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From 3abd1f5e2f31b1c95535ef8c3b4bef6ff78b3fa9 Mon Sep 17 00:00:00 2001
From: Samuel Holland <samuel@sholland.org>
From: Shiz <hi@shiz.me>
Date: Wed, 12 Apr 2017 22:31:06 +0200
Subject: [PATCH] Support dynamically-linked and/or native musl targets

These changes allow native compilation on musl-based distributions and the
use of dynamic libraries on linux-musl targets. This is intended to remove
limitations based on past assumptions about musl targets, while
maintaining existing behavior by default.

Upstream-Issue: https://github.com/rust-lang/rust/pull/40113
See-Also: https://internals.rust-lang.org/t/refining-cross-platform-crt-static-semantics/5085

diff --git a/src/bootstrap/bin/rustc.rs b/src/bootstrap/bin/rustc.rs
index 90fd31ecbd..28520a2c60 100644
--- a/src/bootstrap/bin/rustc.rs
+++ b/src/bootstrap/bin/rustc.rs
@@ -205,6 +205,17 @@ fn main() {
                 }
             }
         }
+
+        if let Ok(s) = env::var("RUST_CRT_STATIC") {
+            if s == "true" {
+                cmd.arg("-Z").arg("unstable-options");
+                cmd.arg("-C").arg("target-feature=+crt-static");
+            }
+            if s == "false" {
+                cmd.arg("-Z").arg("unstable-options");
+                cmd.arg("-C").arg("target-feature=-crt-static");
+            }
+        }
     }
 
     if verbose > 1 {
diff --git a/src/bootstrap/compile.rs b/src/bootstrap/compile.rs
index 7c35151a6d..c83b6cc24c 100644
--- a/src/bootstrap/compile.rs
+++ b/src/bootstrap/compile.rs
@@ -94,14 +94,17 @@ pub fn std_link(build: &Build,
     t!(fs::create_dir_all(&libdir));
     add_to_sysroot(&out_dir, &libdir);
 
-    if target.contains("musl") && !target.contains("mips") {
+    if target.contains("musl") {
         copy_musl_third_party_objects(build, target, &libdir);
     }
 }
 
 /// Copies the crt(1,i,n).o startup objects
 ///
-/// Only required for musl targets that statically link to libc
+/// Since musl supports fully static linking, we can cross link for it even
+/// with a glibc-targeting toolchain, given we have the appropriate startup
+/// files. As those shipped with glibc won't work, copy the ones provided by
+/// musl so we have them on linux-gnu hosts.
 fn copy_musl_third_party_objects(build: &Build, target: &str, into: &Path) {
     for &obj in &["crt1.o", "crti.o", "crtn.o"] {
         copy(&build.musl_root(target).unwrap().join("lib").join(obj), &into.join(obj));
diff --git a/src/bootstrap/config.rs b/src/bootstrap/config.rs
index 6e077691b3..8d9be38959 100644
--- a/src/bootstrap/config.rs
+++ b/src/bootstrap/config.rs
@@ -113,6 +113,7 @@ pub struct Target {
     pub cc: Option<PathBuf>,
     pub cxx: Option<PathBuf>,
     pub ndk: Option<PathBuf>,
+    pub crt_static: Option<bool>,
     pub musl_root: Option<PathBuf>,
 }
 
@@ -221,6 +222,7 @@ struct TomlTarget {
     cc: Option<String>,
     cxx: Option<String>,
     android_ndk: Option<String>,
+    crt_static: Option<bool>,
     musl_root: Option<String>,
 }
 
@@ -359,6 +361,7 @@ impl Config {
                 }
                 target.cxx = cfg.cxx.clone().map(PathBuf::from);
                 target.cc = cfg.cc.clone().map(PathBuf::from);
+                target.crt_static = cfg.crt_static.clone();
                 target.musl_root = cfg.musl_root.clone().map(PathBuf::from);
 
                 config.target_config.insert(triple.clone(), target);
diff --git a/src/bootstrap/lib.rs b/src/bootstrap/lib.rs
index c98dd4751f..e7ee9511d8 100644
--- a/src/bootstrap/lib.rs
+++ b/src/bootstrap/lib.rs
@@ -500,6 +500,10 @@ impl Build {
              .env("RUSTDOC_REAL", self.rustdoc(compiler))
              .env("RUSTC_FLAGS", self.rustc_flags(target).join(" "));
 
