hello_rust

Minimal ESP-IDF project that calls a Rust component from app_main().

• alloc (default): builds core + alloc + panic_abort, enables esp-idf-svc logging, and prints through log::info!.
• no_alloc: builds core + panic_abort, avoids allocator-backed dependencies, and prints through esp_idf_sys::puts().

Prerequisites

• Espressif Rust toolchain installed (components/rust-hello_rust/rust-toolchain.toml uses channel = "esp")

Example:

source ~/.espressif/v6.0/esp-idf/export.sh

Build

The checked-in sdkconfig currently targets esp32p4. If you want a different chip, select it first:

idf.py set-target esp32p4

Build with the default alloc mode:

idf.py build

Flash and monitor:

idf.py flash monitor

Switch Rust Memory Model

The Rust component exposes a CMake cache variable named RUST_MEMORY_MODEL.

Use the default alloc mode:

idf.py -DRUST_MEMORY_MODEL=alloc reconfigure build

Switch to no_alloc mode:

idf.py -DRUST_MEMORY_MODEL=no_alloc reconfigure build

Internally this maps to Cargo features and build-std settings:

• alloc -> --features alloc-mode and -Zbuild-std=core,alloc,panic_abort
• no_alloc -> --features no-alloc-mode and -Zbuild-std=core,panic_abort

Expected Output

main/main.c always prints:

Hello world from C!
Rust returned code: 42

The Rust-side output depends on the selected memory model:

• alloc: emits an ESP log message similar to Hello, world!
• no_alloc: prints Hello, world from Rust (no_alloc)!

Notes

• components/rust-hello_rust/src/lib.rs enforces that exactly one of alloc-mode or no-alloc-mode is enabled at compile time.
• esp_idf_sys::link_patches() is still called before any Rust-side output so ESP-IDF runtime patches are linked correctly.
• components/rust-hello_rust/Cargo.toml keeps temporary master branch patches for esp-idf-sys, esp-idf-hal, esp-idf-svc, and embuild until crates.io support for IDF 6.0 is available.