来自 CMake 的 Emscripten 库无法链接

Question

我在 Windows 10 64 位平台上使用 Grassroot Dicom 查看器版本 2.8.9 编译成 Emscripten 库 bc。

我按照本网站的说明进行操作

emconfigure cmake .
emmake make VERBOSE=1

之后，我得到了以 .a 而不是 .bc 结尾的库文件，类似于

libgdcmcharls.a libgdcmCommon.a libgdcmDICT.a ....

当我查看它开头的每个静态库文件的汇编代码时

！拱。/

代替

公元前

如教程网站中所述注意

使用上述过程，某些构建系统可能无法正确发出位代码，您可能会看到无效的位代码警告。您可以运行 file 来检查文件是否包含位码（您也可以手动检查内容是否以 BC 开头）。还值得运行 emmake make VERBOSE=1 这将打印出它运行的命令 - 您应该看到正在使用 emcc，而不是本机系统编译器。如果不使用 emcc，您可能需要修改 configure 或 cmake 脚本。

我认为这是我无法生成内容以 BC 开头的库的问题，但我得到了！拱 ./ ?

当然这些文件不能从 emcc 链接（找不到参考错误）

error: undefined symbol: _ZN4gdcm11ImageReader8GetImageEv
error: undefined symbol: _ZN4gdcm11ImageReaderC1Ev
error: undefined symbol: _ZN4gdcm11ImageReaderD1Ev
error: undefined symbol: _ZN4gdcm5Trace14GetErrorStreamE

所以我根据这个修改了 GDCM CMakefile.txt

if (EMSCRIPTEN)
    set(CMAKE_AR "emcc" CACHE)
    set(CMAKE_STATIC_LIBRARY_SUFFIX ".bc")
    set(CMAKE_C_CREATE_STATIC_LIBRARY "<CMAKE_AR> -o <TARGET> <LINK_FLAGS> <OBJECTS>")
    set(CMAKE_CXX_CREATE_STATIC_LIBRARY "<CMAKE_AR> -o <TARGET> <LINK_FLAGS> <OBJECTS>")
endif()

但是，它没有任何帮助。“make”仍然生成 .a 库文件

我编译代码的命令如下；我还将所有 .a 文件复制到与 main.cpp 相同的文件夹中

emcc -std=c++17 -O3 -s WASM=1  -s USE_WEBGL2=1 -s FULL_ES3=1 -s ALLOW_MEMORY_GROWTH=1 -o hello.html  -s "EXTRA_EXPORTED_RUNTIME_METHODS=['ccall', 'cwrap']" --no-heap-copy libgdcmcharls.a libgdcmCommon.a libgdcmDICT.a libgdcmDSED.a libgdcmexpat.a libgdcmIOD.a libgdcmjpeg12.a libgdcmjpeg16.a libgdcmjpeg8.a libgdcmMEXD.a libgdcmMSFF.a libgdcmopenjp2.a libgdcmzlib.a libgdcmuuid.a libsocketxx.a main.cpp ...........

该链接是我GDCM 2.8.9库文件。在 Windows10 中使用 emcmake cmake 编译，最后使用 emmake make（基于 mingw32-make）。

