1 files changed, 68 insertions, 0 deletions
diff --git a/src/librustc_target/spec/linux_musl_base.rs b/src/librustc_target/spec/linux_musl_base.rs
new file mode 100644
index 00000000000..293f23eab38
--- /dev/null
+++ b/src/librustc_target/spec/linux_musl_base.rs
@@ -0,0 +1,68 @@
+// 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.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.push("crt1.o".to_string());
+    base.pre_link_objects_exe.push("crti.o".to_string());
+    base.post_link_objects.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
+}