+        if let Some(x) = self.crt_static(target) {
+             cargo.env("RUST_CRT_STATIC", x.to_string());
+        }
+
         // Enable usage of unstable features
         cargo.env("RUSTC_BOOTSTRAP", "1");
         self.add_rust_test_threads(&mut cargo);
@@ -883,6 +887,16 @@ impl Build {
         return base
     }
 
+    /// Returns if this target should statically link the C runtime, if specified
+    fn crt_static(&self, target: &str) -> Option<bool> {
+        if target.contains("pc-windows-msvc") {
+            Some(true)
+        } else {
+            self.config.target_config.get(target)
+                .and_then(|t| t.crt_static)
+        }
+    }
+
     /// Returns the "musl root" for this `target`, if defined
     fn musl_root(&self, target: &str) -> Option<&Path> {
         self.config.target_config.get(target)
diff --git a/src/bootstrap/sanity.rs b/src/bootstrap/sanity.rs
index bc439d6f78..3ee1113516 100644
--- a/src/bootstrap/sanity.rs
+++ b/src/bootstrap/sanity.rs
@@ -157,8 +157,15 @@ pub fn check(build: &mut Build) {
             panic!("the iOS target is only supported on OSX");
         }
 
-        // Make sure musl-root is valid if specified
-        if target.contains("musl") && !target.contains("mips") {
+        // Make sure musl-root is valid
+        if target.contains("musl") {
+            // If this is a native target (host is also musl) and no musl-root is given,
+            // fall back to the system toolchain in /usr before giving up
+            if build.musl_root(target).is_none() && build.config.build == *target {
+                let target = build.config.target_config.entry(target.clone())
+                                 .or_insert(Default::default());
+                target.musl_root = Some("/usr".into());
+            }
             match build.musl_root(target) {
                 Some(root) => {
                     if fs::metadata(root.join("lib/libc.a")).is_err() {
diff --git a/src/librustc/session/mod.rs b/src/librustc/session/mod.rs
index 36a887e062..1075e4f0cf 100644
--- a/src/librustc/session/mod.rs
+++ b/src/librustc/session/mod.rs
@@ -34,6 +34,7 @@ use syntax::parse::ParseSess;
 use syntax::symbol::Symbol;
 use syntax::{ast, codemap};
 use syntax::feature_gate::AttributeType;
+use syntax::feature_gate::UnstableFeatures;
 use syntax_pos::{Span, MultiSpan};
 
 use rustc_back::PanicStrategy;
@@ -380,6 +381,34 @@ impl Session {
         self.opts.debugging_opts.enable_nonzeroing_move_hints
     }
 
+    pub fn crt_static(&self) -> bool {
+        let requested_features = self.opts.cg.target_feature.split(',');
+        let unstable_options = self.opts.debugging_opts.unstable_options;
+        let is_nightly = UnstableFeatures::from_environment().is_nightly_build();
+        let found_negative = requested_features.clone().any(|r| r == "-crt-static");
+        let found_positive = requested_features.clone().any(|r| r == "+crt-static");
+
+        // If the target we're compiling for requests a static crt by default,
+        // then see if the `-crt-static` feature was passed to disable that.
+        // Otherwise if we don't have a static crt by default then see if the
+        // `+crt-static` feature was passed.
+        let crt_static = if self.target.target.options.crt_static_default {
+            !found_negative
+        } else {
+            found_positive
+        };
+
+        // If we switched from the default then that's only allowed on nightly, so
+        // gate that here.
+        if (found_positive || found_negative) && (!is_nightly || !unstable_options) {
+            self.fatal("specifying the `crt-static` target feature is only allowed \
+                on the nightly channel with `-Z unstable-options` passed \
+                as well");
+        }
+
+        return crt_static;
+    }
+
     pub fn must_not_eliminate_frame_pointers(&self) -> bool {
         self.opts.debuginfo != DebugInfoLevel::NoDebugInfo ||
         !self.target.target.options.eliminate_frame_pointer
diff --git a/src/librustc_back/target/linux_musl_base.rs b/src/librustc_back/target/linux_musl_base.rs
index 18cca425a3..076bbe7193 100644
--- a/src/librustc_back/target/linux_musl_base.rs
+++ b/src/librustc_back/target/linux_musl_base.rs
@@ -59,14 +59,7 @@ pub fn opts() -> TargetOptions {
     base.pre_link_objects_exe.push("crti.o".to_string());
     base.post_link_objects.push("crtn.o".to_string());
 
