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feat: ldconfig + ld.so.cache for find_library (maintainer request)
Maintainer: 'Keep the ldconfig binary and continue to generate the ldconfig.so.cache to allow find_library to continue to work'. python3/ parity, ported to python/: - libc-bin added to the image (provides /sbin/ldconfig) via PYTHON_PACKAGES in config.bzl - per-arch ld.so.cache generated by running ldconfig inside the image (python/ldconfig.bzl + ldconfig.sh, ported from python3; bazel run //python:update_ldconfig) and shipped at /etc/ld.so.cache - python/ldconfig.bzl: oci_load + do_load genrules + update_ldconfig + check_ldconfig_{arch}_test + test suite (caches for amd64, arm64, s390x, riscv64 generated and committed) - find_library CST test added to testdata/python3.yaml - check-ldconfig.yaml workflow extended to cover //python too - README find_library section rewritten (works now; regenerate via bazel run //python:update_ldconfig) Verified: find_library('c'/'ssl'/'z') resolve in the image; check_ldconfig tests 4/4 pass; CST (incl. find_library) + smoke test pass.
1 parent 0b6d1ee commit be7c93f

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‎.github/workflows/check-ldconfig.yaml‎

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@@ -23,4 +23,4 @@ jobs:
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uses: docker/setup-qemu-action@96fe6ef7f33517b61c61be40b68a1882f3264fb8 # v4
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- name: Check ldconfig caches
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run: bazel test //python3:check_ldconfig_tests
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run: bazel test //python3:check_ldconfig_tests //python:check_ldconfig_tests

‎python/BUILD‎

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load(":config.bzl", "PYTHON_ARCHITECTURES", "PYTHON_DISTROS", "PYTHON_MAJOR_VERSIONS")
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load("//private/util:tar.bzl", "tar")
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load(":config.bzl", "PYTHON_ARCHITECTURES", "PYTHON_DISTROS", "PYTHON_MAJOR_VERSIONS", "PYTHON_PACKAGES")
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load(":ldconfig.bzl", "python_ldconfig")
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load(":python.bzl", "python_image", "python_image_index")
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package(default_visibility = ["//visibility:public"])
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arch = arch,
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distro = distro,
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major_version = major_version,
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packages = [],
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packages = PYTHON_PACKAGES[distro],
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)
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for distro in PYTHON_DISTROS
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for major_version in PYTHON_MAJOR_VERSIONS
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for distro in PYTHON_DISTROS
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for major_version in PYTHON_MAJOR_VERSIONS
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]
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# ld.so.cache per arch, generated by running ldconfig inside the image
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# (bazel run //python:update_ldconfig), shipped at /etc/ld.so.cache so
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# ctypes.util.find_library() works.
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[
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tar(
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name = "ldconfig_cache_{}".format(arch),
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srcs = ["ldconfig/ld.so.cache.{}".format(arch)],
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args = [
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"--format",
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"gnutar",
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],
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extension = "tar.gz",
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mtree = ["etc/ld.so.cache uid=0 gid=0 uname=root gname=root mode=0644 time=0 type=file content=$(location ldconfig/ld.so.cache.{})".format(arch)],
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)
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for arch in PYTHON_ARCHITECTURES["debian13"]["3.14"]
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]
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python_ldconfig(
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architectures = PYTHON_ARCHITECTURES["debian13"]["3.14"],
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distro = "debian13",
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)

‎python/README.md‎

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@@ -47,9 +47,13 @@ RUN ln -s /usr/local/bin/python3.14 /python/bin/python3.14
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### ctypes.util.find_library
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Unlike the deb-based `python3` images, these images do **not** ship a pre-generated
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`ld.so.cache`, so `ctypes.util.find_library()` returns `None`. Use absolute library
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paths or an explicit `ctypes.CDLL("/lib/.../libX.so.Y")` instead.
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`ctypes.util.find_library()` works: the image ships `/sbin/ldconfig` (from `libc-bin`)
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and a pre-generated `ld.so.cache` at `/etc/ld.so.cache`. The cache is generated per
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arch by running ldconfig inside the image:
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bazel run //python:update_ldconfig
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and verified by `bazel test //python:check_ldconfig_tests` (also in CI).
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## Provenance
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‎python/config.bzl‎

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@@ -13,3 +13,9 @@ PYTHON_ARCHITECTURES = {
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"3.14": ["amd64", "arm64", "s390x", "riscv64"],
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},
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}
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# deb packages added to the image: libc-bin provides /sbin/ldconfig so
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# ctypes.util.find_library() works via a generated ld.so.cache (python3/ parity).
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PYTHON_PACKAGES = {
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"debian13": ["libc-bin"],
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}

