tools/devshell/lib/vars.sh - fuchsia - Git at Google

 # Copyright 2017 The Fuchsia Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.

 if [[ -n "${ZSH_VERSION}" ]]; then
   devshell_lib_dir=${${(%):-%x}:a:h}
 else
   devshell_lib_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" >/dev/null 2>&1 && pwd)"
 fi

 export FUCHSIA_DIR="$(dirname $(dirname $(dirname "${devshell_lib_dir}")))"
 export FUCHSIA_OUT_DIR="${FUCHSIA_OUT_DIR:-${FUCHSIA_DIR}/out}"
 unset devshell_lib_dir

 if [[ "${FUCHSIA_DEVSHELL_VERBOSITY}" -eq 1 ]]; then
   set -x
 fi

 # fx-warn prints a line to stderr with a yellow WARNING: prefix.
 function fx-warn {
   if [[ -t 2 ]]; then
     echo -e >&2 "\033[1;33mWARNING:\033[0m $@"
   else
     echo -e >&2 "WARNING: $@"
   fi
 }

 # fx-error prints a line to stderr with a red ERROR: prefix.
 function fx-error {
   if [[ -t 2 ]]; then
     echo -e >&2 "\033[1;31mERROR:\033[0m $@"
   else
     echo -e >&2 "ERROR: $@"
   fi
 }

 function fx-symbolize {
   if [[ -z "$FUCHSIA_BUILD_DIR" ]]; then
     fx-config-read
   fi
   if [[ -z "$BUILDTOOLS_CLANG_DIR" ]]; then
     source "${FUCHSIA_DIR}/buildtools/vars.sh"
   fi
   local idstxt="${FUCHSIA_BUILD_DIR}/ids.txt"
   if [[ $# -gt 0 ]]; then
     idstxt="$1"
   fi
   local prebuilt_dir="${FUCHSIA_DIR}/zircon/prebuilt/downloads"
   local llvm_symbolizer="${BUILDTOOLS_CLANG_DIR}/bin/llvm-symbolizer"
   "${prebuilt_dir}/symbolize" -ids-rel -ids "$idstxt" -llvm-symbolizer "$llvm_symbolizer"
 }

 function fx-gen {
     (
       set -ex
       cd "${FUCHSIA_DIR}"
       "${FUCHSIA_DIR}/buildtools/gn" gen "${FUCHSIA_BUILD_DIR}"
     ) || return 1
 }

 function fx-build-config-load {
   # Paths are relative to FUCHSIA_DIR unless they're absolute paths.
   if [[ "${FUCHSIA_BUILD_DIR:0:1}" != "/" ]]; then
     FUCHSIA_BUILD_DIR="${FUCHSIA_DIR}/${FUCHSIA_BUILD_DIR}"
   fi

   if [[ ! -f "${FUCHSIA_BUILD_DIR}/fx.config" ]]; then
     if [[ ! -f "${FUCHSIA_BUILD_DIR}/args.gn" ]]; then
       fx-error "Build directory missing or removed. (${FUCHSIA_BUILD_DIR})"
       fx-error "run \"fx set\", or specify a build dir with --dir or \"fx use\""
       return 1
     fi

     fx-gen || return 1
   fi

   if ! source "${FUCHSIA_BUILD_DIR}/fx.config"; then
     fx-error "${FUCHSIA_BUILD_DIR}/fx.config caused internal error"
     return 1
   fi

   # The source of `fx.config` will re-set the build dir to relative, so we need
   # to abspath it again.
   if [[ "${FUCHSIA_BUILD_DIR:0:1}" != "/" ]]; then
     FUCHSIA_BUILD_DIR="${FUCHSIA_DIR}/${FUCHSIA_BUILD_DIR}"
   fi


   export FUCHSIA_BUILD_DIR FUCHSIA_ARCH

   export ZIRCON_BUILDROOT="${FUCHSIA_BUILD_DIR%/}.zircon"
   export ZIRCON_TOOLS_DIR="${ZIRCON_BUILDROOT}/tools"

   return 0
 }

 function fx-build-dir-if-present {
   if [[ -n "${_FX_BUILD_DIR}" ]]; then
     export FUCHSIA_BUILD_DIR="${_FX_BUILD_DIR}"
   else
     if [[ ! -f "${FUCHSIA_DIR}/.fx-build-dir" ]]; then

       # Old path, try to load old default config and migrate it:
       if [[ -f "${FUCHSIA_DIR}/.config" ]]; then
         source "${FUCHSIA_DIR}/.config" || return 1

