scripts/configure - third_party/github/project-chip/connectedhomeip - Git at Google

 #!/bin/bash -e

 # Copyright (c) 2023 Project CHIP Authors
 #
 # 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.

 # Usage: configure [OPTIONS] [--project=... [PROJECT OPTIONS]]
 #
 # Configures a stand-alone build for a CHIP application in the current
 # directory and creates a `ninja-build` wrapper script to build it. Should
 # generally be run from an empty build directory (i.e. out-of-tree).
 #
 # This is intended to be used in the context of an external build system and
 # represents a light-weight alternative to bootstrapping the full Pigweed build
 # environment (via scripts/activate.sh). The pigweed git sub-module must still
 # be present though.
 #
 # External tool dependencies: bash, python3, gn, ninja
 #
 # The zap-cli code generator and a small number of Python modules are
 # downloaded if necessary (see scripts/setup/requirements.build.txt) and
 # installed in a build environment directory. By default this is local to
 # the build directory, but an external directory can be specified using the
 # --build-env-dir option. The build environment directory can be shared by any
 # number of build directories, independently of target / tool chain.

 set -o pipefail
 shopt -s extglob

 function usage() { # status
     info "Usage: $0 [OPTIONS] [--project=... [PROJECT OPTIONS]]"
     info "Options:"
     info "  --build-env-dir=DIR   Directory to create (host) build environment in"
     info "  --project=DIR         directory to build, absolute or relative to chip root,"
     info "                        eg examples/lighting-app/linux or /my/dir/my/app"
     info ""
     info "Project options (mapped to GN build args):"
     info "  --enable-<ARG>[=no]   Enables (or disables with '=no') a bool build arg"
     info "  --<ARG>=<VALUE>       Sets a (non-bool) build arg to the given value"
     info "  GN argument names can be specified with '-' instead of '_' and prefixes"
     info "  like 'chip_' can be ommitted from names. For the full list of available"
     info "  build arguments, see the generated args.configured file."
     info ""
     info "  By default, the toolchain for the GN build will be configured from the usual"
     info "  environment variables (CC, CXX, AR, CFLAGS, CXXFLAGS, ...), falling back to"
     info "  default tool names (CC=cc, ...). When using this script within an external"
     info "  build system, toolchain environment variables should be populated."
     info ""
     info "Code generation:"
     info "  By default, some code generation will happen at build time using zap-cli."
     info "  If zap-cli is not available on PATH, configure will attempt to download it."
     info "  Alternatively, if a directory called 'zzz_pregenerated' exists at the root"
     info "  of the project or the root of the SDK, pre-generated code from this directory"
     info "  will be used. In this case, build time code generation will be disabled and"
     info "  zap-cli is not required."
     exit "$1"
 }

 function main() { # ...
     CHIP_ROOT=$(cd "$(dirname "$0")/.." && pwd)
     BUILD_ENV_DEPS=(
         "${CHIP_ROOT}/scripts/setup/requirements.build.txt"
         "${CHIP_ROOT}/scripts/setup/constraints.txt"
     )
     BUILD_ENV_DEPS_CODEGEN=(
         "${CHIP_ROOT}/scripts/setup/zap.version"
     )

     # Parse global options, process VAR=VALUE style arguments, and collect project options
     BUILD_ENV_DIR=
     PROJECT=
     PROJECT_PATH=
     PROJECT_ARGS=()
     while [[ $# -gt 0 ]]; do
         case "$1" in
         --help) usage 0 ;;
         --build-env-dir=*) BUILD_ENV_DIR="${1#*=}" ;;
         --project=*) PROJECT="${1#*=}" ;;
         +([A-Z_])=*) export "$1" ;;
         *)
             [[ -n "$PROJECT" ]] || fail "Invalid argument: '$1'"
             PROJECT_ARGS+=("$1")
             ;;
         esac
         shift
     done

