Use libunwind from llvm-project submodule for musl targets

src/bootstrap/sanity.rs

@@ -202,10 +202,6 @@ pub fn check(build: &mut Build) {
                         panic!("couldn't find libc.a in musl dir: {}",
                                root.join("lib").display());
                     }
-                    if fs::metadata(root.join("lib/libunwind.a")).is_err() {
-                        panic!("couldn't find libunwind.a in musl dir: {}",
-                               root.join("lib").display());
-                    }
                 }
                 None => {
                     panic!("when targeting MUSL either the rust.musl-root \

src/ci/docker/scripts/musl-toolchain.sh

@@ -54,29 +54,3 @@ if [ "$REPLACE_CC" = "1" ]; then
         ln -s $TARGET-g++ /usr/local/bin/$exec
     done
 fi
-
-export CC=$TARGET-gcc
-export CXX=$TARGET-g++
-
-LLVM=70
-
-# may have been downloaded in a previous run
-if [ ! -d libunwind-release_$LLVM ]; then
-  curl -L https://github.com/llvm-mirror/llvm/archive/release_$LLVM.tar.gz | tar xzf -
-  curl -L https://github.com/llvm-mirror/libunwind/archive/release_$LLVM.tar.gz | tar xzf -
-fi
-
-# fixme(mati865): Replace it with https://github.com/rust-lang/rust/pull/59089
-mkdir libunwind-build
-cd libunwind-build
-cmake ../libunwind-release_$LLVM \
-          -DLLVM_PATH=/build/llvm-release_$LLVM \
-          -DLIBUNWIND_ENABLE_SHARED=0 \
-          -DCMAKE_C_COMPILER=$CC \
-          -DCMAKE_CXX_COMPILER=$CXX \
-          -DCMAKE_C_FLAGS="$CFLAGS" \
-          -DCMAKE_CXX_FLAGS="$CXXFLAGS"
-
-hide_output make -j$(nproc)
-cp lib/libunwind.a $OUTPUT/$TARGET/lib
-cd - && rm -rf libunwind-build

src/ci/docker/scripts/musl.sh

@@ -20,6 +20,8 @@ exit 1
 TAG=$1
 shift
 
+# Ancient binutils versions don't understand debug symbols produced by more recent tools.
+# Apparently applying `-fPIC` everywhere allows them to link successfully.
 export CFLAGS="-fPIC $CFLAGS"
 
 MUSL=musl-1.1.22
@@ -38,27 +40,3 @@ else
 fi
 hide_output make install
 hide_output make clean
-
-cd ..
-
-LLVM=70
-
-# may have been downloaded in a previous run
-if [ ! -d libunwind-release_$LLVM ]; then
-  curl -L https://github.com/llvm-mirror/llvm/archive/release_$LLVM.tar.gz | tar xzf -
-  curl -L https://github.com/llvm-mirror/libunwind/archive/release_$LLVM.tar.gz | tar xzf -
-fi
-
-mkdir libunwind-build
-cd libunwind-build
-cmake ../libunwind-release_$LLVM \
-          -DLLVM_PATH=/build/llvm-release_$LLVM \
-          -DLIBUNWIND_ENABLE_SHARED=0 \
-          -DCMAKE_C_COMPILER=$CC \
-          -DCMAKE_CXX_COMPILER=$CXX \
-          -DCMAKE_C_FLAGS="$CFLAGS" \
-          -DCMAKE_CXX_FLAGS="$CXXFLAGS"
-
-hide_output make -j$(nproc)
-cp lib/libunwind.a /musl-$TAG/lib
-cd ../ && rm -rf libunwind-build

src/libunwind/Cargo.toml

@@ -22,7 +22,7 @@ compiler_builtins = "0.1.0"
 cfg-if = "0.1.8"
 
 [build-dependencies]
-cc = { optional = true, version = "1.0.1" }
+cc = { version = "1.0.1" }
 
 [features]
-llvm-libunwind = ["cc"]
+llvm-libunwind = []

src/libunwind/build.rs

@@ -5,14 +5,14 @@ fn main() {
     let target = env::var("TARGET").expect("TARGET was not set");
 
     if cfg!(feature = "llvm-libunwind") &&
-        (target.contains("linux") ||
+        ((target.contains("linux") && !target.contains("musl")) ||
          target.contains("fuchsia")) {
         // Build the unwinding from libunwind C/C++ source code.
-        #[cfg(feature = "llvm-libunwind")]
         llvm_libunwind::compile();
     } else if target.contains("linux") {
         if target.contains("musl") {
-            // musl is handled in lib.rs
+            // linking for musl is handled in lib.rs
+            llvm_libunwind::compile();
         } else if !target.contains("android") {
             println!("cargo:rustc-link-lib=gcc_s");
         }
@@ -44,7 +44,6 @@ fn main() {
     }
 }
 
-#[cfg(feature = "llvm-libunwind")]
 mod llvm_libunwind {
     use std::env;
     use std::path::Path;
@@ -96,6 +95,15 @@ mod llvm_libunwind {
             cfg.file(root.join("src").join(src));
         }
 
+        if target_env == "musl" {
+            // use the same C compiler command to compile C++ code so we do not need to setup the
+            // C++ compiler env variables on the builders
+            cfg.cpp(false);
+            // linking for musl is handled in lib.rs
+            cfg.cargo_metadata(false);
+            println!("cargo:rustc-link-search=native={}", env::var("OUT_DIR").unwrap());
+        }
+
         cfg.compile("unwind");
     }
 }