         # After transition period, this branch is removed, and only the else
         # branch remains. Transition period to end April 2019.
         fx-build-dir-write "${FUCHSIA_BUILD_DIR}" || return 1
         # We must remove the old default config or it has "sticky" behavior.
         rm -f -- "${FUCHSIA_DIR}/.config"
       else
         return 1
       fi

     fi

     # .fx-build-dir contains $FUCHSIA_BUILD_DIR
     FUCHSIA_BUILD_DIR="$(<"${FUCHSIA_DIR}/.fx-build-dir")"
     if [[ -z "${FUCHSIA_BUILD_DIR}" ]]; then
       return 1
     fi
     # Paths are relative to FUCHSIA_DIR unless they're absolute paths.
     if [[ "${FUCHSIA_BUILD_DIR:0:1}" != "/" ]]; then
       FUCHSIA_BUILD_DIR="${FUCHSIA_DIR}/${FUCHSIA_BUILD_DIR}"
     fi
   fi
   return 0
 }

 function fx-config-read {
   if ! fx-build-dir-if-present; then
     fx-error "No build directory found."
     fx-error "Run \"fx set\" to create a new build directory, or specify one with --dir"
     exit 1
   fi

   if ! fx-build-config-load; then
     exit $?
   fi
   _FX_LOCK_FILE="${FUCHSIA_BUILD_DIR}.build_lock"
 }

 function fx-build-dir-write {
   local build_dir="$1"

   local -r tempfile="$(mktemp)"
   echo "${build_dir}" > "${tempfile}"
   mv -f "${tempfile}" "${FUCHSIA_DIR}/.fx-build-dir"
 }

 function get-device-name {
   fx-config-read
   # If DEVICE_NAME was passed in fx -d, use it
   if [[ "${FUCHSIA_DEVICE_NAME+isset}" == "isset" ]]; then
     echo "${FUCHSIA_DEVICE_NAME}"
     return
   fi
   # Uses a file outside the build dir so that it is not removed by `gn clean`
   local pairfile="${FUCHSIA_BUILD_DIR}.device"
   # If .device file exists, use that
   if [[ -f "${pairfile}" ]]; then
     echo "$(<"${pairfile}")"
     return
   fi
   echo ""
 }

 function get-fuchsia-device-addr {
   fx-command-run netaddr "$(get-device-name)" --fuchsia "$@"
 }

 function get-netsvc-device-addr {
   fx-command-run netaddr "$(get-device-name)" "$@"
 }

 # if $1 is "-d" or "--device" return
 #   - the netaddr if $2 looks like foo-bar-baz-flarg
 #     OR
 #   - $2 if it doesn't
 # else return ""
 # if -z is supplied as the third argument, get the netsvc
 # address instead of the netstack one
 function get-device-addr {
   device=""
   if [[ "$1" == "-d" || "$1" == "--device" ]]; then
     shift
     if [[ "$1" == *"-"* ]]; then
       if [[ "$2" != "-z" ]]; then
         device="$(fx-command-run netaddr "$1" --fuchsia)"
       else
         device="$(fx-command-run netaddr "$1")"
       fi
     else
       device="$1"
     fi
     shift
   fi
   echo "${device}"
 }

 function fx-command-run {
   local -r command_name="$1"
   local -r command_path="${FUCHSIA_DIR}/tools/devshell/${command_name}"

   if [[ ! -f "${command_path}" ]]; then
     fx-error "Unknown command ${command_name}"
     exit 1
   fi

   shift
   "${command_path}" "$@"
 }

 buildtools_whitelist=" gn ninja "

 function fx-buildtool-run {
   local -r command_name="$1"
   local -r command_path="${FUCHSIA_DIR}/buildtools/${command_name}"

   if [[ ! "${buildtools_whitelist}" =~ .*[[:space:]]"${command_name}"[[:space:]].* ]]; then
     fx-error "command ${command_name} not allowed"
     exit 1
   fi

   if [[ ! -f "${command_path}" ]]; then
     fx-error "Unknown command ${command_name}"
     exit 1
   fi

   shift
   "${command_path}" "$@"
 }

 function fx-command-exec {
   local -r command_name="$1"
   local -r command_path="${FUCHSIA_DIR}/tools/devshell/${command_name}"

   if [[ ! -f "${command_path}" ]]; then
     fx-error "Unknown command ${command_name}"
     exit 1
   fi

