在Windows和Linux上的Mingw中使用boost / asio进行故障排除

Question

What I'm trying to do

I'm trying to build a simple communication between an ARM development board and a PC, using boost/asio. I want to build the PC side as a 32 bit DLL, as the tool that will use it is 32 bit only.
For now I'm trying to get the build to work, so my files don't actually contain much code, but import the relevant libraries. Ultimately I want to build on linux, so I compiled boost from source using mingw-w64 on there. However, for now I'm trying to get it to build on windows, using msys2 and mingw32. I installed the mingw32/mingw-w64-i686-boost 1.64.0-3 package.

For now I haven't actually included any code that uses boost, I merely imported it with #include <boost/asio.hpp> in pc/McBSP.cpp.

The Problem

When I'm trying to compile it I get undefined reference to `boost::system::generic_category()' errors, even though I have included -lboost_system in my options.

I'm building in the mingw32 shell, Full output of an attempted build:

$ make pc32
g++ -m32 -DBUILDING_DLL -I board -I common -I pc -c -o common/Addresses-w64-i686.o common/Addresses.cpp
g++ -m32 -DBUILDING_DLL -I board -I common -I pc -c -o common/Audio_Preset-w64-i686.o common/Audio_Preset.cpp
SHA=fe69ff6
echo -n "static const char *GIT_COMMIT_TAG = \"fe69ff6\";" > common/version.h
g++ -m32 -DBUILDING_DLL -I board -I common -I pc -static -lwsock32 -lws2_32 -L/mingw32/lib -lboost_system-mt -c -o pc/McBSP_PC-w64-i686.o pc/McBSP_PC.cpp
g++ -m32 -DBUILDING_DLL -I board -I common -I pc -static -lwsock32 -lws2_32 -L/mingw32/lib -lboost_system-mt common/Addresses-w64-i686.o common/Audio_Preset-w64-i686.o \
    pc/McBSP_PC-w64-i686.o -o McBSP_PC-w64-i686.dll
pc/McBSP_PC-w64-i686.o:McBSP_PC.cpp:(.text+0xc4): undefined reference to `boost::system::generic_category()'
pc/McBSP_PC-w64-i686.o:McBSP_PC.cpp:(.text+0xce): undefined reference to `boost::system::generic_category()'
pc/McBSP_PC-w64-i686.o:McBSP_PC.cpp:(.text+0xd8): undefined reference to `boost::system::system_category()'
pc/McBSP_PC-w64-i686.o:McBSP_PC.cpp:(.text$_ZN5boost4asio5error19get_system_categoryEv[__ZN5boost4asio5error19get_system_categoryEv]+0x7): undefined reference to `boost::system::system_category()'
pc/McBSP_PC-w64-i686.o:McBSP_PC.cpp:(.text$_ZN5boost4asio6detail17winsock_init_base7startupERNS2_4dataEhh[__ZN5boost4asio6detail17winsock_init_base7startupERNS2_4dataEhh]+0x6a): undefined reference to `_imp__WSAStartup@8'
pc/McBSP_PC-w64-i686.o:McBSP_PC.cpp:(.text$_ZN5boost4asio6detail17winsock_init_base7cleanupERNS2_4dataE[__ZN5boost4asio6detail17winsock_init_base7cleanupERNS2_4dataE]+0x30): undefined reference to `_imp__WSACleanup@0'
C:/msys64/mingw32/bin/../lib/gcc/i686-w64-mingw32/7.2.0/../../../../i686-w64-mingw32/lib/../lib\libmingw32.a(lib32_libmingw32_a-crt0_c.o): In function `main':
C:/repo/mingw-w64-crt-git/src/mingw-w64/mingw-w64-crt/crt/crt0_c.c:18: undefined reference to `WinMain@16'
collect2.exe: error: ld returned 1 exit status
make: *** [Makefile:124: McBSP_PC-w64-i686.dll] Error 1

All questions I found on this suggest including -lboost or -lboost_system, which I already have. LD finds boost_system(-mt) just fine, but somehow it seems like it doesn't satisfy the depencendy?

Update

I got it to compile with the following changes:

• I put the libraries at the END of the call, after the object files.
• I changed -static to -shared.

But I am unsure if this DLL now requires boost on the target system? I am under the impression that -shared means the boost lib is now not included in the dll.

Answer 1

I got it to work. Here is how:

Make it build

I needed to move the linker flags after the object files. That was all it took to get rid of the boost::system errors. That introduced a new error, ld could not find WinMain. That was fixed by changing -static to -shared , as I wanted to build a shared library which has no main function.

Making it static

Now the problem arose, that PCs I wanted to run this on needed to have the libraries I used, so I needed to tell the linker to link those statically. I achieved that with these linker flags:

-static-libstdc++ -static-libgcc -Wl,-Bstatic,--whole-archive -lpthread \
    -Wl,--no-whole-archive -L/mingw32/lib -Wl,-Bstatic \
    -lboost_system-mt -lws2_32 -lwsock32

Now it could build the DLL on windows. Porting this build system to my linux environment was now achieved by exchanging g++ for i686-w64-mingw32-g++ and changing -L/mingw32/lib to the path where I installed the cross-compiled boost lib to.