     # Ensure we have something to do
     [[ -n "$PROJECT" || -n "$BUILD_ENV_DIR" ]] || usage 1

     if [[ -n "$PROJECT" ]]; then
         PROJECT_PATH="$(cd "${CHIP_ROOT}" 2>/dev/null && cd "${PROJECT}" 2>/dev/null && pwd)"
         [[ -n "$PROJECT_PATH" && -r "${PROJECT_PATH}/.gn" ]] || fail "Invalid project '${PROJECT}' - missing .gn at '${PROJECT_PATH}'"
     fi

     if [[ -n "$PW_ROOT" ]]; then
         info "WARNING: A Pigweed environment appears to be active, this is usually a misconfiguration."
     fi

     # Check for pre-generated code. CHIP_PREGEN_DIR will be picked up by process_project_args.
     local pregen_dir="zzz_pregenerated"
     if [[ -n "$PROJECT_PATH" && -d "${PROJECT_PATH}/${pregen_dir}" ]]; then
         info "Will use pre-generated code from ${PROJECT}/${pregen_dir}, no zap-cli required."
         export CHIP_PREGEN_DIR="//${pregen_dir}"
     elif [[ -d "${CHIP_ROOT}/${pregen_dir}" ]]; then
         info "Will use pre-generated code from ${pregen_dir}, no zap-cli required."
         export CHIP_PREGEN_DIR="\${chip_root}/${pregen_dir}"
     else
         BUILD_ENV_DEPS+=("${BUILD_ENV_DEPS_CODEGEN[@]}")
         unset CHIP_PREGEN_DIR
     fi

     # Work out build and environment directories
     if [[ "$PWD" == "$CHIP_ROOT" ]]; then
         BUILD_DIR="out/configured"
         NINJA_HINT="ninja -C ${BUILD_DIR}"
     else
         BUILD_DIR="."
         NINJA_HINT="ninja"
     fi

     if [[ -n "$BUILD_ENV_DIR" ]]; then
         mkdir -p "$BUILD_ENV_DIR"
         BUILD_ENV_PATH="$(cd "$BUILD_ENV_DIR" && pwd)"
         [[ -n "$BUILD_ENV_PATH" ]] || fail "Invalid build-env-dir '${BUILD_ENV_DIR}'"
         BUILD_ENV_DIR="$BUILD_ENV_PATH" # absolute
     else
         BUILD_ENV_DIR="build-env" # relative to BUILD_DIR
         BUILD_ENV_PATH="${BUILD_DIR}/${BUILD_ENV_DIR}"
     fi

     # Check required tools are present
     check_binary gn GN
     check_binary ninja NINJA

     # Create the build environment if necessary
     if ! check_build_env; then
         check_python
         configure_python_env
         if [[ -z "$CHIP_PREGEN_DIR" ]] && ! check_binary zap-cli; then
             download_zap
         fi
         finalize_build_env
     fi

     # Configure the project (if requested)
     if [[ -z "$PROJECT" ]]; then
         info "Build environment created. (Specify --project=DIR to configure a build.)"
         return
     fi

     [[ "$BUILD_DIR" != "." ]] && info "Configuring in-tree, will build in ${BUILD_DIR}"

     create_empty_pw_env
     guess_toolchain
     gn_generate "${PROJECT_ARGS[@]}"
     create_ninja_wrapper
     info "You can now run ./ninja-build (or $NINJA_HINT)"
 }

 function create_empty_pw_env() {
     # The Pigweed environment ("//build_overrides/pigweed_environment.gni") is
     # imported unconditionally in various build files, so ensure it exists.
     local gni="build_overrides/pigweed_environment.gni"
     if [[ -d "${CHIP_ROOT}/$(dirname "$gni")" ]]; then
         if safe_to_clobber "$gni"; then
             info "Creating empty $gni in source tree"
             echo "# ${CONFIGURE_MARKER}" >"${CHIP_ROOT}/${gni}"
         else
             info "WARNING: Leaving existing $gni in place, this might affect the build configuration."
         fi
     fi
 }

