nostd libc not link

[adjivas]

I tried this code:

• src/main.rs:

#![feature(lang_items)]
#![feature(start)]
#![no_std]

extern crate libc;

#[start]
fn start(_argc: isize, _argv: *const *const u8) -> isize {
    let buffer: [u8; 1] = [0u8];

    unsafe {
        libc::read(0, buffer.as_ptr() as *mut libc::c_void, 1);
    }

    let character: u8 = unsafe { *buffer.as_ptr() } as u8;
    let _ = 255u8 - character; // The line problem.

    0
}

#[lang = "eh_personality"] extern fn eh_personality() {}
#[lang = "panic_fmt"] fn panic_fmt() -> ! { loop {} }

• Cargo.toml:

[package]
name = "nostd"
version = "0.1.0"
authors = ["adjivas <adjivas@users.noreply.github.com>"]

[profile.release]
lto = true

[dependencies.libc]
version = "*"
default-features = false

I expected to see this happen:

$ cargo rustc -- -Z force-overflow-checks=off
    Updating registry `https://github.com/rust-lang/crates.io-index`
 Downloading libc v0.2.9
   Compiling libc v0.2.9
   Compiling nostd v0.1.0 (file:///home/travis/build/adjivas/nostd)
The command "cargo rustc -- -Z force-overflow-checks=off" exited with 0.
$ nm ./target/debug/nostd | grep " U "
                 U __libc_start_main@@GLIBC_2.2.5
                 U memset@@GLIBC_2.2.5
                 U read@@GLIBC_2.2.5

Instead, this happened:

$ cargo rustc -- -Z force-overflow-checks=off
    Updating registry `https://github.com/rust-lang/crates.io-index`
 Downloading libc v0.2.9
   Compiling libc v0.2.9
   Compiling nostd v0.1.0 (file:///home/travis/build/adjivas/nostd)
error: linking with `cc` failed: exit code: 1
note: "cc" "-Wl,--as-needed" "-Wl,-z,noexecstack" "-m64" "-L" "/home/travis/rust/lib/rustlib/x86_64-unknown-linux-gnu/lib" "/home/travis/build/adjivas/nostd/target/debug/nostd.0.o" "-o" "/home/travis/build/adjivas/nostd/target/debug/nostd" "-Wl,--gc-sections" "-pie" "-nodefaultlibs" "-L" "/home/travis/build/adjivas/nostd/target/debug" "-L" "/home/travis/build/adjivas/nostd/target/debug/deps" "-L" "/home/travis/rust/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-Wl,-Bstatic" "-Wl,-Bdynamic" "/home/travis/build/adjivas/nostd/target/debug/deps/liblibc-00ad8a4a4c184a2d.rlib" "/home/travis/rust/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcore-18402db3.rlib" "-l" "compiler-rt"
note: /usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/Scrt1.o: In function `_start':
(.text+0x12): undefined reference to `__libc_csu_fini'
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/Scrt1.o: In function `_start':
(.text+0x19): undefined reference to `__libc_csu_init'
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/Scrt1.o: In function `_start':
(.text+0x25): undefined reference to `__libc_start_main'
/home/travis/build/adjivas/nostd/target/debug/nostd.0.o: In function `nostd::start::hd7b9118d84e1f51b':
/home/travis/build/adjivas/nostd/src/main.rs:8: undefined reference to `memset'
/home/travis/build/adjivas/nostd/src/main.rs:12: undefined reference to `read'

[steveklabnik]

@alexcrichton seemed to think this might be a bug in the libc crate around configs

[Aatch]

Looks like it's not linking to libc (the real one). There's a nodefaultlibs in the link command, but no -l c.

[alexcrichton]

Yes this is currently a bug with the libc crate, and I've opened a PR: rust-lang/libc#249