Martin Storsjö
2a3cdc9115
The level of maturity is generally quite a bit higher now than when this initially was written.
112 lines
4.2 KiB
Markdown
112 lines
4.2 KiB
Markdown
LLVM MinGW
|
|
==========
|
|
|
|
This is a recipe for reproducibly building a
|
|
[LLVM](https://llvm.org)/[Clang](https://clang.llvm.org/)/[LLD](https://lld.llvm.org/)
|
|
based mingw-w64 toolchain.
|
|
|
|
Benefits of a LLVM based MinGW toolchain are:
|
|
- Support for targeting ARM/ARM64 (while GCC obviously does support
|
|
these architectures, it doesn't support Windows on ARM)
|
|
- A single toolchain targeting all four architectures (i686, x86_64,
|
|
armv7 and arm64) instead of separate compiler binaries for each
|
|
architecture
|
|
- Support for generating debug info in PDB format
|
|
- Support for Address Sanitizer
|
|
|
|
Clang on its own can also be used as compiler in the normal GNU binutils
|
|
based environments though, so the main difference lies in replacing
|
|
binutils with LLVM based tools.
|
|
|
|
The toolchain can be reproducibly built into a Docker image, or be
|
|
built and installed in the host environment (currently only tested
|
|
on Linux and macOS).
|
|
|
|
To build and install all components, just do:
|
|
|
|
./build-all.sh <target-dir>
|
|
|
|
To reduce the size of the installation, removing some files that
|
|
aren't necessary after building, run:
|
|
|
|
./strip-llvm.sh <target-dir>
|
|
|
|
To build a Docker image with the toolchain, run:
|
|
|
|
docker build .
|
|
|
|
Individual components of the toolchain can be (re)built by running
|
|
the standalone shellscripts listed within `build-all.sh`. However, if
|
|
the source already is checked out, no effort is made to check out a
|
|
different version (if the build scripts have been updated to prefer
|
|
a different version) - and likewise, if configure flags in the build-\*.sh
|
|
scripts have changed, you might need to wipe the build directory under
|
|
each project for the new configure options to be taken into use.
|
|
|
|
Prebuilt docker linux images containing llvm-mingw are available from
|
|
[Docker Hub](https://hub.docker.com/r/mstorsjo/llvm-mingw/).
|
|
|
|
|
|
|
|
Status
|
|
------
|
|
|
|
The toolchain currently does support both C and C++, including support
|
|
for exception handling.
|
|
|
|
It is in practice new and hasn't been tested with quite as many projects
|
|
as the regular GCC/binutils based toolchains yet. You might run into issues
|
|
building non-trivial projects.
|
|
|
|
|
|
Known issues
|
|
------------
|
|
|
|
LLD, the LLVM linker, is what causes most of the major differences to the
|
|
normal GCC/binutils based MinGW.
|
|
|
|
- The windres replacement, llvm-rc, isn't very mature and doesn't support
|
|
everything that GNU windres does.
|
|
- The DLL version of libc++ doesn't have a fixed supported ABI, so in theory,
|
|
code built against an older version of the DLL is not guaranteed to work
|
|
with a newer version of the DLL.
|
|
- The toolchain defaults to using the Universal CRT (which is only available
|
|
out of the box since Windows 10, but can be installed on Vista or newer)
|
|
and defaults to targeting Vista. These defaults can be changed in
|
|
`build-mingw-w64.sh` though.
|
|
- The toolchain uses Windows native TLS support, which doesn't work properly
|
|
until Windows Vista. This has no effect on code not using thread local
|
|
variables.
|
|
- The runtime libraries libunwind, libcxxabi and libcxx also assume that the
|
|
target is Vista or newer.
|
|
- Address Sanitizer doesn't produce working backtraces for i686. Address
|
|
Sanitizer requires using a PDB file for symbolizing the error location and
|
|
backtraces.
|
|
|
|
Additionally, one may run into other minor differences between GCC and clang.
|
|
|
|
PDB support
|
|
-----------
|
|
|
|
LLVM does [support](http://blog.llvm.org/2017/08/llvm-on-windows-now-supports-pdb-debug.html)
|
|
generating debug info in the PDB format. Since GNU binutils based mingw
|
|
environments don't support this, there's no predecent for what command
|
|
line parameters to use for this, and llvm-mingw produces debug info in
|
|
DWARF format by default.
|
|
|
|
To produce debug info in PDB format, you currently need to do the following
|
|
changes:
|
|
|
|
- Add `-gcodeview` to the compilation commands (e.g. in
|
|
`wrappers/clang-target-wrapper.sh`), together with using `-g` as usual to
|
|
enable debug info in general.
|
|
- Add `-Wl,-pdb,module.pdb` to linking commands.
|
|
|
|
Even though LLVM supports this, there are a few caveats with using it when
|
|
building in MinGW mode:
|
|
|
|
- Microsoft debuggers might have assumptions about the C++ ABI used, which
|
|
doesn't hold up with the Itanium ABI used in MinGW.
|
|
- This is unimplemented for the armv7 target, and while implemented for aarch64,
|
|
it doesn't seem to work properly there yet.
|