 function guess_toolchain() {
     # There is no widely used standard command for the C++ compiler (analogous to
     # `cc` for the C compiler), so if neither CC nor CXX are defined try to guess.
     if [[ -z "$CC" && -z "$CXX" ]] && have_binary cc; then
         local probe="$(cc -E - <<<'gnu=__GNUC__ clang=__clang__' 2>/dev/null)"
         # Check for clang first because it also defines __GNUC__
         if [[ "$probe" =~ clang=[1-9] ]] && have_binary clang && have_binary clang++; then
             info "Guessing CC=clang CXX=clang++ because cc appears to be clang"
             export CC=clang CXX=clang++
         elif [[ "$probe" =~ gnu=[1-9] ]] && have_binary gcc && have_binary g++; then
             info "Guessing CC=gcc CXX=g++ because cc appears to be gcc"
             export CC=gcc CXX=g++
         else
             info "Unable to guess c++ compiler: $probe"
         fi
     fi
 }

 function gn_generate() { # [project options]
     mkdir -p "${BUILD_DIR}"
     ensure_no_clobber "${BUILD_DIR}/args.gn"

     # Pass --script-executable to all `gn` calls so scripts run in our venv
     local gn=(gn --script-executable="${BUILD_ENV_DIR}/bin/python" --root="${PROJECT_PATH}")

     # Run gn gen with an empty args.gn first so we can list all arguments
     info "Configuring gn build arguments (see $BUILD_DIR/args.configured for full list)"
     {
         echo "# ${CONFIGURE_MARKER}"
         echo "# project root: ${PROJECT_PATH}"
         echo "import(\"//build_overrides/chip.gni\")"
     } >"${BUILD_DIR}/args.gn"
     "${gn[@]}" -q gen "$BUILD_DIR"

     # Use the argument list to drive the mapping of our command line options to GN args
     call_impl process_project_args <("${gn[@]}" args "$BUILD_DIR" --list --json) "$@" >>"${BUILD_DIR}/args.gn"
     "${gn[@]}" args "$BUILD_DIR" --list >"${BUILD_DIR}/args.configured"

     # Now gn gen with the arguments we have configured.
     info "Running gn gen to generate ninja files"
     "${gn[@]}" -q gen "$BUILD_DIR"
 }

 function create_ninja_wrapper() {
     local wrapper="ninja-build"
     ensure_no_clobber "$wrapper"
     {
         echo "#!/bin/bash -e"
         echo "# ${CONFIGURE_MARKER}"
         if [[ "$BUILD_DIR" != "." ]]; then
             echo 'args=(-C "$(dirname "$0")/'"${BUILD_DIR}"'")'
         else
             echo 'args=() dir="$(dirname "$0")"'
             echo '[[ "$dir" != "." ]] && args=(-C "$dir")'
         fi
         echo 'exec ninja "${args[@]}" "$@"'
     } >"$wrapper"
     chmod a+x "$wrapper"
 }

 function check_build_env() {
     generate_build_env_cksum # re-used by finalize_build_env
     [[ -r "${BUILD_ENV_PATH}/.cksum" ]] || return 1
     read -r <"${BUILD_ENV_PATH}/.cksum" || true
     [[ "$REPLY" == "$CURRENT_ENV_CKSUM" ]] || return 1

     [[ -r "${BUILD_ENV_PATH}/bin/activate" ]] || return 1
     info "Using existing build environment: ${BUILD_ENV_PATH}"
     PYTHON="${BUILD_ENV_PATH}/bin/python"
 }

 function configure_python_env() {
     progress "Setting up Python venv"
     # Debian and Ubuntu ship python3 with a broken venv module unless the
     # python3-venv package is installed (https://bugs.launchpad.net/bugs/1290847)
     local withoutpip=() pip="${BUILD_ENV_PATH}/bin/pip"
     if ! "$PYTHON" -m ensurepip --version >/dev/null 2>&1; then
         withoutpip=(--without-pip) pip="${pip}.pyz" # bootstrapped below
     fi
     "$PYTHON" -m venv --clear "${withoutpip[@]}" "$BUILD_ENV_PATH"
     info "$BUILD_ENV_PATH"

     # Download a standalone pip.pyz from pypa.io if necessary
     if [[ -n "$withoutpip" ]]; then
         progress "Bootstrapping pip via pypa.io (venv module is missing ensurepip dependency)"
         call_impl download https://bootstrap.pypa.io/pip/pip.pyz "$pip"
         info "ok"
     fi

