Minimal program w/o std, libc creates binary that seg faults

[mikedilger]

I'm trying to create a program without std and without libc. Based on this page: http://doc.rust-lang.org/guide-unsafe.html (and elsewhere). I still cannot get a minimal program to work. It compiles, but the binary segmentation faults (on x86_64 linux).

Compiled with: rustc --crate-type=bin -C link-args="-nostdlib" -C relocation-model=static start.rs

Program is:

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

extern crate core;
extern crate rlibc;

#[lang = "stack_exhausted"]
extern fn stack_exhausted() {}

#[lang = "eh_personality" ]
extern fn eh_personality() {}

#[lang = "begin_unwind" ]
unsafe extern fn begin_unwind(args: &core::fmt::Arguments,
                       file: &str,
                       line: uint) -> ! {
    loop {}
}

#[start]
fn main(argc: int, argv: *const *const u8) -> int
{
    0
}

[alexcrichton]

This is likely not a rust-specific problem but rather how you're compiling and driving the linker. Most linux distributions need libc to be linked in to have the necessary startup routines, and one may likely be missing from the binary.

For example, if you compile a similar C program you get an odd error:

$ cat foo.c
int main() { return 0; }
$ gcc foo.c -o foo -nostdlib
/usr/bin/ld: warning: cannot find entry symbol _start; defaulting to 0000000000400144
$ ./foo
zsh: segmentation fault (core dumped)  ./foo

Even if the main symbol is switched to _start, this still segfaults. In general a bare bones binary such as this is not meant to run on the host system as it's missing necessary library support.

I don't think this is related to rust, however, so I'm going to close this for now.