使用clang++构建共享库

Question

我正在尝试使用clang++构建一个共享库(Windows的dll)。

我已经运行了以下命令:

clang++ -c -o hello.o hello.cpp
clang++ -shared -v -o hello.dll hello.o

第一个命令工作正常，但当我试图构建dll时，我得到这个错误:

clang version 3.2 (tags/RELEASE_32/final)
Target: i686-pc-mingw32
Thread model: posix
 "c:/MinGW/bin/g++.exe" -shared -v -m32 -o worker.dll worker.o
Using built-in specs.
COLLECT_GCC=c:/MinGW/bin/g++.exe
COLLECT_LTO_WRAPPER=c:/mingw/bin/../libexec/gcc/mingw32/4.6.2/lto-wrapper.exe
Target: mingw32
Configured with: ../gcc-4.6.2/configure --enable-languages=c,c++,ada,fortran,objc,obj-c++ --disable-sjlj-exceptions --with-dwarf2 --enable-shared --enable-libgomp --disable-win32-registry --enable-libstdcxx-debug --enable-version-specific-runtime-libs --build=mingw32 --prefix=/mingw
Thread model: win32
gcc version 4.6.2 (GCC)
COMPILER_PATH=c:/mingw/bin/../libexec/gcc/mingw32/4.6.2/;c:/mingw/bin/../libexec/gcc/;c:/mingw/bin/../lib/gcc/mingw32/4.6.2/../../../../mingw32/bin/
LIBRARY_PATH=c:/mingw/bin/../lib/gcc/mingw32/4.6.2/;c:/mingw/bin/../lib/gcc/;c:/mingw/bin/../lib/gcc/mingw32/4.6.2/../../../../mingw32/lib/;c:/mingw/bin/../lib/gcc/mingw32/4.6.2/../../../;/mingw/lib/
COLLECT_GCC_OPTIONS='-shared' '-v' '-m32' '-o' 'worker.dll' '-shared-libgcc' '-mtune=i386' '-march=i386'
 c:/mingw/bin/../libexec/gcc/mingw32/4.6.2/collect2.exe --shared -Bdynamic -e _DllMainCRTStartup@12 --enable-auto-image-base -u ___register_frame_info -u ___deregister_frame_info -o worker.dll c:/mingw/bin/../lib/gcc/mingw32/4.6.2/../../../dllcrt2.o c:/mingw/bin/../lib/gcc/mingw32/4.6.2/crtbegin.o -Lc:/mingw/bin/../lib/gcc/mingw32/4.6.2 -Lc:/mingw/bin/../lib/gcc -Lc:/mingw/bin/../lib/gcc/mingw32/4.6.2/../../../../mingw32/lib -Lc:/mingw/bin/../lib/gcc/mingw32/4.6.2/../../.. -L/mingw/lib worker.o -lstdc++ -lmingw32 -lgcc_s -lgcc -lmoldname -lmingwex -lmsvcrt -ladvapi32 -lshell32 -luser32 -lkernel32 -lmingw32 -lgcc_s -lgcc -lmoldname -lmingwex -lmsvcrt c:/mingw/bin/../lib/gcc/mingw32/4.6.2/crtend.o
Cannot export _hello: symbol not found
collect2: ld returned 1 exit status
clang++: error: linker (via gcc) command failed with exit code 1 (use -v to see invocation)

这是我正在编译的文件:

// hello.cpp
#include <iostream>
#if defined(_WIN32)
  #define LIBRARY_API __declspec(dllexport)
#else
  #define LIBRARY_API
#endif
extern "C" void LIBRARY_API hello();
void hello()
{
  std::cout << "Hello, World!" << std::endl;
}

Answer 1

这个重要问题的后续问题是，从clang++ 6.0版本开始，clang编译DLL是可以的。对于MSVC和CLang, c++中c++函数的名称混淆存在差异，这可能会影响DLL在混合环境中的使用，但这些差异很容易发现和纠正。