   shift
   exec "${command_path}" "$@"
 }

 function fx-print-command-help {
   local -r command_path="$1"
   if grep '^## ' "$command_path" > /dev/null; then
     sed -n -e 's/^## //p' -e 's/^##$//p' < "$command_path"
   else
     local -r command_name=$(basename "$command_path")
     echo "No help found. Try \`fx $command_name -h\`"
   fi
 }

 function fx-command-help {
   fx-print-command-help "$0"
 }

 # This function massages arguments to an fx subcommand so that a single
 # argument `--switch=value` becomes two arguments `--switch` `value`.
 # This lets each subcommand's main function use simpler argument parsing
 # while still supporting the preferred `--switch=value` syntax.  It also
 # handles the `--help` argument by redirecting to what `fx help command`
 # would do.  Because of the complexities of shell quoting and function
 # semantics, the only way for this function to yield its results
 # reasonably is via a global variable.  FX_ARGV is an array of the
 # results.  The standard boilerplate for using this looks like:
 #   function main {
 #     fx-standard-switches "$@"
 #     set -- "${FX_ARGV[@]}"
 #     ...
 #     }
 # Arguments following a `--` are also added to FX_ARGV but not split, as they
 # should usually be forwarded as-is to subprocesses.
 function fx-standard-switches {
   # In bash 4, this can be `declare -a -g FX_ARGV=()` to be explicit
   # about setting a global array.  But bash 3 (shipped on macOS) does
   # not support the `-g` flag to `declare`.
   FX_ARGV=()
   while [[ $# -gt 0 ]]; do
     if [[ "$1" = "--help" || "$1" = "-h" ]]; then
       fx-print-command-help "$0"
       # Exit rather than return, so we bail out of the whole command early.
       exit 0
     elif [[ "$1" == --*=* ]]; then
       # Turn --switch=value into --switch value.
       FX_ARGV+=("${1%%=*}" "${1#*=}")
     elif [[ "$1" == "--" ]]; then
       # Do not parse remaining parameters after --
       FX_ARGV+=("$@")
       return
     else
       FX_ARGV+=("$1")
     fi
     shift
   done
 }

 function fx-choose-build-concurrency {
   if grep -q "use_goma = true" "${FUCHSIA_BUILD_DIR}/args.gn"; then
     # The recommendation from the Goma team is to use 10*cpu-count.
     local cpus="$(fx-cpu-count)"
     echo $((cpus * 10))
   else
     fx-cpu-count
   fi
 }

 function fx-cpu-count {
   local -r cpu_count=$(getconf _NPROCESSORS_ONLN)
   echo "$cpu_count"
 }


 # Use a lock file around a command if possible.
 # Print a message if the lock isn't immediately entered,
 # and block until it is.
 function fx-try-locked {
   if [[ -z "${_FX_LOCK_FILE}" ]]; then
     fx-error "fx internal error: attempt to run locked command before fx-config-read"
     exit 1
   fi
   if ! command -v shlock >/dev/null; then
     # Can't lock! Fall back to unlocked operation.
     fx-exit-on-failure "$@"
   elif shlock -f "${_FX_LOCK_FILE}" -p $$; then
     # This will cause a deadlock if any subcommand calls back to fx build,
     # because shlock isn't reentrant by forked processes.
     fx-cmd-locked "$@"
   else
     echo "Locked by ${_FX_LOCK_FILE}..."
     while ! shlock -f "${_FX_LOCK_FILE}" -p $$; do sleep .1; done
     fx-cmd-locked "$@"
   fi
 }

 function fx-cmd-locked {
   if [[ -z "${_FX_LOCK_FILE}" ]]; then
     fx-error "fx internal error: attempt to run locked command before fx-config-read"
     exit 1
   fi
   # Exit trap to clean up lock file
   trap "[[ -n \"${_FX_LOCK_FILE}\" ]] && rm -f \"${_FX_LOCK_FILE}\"" EXIT
   fx-exit-on-failure "$@"
 }

 function fx-exit-on-failure {
   "$@" || exit $?
 }

 # Massage a ninja command line to add default -j and/or -l switches.
 # Note this takes the ninja command itself as first argument.
 # This can be used both to run ninja directly or to run a wrapper script.
 function fx-run-ninja {
   # Separate the command from the arguments so we can prepend default -j/-l
   # switch arguments.  They need to come before the user's arguments in case
   # those include -- or something else that makes following arguments not be
   # handled as normal switches.
   local cmd="$1"
   shift

