Rust instrumentation

This page covers how to enable coverage instrumentation for a Rust binary you plan to run in Antithesis. You’ll add a crate, reference it once in your code, and pass a handful of build flags. Find the crate here.

If you enabled rust instrumentation before May 22, 2026, you’re probably using the legacy method. We recommend switching to this method when you can, for now the other method is still supported.

Step 1: Add the dependency to .cargo/config.toml

[dependencies]
antithesis-instrumentation = "0.1"

Step 2: Include a reference to the library in your code

Somewhere in your Rust code, add this line at least once:

use antithesis_instrumentation as _;

Without it, Cargo treats the crate as unused and the linker drops the runtime shim. You can include this line in any Rust file in your project, it doesn’t matter which. You may also want to put this under a #[cfg].

Step 3: Adjust your build flags

There are two ways to do this: either at the command line or via a .toml file. You can pick either; you don’t need to do both.

Option A: Build flags at the command line

You’ll need to specify the —config options below. Your full command line will look something like this:

cargo build --bin main \
    --config 'build.target = "x86_64-unknown-linux-gnu"' \
    --config 'target.x86_64-unknown-linux-gnu.rustflags = [
        "-Ccodegen-units=1",
        "-Cpasses=sancov-module",
        "-Cllvm-args=-sanitizer-coverage-level=3",
        "-Cllvm-args=-sanitizer-coverage-trace-pc-guard",
        "-Clink-args=-Wl,--build-id",
    ]'

Option B: Build flags in a .toml file

You can put the flags into .cargo/config.toml file instead like this:

[build]
target = "x86_64-unknown-linux-gnu"

[target.x86_64-unknown-linux-gnu]
rustflags = [
    "-Ccodegen-units=1",
    "-Cpasses=sancov-module",
    "-Cllvm-args=-sanitizer-coverage-level=3",
    "-Cllvm-args=-sanitizer-coverage-trace-pc-guard",
    "-Clink-args=-Wl,--build-id",
]

Validation

To confirm that the instrumentation process was successful, you can run the command nm to list all the symbols in a binary, and then grep the string “antithesis_load_libvoidstar”.

nm client_binary | grep "antithesis_load_libvoidstar"
T antithesis_load_libvoidstar

Notice the “T” character in the previous code block: it means the symbol is in the text (code) section.

Symbolization

The LLVM compiler infrastructure will output debug symbols in the DWARF format. They could be separate debug info or just the original unstripped binary. These files should be symlinked (or moved) into a directory named /symbols in the root of the appropriate container image.

Help

If you need help with this, write to us at support@antithesis.com or talk to your forward deployed engineer.