no_std | rust-lld: error: undefined symbol: fmod

[senseiod]

The following error occurred when I compiled. I used [no_std]

error: linking with rust-lld failed: exit code: 1
|
= note: "rust-lld" "-flavor" "gnu" "--script=kernel/.cargo/linker-amd64.ld" "--eh-frame-hdr" "-L" "/Users/moyan/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/x86_64-unknown-none/lib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/kernel-14f138026edce7e1.kernel.cqsbvbmg-cgu.0.rcgu.o" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/kernel-14f138026edce7e1.kernel.cqsbvbmg-cgu.1.rcgu.o" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/kernel-14f138026edce7e1.kernel.cqsbvbmg-cgu.10.rcgu.o" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/kernel-14f138026edce7e1.kernel.cqsbvbmg-cgu.11.rcgu.o" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/kernel-14f138026edce7e1.kernel.cqsbvbmg-cgu.12.rcgu.o" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/kernel-14f138026edce7e1.kernel.cqsbvbmg-cgu.13.rcgu.o" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/kernel-14f138026edce7e1.kernel.cqsbvbmg-cgu.14.rcgu.o" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/kernel-14f138026edce7e1.kernel.cqsbvbmg-cgu.15.rcgu.o" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/kernel-14f138026edce7e1.kernel.cqsbvbmg-cgu.2.rcgu.o" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/kernel-14f138026edce7e1.kernel.cqsbvbmg-cgu.3.rcgu.o" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/kernel-14f138026edce7e1.kernel.cqsbvbmg-cgu.4.rcgu.o" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/kernel-14f138026edce7e1.kernel.cqsbvbmg-cgu.5.rcgu.o" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/kernel-14f138026edce7e1.kernel.cqsbvbmg-cgu.6.rcgu.o" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/kernel-14f138026edce7e1.kernel.cqsbvbmg-cgu.7.rcgu.o" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/kernel-14f138026edce7e1.kernel.cqsbvbmg-cgu.8.rcgu.o" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/kernel-14f138026edce7e1.kernel.cqsbvbmg-cgu.9.rcgu.o" "-o" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/kernel-14f138026edce7e1" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/kernel-14f138026edce7e1.55q3sd5wjw65l95x.rcgu.o" "--gc-sections" "-L" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps" "-L" "/Users/moyan/Desktop/Nitrogen/target/release/deps" "-L" "/Users/moyan/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/x86_64-unknown-none/lib" "-Bstatic" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libx86_smpboot-8e81c0d798b60932.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libbuddy_system_allocator-f8b66032220abdc5.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libbitmap_allocator-af9b094d1a519536.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libfatpart-0727f15f7734052e.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libuart_16550-e2cf326f1958c62e.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libpc_keyboard-b739eda1d27e408b.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libcrossbeam_queue-a14c63777446712d.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libcrossbeam_utils-87694ca9ab9c652e.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/librcore_console-ffc729f7eb5b9cfe.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libvte-a8eccd6610fff71b.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libutf8parse-91de4d4412f850a4.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libarrayvec-e93cb97575e4608a.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libembedded_graphics-e840ebe5eadc83a7.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libbyteorder-a4e730b8cfbf0f3d.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libpci-972d6dc714e5b900.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libisomorphic_drivers-96d5970aa9609774.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libvolatile-1c4fbe3073bb0b5c.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libchrono-496d2cef901a62cd.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libnum_integer-0a904a802b3d5592.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libnum_traits-8ec2c0f81f480d93.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/liblibm-29ba16972c9545ab.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libapic-a723727ea4151acd.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libx86-6f96f44b6c430612.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libraw_cpuid-05a4c6f5e8dcf87f.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libspin-80c7ddac49bf0f46.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/liblazy_static-87454fbe3a37561d.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libspin-1e6619332c8da860.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libbootlib-5858c658c3bdfbd3.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libxmas_elf-060ce72ae41a618e.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libzero-cfd2e85cd7004aa9.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libuefi-8c54833f0be43ca1.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libucs2-b0c3f8b296a258ad.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libacpi-7c1e8da1b95f9305.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libbit_field-7fe43b8b59f50498.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libx86_64-0067b45b8d99ac1c.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libbitflags-88049f10c38d6614.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libbit_field-4784ed1f0f9b9c61.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/liblog-99364cdc9ec59178.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libcfg_if-e421a2c73879a02a.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/liballoc-1ef765c4ad8ae6df.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/librustc_std_workspace_core-cc550d870d19b846.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libcore-456e8934ceb2165f.rlib" "/Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/libcompiler_builtins-e4104c4a6d948d19.rlib" "-Bdynamic"
= note: rust-lld: error: undefined symbol: fmod
>>> referenced by kernel.cqsbvbmg-cgu.8
>>> /Users/moyan/Desktop/Nitrogen/target/x86_64-unknown-none/release/deps/kernel-14f138026edce7e1.kernel.cqsbvbmg-cgu.8.rcgu.o:(kernel::formats::format_size::h3751f48305e53fa9)