   local args=()
   local have_load=false
   local have_jobs=false
   while [[ $# -gt 0 ]]; do
     case "$1" in
     -l) have_load=true ;;
     -j) have_jobs=true ;;
     esac
     args+=("$1")
     shift
   done

   if ! $have_load; then
     if [[ "$(uname -s)" == "Darwin" ]]; then
       # Load level on Darwin is quite different from that of Linux, wherein a
       # load level of 1 per CPU is not necessarily a prohibitive load level. An
       # unscientific study of build side effects suggests that cpus*20 is a
       # reasonable value to prevent catastrophic load (i.e. user can not kill
       # the build, can not lock the screen, etc).
       local cpus="$(fx-cpu-count)"
       args=("-l" $((cpus * 20)) "${args[@]}")
     fi
   fi

   if ! $have_jobs; then
     local concurrency="$(fx-choose-build-concurrency)"
     # macOS in particular has a low default for number of open file descriptors
     # per process, which is prohibitive for higher job counts. Here we raise
     # the number of allowed file descriptors per process if it appears to be
     # low in order to avoid failures due to the limit. See `getrlimit(2)` for
     # more information.
     local min_limit=$((concurrency * 2))
     if [[ $(ulimit -n) -lt "${min_limit}" ]]; then
       ulimit -n "${min_limit}"
     fi
     args=("-j" "${concurrency}" "${args[@]}")
   fi

   # TERM is passed for the pretty ninja UI
   # PATH is passed as some tools are referenced via $PATH due to platform differences.
   # TMPDIR is passed for Goma on macOS. TMPDIR must be set, or unset, not
   # empty. Some Dart build tools have been observed writing into source paths
   # when TMPDIR="" - it is deliberately unquoted and using the ${+} expansion
   # expression).
   fx-try-locked env -i TERM="${TERM}" PATH="${PATH}" \
     ${NINJA_STATUS+"NINJA_STATUS=${NINJA_STATUS}"} \
     ${TMPDIR+"TMPDIR=$TMPDIR"} \
     "$cmd" "${args[@]}"
 }
	# Copyright 2017 The Fuchsia Authors. All rights reserved.
	# Use of this source code is governed by a BSD-style license that can be
	# found in the LICENSE file.

	if [[ -n "${ZSH_VERSION}" ]]; then
	devshell_lib_dir=${${(%):-%x}:a:h}
	else
	devshell_lib_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" >/dev/null 2>&1 && pwd)"
	fi

	export FUCHSIA_DIR="$(dirname $(dirname $(dirname "${devshell_lib_dir}")))"
	export FUCHSIA_OUT_DIR="${FUCHSIA_OUT_DIR:-${FUCHSIA_DIR}/out}"
	unset devshell_lib_dir

	if [[ "${FUCHSIA_DEVSHELL_VERBOSITY}" -eq 1 ]]; then
	set -x
	fi

	# fx-warn prints a line to stderr with a yellow WARNING: prefix.
	function fx-warn {
	if [[ -t 2 ]]; then
	echo -e >&2 "\033[1;33mWARNING:\033[0m $@"
	else
	echo -e >&2 "WARNING: $@"
	fi
	}

	# fx-error prints a line to stderr with a red ERROR: prefix.
	function fx-error {
	if [[ -t 2 ]]; then
	echo -e >&2 "\033[1;31mERROR:\033[0m $@"
	else
	echo -e >&2 "ERROR: $@"
	fi
	}

	function fx-symbolize {
	if [[ -z "$FUCHSIA_BUILD_DIR" ]]; then
	fx-config-read
	fi
	if [[ -z "$BUILDTOOLS_CLANG_DIR" ]]; then
	source "${FUCHSIA_DIR}/buildtools/vars.sh"
	fi
	local idstxt="${FUCHSIA_BUILD_DIR}/ids.txt"
	if [[ $# -gt 0 ]]; then
	idstxt="$1"
	fi
	local prebuilt_dir="${FUCHSIA_DIR}/zircon/prebuilt/downloads"
	local llvm_symbolizer="${BUILDTOOLS_CLANG_DIR}/bin/llvm-symbolizer"
	"${prebuilt_dir}/symbolize" -ids-rel -ids "$idstxt" -llvm-symbolizer "$llvm_symbolizer"
	}

	function fx-gen {
	(
	set -ex
	cd "${FUCHSIA_DIR}"
	"${FUCHSIA_DIR}/buildtools/gn" gen "${FUCHSIA_BUILD_DIR}"
	) \|\| return 1
	}

