c++ - CMake:使静态库有效但动态库无效

Question

我正在尝试使用 CMake 创建一个共享库，但它有线，如果我静态地创建它，它运行良好，但动态的则不然:

CMAKE_MINIMUM_REQUIRED(VERSION 3.6)
PROJECT(TestDemo)

SET(CMAKE_CXX_STANDARD 11)
SET(CMAKE_CXX_COMPILER clang++)

# Headers
INCLUDE_DIRECTORIES(src)
INCLUDE_DIRECTORIES(src/xxx)
INCLUDE_DIRECTORIES(3rdparty/zstd)
INCLUDE_DIRECTORIES(/usr/local/include)

# CORE LIB
FILE(GLOB CORE_SRC src/xxx/*.cpp
        src/xxx/io/*.cpp
        src/xxx/util/*.cpp
        src/xxx/thread/*.cpp)
LIST(REMOVE_ITEM CORE_SRC ${CMAKE_CURRENT_SOURCE_DIR}/src/xxx/io/BzipStream.cpp
        ${CMAKE_CURRENT_SOURCE_DIR}/src/xxx/io/GzipStream.cpp)

# This works
ADD_LIBRARY(xxx-core STATIC ${CORE_SRC})
# This doesn't
#ADD_LIBRARY(xxx-core SHARED ${CORE_SRC})

错误信息是:

[100%] Linking CXX shared library libxxxdb-core.dylib
Undefined symbols for architecture x86_64:
  "_mpool_get_global", referenced from:
      xxx::mpoolxx<xxx::alloc_to_mpool_bridge<xxx::mpoolxx<long>, 1>::MemBlock>::get_vtab() in trb_cxx.cpp.o
  "_sfixed_mpool_destroy", referenced from:
      xxx::fixed_mpool_wrapper<24>::~fixed_mpool_wrapper() in trb_cxx.cpp.o
  "_sfixed_mpool_init", referenced from:
      xxx::fixed_mpool_wrapper<24>::fixed_mpool_wrapper() in trb_cxx.cpp.o
  "_trb_destroy", referenced from:
      xxx::trbstrmap_imp<int, unsigned char, &(xxx_trb_compare_less_tag), xxx::mpoolxx<long>, 0, 16>::~trbstrmap_imp() in trb_cxx.cpp.o
      xxx::trbtab<int const, std::__1::pair<int const, int>, 0, &(xxx_trb_compare_less_tag), xxx::fixed_mpoolxx<long>, 0, 16>::~trbtab() in trb_cxx.cpp.o
  "_trb_erase", referenced from:
      xxx::trbtab<int const, std::__1::pair<int const, int>, 0, &(xxx_trb_compare_less_tag), xxx::fixed_mpoolxx<long>, 0, 16>::erase(int const&) in trb_cxx.cpp.o
      xxx::trbtab<int const, std::__1::pair<int const, int>, 0, &(xxx_trb_compare_less_tag), xxx::fixed_mpoolxx<long>, 0, 16>::erase(xxx::trb_iterator<std::__1::pair<int const, int>, 16, 0>) in trb_cxx.cpp.o
  "_trb_iter_first", referenced from:
      xxx::trbtab<int const, std::__1::pair<int const, int>, 0, &(xxx_trb_compare_less_tag), xxx::fixed_mpoolxx<long>, 0, 16>::begin() const in trb_cxx.cpp.o
  "_trb_iter_next", referenced from:
      xxx::trb_iterator<std::__1::pair<int const, int>, 16, 0>::operator++() in trb_cxx.cpp.o
  "_trb_probe", referenced from:
      xxx::trbtab<int const, std::__1::pair<int const, int>, 0, &(xxx_trb_compare_less_tag), xxx::fixed_mpoolxx<long>, 0, 16>::insert(std::__1::pair<int const, int> const&) in trb_cxx.cpp.o
      xxx::trbmap<int, int, &(xxx_trb_compare_less_tag), xxx::fixed_mpoolxx<long>, 0, 16>::operator[](int const&) in trb_cxx.cpp.o
  "_trb_probe_node", referenced from:
      xxx::trbstrmap_imp<int, unsigned char, &(xxx_trb_compare_less_tag), xxx::mpoolxx<long>, 0, 16>::probe_raw(char const*, unsigned long, char const*) in trb_cxx.cpp.o
  "_trb_vtab_init", referenced from:
      xxx::trbxx_vtab_init_by_cxx_type(trb_vtab*, field_type_t, int (*)(trb_vtab const*, trb_tree const*, void const*, void const*), int (*)(trb_vtab const*, trb_tree const*, void const*, void const*)) in trb_cxx.cpp.o
      xxx::trbxx_vtab_init(trb_vtab*, field_type_t, int (*)(trb_vtab const*, trb_tree const*, void const*, void const*)) in trb_cxx.cpp.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

在创建静态库时没有链接发生，因为静态库不是由链接器生成的:它只是创建的目标文件的存档与存档器 ar .所以不能创建静态库时出现任何 undefined reference 或其他链接错误，就像您创建目标文件的 .tar 或 .zip 存档一样。参见 static-libraries ,

一个共享库，就像一个程序，是由链接器和 Mac OS/Darwin 产生的链接器(不同于 GNU/Linux 链接器)默认情况下不允许 undefined symbol 共享库中的引用。

你有两个选择:

你可以指定xxx-core链接所依赖的所有库，与 target_link_libraries

或者，您可以使用链接选项覆盖链接器的默认行为 -undefined=dynamic_lookup , 表示共享库中 undefined reference 将由加载程序在运行时解析。在您的 CMakeLists.txt 中，使用 set_target_properties在定义了 xxx-core 目标之后:

ADD_LIBRARY(xxx-core SHARED ${CORE_SRC})
SET_TARGET_PROPERTIES(xxx-core LINK_FLAGS Wl,-undefined=dynamic_lookup)