-    // MUSL support doesn't currently include dynamic linking, so there's no
-    // need for dylibs or rpath business. Additionally `-pie` is incompatible
-    // with `-static`, so we can't pass `-pie`.
-    base.dynamic_linking = false;
-    base.has_rpath = false;
-    base.position_independent_executables = false;
-
-    // These targets statically link libc by default
+    // Except for on MIPS, these targets statically link libc by default.
     base.crt_static_default = true;
 
     base
diff --git a/src/librustc_back/target/mips_unknown_linux_musl.rs b/src/librustc_back/target/mips_unknown_linux_musl.rs
index e4a6d2a55d..77fcf9770d 100644
--- a/src/librustc_back/target/mips_unknown_linux_musl.rs
+++ b/src/librustc_back/target/mips_unknown_linux_musl.rs
@@ -25,6 +25,7 @@ pub fn target() -> TargetResult {
             features: "+mips32r2,+soft-float".to_string(),
             max_atomic_width: Some(32),
 
+            crt_static_default: false,
             // see #36994
             exe_allocation_crate: "alloc_system".to_string(),
 
diff --git a/src/librustc_back/target/mipsel_unknown_linux_musl.rs b/src/librustc_back/target/mipsel_unknown_linux_musl.rs
index 5693bddd04..6339e719e1 100644
--- a/src/librustc_back/target/mipsel_unknown_linux_musl.rs
+++ b/src/librustc_back/target/mipsel_unknown_linux_musl.rs
@@ -25,6 +25,7 @@ pub fn target() -> TargetResult {
             features: "+mips32,+soft-float".to_string(),
             max_atomic_width: Some(32),
 
+            crt_static_default: false,
             // see #36994
             exe_allocation_crate: "alloc_system".to_string(),
 
diff --git a/src/librustc_driver/target_features.rs b/src/librustc_driver/target_features.rs
index 124e7aafcc..492ceecaf1 100644
--- a/src/librustc_driver/target_features.rs
+++ b/src/librustc_driver/target_features.rs
@@ -12,7 +12,6 @@ use syntax::ast;
 use llvm::LLVMRustHasFeature;
 use rustc::session::Session;
 use rustc_trans::back::write::create_target_machine;
-use syntax::feature_gate::UnstableFeatures;
 use syntax::symbol::Symbol;
 use libc::c_char;
 
@@ -49,31 +48,7 @@ pub fn add_configuration(cfg: &mut ast::CrateConfig, sess: &Session) {
         }
     }
 
-    let requested_features = sess.opts.cg.target_feature.split(',');
-    let unstable_options = sess.opts.debugging_opts.unstable_options;
-    let is_nightly = UnstableFeatures::from_environment().is_nightly_build();
-    let found_negative = requested_features.clone().any(|r| r == "-crt-static");
-    let found_positive = requested_features.clone().any(|r| r == "+crt-static");
-
-    // If the target we're compiling for requests a static crt by default,
-    // then see if the `-crt-static` feature was passed to disable that.
-    // Otherwise if we don't have a static crt by default then see if the
-    // `+crt-static` feature was passed.
-    let crt_static = if sess.target.target.options.crt_static_default {
-        !found_negative
-    } else {
-        found_positive
-    };
-
-    // If we switched from the default then that's only allowed on nightly, so
-    // gate that here.
-    if (found_positive || found_negative) && (!is_nightly || !unstable_options) {
-        sess.fatal("specifying the `crt-static` target feature is only allowed \
-                    on the nightly channel with `-Z unstable-options` passed \
-                    as well");
-    }
-
-    if crt_static {
+    if sess.crt_static() {
         cfg.insert((tf, Some(Symbol::intern("crt-static"))));
     }
 }
diff --git a/src/librustc_trans/back/link.rs b/src/librustc_trans/back/link.rs
index defbb44448..f10c7d5c83 100644
--- a/src/librustc_trans/back/link.rs
+++ b/src/librustc_trans/back/link.rs
@@ -703,13 +703,15 @@ fn link_natively(sess: &Session,
     let root = sess.target_filesearch(PathKind::Native).get_lib_path();
     cmd.args(&sess.target.target.options.pre_link_args);
 
