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@@ -9,17 +9,19 @@ Please read or review our documentation on Rust coding standards
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(`.../doc/HACKING/CodingStandardsRust.md`) before doing anything.
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Please also read
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-[the Rust Code of Conduct](https://www.rust-lang.org/en-US/conduct.html). We aim
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-to follow the good example set by the Rust community and be excellent to one
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-another. Let's be careful with each other, so we can be memory-safe together!
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-
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-Next, please contact us before rewriting anything! Rust in Tor is still an
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-experiment. It is an experiment that we very much want to see succeed, so we're
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-going slowly and carefully. For the moment, it's also a completely
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-volunteer-driven effort: while many, if not most, of us are paid to work on Tor,
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-we are not yet funded to write Rust code for Tor. Please be patient with the
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-other people who are working on getting more Rust code into Tor, because they
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-are graciously donating their free time to contribute to this effort.
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+[the Rust Code of Conduct](https://www.rust-lang.org/en-US/conduct.html). We
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+aim to follow the good example set by the Rust community and be
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+excellent to one another. Let's be careful with each other, so we can
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+be memory-safe together!
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+
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+Next, please contact us before rewriting anything! Rust in Tor is still
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+an experiment. It is an experiment that we very much want to see
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+succeed, so we're going slowly and carefully. For the moment, it's also
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+a completely volunteer-driven effort: while many, if not most, of us are
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+paid to work on Tor, we are not yet funded to write Rust code for Tor.
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+Please be patient with the other people who are working on getting more
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+Rust code into Tor, because they are graciously donating their free time
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+to contribute to this effort.
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Resources for learning Rust
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-----------------------------
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@@ -33,14 +35,15 @@ Rust immediately, without waiting for anything to install, there is
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**Advanced resources**
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-If you're interested in playing with various Rust compilers and viewing a very
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-nicely displayed output of the generated assembly, there is
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+If you're interested in playing with various Rust compilers and viewing
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+a very nicely displayed output of the generated assembly, there is
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[the Godbolt compiler explorer](https://rust.godbolt.org/)
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For learning how to write unsafe Rust, read
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[The Rustonomicon](https://doc.rust-lang.org/nomicon/).
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-For learning everything you ever wanted to know about Rust macros, there is
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+For learning everything you ever wanted to know about Rust macros, there
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+is
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[The Little Book of Rust Macros](https://danielkeep.github.io/tlborm/book/index.html).
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For learning more about FFI and Rust, see Jake Goulding's
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@@ -49,10 +52,10 @@ For learning more about FFI and Rust, see Jake Goulding's
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Compiling Tor with Rust enabled
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---------------------------------
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-You will need to run the `configure` script with the `--enable-rust` flag to
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-explicitly build with Rust. Additionally, you will need to specify where to
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-fetch Rust dependencies, as we allow for either fetching dependencies from Cargo
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-or specifying a local directory.
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+You will need to run the `configure` script with the `--enable-rust`
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+flag to explicitly build with Rust. Additionally, you will need to
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+specify where to fetch Rust dependencies, as we allow for either
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+fetching dependencies from Cargo or specifying a local directory.
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**Fetch dependencies from Cargo**
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@@ -65,21 +68,22 @@ You'll need the following Rust dependencies (as of this writing):
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libc==0.2.22
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We vendor our Rust dependencies in a separate repo using
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-[cargo-vendor](https://github.com/alexcrichton/cargo-vendor). To use them, do:
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+[cargo-vendor](https://github.com/alexcrichton/cargo-vendor). To use
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+them, do:
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git submodule init
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git submodule update
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-To specify the local directory containing the dependencies, (assuming you are in
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-the top level of the repository) configure tor with:
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+To specify the local directory containing the dependencies, (assuming
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+you are in the top level of the repository) configure tor with:
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TOR_RUST_DEPENDENCIES='path_to_dependencies_directory' ./configure --enable-rust
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-(Note that RUST_DEPENDENCIES must be the full path to the directory; it cannot
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-be relative.)
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+(Note that RUST_DEPENDENCIES must be the full path to the directory; it
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+cannot be relative.)
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-Assuming you used the above `git submodule` commands and you're in the topmost
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-directory of the repository, this would be:
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+Assuming you used the above `git submodule` commands and you're in the
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+topmost directory of the repository, this would be:
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TOR_RUST_DEPENDENCIES=`pwd`/src/ext/rust/crates ./configure --enable-rust
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@@ -87,19 +91,20 @@ directory of the repository, this would be:
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Identifying which modules to rewrite
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======================================
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-The places in the Tor codebase that are good candidates for porting to Rust are:
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+The places in the Tor codebase that are good candidates for porting to
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+Rust are:
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1. loosely coupled to other Tor submodules,
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2. have high test coverage, and
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3. would benefit from being implemented in a memory safe language.
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-Help in either identifying places such as this, or working to improve existing
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-areas of the C codebase by adding regression tests and simplifying dependencies,
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-would be really helpful.
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+Help in either identifying places such as this, or working to improve
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+existing areas of the C codebase by adding regression tests and
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+simplifying dependencies, would be really helpful.
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Furthermore, as submodules in C are implemented in Rust, this is a good
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-opportunity to refactor, add more tests, and split modules into smaller areas of
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-responsibility.
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+opportunity to refactor, add more tests, and split modules into smaller
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+areas of responsibility.
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A good first step is to build a module-level callgraph to understand how
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interconnected your target module is.
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@@ -117,21 +122,22 @@ the module calls. Modules which call fewer other modules are better targets.
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Strive to change the C API as little as possible.
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-We are currently targeting Rust nightly, *for now*. We expect this to change
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-moving forward, as we understand more about which nightly features we need. It
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-is on our TODO list to try to cultivate good standing with various distro
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-maintainers of `rustc` and `cargo`, in order to ensure that whatever version we
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-solidify on is readily available.
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+We are currently targeting Rust nightly, *for now*. We expect this to
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+change moving forward, as we understand more about which nightly
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+features we need. It is on our TODO list to try to cultivate good
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+standing with various distro maintainers of `rustc` and `cargo`, in
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+order to ensure that whatever version we solidify on is readily
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+available.
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-If parts of your Rust code needs to stay in sync with C code (such as handling
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-enums across the FFI boundary), annonotate these places in a comment structured
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-as follows:
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+If parts of your Rust code needs to stay in sync with C code (such as
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+handling enums across the FFI boundary), annonotate these places in a
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+comment structured as follows:
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/// C_RUST_COUPLED: <path_to_file> `<name_of_c_object>`
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-Where <name_of_c_object> can be an enum, struct, constant, etc. Then, do the
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-same in the C code, to note that rust will need to be changed when the C
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-does.
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+Where <name_of_c_object> can be an enum, struct, constant, etc. Then,
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+do the same in the C code, to note that rust will need to be changed
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+when the C does.
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Adding your Rust module to Tor's build system
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-----------------------------------------------
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@@ -153,8 +159,9 @@ dependency of other Rust modules):
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Everything should be tested full stop. Even non-public functionality.
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-Be sure to edit `.../tor/src/test/test_rust.sh` to add the name of your crate to
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-the `crates` variable! This will ensure that `cargo test` is run on your crate.
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+Be sure to edit `.../tor/src/test/test_rust.sh` to add the name of your
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+crate to the `crates` variable! This will ensure that `cargo test` is
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+run on your crate.
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Configure Tor's build system to build with Rust enabled:
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