[LLVMdev] LLVM+Clang 3.2rc2 MinGW binaries' libstdc++ requirement

[Ryan Prichard]

I attempted to run the 3.2rc2 experimental LLVM+Clang package for 
Mingw32/x86 [1], and ran into difficulty finding a suitable version of 
MinGW to run it with.  Part of the problem is that Windows G++ changed 
its C++ ABI in 4.7 [2].

Through experimentation, I've determined that the LLVM binaries do not 
run using the libraries shipped with TDM-GCC 4.5 because there is a 
missing symbol.  They segfault with TDM-GCC 4.7, which I assume is 
caused by the ABI change.  (Through inspection of the assembly, it 
appears that Clang was not built with 4.7 -- the code doesn't use 
thiscall.)  TDM-GCC 4.6 is just right, though, so perhaps that should be 
noted somewhere.  Perhaps the filename should include something like 
"mingw32-46" in it.

I had to download these three files to run LLVM binaries:

http://sourceforge.net/projects/tdm-gcc/files/TDM-GCC%204.6%20series/4.6.1-tdm-1%20DW2/

     gcc-4.6.1-tdm-1-dw2-core.zip
     gcc-4.6.1-tdm-1-dw2-c++.zip
     gcc-4.6.1-tdm-1-dw2-openmp.zip

The openmp package is needed for pthreadGC2.dll.  It's also important to 
use DW2.  TDM-GCC also provides SJLJ libraries that do not work with Clang.

I am wondering whether the Clang project will attempt to match MinGW's 
new ABI.[3]  AIUI, the 4.7 breakage is not intended to be a one-time 
event.  A stable ABI would be a nice thing.

[1] 
http://llvm.org/pre-releases/3.2/rc2/clang+llvm-3.2rc2-i386-mingw32-EXPERIMENTAL.tar.gz

[2] MinGW 4.7 enabled the thiscall convention, which changes the 
register/stack usage for all member function calls.  See 
http://mingw-users.1079350.n2.nabble.com/MinGW-GCC-4-7-0-released-td7578133.html.

[3] http://llvm.org/bugs/show_bug.cgi?id=12684

-Ryan