Display:= note: rust-lld: error: undefined symbol: fmod. I don't know what's going on

[cuviper]

Is kernel::formats::format_size using floating-point? Does your target allow that?

[senseiod]

Yes, I use floating-point numbers

[senseiod]

This is my code

use alloc::format;
use alloc::string::String;
use num_traits::float::FloatCore;

const KB: f64 = 1024.0;
const MB: f64 = 1024.0 * KB;
const GB: f64 = 1024.0 * MB;

pub fn format_size(size: f64) -> String {
    let a = size.trunc();
    if size < KB {
        format!("{} B", size as usize)
    } else if size < MB {
        format!("{} KB", (size / KB) as usize)
    } else if size < GB {
        format!("{} MB", (size / MB) as usize)
    } else {
        format!("{} GB", (size / GB) as usize)
    }
}

The problem is let a= size.trunc ();
In [no_std] The compiler recommends that I use num-traits crate

[cuviper]

Is your target set for +soft-float? Kernels usually are, so they don't have to save and restore the userspace floating point state. I would avoid all floating point if possible in such contexts, and it seems to me that you could write that function with integers.

The normal std version of f64::trunc() uses intrinsics::truncf64(), which maps to llvm.trunc.f64. For targets that don't have native instructions for this (like soft-float!), that may generate an external call to the C libm or some compiler-builtin function.

FloatCore implements trunc() using fract(), and that's implemented using self % Self::one(). For a soft-float target, LLVM translates that to an external call to the C libm function fmod, which is what you're seeing.

I do have pull request #196 to use the Rust libm crate for parts of FloatCore, including trunc() and fract(). I'm not sure if that will work in your kernel context, but you could try that with a dependency like this:

[dependencies.num-traits]
git = "https://github.com/cuviper/num-traits"
branch = "more-libm"
default-features = false
features = ["libm"]

[senseiod]

Is your target set for +soft-float? Kernels usually are, so they don't have to save and restore the userspace floating point state. I would avoid all floating point if possible in such contexts, and it seems to me that you could write that function with integers.

The normal std version of f64::trunc() uses intrinsics::truncf64(), which maps to llvm.trunc.f64. For targets that don't have native instructions for this (like soft-float!), that may generate an external call to the C libm or some compiler-builtin function.

FloatCore implements trunc() using fract(), and that's implemented using self % Self::one(). For a soft-float target, LLVM translates that to an external call to the C libm function fmod, which is what you're seeing.

I do have pull request #196 to use the Rust libm crate for parts of FloatCore, including trunc() and fract(). I'm not sure if that will work in your kernel context, but you could try that with a dependency like this:

[dependencies.num-traits]
git = "https://github.com/cuviper/num-traits"
branch = "more-libm"
default-features = false
features = ["libm"]

oh Thank you. It's normal now. Thank you for answering my questions