00mjk / gccrs

GCC Front-End for Rust

Home Page:https://rust-gcc.github.io/

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GCC Rust

GCC Rust

Please note, the compiler is in a very early stage and not usable yet for compiling real Rust programs.

gccrs is a full alternative implementation of the Rust language ontop of GCC with the goal to become fully upstream with the GNU toolchain.

The origin of this project was a community effort several years ago where Rust was still at version 0.9; the language was subject to so much change that it became difficult for a community effort to play catch up. Now that the language is stable, it is an excellent time to create alternative compilers. The developers of the project are keen “Rustaceans” with a desire to give back to the Rust community and to learn what GCC is capable of when it comes to a modern language.


Please find the answers to frequently asked questions over on: https://github.com/Rust-GCC/gccrs/wiki/Frequently-Asked-Questions

Development Environment


Fetch dependencies for Ubuntu:

$ apt install build-essential libgmp3-dev libmpfr-dev libmpc-dev flex bison autogen gcc-multilib dejagnu

Clone the repository

$ git clone git@github.com:Rust-GCC/gccrs.git


It is important to remember that GNU toolchain projects are designed to be built outside of their source directory which is why a build directory is created.

$ mkdir gccrs-build
$ cd gccrs-build
$ ../gccrs/configure --prefix=$HOME/gccrs-install --disable-bootstrap --enable-multilib --enable-languages=rust
$ make


The path of header dir and sysroot should be specified when you configure the project.

$ mkdir mac-build
$ cd mac-build
$ ../gccrs/configure --prefix=$HOME/gccrs-install --disable-bootstrap --enable-multilib --enable-languages=rust --with-native-system-header-dir=/usr/include --with-sysroot=/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk 
$ make

Running GCC Rust

Running the compiler itself without make install we can simply invoke the compiler proper:

$ ./gcc/rust1 test.rs -frust-debug -frust-dump-parse -Warray-bounds -dumpbase test.rs -mtune=generic -march=x86-64 -O0 -version -fdump-tree-gimple -o test.s -L/lib/x86_64-linux-gnu -L/lib/../lib64 -L/usr/lib/x86_64-linux-gnu -L/usr/lib/../lib64

To invoke the compiler driver (gccrs) we need to:

$ make install

Then invoke the compiler from the installation directory:

$ $HOME/gccrs-install/gccrs -g -O2 -c test.rs -o test.o
$ $HOME/gccrs-install/gccrs -o test test.o

You can also setup your shell to automatically find the installed compiler. For example for bash, add the following in your $HOME/.bashrc:

export PATH=$HOME/gccrs-install/bin:$PATH


Invoke the full testsuite from the build directory (gccrs-build in the previous commands):

$ make check-rust

Invoke a subset of the testsuite. For example, to only run tests that are currently known/expected to fail:

$ make check-rust RUNTESTFLAGS="xfail.exp"

There are the following sets of tests:

  • compile.exp : compilation tests
  • execute.exp : execution tests
  • xfail.exp : tests that are currently known/expected to fail

Invoke only a specific test :

$ make check-rust RUNTESTFLAGS="--all compile.exp=continue1.rs"

Logs (with corresponding commands) can be found in : gccrs-build/gcc/testsuite/rust/rust.log.

See GCC Testing documentation for more details.

Test cases are located within gcc/testsuite/rust/. Please contribute your specific test cases referencing any issues on Github.


Enabling internal checks

GCC has several internal checks that can be enabled during configuration. In the case of gccrs, you can enable the following:

$ ../gccrs/configure --prefix=$HOME/gccrs-install --disable-bootstrap --enable-multilib --enable-languages=rust --enable-checking=gimple,tree,types


You can directly invoke gdb on the rust1 compiler process (you can find the exact command adding --verbose to your gccrs invocation):

$ gccrs test.rs -O0 -S -o arithmetic_expressions1.s --verbose
 /some/path/../../rust1 test.rs -quiet -dumpbase arithmetic_expressions1.rs -dumpbase-ext .rs
 -mtune=generic -march=x86-64 -O0 -w -version -fdiagnostics-color=never -fno-diagnostics-show-caret -fno-diagnostics-show-line-numbers -fdiagnostics-urls=never -fdiagnostics-path-format=separate-events -o test.s -L/lib/x86_64-linux-gnu -L/lib/../lib64 -L/usr/lib/x86_64-linux-gnu
$ gdb --args  /some/path/../../rust1 test.rs -quiet -dumpbase arithmetic_expressions1.rs -dumpbase-ext .rs
 -mtune=generic -march=x86-64 -O0 -w -version -fdiagnostics-color=never -fno-diagnostics-show-caret -fno-diagnostics-show-line-numbers -fdiagnostics-urls=never -fdiagnostics-path-format=separate-events -o test.s -L/lib/x86_64-linux-gnu -L/lib/../lib64 -L/usr/lib/x86_64-linux-gnu

Or simply add the -wrapper gdb,--args option. This will call each subcommand in gdb and you simply have to break/debug in rust1:

$ gccrs test.rs -O0 -S -o arithmetic_expressions1.s -wrapper gdb,--args

Docker image

There is a docker image hosted over on:


$ docker pull philberty/gccrs

Or you can build your own image:

$ docker build . -t gccrs-dev

If you want to build an object file:

$ docker run --rm -v "$PWD":/usr/src/myapp -w /usr/src/myapp \
    gccrs-dev:latest gccrs -g -O2 -c \
    gcc/testsuite/rust/compile/torture/type_infer1.rs -o type_infer1.o

If you want to build an executable file:

$ docker run --rm -v "$PWD":/usr/src/myapp -w /usr/src/myapp \
    gccrs-dev:latest gccrs -g -O2 \
    gcc/testsuite/rust/compile/torture/type_infer1.rs -o type_infer1

To emit assembly :

$ docker run --rm -v "$PWD":/usr/src/myapp -w /usr/src/myapp \
    gccrs-dev:latest gccrs -g -O2 \
    gcc/testsuite/rust/compile/torture/type_infer1.rs -S -o type_infer1.s 

To emit Rust front end debug output, you may add options like -frust-debug, -frust-dump-all.


If you want to contribute to GCC Rust, you can find more information in CONTRIBUTING.md.

Please be aware this project is designed to be pushed upstream to GCC when we reach some milestones, and this means we require copyright assignment or the Developer's Certificate of Origin sign-off. Please see the Contributing to GCC guide or Developer's Certificate of Origin (DCO) Sign-off guide.

Not all contributions must be code; we would love to see new test cases or bugs and issues to be reported. Feel free to add any comments on open PRs


We can be found on all usual Rust channels such as Zulip, but we also have our own channels:

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GCC Front-End for Rust