// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use spec::{LinkerFlavor, TargetOptions};
pub fn opts() -> TargetOptions {
let mut base = super::linux_base::opts();
// Make sure that the linker/gcc really don't pull in anything, including
// default objects, libs, etc.
base.pre_link_args_crt.insert(LinkerFlavor::Gcc, Vec::new());
base.pre_link_args_crt.get_mut(&LinkerFlavor::Gcc).unwrap().push("-nostdlib".to_string());
// At least when this was tested, the linker would not add the
// `GNU_EH_FRAME` program header to executables generated, which is required
// when unwinding to locate the unwinding information. I'm not sure why this
// argument is *not* necessary for normal builds, but it can't hurt!
base.pre_link_args.get_mut(&LinkerFlavor::Gcc).unwrap().push("-Wl,--eh-frame-hdr".to_string());
// There's a whole bunch of circular dependencies when dealing with MUSL
// unfortunately. To put this in perspective libc is statically linked to
// liblibc and libunwind is statically linked to libstd:
//
// * libcore depends on `fmod` which is in libc (transitively in liblibc).
// liblibc, however, depends on libcore.
// * compiler-rt has personality symbols that depend on libunwind, but
// libunwind is in libstd which depends on compiler-rt.
//
// Recall that linkers discard libraries and object files as much as
// possible, and with all the static linking and archives flying around with
// MUSL the linker is super aggressively stripping out objects. For example
// the first case has fmod stripped from liblibc (it's in its own object
// file) so it's not there when libcore needs it. In the second example all
// the unused symbols from libunwind are stripped (each is in its own object
// file in libstd) before we end up linking compiler-rt which depends on
// those symbols.
//
// To deal with these circular dependencies we just force the compiler to
// link everything as a group, not stripping anything out until everything
// is processed. The linker will still perform a pass to strip out object
// files but it won't do so until all objects/archives have been processed.
base.pre_link_args.get_mut(&LinkerFlavor::Gcc).unwrap().push("-Wl,-(".to_string());
base.post_link_args.insert(LinkerFlavor::Gcc, vec!["-Wl,-)".to_string()]);
// When generating a statically linked executable there's generally some
// small setup needed which is listed in these files. These are provided by
// a musl toolchain and are linked by default by the `musl-gcc` script. Note
// that `gcc` also does this by default, it just uses some different files.
//
// Each target directory for musl has these object files included in it so
// they'll be included from there.
base.pre_link_objects_exe_crt.push("crt1.o".to_string());
base.pre_link_objects_exe_crt.push("crti.o".to_string());
base.pre_link_objects_exe_crt_sys.push("crtbegin.o".to_string());
base.post_link_objects_crt_sys.push("crtend.o".to_string());
base.post_link_objects_crt.push("crtn.o".to_string());
// These targets statically link libc by default
base.crt_static_default = true;
// These targets allow the user to choose between static and dynamic linking.
base.crt_static_respected = true;
base
}