如何解决使用 scons 构建 dll 时,如何修复未解析的外部符号 _DllMainCRTStartup?
编辑:原来是用户错误。我的来源不在NativeLib/
,它在NativeLib/NativeLib/
。始终检查您的路径!
我正在尝试使用 Visual Studio Community 2019 和 scons 4.1.0 构建一个 dll,但我得到了一个未解析的外部符号。
E:\Projects\GodotProjects\Units\Units>scons -c platform=windows
scons: Reading sconscript files ...
scons: done reading sconscript files.
scons: Cleaning targets ...
scons: done cleaning targets.
E:\Projects\GodotProjects\Units\Units>scons platform=windows
scons: Reading sconscript files ...
scons: done reading sconscript files.
scons: Building targets ...
link /nologo /dll /out:Godot\bin\win64\libgdexample.dll /implib:Godot\bin\win64\libgdexample.lib /LIBPATH:E:\Projects\GodotProjects\Units\godot-cpp\bin libgodot-cpp.windows.debug.64.lib
LINK : warning LNK4001: no object files specified; libraries used
LINK : warning LNK4068: /MACHINE not specified; defaulting to X64
LINK : error LNK2001: unresolved external symbol _DllMainCRTStartup
Godot\bin\win64\libgdexample.dll : Fatal error LNK1120: 1 unresolved externals
scons: *** [Godot\bin\win64\libgdexample.dll] Error 1120
scons: building terminated because of errors.
根据文档 (DLLs and Visual C++ run-time library behavior),“当您使用 Visual Studio 构建动态链接库 (DLL) 时,默认情况下,链接器包含 Visual C++ 运行时库 (VCRuntime)。. .. 当链接到 DLL 时,VCRuntime 代码提供了一个名为 _DllMainCRTStartup 的内部 DLL 入口点函数,该函数处理到 DLL 的 Windows 操作系统消息,以附加到进程或线程或从进程或线程分离。”
所以听起来我需要以某种方式包含 VCRuntime,但我找不到它的库。根据 this,_DllMainCRTStartup 在 corelibc.lib 中,但我找不到任何关于在哪里找到或如何包含它的信息。
我也不知道 _DllMainCRTStartup 的引用在哪里。它不在我的任何 .cpp 或 .h 文件中,我在 sconstruct 文件或任何 Visual Studio 文件中都找不到它。我认为我对编译器的了解还不够多,无法进一步调试。
这是我的 SConstruct 文件:
#!python
import os,subprocess
opts = Variables([],ARGUMENTS)
# Gets the standard flags CC,CCX,etc.
# env = DefaultEnvironment() - changed at request of bdbaddog
env = Environment()
# Define our options
opts.Add(EnumVariable('target',"Compilation target",'debug',['d','r','release']))
opts.Add(EnumVariable('platform',"Compilation platform",'',['','windows','x11','linux','osx']))
opts.Add(EnumVariable('p',"Compilation target,alias for 'platform'",'osx']))
opts.Add(BoolVariable('use_llvm',"Use the LLVM / Clang compiler",'no'))
opts.Add(PathVariable('target_path','The path where the lib is installed.','Godot/bin/'))
opts.Add(PathVariable('target_name','The library name.','libgdexample',PathVariable.PathAccept))
# Local dependency paths,adapt them to your setup
godot_headers_path = "../godot-cpp/godot-headers/"
cpp_bindings_path = "../godot-cpp/"
cpp_library = "libgodot-cpp"
# only support 64 at this time..
bits = 64
# Updates the environment with the option variables.
opts.Update(env)
# Process some arguments
if env['use_llvm']:
env['CC'] = 'clang'
env['CXX'] = 'clang++'
if env['p'] != '':
env['platform'] = env['p']
if env['platform'] == '':
print("No valid target platform selected.")
quit();
# Check our platform specifics
if env['platform'] == "osx":
env['target_path'] += 'osx/'
cpp_library += '.osx'
if env['target'] in ('debug','d'):
env.Append(CCFLAGS = ['-g','-O2','-arch','x86_64','-std=c++17'])
env.Append(LINKFLAGS = ['-arch','x86_64'])
else:
env.Append(CCFLAGS = ['-g','-O3','x86_64'])
elif env['platform'] in ('x11','linux'):
env['target_path'] += 'x11/'
cpp_library += '.linux'
if env['target'] in ('debug','d'):
env.Append(CCFLAGS = ['-fPIC','-g3','-Og','-std=c++17'])
else:
env.Append(CCFLAGS = ['-fPIC','-g','-std=c++17'])
elif env['platform'] == "windows":
env['target_path'] += 'win64/'
cpp_library += '.windows'
# This makes sure to keep the session environment variables on windows,# that way you can run scons in a vs 2017 prompt and it will find all the required tools
# env.Append(ENV = os.environ)
#env.Append(CCFLAGS = ['-DWIN32','-D_WIN32','-D_WINDOWS','-W3','-GR','-D_CRT_SECURE_NO_WARNINGS']) - changed at request of bdbaddog
env.Append(CCFLAGS = ['-D_WIN32','-D_CRT_SECURE_NO_WARNINGS'])
env.Append(CPPDEFInes = ['WIN32'])
if env['target'] in ('debug','d'):
env.Append(CCFLAGS = ['-EHsc','-D_DEBUG','-MDd'])
else:
env.Append(CCFLAGS = ['-O2','-EHsc','-DNDEBUG','-MD'])
if env['target'] in ('debug','d'):
cpp_library += '.debug'
else:
cpp_library += '.release'
cpp_library += '.' + str(bits)
# make sure our binding library is properly includes
env.Append(CPPPATH=['.',godot_headers_path,cpp_bindings_path + 'include/',cpp_bindings_path + 'include/core/',cpp_bindings_path + 'include/gen/'])
env.Append(LIBPATH=[cpp_bindings_path + 'bin/'])
env.Append(LIBS=[cpp_library])
# tweak this if you want to use different folders,or more folders,to store your source code in.
env.Append(CPPPATH=['NativeLib/'])
sources = Glob('NativeLib/*.cpp')
library = env.SharedLibrary(target=env['target_path'] + env['target_name'],source=sources)
Default(library)
# Generates help for the -h scons option.
Help(opts.GenerateHelpText(env))
解决方法
从这一行
link /nologo /dll /out:Godot\bin\win64\libgdexample.dll /implib:Godot\bin\win64\libgdexample.lib /LIBPATH:E:\Projects\GodotProjects\Units\godot-cpp\bin libgodot-cpp.windows.debug.64.lib
我可以看到您仍然没有编译任何源文件..这可能是您真正的问题。
在您的 Glob for sources 之后添加此内容
for s in sources:
print("Source:%s"%s)
运行并更新上面的输出。
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