I had used LLVM 3.4 on Windows for quite some time. It had worked well, and had all the features I needed—mostly the beautiful C++11/C++14 compiler and the easy-to-use Clang-Format. However, the C++ compiler only works when some specific GCC versions are installed together, and the GCC version 4.6.3 I installed for Clang has a conflict with the GCC 4.9 I use. The major issue is the C++ run-time library libstdc++-6.dll, which actually has many variants due to the combination of different thread models and different exception handling methods. The result is that GCC 4.9 generated executables will crash when the libstdc++-6.dll from GCC 4.6.3 appears earlier in path, and Clang generated executables will crash when the libstdc++-6.dll from GCC 4.9 appears earlier in path. I do not like this situation. So recently I tried new combinations when I installed LLVM 3.5, and made sure everything work together. I would like to share the result.
Let me first list the binary files one needs to download:
- Clang 3.5 for Windows
- MinGW-w64 build of GCC 4.8.2 (POSIX threads and Dwarf exception handling)
- MinGW-w64 build of GCC 4.9.2 (POSIX threads and Dwarf exception handling)
I install Clang to the default location, C:\Program Files (x86)\LLVM. For the rest of this article, I assume GCC 4.9.2 is extracted to C:\ (so all files are under C:\mingw32), and GCC 4.8.2 is extracted to C:\Temp (all files are under C:\Temp\mingw32).
Although I need GCC 4.9 for the best and latest C++ features, Clang does not work with it. One can tell from the error output of Clang that it should work with the MinGW-w64 GCC 4.8.2:
ignoring nonexistent directory "C:\Program Files (x86)\LLVM\bin\..\lib\clang\3.5.0/../../../include/c++/4.7.0"
ignoring nonexistent directory "C:\Program Files (x86)\LLVM\bin\..\lib\clang\3.5.0/../../../include/c++/4.7.0/x86_64-w64-mingw32"
ignoring nonexistent directory "C:\Program Files (x86)\LLVM\bin\..\lib\clang\3.5.0/../../../include/c++/4.7.0/i686-w64-mingw32"
ignoring nonexistent directory "C:\Program Files (x86)\LLVM\bin\..\lib\clang\3.5.0/../../../include/c++/4.7.0/backward"
ignoring nonexistent directory "C:\Program Files (x86)\LLVM\bin\..\lib\clang\3.5.0/../../../include/c++/4.7.1"
ignoring nonexistent directory "C:\Program Files (x86)\LLVM\bin\..\lib\clang\3.5.0/../../../include/c++/4.7.1/x86_64-w64-mingw32"
ignoring nonexistent directory "C:\Program Files (x86)\LLVM\bin\..\lib\clang\3.5.0/../../../include/c++/4.7.1/i686-w64-mingw32"
ignoring nonexistent directory "C:\Program Files (x86)\LLVM\bin\..\lib\clang\3.5.0/../../../include/c++/4.7.1/backward"
ignoring nonexistent directory "C:\Program Files (x86)\LLVM\bin\..\lib\clang\3.5.0/../../../include/c++/4.7.2"
ignoring nonexistent directory "C:\Program Files (x86)\LLVM\bin\..\lib\clang\3.5.0/../../../include/c++/4.7.2/x86_64-w64-mingw32"
ignoring nonexistent directory "C:\Program Files (x86)\LLVM\bin\..\lib\clang\3.5.0/../../../include/c++/4.7.2/i686-w64-mingw32"
ignoring nonexistent directory "C:\Program Files (x86)\LLVM\bin\..\lib\clang\3.5.0/../../../include/c++/4.7.2/backward"
ignoring nonexistent directory "C:\Program Files (x86)\LLVM\bin\..\lib\clang\3.5.0/../../../include/c++/4.7.3"
ignoring nonexistent directory "C:\Program Files (x86)\LLVM\bin\..\lib\clang\3.5.0/../../../include/c++/4.7.3/x86_64-w64-mingw32"
ignoring nonexistent directory "C:\Program Files (x86)\LLVM\bin\..\lib\clang\3.5.0/../../../include/c++/4.7.3/i686-w64-mingw32"
ignoring nonexistent directory "C:\Program Files (x86)\LLVM\bin\..\lib\clang\3.5.0/../../../include/c++/4.7.3/backward"
ignoring nonexistent directory "C:\Program Files (x86)\LLVM\bin\..\lib\clang\3.5.0/../../../include/c++/4.8.0"
ignoring nonexistent directory "C:\Program Files (x86)\LLVM\bin\..\lib\clang\3.5.0/../../../include/c++/4.8.0/x86_64-w64-mingw32"
ignoring nonexistent directory "C:\Program Files (x86)\LLVM\bin\..\lib\clang\3.5.0/../../../include/c++/4.8.0/i686-w64-mingw32"