     # Install our auto-loading venvactivate module so that running scripts via
     # the venv python has the side-effect of fully activating the environment.
     local sitepkgs=("${BUILD_ENV_PATH}/lib/python"*"/site-packages")
     [[ -d "$sitepkgs" ]] || fail "Failed to locate venv site-packages"
     cp "${CHIP_ROOT}/scripts/configure.venv/venvactivate".{pth,py} "${sitepkgs}/"

     progress "Installing Python build dependencies"
     # Ensure pip and wheel are up to date first (using pip.pyz if necessary)
     "${BUILD_ENV_PATH}/bin/python3" "$pip" install --require-virtualenv --quiet --upgrade pip wheel

     "${BUILD_ENV_PATH}/bin/pip" install --require-virtualenv --quiet \
         -r "${CHIP_ROOT}/scripts/setup/requirements.build.txt" \
         -c "${CHIP_ROOT}/scripts/setup/constraints.txt"
     info "ok"
 }

 function generate_build_env_cksum() {
     # Conservatively assume that any change to this script or BUILD_ENV_DEPS invalidates the environment
     CURRENT_ENV_CKSUM="$(cat "$0" "${BUILD_ENV_DEPS[@]}" | cksum)"
     [[ -n "$CURRENT_ENV_CKSUM" ]] || fail "Failed to generate build environment checksum"
 }

 function finalize_build_env() {
     echo "$CURRENT_ENV_CKSUM" >"${BUILD_ENV_PATH}/.cksum"
 }

 function download_zap() {
     local version
     read -r version <"${CHIP_ROOT}/scripts/setup/zap.version"
     local platform="$(uname -sm)" flavor
     case "$platform" in
     Linux\ x86_64) flavor=linux-x64 ;;
     Linux\ arm64) flavor=linux-arm64 ;;
     Linux\ aarch64) flavor=linux-arm64 ;;
     Darwin\ x86_64) flavor=mac-x64 ;;
     Darwin\ arm64) flavor=mac-arm64 ;;
     *) fail "Unable to determine zap flavor for $platform" ;;
     esac
     local url="https://github.com/project-chip/zap/releases/download/${version}/zap-${flavor}.zip"

     progress "Installing zap-cli from $url"
     call_impl download_and_extract_zip "$url" "${BUILD_ENV_PATH}/bin" zap-cli
     chmod a+x "${BUILD_ENV_PATH}/bin/zap-cli" # ZipFile.extract() does not handle permissions
     info "ok"
 }

 function call_impl() { # func ...
     "$PYTHON" "${CHIP_ROOT}/scripts/configure.impl.py" "$@"
 }

 function check_python() {
     progress "Checking for Python 3"
     if have_binary python3; then
         PYTHON="$(hash -t python3)"
     elif have_binary python; then
         PYTHON="$(hash -t python)"
         local ver="$("$PYTHON" --version)"
         if [[ "$ver" != "Python 3."* ]]; then
             info "need Python 3 but found $ver"
             return 1
         fi
     else
         info "not found"
         return 1
     fi
     info "$PYTHON"
 }

 function check_binary() { # binary [VAR]
     progress "Checking for $1"
     if ! have_binary "$1"; then
         info "not found"
         return 1
     fi
     local path="$(hash -t "$1")"
     [[ -n "$2" ]] && eval "$2=\$path"
     info "$path"
 }

 function have_binary() { # binary
     hash "$1" 2>/dev/null
 }

 function ensure_no_clobber() { # file
     safe_to_clobber "$1" || fail "Won't overwrite file not generated by configure: $1"
 }

 function safe_to_clobber() { # file
     CONFIGURE_MARKER="Auto-generated by configure, do not edit"
     [[ -s "$1" ]] || return 0
     read -r -n 512 -d '' <"$1" || true
     [[ "${REPLY/$CONFIGURE_MARKER/}" != "$REPLY" ]] && return 0
     return 1
 }

