osx_cc_wrapper.sh.tpl

#!/bin/bash
#
# Copyright 2015 The Bazel Authors. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
# OS X relpath is not really working. This is a wrapper script around gcc
# to simulate relpath behavior.
#
# This wrapper uses install_name_tool to replace all paths in the binary
# (bazel-out/.../path/to/original/library.so) by the paths relative to
# the binary. It parses the command line to behave as rpath is supposed
# to work.
#
# See https://blogs.oracle.com/dipol/entry/dynamic_libraries_rpath_and_mac
# on how to set those paths for Mach-O binaries.
#
set -eu

INSTALL_NAME_TOOL="/usr/bin/install_name_tool"

LIBS=
LIB_DIRS=
RPATHS=
OUTPUT=

function parse_option() {
    local -r opt="$1"
    if [[ "${OUTPUT}" = "1" ]]; then
        OUTPUT=$opt
    elif [[ "$opt" =~ ^-l(.*)$ ]]; then
        LIBS="${BASH_REMATCH[1]} $LIBS"
    elif [[ "$opt" =~ ^-L(.*)$ ]]; then
        LIB_DIRS="${BASH_REMATCH[1]} $LIB_DIRS"
    elif [[ "$opt" =~ ^-Wl,-rpath,\@loader_path/(.*)$ ]]; then
        RPATHS="${BASH_REMATCH[1]} ${RPATHS}"
    elif [[ "$opt" = "-o" ]]; then
        # output is coming
        OUTPUT=1
    fi
}

# let parse the option list
for i in "$@"; do
    if [[ "$i" = @* ]]; then
        while IFS= read -r opt
        do
            parse_option "$opt"
        done < "${i:1}" || exit 1
    else
        parse_option "$i"
    fi
done

# On macOS, we use ld as the linker for single-platform builds (i.e., when not
# cross-compiling). Some applications may remove /usr/bin from PATH before
# calling this script, which would make /usr/bin/ld unreachable.  For example,
# rules_rust does not set PATH (unless the user explicitly sets PATH in env
# through attributes) [1] when calling rustc, and rustc does not replace an
# unset PATH with a reasonable default either ([2], [3]), which results in CC
# being called with PATH={sysroot}/{rust_lib}/bin. Note that rules_cc [4] and
# rules_go [5] do ensure that /usr/bin is in PATH.
# [1]: https://github.com/bazelbuild/rules_rust/blob/e589105b4e8181dd1d0d8ccaa0cf3267efb06e86/cargo/cargo_build_script.bzl#L66-L68
# [2]: https://github.com/rust-lang/rust/blob/1c03f0d0ba4fee54b7aa458f4d3ad989d8bf7b34/compiler/rustc_session/src/session.rs#L804-L813
# [3]: https://github.com/rust-lang/rust/blob/1c03f0d0ba4fee54b7aa458f4d3ad989d8bf7b34/compiler/rustc_codegen_ssa/src/back/link.rs#L640-L645
# [4]: https://cs.opensource.google/bazel/bazel/+/master:src/main/java/com/google/devtools/build/lib/bazel/rules/BazelRuleClassProvider.java;l=529;drc=72caead7b428fd50164079956ec368fc54a9567c
# [5]: https://github.com/bazelbuild/rules_go/blob/63dfd99403076331fef0775d52a8039d502d4115/go/private/context.bzl#L434
# Let's restore /usr/bin to PATH in such cases. Note that /usr/bin is not a
# writeable directory on macOS even with sudo privileges, so it should be safe
# to add it to PATH even when the application wants to use a very strict PATH.
if [[ ":${PATH}:" != *":/usr/bin:"* ]]; then
  PATH="${PATH}:/usr/bin"
fi

# Call the C++ compiler.
if [[ -f %{toolchain_path_prefix}bin/clang ]]; then
  %{toolchain_path_prefix}bin/clang "$@"
elif [[ "${BASH_SOURCE[0]}" == "/"* ]]; then
  # Some consumers of `CcToolchainConfigInfo` (e.g. `cmake` from rules_foreign_cc)
  # change CWD and call $CC (this script) with its absolute path.
  # the execroot (i.e. `cmake` from `rules_foreign_cc`) and call CC . For cases like this,
  # we'll try to find `clang` relative to this script.
  # This script is at _execroot_/external/_repo_name_/bin/cc_wrapper.sh
  execroot_path="${BASH_SOURCE[0]%/*/*/*/*}"
  clang="${execroot_path}/%{toolchain_path_prefix}bin/clang"
  "${clang}" "${@}"
else
  >&2 echo "ERROR: could not find clang; PWD=\"$(pwd)\"; PATH=\"${PATH}\"."
  exit 5
fi

function get_library_path() {
    for libdir in ${LIB_DIRS}; do
        if [ -f ${libdir}/lib$1.so ]; then
            echo "${libdir}/lib$1.so"
        elif [ -f ${libdir}/lib$1.dylib ]; then
            echo "${libdir}/lib$1.dylib"
        fi
    done
}

# A convenient method to return the actual path even for non symlinks
# and multi-level symlinks.
function get_realpath() {
    local previous="$1"
    local next=$(readlink "${previous}")
    while [ -n "${next}" ]; do
        previous="${next}"
        next=$(readlink "${previous}")
    done
    echo "${previous}"
}

# Get the path of a lib inside a tool
function get_otool_path() {
    # the lib path is the path of the original lib relative to the workspace
    get_realpath $1 | sed 's|^.*/bazel-out/|bazel-out/|'
}

# Do replacements in the output
for rpath in ${RPATHS}; do
    for lib in ${LIBS}; do
        unset libname
        if [ -f "$(dirname ${OUTPUT})/${rpath}/lib${lib}.so" ]; then
            libname="lib${lib}.so"
        elif [ -f "$(dirname ${OUTPUT})/${rpath}/lib${lib}.dylib" ]; then
            libname="lib${lib}.dylib"
        fi
        # ${libname-} --> return $libname if defined, or undefined otherwise. This is to make
        # this set -e friendly
        if [[ -n "${libname-}" ]]; then
            libpath=$(get_library_path ${lib})
            if [ -n "${libpath}" ]; then
                ${INSTALL_NAME_TOOL} -change $(get_otool_path "${libpath}") \
                    "@loader_path/${rpath}/${libname}" "${OUTPUT}"
            fi
        fi
    done
done