ignoring nonexistent directory "C:\Program Files (x86)\LLVM\bin\..\lib\clang\3.5.0/../../../include/c++/4.8.0/backward"
ignoring nonexistent directory "C:\Program Files (x86)\LLVM\bin\..\lib\clang\3.5.0/../../../include/c++/4.8.1"
ignoring nonexistent directory "C:\Program Files (x86)\LLVM\bin\..\lib\clang\3.5.0/../../../include/c++/4.8.1/x86_64-w64-mingw32"
ignoring nonexistent directory "C:\Program Files (x86)\LLVM\bin\..\lib\clang\3.5.0/../../../include/c++/4.8.1/i686-w64-mingw32"
ignoring nonexistent directory "C:\Program Files (x86)\LLVM\bin\..\lib\clang\3.5.0/../../../include/c++/4.8.1/backward"
ignoring nonexistent directory "C:\Program Files (x86)\LLVM\bin\..\lib\clang\3.5.0/../../../include/c++/4.8.2"
ignoring nonexistent directory "C:\Program Files (x86)\LLVM\bin\..\lib\clang\3.5.0/../../../include/c++/4.8.2/x86_64-w64-mingw32"
ignoring nonexistent directory "C:\Program Files (x86)\LLVM\bin\..\lib\clang\3.5.0/../../../include/c++/4.8.2/i686-w64-mingw32"
ignoring nonexistent directory "C:\Program Files (x86)\LLVM\bin\..\lib\clang\3.5.0/../../../include/c++/4.8.2/backward"
ignoring nonexistent directory "c:/MinGW/lib/gcc/mingw32/4.7.0/include/c++"
ignoring nonexistent directory "c:/MinGW/lib/gcc/mingw32/4.7.0/include/c++/mingw32"
ignoring nonexistent directory "c:/MinGW/lib/gcc/mingw32/4.7.0/include/c++/backward"
ignoring nonexistent directory "c:/MinGW/lib/gcc/mingw32/4.7.1/include/c++"
ignoring nonexistent directory "c:/MinGW/lib/gcc/mingw32/4.7.1/include/c++/mingw32"
ignoring nonexistent directory "c:/MinGW/lib/gcc/mingw32/4.7.1/include/c++/backward"
ignoring nonexistent directory "c:/MinGW/lib/gcc/mingw32/4.7.2/include/c++"
ignoring nonexistent directory "c:/MinGW/lib/gcc/mingw32/4.7.2/include/c++/mingw32"
ignoring nonexistent directory "c:/MinGW/lib/gcc/mingw32/4.7.2/include/c++/backward"
ignoring nonexistent directory "c:/MinGW/lib/gcc/mingw32/4.7.3/include/c++"
ignoring nonexistent directory "c:/MinGW/lib/gcc/mingw32/4.7.3/include/c++/mingw32"
ignoring nonexistent directory "c:/MinGW/lib/gcc/mingw32/4.7.3/include/c++/backward"
ignoring nonexistent directory "c:/MinGW/lib/gcc/mingw32/4.8.0/include/c++"
ignoring nonexistent directory "c:/MinGW/lib/gcc/mingw32/4.8.0/include/c++/mingw32"
ignoring nonexistent directory "c:/MinGW/lib/gcc/mingw32/4.8.0/include/c++/backward"
ignoring nonexistent directory "c:/MinGW/lib/gcc/mingw32/4.8.1/include/c++"
ignoring nonexistent directory "c:/MinGW/lib/gcc/mingw32/4.8.1/include/c++/mingw32"
ignoring nonexistent directory "c:/MinGW/lib/gcc/mingw32/4.8.1/include/c++/backward"
ignoring nonexistent directory "c:/MinGW/lib/gcc/mingw32/4.8.2/include/c++"
ignoring nonexistent directory "c:/MinGW/lib/gcc/mingw32/4.8.2/include/c++/mingw32"
ignoring nonexistent directory "c:/MinGW/lib/gcc/mingw32/4.8.2/include/c++/backward"
ignoring nonexistent directory "/usr/include/c++/4.4"
ignoring nonexistent directory "/usr/local/include"
ignoring nonexistent directory "C:\Program Files (x86)\LLVM\bin\..\lib\clang\3.5.0\../../../x86_64-w64-mingw32/include"
ignoring nonexistent directory "/mingw/include"
ignoring nonexistent directory "c:/mingw/include"
ignoring nonexistent directory "/usr/include"
(As one may expect from the error messages, the official MinGW GCC, currently at version 4.8.1, also works with Clang. I personally prefer MinGW-w64, as its GCC is more usable—e.g., the MinGW version supports only Win32 threads, and therefore does not support std::thread. MinGW does not provide GCC 4.9 yet, and you can’t put C:\MinGW\bin in the path, if you want to use MinGW-w64 GCC 4.9 simultaneously. You do need to put either C:\MinGW\bin or C:\mingw32\bin—for MinGW-w64 GCC 4.9—in the path, as Clang cannot find a working GCC for linking otherwise. If you use only MinGW GCC 4.8.1, or only MinGW-w64 GCC 4.9, this configuration works.)