 function info() { # message
     echo "$*" >&2
 }

 function progress() { # message
     echo -n "$*... " >&2
 }

 function fail() { # message
     echo "Error: $*" >&2
     exit 1
 }

 main "$@"
	#!/bin/bash -e

	# Copyright (c) 2023 Project CHIP Authors
	#
	# 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.

	# Usage: configure [OPTIONS] [--project=... [PROJECT OPTIONS]]
	#
	# Configures a stand-alone build for a CHIP application in the current
	# directory and creates a `ninja-build` wrapper script to build it. Should
	# generally be run from an empty build directory (i.e. out-of-tree).
	#
	# This is intended to be used in the context of an external build system and
	# represents a light-weight alternative to bootstrapping the full Pigweed build
	# environment (via scripts/activate.sh). The pigweed git sub-module must still
	# be present though.
	#
	# External tool dependencies: bash, python3, gn, ninja
	#
	# The zap-cli code generator and a small number of Python modules are
	# downloaded if necessary (see scripts/setup/requirements.build.txt) and
	# installed in a build environment directory. By default this is local to
	# the build directory, but an external directory can be specified using the
	# --build-env-dir option. The build environment directory can be shared by any
	# number of build directories, independently of target / tool chain.

	set -o pipefail
	shopt -s extglob

	function usage() { # status
	info "Usage: $0 [OPTIONS] [--project=... [PROJECT OPTIONS]]"
	info "Options:"
	info " --build-env-dir=DIR Directory to create (host) build environment in"
	info " --project=DIR directory to build, absolute or relative to chip root,"
	info " eg examples/lighting-app/linux or /my/dir/my/app"
	info ""
	info "Project options (mapped to GN build args):"
	info " --enable-<ARG>[=no] Enables (or disables with '=no') a bool build arg"
	info " --<ARG>=<VALUE> Sets a (non-bool) build arg to the given value"
	info " GN argument names can be specified with '-' instead of '_' and prefixes"
	info " like 'chip_' can be ommitted from names. For the full list of available"
	info " build arguments, see the generated args.configured file."
	info ""
	info " By default, the toolchain for the GN build will be configured from the usual"
	info " environment variables (CC, CXX, AR, CFLAGS, CXXFLAGS, ...), falling back to"
	info " default tool names (CC=cc, ...). When using this script within an external"
	info " build system, toolchain environment variables should be populated."
	info ""
	info "Code generation:"
	info " By default, some code generation will happen at build time using zap-cli."
	info " If zap-cli is not available on PATH, configure will attempt to download it."
	info " Alternatively, if a directory called 'zzz_pregenerated' exists at the root"
	info " of the project or the root of the SDK, pre-generated code from this directory"
	info " will be used. In this case, build time code generation will be disabled and"
	info " zap-cli is not required."
	exit "$1"
	}

	function main() { # ...
	CHIP_ROOT=$(cd "$(dirname "$0")/.." && pwd)
	BUILD_ENV_DEPS=(
	"${CHIP_ROOT}/scripts/setup/requirements.build.txt"
	"${CHIP_ROOT}/scripts/setup/constraints.txt"
	)
	BUILD_ENV_DEPS_CODEGEN=(
	"${CHIP_ROOT}/scripts/setup/zap.version"
	)

	# Parse global options, process VAR=VALUE style arguments, and collect project options
	BUILD_ENV_DIR=
	PROJECT=
	PROJECT_PATH=
	PROJECT_ARGS=()
	while [[ $# -gt 0 ]]; do
	case "$1" in
	--help) usage 0 ;;
	--build-env-dir=) BUILD_ENV_DIR="${1#=}" ;;
	--project=) PROJECT="${1#=}" ;;
	+([A-Z_])=*) export "$1" ;;
	*)
	[[ -n "$PROJECT" ]] \|\| fail "Invalid argument: '$1'"
	PROJECT_ARGS+=("$1")
	;;
	esac
	shift
	done

	# Ensure we have something to do
	[[ -n "$PROJECT" \|\| -n "$BUILD_ENV_DIR" ]] \|\| usage 1

	if [[ -n "$PROJECT" ]]; then
	PROJECT_PATH="$(cd "${CHIP_ROOT}" 2>/dev/null && cd "${PROJECT}" 2>/dev/null && pwd)"
	[[ -n "$PROJECT_PATH" && -r "${PROJECT_PATH}/.gn" ]] \|\| fail "Invalid project '${PROJECT}' - missing .gn at '${PROJECT_PATH}'"
	fi

	if [[ -n "$PW_ROOT" ]]; then
	info "WARNING: A Pigweed environment appears to be active, this is usually a misconfiguration."
	fi

