80 lines
2.9 KiB
Markdown
80 lines
2.9 KiB
Markdown
LLVM MinGW
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==========
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This is a recipe for reproducibly building a
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[LLVM](https://llvm.org)/[Clang](https://clang.llvm.org/)/[LLD](https://lld.llvm.org/)
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based mingw-w64 toolchain.
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Benefits of a LLVM based MinGW toolchain are:
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- Support for targeting ARM/ARM64 (while GCC obviously does support
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these architectures, it doesn't support Windows on ARM)
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- A single toolchain targeting all four architectures (i686, x86_64,
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armv7 and arm64) instead of separate compiler binaries for each
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architecture
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Clang on its own can also be used as compiler in the normal GNU binutils
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based environments though, so the main difference lies in replacing
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binutils with LLVM based tools.
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This is similar to https://github.com/martell/mingw-w64-clang, with
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the exact same goal but with a slightly different mechanism for
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building it, allowing a full from-scratch build of all components
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in one command.
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The toolchain can be reproducibly built into a Docker image, or be
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built and installed in the host environment (currently only tested
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on Linux and macOS).
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To build and install all components, just do:
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./build-all.sh <target-dir>
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To reduce the size of the installation, removing some files that
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aren't necessary after building, run:
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./strip-llvm.sh <target-dir>
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To build a Docker image with the toolchain, run:
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docker build .
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Individual components of the toolchain can be (re)built by running
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the standalone shellscripts listed within `build-all.sh`. However, if
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the source already is checked out, no effort is made to check out a
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different version (if the build scripts have been updated to prefer
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a different version) - and likewise, if configure flags in the build-*.sh
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scripts have changed, you might need to wipe the build directory under
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each project for the new configure options to be taken into use.
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Status
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------
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The toolchain currently does support both C and C++, including support
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for exception handling.
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It is in practice quite new and immature and haven't been proven with a
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large number of projects yet though. You will probably run into issues
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building non-trivial projects.
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Known issues
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------------
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LLD, the LLVM linker, is what causes most of the major differences to the
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normal GCC/binutils based MinGW.
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- LLD doesn't support using import libraries created by GNU tools.
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- LLD doesn't automatically fix up use of data symbols from DLLs without
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the dllimport attributes.
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- The C++ libraries ([libcxxabi](http://libcxxabi.llvm.org/), [libcxx](http://libcxx.llvm.org/)) can only be linked statically
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at the moment.
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- The C++ exception unwinding in libunwind uses APIs that aren't available
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in the UWP/WinRT API subset.
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- The windres replacement, llvm-rc, isn't very mature and doesn't support
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everything that GNU windres does. Additionally, some part of the preprocessing
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is currently implemented in shell script, making it a bit slow.
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Additionally, one may run into other minor differences between GCC and clang.
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