Build shared library with Clang++ - windows

Question

I am trying to build a shared library (dll for Windows) using Clang++.
I have run the following commands:
clang++ -c -o hello.o hello.cpp
clang++ -shared -v -o hello.dll hello.o
The first command works fine but when I try to build the dll I get this error:
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)
Here is the file I am compiling:
// 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

A follow up to this important question is that as of clang++ version 6.0, the compilation of a DLL by clang is fine. There are differences for the name mangling of C++ functions in C++ for MSVC and CLang, that can impair the use of DLL's in mixed environments but these differences are easy to spot and correct.