‎python/ldconfig.bzl‎

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"Macros for generating ldconfig cache for python images"
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load("@rules_oci//oci:defs.bzl", "oci_load")
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def python_ldconfig(architectures, distro):
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"""Generates ldconfig cache targets for python images.
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Args:
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architectures: list of architectures to support
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distro: the distribution name (e.g. debian13)
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"""
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# 1. Create the oci_load targets (the scripts that load images into docker)
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for arch in architectures:
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oci_load(
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name = "load_python314_root_{}_{}".format(arch, distro),
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image = ":python314_root_{}_{}".format(arch, distro),
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repo_tags = ["bazel/python:python314_root_{}_{}".format(arch, distro)],
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)
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# 2. Create the genrules that actually trigger the loading during 'bazel build'
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for arch in architectures:
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native.genrule(
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name = "do_load_{}".format(arch),
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outs = ["do_load_{}.done".format(arch)],
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cmd = "$(location :load_python314_root_{arch}_{distro}) && touch $@".format(
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arch = arch,
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distro = distro,
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),
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tags = [
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"local",
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"no-sandbox",
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],
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tools = [":load_python314_root_{}_{}".format(arch, distro)],
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)
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# 3. Create the update_ldconfig binary
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native.sh_binary(
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name = "update_ldconfig",
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srcs = ["ldconfig/ldconfig.sh"],
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args = ["update"] + architectures,
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data = ["ldconfig/ldconfig.sh"] + [":do_load_{}".format(arch) for arch in architectures],
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tags = ["local"],
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)
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# 4. Create the architecture-specific tests
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for arch in architectures:
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native.sh_test(
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name = "check_ldconfig_{}_test".format(arch),
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srcs = ["ldconfig/ldconfig.sh"],
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args = [
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"check",
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arch,
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],
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data = [
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"ldconfig/ld.so.cache.{}".format(arch),
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":do_load_{}".format(arch),
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],
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tags = [
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arch,
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"local",
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"manual",
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"external",
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"no-cache",
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],
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)
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# 5. Create the test suite
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native.test_suite(
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name = "check_ldconfig_tests",
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tests = [
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":check_ldconfig_{}_test".format(arch)
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for arch in architectures
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],
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tags = ["manual"],
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)

‎python/ldconfig/ld.so.cache.amd64‎

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‎python/ldconfig/ld.so.cache.arm64‎

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‎python/ldconfig/ld.so.cache.riscv64‎

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‎python/ldconfig/ld.so.cache.s390x‎

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‎python/ldconfig/ldconfig.sh‎

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#!/usr/bin/env bash
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set -eo pipefail
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MODE=$1
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shift
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if [[ "${MODE}" != "update" && "${MODE}" != "check" ]]; then
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echo "Usage: $0 <update|check> <arch>..." >&2
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exit 1
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fi
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# Root to find the reference cache files
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ROOT="python/ldconfig"
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if [[ -n "${BUILD_WORKSPACE_DIRECTORY}" ]]; then
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cd "${BUILD_WORKSPACE_DIRECTORY}"
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elif [[ ! -d "${ROOT}" ]]; then
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# Fallback to finding it in the same dir as the script
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ROOT=$(dirname "$0")
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fi
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CID=""
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TEMP_DIR=""
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cleanup() {
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local exit_status=$?
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if [[ -n "${CID}" ]]; then docker rm -f "${CID}"; fi
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if [[ -n "${TEMP_DIR}" ]]; then rm -rf "${TEMP_DIR}"; fi
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exit "${exit_status}"
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}
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trap cleanup EXIT
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for arch in "$@"; do
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if [ "$MODE" = "update" ]; then echo "===> Updating ldconfig cache for ${arch}..."; else echo "===> Checking ldconfig cache for ${arch}..."; fi
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# Run ldconfig and extract the cache.
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# We assume the image is ALREADY loaded (handled by Bazel build dependencies)
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CID=$(docker create --platform "linux/${arch}" --entrypoint /sbin/ldconfig "bazel/python:python314_root_${arch}_debian13")
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docker start -a "${CID}"
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if [[ "${MODE}" == "update" ]]; then
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docker cp "${CID}:/etc/ld.so.cache" "${ROOT}/ld.so.cache.${arch}"
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echo "✅ Updated ${arch} cache."
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else
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TEMP_DIR=$(mktemp -d)
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docker cp "${CID}:/etc/ld.so.cache" "${TEMP_DIR}/ld.so.cache.${arch}"
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if ! cmp -s "${TEMP_DIR}/ld.so.cache.${arch}" "${ROOT}/ld.so.cache.${arch}"; then
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echo "❌ ERROR: ldconfig cache for ${arch} is out of date!" >&2
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echo "Run 'bazel run //python:update_ldconfig' to regenerate." >&2
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exit 1
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fi
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rm -rf "${TEMP_DIR}"
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TEMP_DIR=""
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echo "✅ ldconfig cache for ${arch} is up to date."
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fi
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docker rm -f "${CID}"
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CID=""
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done

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