Rust bindings to LLVM's C API.
[dependencies] llvm-sys = "70"
There must be a compatible version of LLVM available. By default
will look for
PATH to find a system-wide copy of LLVM and
use that if it is a compatible version. Custom options for finding LLVM
on your system can be specified via environment variables. See
LLVM compatibility for more information.
examples directory in this repository for API examples. There also
exist some other projects using these bindings which may be
- Tari's merthc
- Wilfred's BF compiler
- Jay Phelps wrote about building a minimal compiler targeting WebAssembly
If you have your own project using these bindings that you think is worth mentioning here, by all means let me know.
Because the LLVM C API stability guarantees are relatively
weak, this crate enforces that the LLVM release in use match the one it was made
for. The crate version is constructed by treating the LLVM version as a real
number and multiplying by 10, ignoring any fractional part. Thus
version 37 is compatible with LLVM 3.7.x, and
llvm-sys 41 would be compatible
with LLVM 4.1.x.
The following table is a compatibility matrix with LLVM versions (rows) and versions of this crate (columns). ● denotes an exactly-compatible version, and ◑ is a binary-compatible version but with elements deprecated (implying that movement to the next crate version in the same table row will still compile, but may introduce new warnings).
The build scripts will not enforce this compatibility matrix strictly, permitting compilation against any version of LLVM that is at least as new as the crate target version. This is safe in most cases because the LLVM C API is meant to maintain binary compatibility across releases with the exception of when functions are deprecated and later removed. An incompatible LLVM version will generally fail to compile with a link-time error, rather than cause runtime errors. Where versions are known to break binary compatibility, the build script will prevent compilation.
Depending on your use of the C API, your program may require that only a
version of LLVM exactly matching your crate version be allowed. This can be set
with the cargo feature flag
strict-versioning or by setting the environment
<version> is the target
crate version) to any value.
llvm-sys blacklists some versions of LLVM that are known to be
binary-incompatible. If you're feeling lucky, setting
LLVM_SYS_<version>_IGNORE_BLACKLIST to "YES" will permit the use of
blacklisted library versions (which may cause vexing bugs).
It may be difficult or even impossible to provide a compatible LLVM version system-wide for a given project (consider a program using two libraries that internally use different versions of LLVM!) so environment variables can be set to help the build scripts find your copy of the libraries. This is also helpful if you are unable to provide a system-wide version of LLVM but can still compile it yourself.
LLVM_SYS_<version>_PREFIX specifies the install prefix for a compiled and
installed copy of the libraries, where
<version> is the major version of
llvm-sys (for example,
LLVM_SYS_37_PREFIX). For information on compiling
a copy of LLVM yourself, see Compiling LLVM.
In the future this library may offer the ability to download and compile LLVM automatically, but such a feature should only be considered for building one-off releases because its high cost is ill-suited to repeated builds.
If you need to compile LLVM or manage multiple versions, llvmenv may simplify the process. Consider using it if you don't have special requirements or previous experience with LLVM!
While the getting started guide is the official guide to compiling LLVM, this section will attempt to provide minimum guidance in creating usable libraries. If you encounter problems, refer to the official documentation.
Download and unpack a copy of the source for the required version.
wget https://llvm.org/releases/3.9.0/llvm-3.9.0.src.tar.xz tar xJf llvm-3.9.0.src.tar.xz
Note that you do not need to compile Clang or the test suite.
Configure the build using CMake (you will need a copy of CMake installed).
mkdir -p llvm-3.9.0.src/build cd llvm-3.9.0.src/build cmake .. -DCMAKE_INSTALL_PREFIX=$HOME/llvm-3.9.0
Some of the useful options that can be specified at configuration-time
-D passed to CMake):
CMAKE_INSTALL_PREFIXsets the location to install everything in the install step (later). In the above example this is under your home directory.
CMAKE_BUILD_TYPEspecifies the build mode, one of Debug, Release, MinSizeRel or RelWithDebInfo. Unless you plan to debug LLVM itself, Release or MinSizeRel is probably a good choice.
LLVM_ENABLE_ASSERTIONSenables internal sanity checks, highly recommended when writing and debugging your own program that uses LLVM because it can detect many usage errors that could otherwise result in hard-to-debug crashes.
-G <generator> to CMake will make it use a different build system, but
by default it will select one appropriate to your system. If you have
ninja available, it is recommended due to its speed (
Compile and install
cmake --build . --target install
This will automatically invoke the build system and copy binaries into the prefix specified at configuration-time when done. Then you can compile llvm-sys against it.
cd your/crate/path LLVM_SYS_39_PREFIX=$HOME/llvm-3.9.0 cargo build
Some build tools (like Visual Studio on Windows) support all configurations
concurrently so you also need to specify the build type (which defaults to Debug
on Windows), adding an option like
--config MinSizeRel to this invocation of
You must use a version of Rust that uses the same compiler as you build LLVM with, either MSVC or MinGW. Fortunately, a mismatch like this will cause errors at compile-time when llvm-config provides options which are supported by only one of them, so if you're using the other it will cause the build to fail.
Will theoretically work, but hasn't been tested. Let us know if you try.