Try #1063: --target mips*musl --cpp 1

Author: bors[bot]

.changes/1063.json

@@ -0,0 +1,13 @@
+[
+    {
+        "type": "changed",
+        "description": "changed musl targets to use static-pie linkage by default, consistent with Alpine.",
+        "breaking": true
+    },
+    {
+        "type": "fixed",
+        "description": "fixed C++ support for musl targets.",
+        "issues": [902],
+        "breaking": true
+    }
+]

docker/musl-symlink.sh

@@ -49,6 +49,19 @@ main() {
         fi
     done
 
+    # despite using a completely static build, the 32-bit MIPS targets
+    # link to libgcc_s, the shared libgcc, erroneously.
+    if [[ "${arch}" == "mips-sf" ]] || [[ "${arch}" == "mipsel-sf" ]]; then
+        local toolchain=
+        local gcc_lib=
+        local gcc_ver=
+        toolchain=$(basename "${sysroot}")
+        gcc_lib="/usr/local/lib/gcc/${toolchain}"
+        # shellcheck disable=SC2012
+        gcc_ver=$(ls -1 "${gcc_lib}" | head -n 1)
+        ln -s "${gcc_lib}/${gcc_ver}/libgcc.a" "${gcc_lib}/${gcc_ver}/libgcc_s.a"
+    fi
+
     echo "${sysroot}/lib" >> "/etc/ld-musl-${arch}.path"
 
     rm -rf "${0}"

docker/musl.sh

@@ -36,13 +36,33 @@ main() {
     # Don't depend on the mirrors of sabotage linux that musl-cross-make uses.
     local linux_headers_site=https://ci-mirrors.rust-lang.org/rustc/sabotage-linux-tarballs
 
+    # we need -fPIC for CFLAGS because old binutils versions
+    # don't understand debug symbols for more recent builds
+    set +u
+    export CFLAGS="-fPIC -fPIE ${CFLAGS}"
+    export CXXFLAGS="-fPIC -fPIE ${CXXFLAGS}"
+    set -u
+    # we need to enable `-fPIE` or to avoid relocations in libstdc++
+    # we also don't want dynamic linking to the standard libraries
+    # enable -fPIC just to be safe. alpine GCC is built with
+    # `--enable-default-pie`, so we want to ensure we use that.
+    # `--disable-shared` is required to avoid issues when linking
+    # to the wrong standard library, which would cause a segfault.
+    # rust itself disables shared libraries with musl:
+    # https://github.com/rust-lang/rust/blob/e42c4d7218b2596276152c5eb1e69335621f3086/src/ci/docker/scripts/musl.sh#L36
+    #
+    # on alpine, binaries use static-pie linked, so our behavior has
+    # maximum portability, and is consistent with popular musl distros.
     hide_output make install "-j$(nproc)" \
         GCC_VER=9.2.0 \
         MUSL_VER=1.1.24 \
         BINUTILS_VER=2.33.1 \
         DL_CMD='curl --retry 3 -sSfL -C - -o' \
-        LINUX_HEADERS_SITE=$linux_headers_site \
+        LINUX_HEADERS_SITE="${linux_headers_site}" \
         OUTPUT=/usr/local/ \
+        "COMMON_CONFIG += --disable-shared" \
+        "COMMON_CONFIG += CFLAGS=\"-fPIC -fPIE\" CXXFLAGS=\"-fPIC -fPIE\"" \
+        "GCC_CONFIG += --enable-default-pie" \
         "${@}"
 
     purge_packages

targets.toml

@@ -22,8 +22,11 @@ deploy = true
 [[target]]
 target = "x86_64-unknown-linux-musl"
 os = "ubuntu-latest"
+cpp = true
+dylib = true
 std = true
 run = true
+runners = "native qemu-user"
 deploy = true
 
 [[target]]