	function fx-build-config-load {
	# Paths are relative to FUCHSIA_DIR unless they're absolute paths.
	if [[ "${FUCHSIA_BUILD_DIR:0:1}" != "/" ]]; then
	FUCHSIA_BUILD_DIR="${FUCHSIA_DIR}/${FUCHSIA_BUILD_DIR}"
	fi

	if [[ ! -f "${FUCHSIA_BUILD_DIR}/fx.config" ]]; then
	if [[ ! -f "${FUCHSIA_BUILD_DIR}/args.gn" ]]; then
	fx-error "Build directory missing or removed. (${FUCHSIA_BUILD_DIR})"
	fx-error "run \"fx set\", or specify a build dir with --dir or \"fx use\""
	return 1
	fi

	fx-gen \|\| return 1
	fi

	if ! source "${FUCHSIA_BUILD_DIR}/fx.config"; then
	fx-error "${FUCHSIA_BUILD_DIR}/fx.config caused internal error"
	return 1
	fi

	# The source of `fx.config` will re-set the build dir to relative, so we need
	# to abspath it again.
	if [[ "${FUCHSIA_BUILD_DIR:0:1}" != "/" ]]; then
	FUCHSIA_BUILD_DIR="${FUCHSIA_DIR}/${FUCHSIA_BUILD_DIR}"
	fi


	export FUCHSIA_BUILD_DIR FUCHSIA_ARCH

	export ZIRCON_BUILDROOT="${FUCHSIA_BUILD_DIR%/}.zircon"
	export ZIRCON_TOOLS_DIR="${ZIRCON_BUILDROOT}/tools"

	return 0
	}

	function fx-build-dir-if-present {
	if [[ -n "${_FX_BUILD_DIR}" ]]; then
	export FUCHSIA_BUILD_DIR="${_FX_BUILD_DIR}"
	else
	if [[ ! -f "${FUCHSIA_DIR}/.fx-build-dir" ]]; then

	# Old path, try to load old default config and migrate it:
	if [[ -f "${FUCHSIA_DIR}/.config" ]]; then
	source "${FUCHSIA_DIR}/.config" \|\| return 1

	# After transition period, this branch is removed, and only the else
	# branch remains. Transition period to end April 2019.
	fx-build-dir-write "${FUCHSIA_BUILD_DIR}" \|\| return 1
	# We must remove the old default config or it has "sticky" behavior.
	rm -f -- "${FUCHSIA_DIR}/.config"
	else
	return 1
	fi

	fi

	# .fx-build-dir contains $FUCHSIA_BUILD_DIR
	FUCHSIA_BUILD_DIR="$(<"${FUCHSIA_DIR}/.fx-build-dir")"
	if [[ -z "${FUCHSIA_BUILD_DIR}" ]]; then
	return 1
	fi
	# Paths are relative to FUCHSIA_DIR unless they're absolute paths.
	if [[ "${FUCHSIA_BUILD_DIR:0:1}" != "/" ]]; then
	FUCHSIA_BUILD_DIR="${FUCHSIA_DIR}/${FUCHSIA_BUILD_DIR}"
	fi
	fi
	return 0
	}

	function fx-config-read {
	if ! fx-build-dir-if-present; then
	fx-error "No build directory found."
	fx-error "Run \"fx set\" to create a new build directory, or specify one with --dir"
	exit 1
	fi

	if ! fx-build-config-load; then
	exit $?
	fi
	_FX_LOCK_FILE="${FUCHSIA_BUILD_DIR}.build_lock"
	}

	function fx-build-dir-write {
	local build_dir="$1"

	local -r tempfile="$(mktemp)"
	echo "${build_dir}" > "${tempfile}"
	mv -f "${tempfile}" "${FUCHSIA_DIR}/.fx-build-dir"
	}

	function get-device-name {
	fx-config-read
	# If DEVICE_NAME was passed in fx -d, use it
	if [[ "${FUCHSIA_DEVICE_NAME+isset}" == "isset" ]]; then
	echo "${FUCHSIA_DEVICE_NAME}"
	return
	fi
	# Uses a file outside the build dir so that it is not removed by `gn clean`
	local pairfile="${FUCHSIA_BUILD_DIR}.device"
	# If .device file exists, use that
	if [[ -f "${pairfile}" ]]; then
	echo "$(<"${pairfile}")"
	return
	fi
	echo ""
	}

	function get-fuchsia-device-addr {
	fx-command-run netaddr "$(get-device-name)" --fuchsia "$@"
	}

	function get-netsvc-device-addr {
	fx-command-run netaddr "$(get-device-name)" "$@"
	}