-    let pre_link_objects = if crate_type == config::CrateTypeExecutable {
-        &sess.target.target.options.pre_link_objects_exe
-    } else {
-        &sess.target.target.options.pre_link_objects_dll
-    };
-    for obj in pre_link_objects {
-        cmd.arg(root.join(obj));
+    if sess.crt_static() {
+        let pre_link_objects = if crate_type == config::CrateTypeExecutable {
+            &sess.target.target.options.pre_link_objects_exe
+        } else {
+            &sess.target.target.options.pre_link_objects_dll
+        };
+        for obj in pre_link_objects {
+            cmd.arg(root.join(obj));
+        }
     }
 
     {
@@ -718,8 +720,10 @@ fn link_natively(sess: &Session,
                   objects, out_filename, outputs, trans);
     }
     cmd.args(&sess.target.target.options.late_link_args);
-    for obj in &sess.target.target.options.post_link_objects {
-        cmd.arg(root.join(obj));
+    if sess.crt_static() {
+        for obj in &sess.target.target.options.post_link_objects {
+            cmd.arg(root.join(obj));
+        }
     }
     cmd.args(&sess.target.target.options.post_link_args);
 
diff --git a/src/libstd/build.rs b/src/libstd/build.rs
index 9504194393..dd2008c206 100644
--- a/src/libstd/build.rs
+++ b/src/libstd/build.rs
@@ -35,7 +35,7 @@ fn main() {
             println!("cargo:rustc-link-lib=dl");
             println!("cargo:rustc-link-lib=log");
             println!("cargo:rustc-link-lib=gcc");
-        } else if !target.contains("musl") || target.contains("mips") {
+        } else if !target.contains("musl") {
             println!("cargo:rustc-link-lib=dl");
             println!("cargo:rustc-link-lib=rt");
             println!("cargo:rustc-link-lib=pthread");
diff --git a/src/libunwind/build.rs b/src/libunwind/build.rs
index db41a368a1..b1a86f04ef 100644
--- a/src/libunwind/build.rs
+++ b/src/libunwind/build.rs
@@ -16,8 +16,8 @@ fn main() {
     let target = env::var("TARGET").expect("TARGET was not set");
 
     if target.contains("linux") {
-        if target.contains("musl") && !target.contains("mips") {
-            println!("cargo:rustc-link-lib=static=unwind");
+        if target.contains("musl") {
+            println!("cargo:rustc-link-lib=unwind");
         } else if !target.contains("android") {
             println!("cargo:rustc-link-lib=gcc_s");
         }
diff --git a/src/liblibc/src/unix/mod.rs b/src/liblibc/src/unix/mod.rs
--- a/src/liblibc/src/unix/mod.rs
+++ b/src/liblibc/src/unix/mod.rs
@@ -210,8 +210,7 @@ cfg_if! {
         // cargo build, don't pull in anything extra as the libstd  dep
         // already pulls in all libs.
-    } else if #[cfg(any(all(target_env = "musl", not(target_arch = "mips"))))] {
+    } else if #[cfg(target_env = "musl")] {
-        #[link(name = "c", kind = "static", cfg(target_feature = "crt-static"))]
-        #[link(name = "c", cfg(not(target_feature = "crt-static")))]
+        #[link(name = "c")]
         extern {}
     } else if #[cfg(target_os = "emscripten")] {
         #[link(name = "c")]
-- 
2.12.2