经 end-up 安装 leveldb 和 brew。同样重要的是将 XCode 中的路径添加到 User Header Search Paths，屏幕如下：

无法编译具有 snappy 支持的 leveldb

Unable to compile leveldb with snappy support

c++

cmake

leveldb

snappy