Now back to MinGW-w64 GCC 4.8.2. Depending on the size of your hard disk, you may want to tailor it. In my case, I removed all traces of Fortran, Ada, and Objective-C, as well as build-info.txt, etc, license, opt, and shared from C:\Temp\mingw32. After that, you need to do the following to make GCC 4.8.2 work for Clang:
- Make directory
c++underC:\Temp\mingw32\include. - Make directory
4.8.2underC:\Temp\mingw32\include\c++. - Copy all contents under
C:\Temp\mingw32\i686-w64-mingw32\include\c++toC:\Temp\mingw32\include\c++\4.8.2. - Move all contents under
C:\Temp\mingw32toC:\Program Files (x86)\LLVM, merging with existing directories there. - Remove the empty
C:\Temp\mingw32.
You can now add both C:\mingw32\bin and C:\Program Files (x86)\LLVM to the path: both Clang and GCC are at your hand and won’t conflict with each other.
Yongwei’s Blog 
Hello. I’m trying to migrate to using Clang on Windows, as well. I’m curious; do you install MSYS for handling make files or use mingw32-make? Clang 3.8 has compatibility with MSVC now. Have you any experience with that?
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Hi Tom,
I do not use MSYS. I use either mingw32-make, or the Cygwin make.
Clang has some MSVC compatibility from quite long ago. However, last time I tried it was not useful, as C++ compatibility was pretty weak (could not compile a simple program with iostreams). I have not tried 3.8 yet. Please leave me a message, if you see big improvements.
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So far, I’ve been using Clang via Visual Studio, which makes it easy to flip back and forth between the Clang and MSVC toolset. From the standpoint of building an executable and running, I’ve had the exact same results with both. If it builds with MSVC, it builds with Clang. If there’s a run time error when built with Clang, I get the same runtime error when I build with MSVC. I wrote an application that uses Win32 to set thread priority, use high-precision timers, open and setup an asynchronous serial port connection, collect data from the port and output the data to the terminal using iostreams. C++ compatibility hasn’t been a problem thus-far, although I haven’t tried using MFC (and probably won’t, since I detest it).
The only problem I’ve had is debugging; if you compile under Clang in Visual Studio, none of the symbols get loaded. I think they’ve got a ways to go on that front.
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Is there something special you need to do to ensure that clang is able to find gcc version located at C:\mingw32? At the beginning of your guide you show how clang lists a bunch of “ignoring nonexistent directory” errors if you run clang while you have gcc 4.8.2 installed. Unfortunately, if I install 4.8.2 and clang 3.5.0 in the default locations I just get “fatal error: ‘iostream’ file not found” when trying to use clang++ to compile a simple hello world program.
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The paths are hard-coded in the clang binaries. I think you can manipulate its source code to make it recognize other paths, but I chose an easy way.
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I guess I’m just a bit confused then. Did you install 4.9.2 only for when you are not using clang? ie. running “g++ …”?
I was also wondering, have you had any luck getting clang to compile with the 64 bit version of g++? I’ve tried downloading the corresponding 64 bit version of mingw-w64 and have not been able to get it to work.
As a side note, often when I try to comment on your site I get this error: http://i.imgur.com/0uBc7P1.png
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Yes, my purpose of mentioning GCC 4.9.2 was only to ensure it would not conflict with Clang.
I did not try 64-bit building. As Clang prebuilt binaries are 32-bit only, maybe you can try the 32-bit SJLJ version of MinGW-w64. I think it supports the -m64 option, but I am not sure whether Clang can accept the option and pass it to GCC.
I do not have ideas about the error. I cannot control what the WordPress site does.
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