Use a wrapper around gcc on OSX to simulate rpath

OS X does not have rpath so binary fails when not executing
from the good path. This wrapper rewrite the path after the
compilation to fix that behavior.

Fixes #46

--
MOS_MIGRATED_REVID=89527942

2 files changed, 95 insertions, 1 deletions

diff --git a/tools/cpp/CROSSTOOL b/tools/cpp/CROSSTOOL
index 073714d6bc..8bf19dea43 100644
--- a/tools/cpp/CROSSTOOL
+++ b/tools/cpp/CROSSTOOL
@@ -69,7 +69,7 @@ toolchain {
   tool_path { name: "compat-ld" path: "/usr/bin/ld" }
   tool_path { name: "cpp" path: "/usr/bin/cpp" }
   tool_path { name: "dwp" path: "/usr/bin/dwp" }
-  tool_path { name: "gcc" path: "/usr/bin/gcc" }
+  tool_path { name: "gcc" path: "osx_gcc_wrapper.sh" }
   cxx_flag: "-std=c++0x"
   ar_flag: "-static"
   ar_flag: "-s"
diff --git a/tools/cpp/osx_gcc_wrapper.sh b/tools/cpp/osx_gcc_wrapper.sh
new file mode 100755
index 0000000000..a8eb46ab8f
--- /dev/null
+++ b/tools/cpp/osx_gcc_wrapper.sh
@@ -0,0 +1,94 @@
+#!/bin/bash
+#
+# Copyright 2015 Google Inc. 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 rpath is not really working. This is a wrapper script around gcc
+# to simulate rpath 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 behaves 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
+
+GCC="/usr/bin/gcc"
+INSTALL_NAME_TOOL="/usr/bin/install_name_tool"
+
+LIBS=
+LIB_DIRS=
+RPATH=
+OUTPUT=
+# let parse the option list
+for i in "$@"; do
+    if [[ "${OUTPUT}" = "1" ]]; then
+        OUTPUT=$i
+    elif [[ "$i" =~ ^-l(.*)$ ]]; then
+        # lib
+        LIBS="${BASH_REMATCH[1]} $LIBS"
+    elif [[ "$i" =~ ^-L(.*)$ ]]; then
+        # lib
+        LIB_DIRS="${BASH_REMATCH[1]} $LIB_DIRS"
+    elif [[ "$i" =~ ^-Wl,-rpath,\$ORIGIN/(.*)$ ]]; then
+        # rpath
+        RPATH=${BASH_REMATCH[1]}
+    elif [[ "$i" = "-o" ]]; then
+        # output is coming
+        OUTPUT=1
+    fi
+done
+
+# Call gcc
+${GCC} "$@"
+
+function get_library_path() {
+    for libdir in ${LIB_DIRS}; do
+        if [ -f ${libdir}/lib$1.so ]; then
+            echo "${libdir}/lib$1.so"
+        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 $1 | sed 's|^.*/bazel-out/|bazel-out/|'
+}
+
+# Do replacements in the output
+if [ -n "${RPATH}" ]; then
+    for lib in ${LIBS}; do
+        libpath=$(get_library_path ${lib})
+        if [ -n "${libpath}" ]; then
+            ${INSTALL_NAME_TOOL} -change $(get_otool_path "${libpath}") "@loader_path/${RPATH}/lib${lib}.so" "${OUTPUT}"
+        fi
+    done
+fi
+