Repack libgcc.a to only include required objects

Previous solution by using objcopy uses a quirky behaviour of the GNU
objcopy and there is no equivalent option in llvm-objcopy.

Instead of removing symbols, extract and repack libgcc to only include
required objects.

Bug: 142585047
Test: presubmit
Change-Id: I58af74c18838f797e481da38c3265f0624fddf99

1 files changed, 87 insertions, 0 deletions

diff --git a/scripts/archive_repack.sh b/scripts/archive_repack.sh
new file mode 100755
index 00000000..f09372dd
--- /dev/null
+++ b/scripts/archive_repack.sh
@@ -0,0 +1,87 @@
+#!/bin/bash -e
+
+# Copyright 2019 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.
+
+# Script to extract and repack an archive with specified object files.
+# Inputs:
+#  Environment:
+#   CLANG_BIN: path to the clang bin directory
+#  Arguments:
+#   -i ${file}: input file
+#   -o ${file}: output file
+#   -d ${file}: deps file
+
+set -o pipefail
+
+OPTSTRING=d:i:o:
+
+usage() {
+    cat <<EOF
+Usage: archive_repack.sh [options] <objects to repack>
+
+OPTIONS:
+    -i <file>: input file
+    -o <file>: output file
+    -d <file>: deps file
+EOF
+    exit 1
+}
+
+while getopts $OPTSTRING opt; do
+    case "$opt" in
+        d) depsfile="${OPTARG}" ;;
+        i) infile="${OPTARG}" ;;
+        o) outfile="${OPTARG}" ;;
+        ?) usage ;;
+    esac
+done
+shift "$(($OPTIND -1))"
+
+if [ -z "${infile}" ]; then
+    echo "-i argument is required"
+    usage
+fi
+
+if [ -z "${outfile}" ]; then
+    echo "-o argument is required"
+    usage
+fi
+
+# Produce deps file
+if [ ! -z "${depsfile}" ]; then
+    cat <<EOF > "${depsfile}"
+${outfile}: ${infile} ${CLANG_BIN}/llvm-ar
+EOF
+fi
+
+# Get absolute path for outfile and llvm-ar.
+LLVM_AR="${PWD}/${CLANG_BIN}/llvm-ar"
+if [[ "$outfile" != /* ]]; then
+    outfile="${PWD}/${outfile}"
+fi
+
+tempdir="${outfile}.tmp"
+
+# Clean up any previous temporary files.
+rm -f "${outfile}"
+rm -rf "${tempdir}"
+
+# Do repack
+# We have to change working directory since ar only allows extracting to CWD.
+mkdir "${tempdir}"
+cp "${infile}" "${tempdir}/archive"
+cd "${tempdir}"
+"${LLVM_AR}" x "archive"
+"${LLVM_AR}" --format=gnu qc "${outfile}" "$@"