	# Check for pre-generated code. CHIP_PREGEN_DIR will be picked up by process_project_args.
	local pregen_dir="zzz_pregenerated"
	if [[ -n "$PROJECT_PATH" && -d "${PROJECT_PATH}/${pregen_dir}" ]]; then
	info "Will use pre-generated code from ${PROJECT}/${pregen_dir}, no zap-cli required."
	export CHIP_PREGEN_DIR="//${pregen_dir}"
	elif [[ -d "${CHIP_ROOT}/${pregen_dir}" ]]; then
	info "Will use pre-generated code from ${pregen_dir}, no zap-cli required."
	export CHIP_PREGEN_DIR="\${chip_root}/${pregen_dir}"
	else
	BUILD_ENV_DEPS+=("${BUILD_ENV_DEPS_CODEGEN[@]}")
	unset CHIP_PREGEN_DIR
	fi

	# Work out build and environment directories
	if [[ "$PWD" == "$CHIP_ROOT" ]]; then
	BUILD_DIR="out/configured"
	NINJA_HINT="ninja -C ${BUILD_DIR}"
	else
	BUILD_DIR="."
	NINJA_HINT="ninja"
	fi

	if [[ -n "$BUILD_ENV_DIR" ]]; then
	mkdir -p "$BUILD_ENV_DIR"
	BUILD_ENV_PATH="$(cd "$BUILD_ENV_DIR" && pwd)"
	[[ -n "$BUILD_ENV_PATH" ]] \|\| fail "Invalid build-env-dir '${BUILD_ENV_DIR}'"
	BUILD_ENV_DIR="$BUILD_ENV_PATH" # absolute
	else
	BUILD_ENV_DIR="build-env" # relative to BUILD_DIR
	BUILD_ENV_PATH="${BUILD_DIR}/${BUILD_ENV_DIR}"
	fi

	# Check required tools are present
	check_binary gn GN
	check_binary ninja NINJA

	# Create the build environment if necessary
	if ! check_build_env; then
	check_python
	configure_python_env
	if [[ -z "$CHIP_PREGEN_DIR" ]] && ! check_binary zap-cli; then
	download_zap
	fi
	finalize_build_env
	fi

	# Configure the project (if requested)
	if [[ -z "$PROJECT" ]]; then
	info "Build environment created. (Specify --project=DIR to configure a build.)"
	return
	fi

	[[ "$BUILD_DIR" != "." ]] && info "Configuring in-tree, will build in ${BUILD_DIR}"

	create_empty_pw_env
	guess_toolchain
	gn_generate "${PROJECT_ARGS[@]}"
	create_ninja_wrapper
	info "You can now run ./ninja-build (or $NINJA_HINT)"
	}

	function create_empty_pw_env() {
	# The Pigweed environment ("//build_overrides/pigweed_environment.gni") is
	# imported unconditionally in various build files, so ensure it exists.
	local gni="build_overrides/pigweed_environment.gni"
	if [[ -d "${CHIP_ROOT}/$(dirname "$gni")" ]]; then
	if safe_to_clobber "$gni"; then
	info "Creating empty $gni in source tree"
	echo "# ${CONFIGURE_MARKER}" >"${CHIP_ROOT}/${gni}"
	else
	info "WARNING: Leaving existing $gni in place, this might affect the build configuration."
	fi
	fi
	}

