Search code examples
rustembeddedcortex-m

sin(), cos(), log10() (float) not found for target thumbv7em-none-eabihf

I'm using Rust 1.51 and this minimal crate:

#![no_std]

fn main() {
    let a = 2.0.cos();
}

I'm building it with cargo check --target thumbv7em-none-eabihf and the compiler complains with this message: no method named 'cos' found for type '{float}' in the current scope. Same for sin() and log10().

I found https://docs.rust-embedded.org/cortex-m-quickstart/cortex_m_quickstart/ and I would expect the above message for targets thumbv6m-none-eabi or thumbv7em-none-eabi but not for thumbv7em-none-eabihf which has FPU support.

How can I solve this?

Solution

  • In Rust 1.51 (and below) functions like sin, cos, or log10 are not part of the core library (core::) but only the standard library (std::), therefore they are not available.

    A practical solution is to use the crate libm which offers typical mathematic functions for no_std-environments.

    #![no_std]

fn main() {
    let a = libm::cosf(2.0);
}

    See: