mmastrac / rust-libc-print

#[no_std] print equivalent for Rust

no_std libc print/println/eprint/eprintln/dbg

Implements println!, eprintln! and dbg! on the libc crate without requiring the use of an allocator.

Allows you to use these macros in a #![no_std] context, or in a situation where the traditional Rust streams might not be available (ie: at process shutdown time).

By default this crate provides libc_-prefixed macros, but also allows consumers to import macros with the same name as the stdlib printing macros via the std_name module.

Usage

Exactly as you'd use println!, eprintln! and dbg!.

#![no_std]

// Use the default `libc_`-prefixed macros:
libc_println!("Hello {}!", "stdout");
libc_eprintln!("Hello {}!", "stderr");
let a = 2;
let b = libc_dbg!(a * 2) + 1;
assert_eq!(b, 5);

Or you can import aliases to std names:

use libc_print::std_name::{println, eprintln, dbg};

println!("Hello {}!", "stdout");
eprintln!("Hello {}!", "stderr");
let a = 2;
let b = dbg!(a * 2) + 1;
assert_eq!(b, 5);

rust-libc-print's Issues

Suggestion for flushing stdout?

Hello, thank you for sharing this crate. 👍
println! macros in std don't immediately flush stdout, and therefore may need something like std::io::stdout().flush().expect("error while flushing stdin"); to ensure immediate printing behavior.

Is there a recommended way to flush stdout while using this crate in #![no_std]?
Thank you 😄

Document usage using original stdlib names and new dbg! macro

The README currently shows an example of prefixed usage (libc_XXX). We should also demonstrate usage using un-prefixed names. In addition, we should show the usage of dbg in the README.

Port travis builder to Github actions

travis.org no longer exists: we need to migrate to Github actions.

Fix "warning: attribute should be applied to an `extern` block"

See message in #70

add libc_dbg! macro

Hi, thanks for the crate, really useful.

I've mainly been using this crate for debugging in a #![no_std] context. I think t would be useful to have the dbg! macro available too.

Unusable without std

Whenever I add this crate to Cargo.toml linking fails:

error: linking with `cc` failed: exit code: 1
  |
  = note: "cc" "-Wl,--as-needed" "-Wl,-z,noexecstack" "-m64" "-L" "/home/rafalh/.rustup/toolchains/nightly-2019-07-01-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib" "/mnt/storage/Rust/fatfs-test/target/debug/deps/fatfs_test-8da1ad26e70363f0.1eyj4q01wj34higz.rcgu.o" "/mnt/storage/Rust/fatfs-test/target/debug/deps/fatfs_test-8da1ad26e70363f0.2s5qo53vqjbghd43.rcgu.o" "-o" "/mnt/storage/Rust/fatfs-test/target/debug/deps/fatfs_test-8da1ad26e70363f0" "-Wl,--gc-sections" "-pie" "-Wl,-zrelro" "-Wl,-znow" "-nodefaultlibs" "-L" "/mnt/storage/Rust/fatfs-test/target/debug/deps" "-L" "/home/rafalh/.rustup/toolchains/nightly-2019-07-01-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-Wl,-Bstatic" "/mnt/storage/Rust/fatfs-test/target/debug/deps/liblibc-8c525ceb5ef9877e.rlib" "/home/rafalh/.rustup/toolchains/nightly-2019-07-01-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/librustc_std_workspace_core-745a89ce61515994.rlib" "/home/rafalh/.rustup/toolchains/nightly-2019-07-01-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcore-18d07502766ba5a6.rlib" "/home/rafalh/.rustup/toolchains/nightly-2019-07-01-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcompiler_builtins-a5d932270c582439.rlib" "-Wl,-Bdynamic" "-lutil" "-lutil"
  = note: /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o: In function `_start':
          (.text+0x12): undefined reference to `__libc_csu_fini'
          (.text+0x19): undefined reference to `__libc_csu_init'
          (.text+0x26): undefined reference to `__libc_start_main'
          /mnt/storage/Rust/fatfs-test/target/debug/deps/fatfs_test-8da1ad26e70363f0.1eyj4q01wj34higz.rcgu.o: In function `main':
          /mnt/storage/Rust/fatfs-test/src/main.rs:30: undefined reference to `printf'
          collect2: error: ld returned 1 exit status

I'm pretty sure it's caused by missing default-features = False flag for libc dependency in this crate.

libc::write not found in `libc`

Thanks for the great library.
I am trying it with cargo build --target thumbv8m.main-none-eabihf

I am having these two compilation errors.

error[E0425]: cannot find function `write` in crate `libc`
  --> .../.cargo/registry/src/github.com-1ecc6299db9ec823/libc-print-0.1.17/src/lib.rs:70:15
   |
70 |         libc::write(
   |               ^^^^^ not found in `libc`
   |
help: consider importing one of these items
   |
17 | use core::fmt::write;
   |
17 | use core::ptr::write;
   |

error[E0412]: cannot find type `size_t` in crate `libc`
  --> .../.cargo/registry/src/github.com-1ecc6299db9ec823/libc-print-0.1.17/src/lib.rs:73:32
   |
73 |             msg.len() as libc::size_t,
   |                                ^^^^^^ not found in `libc`

Any ideas?

when i use it time , it tell link.exe error

linking with link.exe failed: exit code: 1120
but i add .cargo/config.toml
[target.'cfg(target_os = "linux")']
rustflags = ["-C", "link-arg=-nostartfiles"]

[target.'cfg(target_os = "windows")']
rustflags = ["-C", "link-args=/ENTRY:_start /SUBSYSTEM:console"]

[target.'cfg(target_os = "macos")']
rustflags = ["-C", "link-args=-e __start -static -nostartfiles"]

so i want konw why?

"attributes on expressions are experimental" when not used as a statement

Offending excerpt from my code:

use libc_print::std_name::*;

// ...

foo().unwrap_or_else(|err| eprintln!("error: {:?}", err));

My best guess is that there needs to be some added block level and/or semicolon to get the macro call to compile in all cases without needing #![feature(stmt_expr_attributes)].