	function guess_toolchain() {
	# There is no widely used standard command for the C++ compiler (analogous to
	# `cc` for the C compiler), so if neither CC nor CXX are defined try to guess.
	if [[ -z "$CC" && -z "$CXX" ]] && have_binary cc; then
	local probe="$(cc -E - <<<'gnu=__GNUC__ clang=__clang__' 2>/dev/null)"
	# Check for clang first because it also defines __GNUC__
	if [[ "$probe" =~ clang=[1-9] ]] && have_binary clang && have_binary clang++; then
	info "Guessing CC=clang CXX=clang++ because cc appears to be clang"
	export CC=clang CXX=clang++
	elif [[ "$probe" =~ gnu=[1-9] ]] && have_binary gcc && have_binary g++; then
	info "Guessing CC=gcc CXX=g++ because cc appears to be gcc"
	export CC=gcc CXX=g++
	else
	info "Unable to guess c++ compiler: $probe"
	fi
	fi
	}

	function gn_generate() { # [project options]
	mkdir -p "${BUILD_DIR}"
	ensure_no_clobber "${BUILD_DIR}/args.gn"

	# Pass --script-executable to all `gn` calls so scripts run in our venv
	local gn=(gn --script-executable="${BUILD_ENV_DIR}/bin/python" --root="${PROJECT_PATH}")

	# Run gn gen with an empty args.gn first so we can list all arguments
	info "Configuring gn build arguments (see $BUILD_DIR/args.configured for full list)"
	{
	echo "# ${CONFIGURE_MARKER}"
	echo "# project root: ${PROJECT_PATH}"
	echo "import(\"//build_overrides/chip.gni\")"
	} >"${BUILD_DIR}/args.gn"
	"${gn[@]}" -q gen "$BUILD_DIR"

	# Use the argument list to drive the mapping of our command line options to GN args
	call_impl process_project_args <("${gn[@]}" args "$BUILD_DIR" --list --json) "$@" >>"${BUILD_DIR}/args.gn"
	"${gn[@]}" args "$BUILD_DIR" --list >"${BUILD_DIR}/args.configured"

	# Now gn gen with the arguments we have configured.
	info "Running gn gen to generate ninja files"
	"${gn[@]}" -q gen "$BUILD_DIR"
	}

	function create_ninja_wrapper() {
	local wrapper="ninja-build"
	ensure_no_clobber "$wrapper"
	{
	echo "#!/bin/bash -e"
	echo "# ${CONFIGURE_MARKER}"
	if [[ "$BUILD_DIR" != "." ]]; then
	echo 'args=(-C "$(dirname "$0")/'"${BUILD_DIR}"'")'
	else
	echo 'args=() dir="$(dirname "$0")"'
	echo '[[ "$dir" != "." ]] && args=(-C "$dir")'
	fi
	echo 'exec ninja "${args[@]}" "$@"'
	} >"$wrapper"
	chmod a+x "$wrapper"
	}

	function check_build_env() {
	generate_build_env_cksum # re-used by finalize_build_env
	[[ -r "${BUILD_ENV_PATH}/.cksum" ]] \|\| return 1
	read -r <"${BUILD_ENV_PATH}/.cksum" \|\| true
	[[ "$REPLY" == "$CURRENT_ENV_CKSUM" ]] \|\| return 1

	[[ -r "${BUILD_ENV_PATH}/bin/activate" ]] \|\| return 1
	info "Using existing build environment: ${BUILD_ENV_PATH}"
	PYTHON="${BUILD_ENV_PATH}/bin/python"
	}

	function configure_python_env() {
	progress "Setting up Python venv"
	# Debian and Ubuntu ship python3 with a broken venv module unless the
	# python3-venv package is installed (https://bugs.launchpad.net/bugs/1290847)
	local withoutpip=() pip="${BUILD_ENV_PATH}/bin/pip"
	if ! "$PYTHON" -m ensurepip --version >/dev/null 2>&1; then
	withoutpip=(--without-pip) pip="${pip}.pyz" # bootstrapped below
	fi
	"$PYTHON" -m venv --clear "${withoutpip[@]}" "$BUILD_ENV_PATH"
	info "$BUILD_ENV_PATH"

	# Download a standalone pip.pyz from pypa.io if necessary
	if [[ -n "$withoutpip" ]]; then
	progress "Bootstrapping pip via pypa.io (venv module is missing ensurepip dependency)"
	call_impl download https://bootstrap.pypa.io/pip/pip.pyz "$pip"
	info "ok"
	fi