这是我调用 emconfigure cmake 后的 CMakeCXXCompiler.cmake 。

set(CMAKE_CXX_COMPILER "C:/workspace/emsdk/emscripten/1.38.14/em++.bat")
set(CMAKE_CXX_COMPILER_ARG1 "")
set(CMAKE_CXX_COMPILER_ID "Clang")
set(CMAKE_CXX_COMPILER_VERSION "6.0.1")
set(CMAKE_CXX_COMPILER_VERSION_INTERNAL "")
set(CMAKE_CXX_COMPILER_WRAPPER "")
set(CMAKE_CXX_STANDARD_COMPUTED_DEFAULT "98")
set(CMAKE_CXX_COMPILE_FEATURES "cxx_std_98;cxx_template_template_parameters;cxx_std_11;cxx_alias_templates;cxx_alignas;cxx_alignof;cxx_attributes;cxx_auto_type;cxx_constexpr;cxx_decltype;cxx_decltype_incomplete_return_types;cxx_default_function_template_args;cxx_defaulted_functions;cxx_defaulted_move_initializers;cxx_delegating_constructors;cxx_deleted_functions;cxx_enum_forward_declarations;cxx_explicit_conversions;cxx_extended_friend_declarations;cxx_extern_templates;cxx_final;cxx_func_identifier;cxx_generalized_initializers;cxx_inheriting_constructors;cxx_inline_namespaces;cxx_lambdas;cxx_local_type_template_args;cxx_long_long_type;cxx_noexcept;cxx_nonstatic_member_init;cxx_nullptr;cxx_override;cxx_range_for;cxx_raw_string_literals;cxx_reference_qualified_functions;cxx_right_angle_brackets;cxx_rvalue_references;cxx_sizeof_member;cxx_static_assert;cxx_strong_enums;cxx_thread_local;cxx_trailing_return_types;cxx_unicode_literals;cxx_uniform_initialization;cxx_unrestricted_unions;cxx_user_literals;cxx_variadic_macros;cxx_variadic_templates;cxx_std_14;cxx_aggregate_default_initializers;cxx_attribute_deprecated;cxx_binary_literals;cxx_contextual_conversions;cxx_decltype_auto;cxx_digit_separators;cxx_generic_lambdas;cxx_lambda_init_captures;cxx_relaxed_constexpr;cxx_return_type_deduction;cxx_variable_templates;cxx_std_17")
set(CMAKE_CXX98_COMPILE_FEATURES "cxx_std_98;cxx_template_template_parameters")
set(CMAKE_CXX11_COMPILE_FEATURES "cxx_std_11;cxx_alias_templates;cxx_alignas;cxx_alignof;cxx_attributes;cxx_auto_type;cxx_constexpr;cxx_decltype;cxx_decltype_incomplete_return_types;cxx_default_function_template_args;cxx_defaulted_functions;cxx_defaulted_move_initializers;cxx_delegating_constructors;cxx_deleted_functions;cxx_enum_forward_declarations;cxx_explicit_conversions;cxx_extended_friend_declarations;cxx_extern_templates;cxx_final;cxx_func_identifier;cxx_generalized_initializers;cxx_inheriting_constructors;cxx_inline_namespaces;cxx_lambdas;cxx_local_type_template_args;cxx_long_long_type;cxx_noexcept;cxx_nonstatic_member_init;cxx_nullptr;cxx_override;cxx_range_for;cxx_raw_string_literals;cxx_reference_qualified_functions;cxx_right_angle_brackets;cxx_rvalue_references;cxx_sizeof_member;cxx_static_assert;cxx_strong_enums;cxx_thread_local;cxx_trailing_return_types;cxx_unicode_literals;cxx_uniform_initialization;cxx_unrestricted_unions;cxx_user_literals;cxx_variadic_macros;cxx_variadic_templates")
set(CMAKE_CXX14_COMPILE_FEATURES "cxx_std_14;cxx_aggregate_default_initializers;cxx_attribute_deprecated;cxx_binary_literals;cxx_contextual_conversions;cxx_decltype_auto;cxx_digit_separators;cxx_generic_lambdas;cxx_lambda_init_captures;cxx_relaxed_constexpr;cxx_return_type_deduction;cxx_variable_templates")
set(CMAKE_CXX17_COMPILE_FEATURES "")
set(CMAKE_CXX20_COMPILE_FEATURES "")

set(CMAKE_CXX_PLATFORM_ID "emscripten")
set(CMAKE_CXX_SIMULATE_ID "")
set(CMAKE_CXX_SIMULATE_VERSION "")



