1 // Copyright 2016 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
12 use target::TargetOptions;
14 pub fn opts() -> TargetOptions {
15 let mut base = super::linux_base::opts();
17 // Make sure that the linker/gcc really don't pull in anything, including
18 // default objects, libs, etc.
19 base.pre_link_args.get_mut(&LinkerFlavor::Gcc).unwrap().push("-nostdlib".to_string());
21 // At least when this was tested, the linker would not add the
22 // `GNU_EH_FRAME` program header to executables generated, which is required
23 // when unwinding to locate the unwinding information. I'm not sure why this
24 // argument is *not* necessary for normal builds, but it can't hurt!
25 base.pre_link_args.get_mut(&LinkerFlavor::Gcc).unwrap().push("-Wl,--eh-frame-hdr".to_string());
27 // There's a whole bunch of circular dependencies when dealing with MUSL
28 // unfortunately. To put this in perspective libc is statically linked to
29 // liblibc and libunwind is statically linked to libstd:
31 // * libcore depends on `fmod` which is in libc (transitively in liblibc).
32 // liblibc, however, depends on libcore.
33 // * compiler-rt has personality symbols that depend on libunwind, but
34 // libunwind is in libstd which depends on compiler-rt.
36 // Recall that linkers discard libraries and object files as much as
37 // possible, and with all the static linking and archives flying around with
38 // MUSL the linker is super aggressively stripping out objects. For example
39 // the first case has fmod stripped from liblibc (it's in its own object
40 // file) so it's not there when libcore needs it. In the second example all
41 // the unused symbols from libunwind are stripped (each is in its own object
42 // file in libstd) before we end up linking compiler-rt which depends on
45 // To deal with these circular dependencies we just force the compiler to
46 // link everything as a group, not stripping anything out until everything
47 // is processed. The linker will still perform a pass to strip out object
48 // files but it won't do so until all objects/archives have been processed.
49 base.pre_link_args.get_mut(&LinkerFlavor::Gcc).unwrap().push("-Wl,-(".to_string());
50 base.post_link_args.insert(LinkerFlavor::Gcc, vec!["-Wl,-)".to_string()]);
52 // When generating a statically linked executable there's generally some
53 // small setup needed which is listed in these files. These are provided by
54 // a musl toolchain and are linked by default by the `musl-gcc` script. Note
55 // that `gcc` also does this by default, it just uses some different files.
57 // Each target directory for musl has these object files included in it so
58 // they'll be included from there.
59 base.pre_link_objects_exe.push("crt1.o".to_string());
60 base.pre_link_objects_exe.push("crti.o".to_string());
61 base.post_link_objects.push("crtn.o".to_string());
63 // MUSL support doesn't currently include dynamic linking, so there's no
64 // need for dylibs or rpath business. Additionally `-pie` is incompatible
65 // with `-static`, so we can't pass `-pie`.
66 base.dynamic_linking = false;
67 base.has_rpath = false;
68 base.position_independent_executables = false;
70 // These targets statically link libc by default
71 base.crt_static_default = true;