	# Install our auto-loading venvactivate module so that running scripts via
	# the venv python has the side-effect of fully activating the environment.
	local sitepkgs=("${BUILD_ENV_PATH}/lib/python"*"/site-packages")
	[[ -d "$sitepkgs" ]] \|\| fail "Failed to locate venv site-packages"
	cp "${CHIP_ROOT}/scripts/configure.venv/venvactivate".{pth,py} "${sitepkgs}/"

	progress "Installing Python build dependencies"
	# Ensure pip and wheel are up to date first (using pip.pyz if necessary)
	"${BUILD_ENV_PATH}/bin/python3" "$pip" install --require-virtualenv --quiet --upgrade pip wheel

	"${BUILD_ENV_PATH}/bin/pip" install --require-virtualenv --quiet \
	-r "${CHIP_ROOT}/scripts/setup/requirements.build.txt" \
	-c "${CHIP_ROOT}/scripts/setup/constraints.txt"
	info "ok"
	}

	function generate_build_env_cksum() {
	# Conservatively assume that any change to this script or BUILD_ENV_DEPS invalidates the environment
	CURRENT_ENV_CKSUM="$(cat "$0" "${BUILD_ENV_DEPS[@]}" \| cksum)"
	[[ -n "$CURRENT_ENV_CKSUM" ]] \|\| fail "Failed to generate build environment checksum"
	}

	function finalize_build_env() {
	echo "$CURRENT_ENV_CKSUM" >"${BUILD_ENV_PATH}/.cksum"
	}

	function download_zap() {
	local version
	read -r version <"${CHIP_ROOT}/scripts/setup/zap.version"
	local platform="$(uname -sm)" flavor
	case "$platform" in
	Linux\ x86_64) flavor=linux-x64 ;;
	Linux\ arm64) flavor=linux-arm64 ;;
	Linux\ aarch64) flavor=linux-arm64 ;;
	Darwin\ x86_64) flavor=mac-x64 ;;
	Darwin\ arm64) flavor=mac-arm64 ;;
	*) fail "Unable to determine zap flavor for $platform" ;;
	esac
	local url="https://github.com/project-chip/zap/releases/download/${version}/zap-${flavor}.zip"

	progress "Installing zap-cli from $url"
	call_impl download_and_extract_zip "$url" "${BUILD_ENV_PATH}/bin" zap-cli
	chmod a+x "${BUILD_ENV_PATH}/bin/zap-cli" # ZipFile.extract() does not handle permissions
	info "ok"
	}

	function call_impl() { # func ...
	"$PYTHON" "${CHIP_ROOT}/scripts/configure.impl.py" "$@"
	}

	function check_python() {
	progress "Checking for Python 3"
	if have_binary python3; then
	PYTHON="$(hash -t python3)"
	elif have_binary python; then
	PYTHON="$(hash -t python)"
	local ver="$("$PYTHON" --version)"
	if [[ "$ver" != "Python 3."* ]]; then
	info "need Python 3 but found $ver"
	return 1
	fi
	else
	info "not found"
	return 1
	fi
	info "$PYTHON"
	}

	function check_binary() { # binary [VAR]
	progress "Checking for $1"
	if ! have_binary "$1"; then
	info "not found"
	return 1
	fi
	local path="$(hash -t "$1")"
	[[ -n "$2" ]] && eval "$2=\$path"
	info "$path"
	}

	function have_binary() { # binary
	hash "$1" 2>/dev/null
	}

	function ensure_no_clobber() { # file
	safe_to_clobber "$1" \|\| fail "Won't overwrite file not generated by configure: $1"
	}

	function safe_to_clobber() { # file
	CONFIGURE_MARKER="Auto-generated by configure, do not edit"
	[[ -s "$1" ]] \|\| return 0
	read -r -n 512 -d '' <"$1" \|\| true
	[[ "${REPLY/$CONFIGURE_MARKER/}" != "$REPLY" ]] && return 0
	return 1
	}

	function info() { # message
	echo "$*" >&2
	}

	function progress() { # message
	echo -n "$*... " >&2
	}

	function fail() { # message
	echo "Error: $*" >&2
	exit 1
	}

	main "$@"