set(CMAKE_AR "C:/workspace/emsdk/emscripten/1.38.14/emar.bat")
set(CMAKE_CXX_COMPILER_AR "C:/Program Files/LLVM/bin/llvm-ar.exe")
set(CMAKE_RANLIB "C:/workspace/emsdk/emscripten/1.38.14/emranlib.bat")
set(CMAKE_CXX_COMPILER_RANLIB "C:/Program Files/LLVM/bin/llvm-ranlib.exe")
set(CMAKE_LINKER "C:/Program Files/LLVM/bin/wasm-ld.exe")
set(CMAKE_COMPILER_IS_GNUCXX )
set(CMAKE_CXX_COMPILER_LOADED 1)
set(CMAKE_CXX_COMPILER_WORKS TRUE)
set(CMAKE_CXX_ABI_COMPILED )
set(CMAKE_COMPILER_IS_MINGW )
set(CMAKE_COMPILER_IS_CYGWIN )
if(CMAKE_COMPILER_IS_CYGWIN)
  set(CYGWIN 1)
  set(UNIX 1)
endif()

set(CMAKE_CXX_COMPILER_ENV_VAR "CXX")

if(CMAKE_COMPILER_IS_MINGW)
  set(MINGW 1)
endif()
set(CMAKE_CXX_COMPILER_ID_RUN 1)
set(CMAKE_CXX_IGNORE_EXTENSIONS inl;h;hpp;HPP;H;o;O;obj;OBJ;def;DEF;rc;RC)
set(CMAKE_CXX_SOURCE_FILE_EXTENSIONS C;M;c++;cc;cpp;cxx;mm;CPP)
set(CMAKE_CXX_LINKER_PREFERENCE 30)
set(CMAKE_CXX_LINKER_PREFERENCE_PROPAGATES 1)

# Save compiler ABI information.
set(CMAKE_CXX_SIZEOF_DATA_PTR "4")
set(CMAKE_CXX_COMPILER_ABI "")
set(CMAKE_CXX_LIBRARY_ARCHITECTURE "")

if(CMAKE_CXX_SIZEOF_DATA_PTR)
  set(CMAKE_SIZEOF_VOID_P "${CMAKE_CXX_SIZEOF_DATA_PTR}")
endif()

if(CMAKE_CXX_COMPILER_ABI)
  set(CMAKE_INTERNAL_PLATFORM_ABI "${CMAKE_CXX_COMPILER_ABI}")
endif()

if(CMAKE_CXX_LIBRARY_ARCHITECTURE)
  set(CMAKE_LIBRARY_ARCHITECTURE "")
endif()

set(CMAKE_CXX_CL_SHOWINCLUDES_PREFIX "")
if(CMAKE_CXX_CL_SHOWINCLUDES_PREFIX)
  set(CMAKE_CL_SHOWINCLUDES_PREFIX "${CMAKE_CXX_CL_SHOWINCLUDES_PREFIX}")
endif()





set(CMAKE_CXX_IMPLICIT_LINK_LIBRARIES "")
set(CMAKE_CXX_IMPLICIT_LINK_DIRECTORIES "")
set(CMAKE_CXX_IMPLICIT_LINK_FRAMEWORK_DIRECTORIES "")

Answer 1

最后我发现了问题。命令生成的库；

配置 cmake 。

与 emcc 不兼容，即使我看到它使用 em++.bat 作为编译器的编译器。

如何发现问题。

我使用一个名为“Hex Editor Neo”的程序来打开库文件（仅使用小库文件进行测试，大库文件会导致程序崩溃）。

如果与emcc不兼容使用。前几个字符将是！拱 这行不通。cmake生成错误的库文件见下图；

确保您拥有如下图所示的 BC；

但如何做到这一点

你不能只使用

emconfigure cmake .  <---------- wrong

您需要通过以下命令放置一个选项来生成位码（.bc）

emconfigure cmake . -DEMSCRIPTEN_GENERATE_BITCODE_STATIC_LIBRARIES=1

然后它会生成所有以 .bc 结尾的库文件，这些库文件可以用 emcc 链接