	# if $1 is "-d" or "--device" return
	# - the netaddr if $2 looks like foo-bar-baz-flarg
	# OR
	# - $2 if it doesn't
	# else return ""
	# if -z is supplied as the third argument, get the netsvc
	# address instead of the netstack one
	function get-device-addr {
	device=""
	if [[ "$1" == "-d" \|\| "$1" == "--device" ]]; then
	shift
	if [[ "$1" == "-" ]]; then
	if [[ "$2" != "-z" ]]; then
	device="$(fx-command-run netaddr "$1" --fuchsia)"
	else
	device="$(fx-command-run netaddr "$1")"
	fi
	else
	device="$1"
	fi
	shift
	fi
	echo "${device}"
	}

	function fx-command-run {
	local -r command_name="$1"
	local -r command_path="${FUCHSIA_DIR}/tools/devshell/${command_name}"

	if [[ ! -f "${command_path}" ]]; then
	fx-error "Unknown command ${command_name}"
	exit 1
	fi

	shift
	"${command_path}" "$@"
	}

	buildtools_whitelist=" gn ninja "

	function fx-buildtool-run {
	local -r command_name="$1"
	local -r command_path="${FUCHSIA_DIR}/buildtools/${command_name}"

	if [[ ! "${buildtools_whitelist}" =~ .[[:space:]]"${command_name}"[[:space:]]. ]]; then
	fx-error "command ${command_name} not allowed"
	exit 1
	fi

	if [[ ! -f "${command_path}" ]]; then
	fx-error "Unknown command ${command_name}"
	exit 1
	fi

	shift
	"${command_path}" "$@"
	}

	function fx-command-exec {
	local -r command_name="$1"
	local -r command_path="${FUCHSIA_DIR}/tools/devshell/${command_name}"

	if [[ ! -f "${command_path}" ]]; then
	fx-error "Unknown command ${command_name}"
	exit 1
	fi

	shift
	exec "${command_path}" "$@"
	}

	function fx-print-command-help {
	local -r command_path="$1"
	if grep '^## ' "$command_path" > /dev/null; then
	sed -n -e 's/^## //p' -e 's/^##$//p' < "$command_path"
	else
	local -r command_name=$(basename "$command_path")
	echo "No help found. Try \`fx $command_name -h\`"
	fi
	}

	function fx-command-help {
	fx-print-command-help "$0"
	}

	# This function massages arguments to an fx subcommand so that a single
	# argument `--switch=value` becomes two arguments `--switch` `value`.
	# This lets each subcommand's main function use simpler argument parsing
	# while still supporting the preferred `--switch=value` syntax. It also
	# handles the `--help` argument by redirecting to what `fx help command`
	# would do. Because of the complexities of shell quoting and function
	# semantics, the only way for this function to yield its results
	# reasonably is via a global variable. FX_ARGV is an array of the
	# results. The standard boilerplate for using this looks like:
	# function main {
	# fx-standard-switches "$@"
	# set -- "${FX_ARGV[@]}"
	# ...
	# }
	# Arguments following a `--` are also added to FX_ARGV but not split, as they
	# should usually be forwarded as-is to subprocesses.
	function fx-standard-switches {
	# In bash 4, this can be `declare -a -g FX_ARGV=()` to be explicit
	# about setting a global array. But bash 3 (shipped on macOS) does
	# not support the `-g` flag to `declare`.
	FX_ARGV=()
	while [[ $# -gt 0 ]]; do
	if [[ "$1" = "--help" \|\| "$1" = "-h" ]]; then
	fx-print-command-help "$0"
	# Exit rather than return, so we bail out of the whole command early.
	exit 0
	elif [[ "$1" == --= ]]; then
	# Turn --switch=value into --switch value.
	FX_ARGV+=("${1%%=}" "${1#=}")
	elif [[ "$1" == "--" ]]; then
	# Do not parse remaining parameters after --
	FX_ARGV+=("$@")
	return
	else
	FX_ARGV+=("$1")
	fi
	shift
	done
	}

	function fx-choose-build-concurrency {
	if grep -q "use_goma = true" "${FUCHSIA_BUILD_DIR}/args.gn"; then
	# The recommendation from the Goma team is to use 10*cpu-count.
	local cpus="$(fx-cpu-count)"
	echo $((cpus * 10))
	else
	fx-cpu-count
	fi
	}

	function fx-cpu-count {
	local -r cpu_count=$(getconf _NPROCESSORS_ONLN)
	echo "$cpu_count"
	}


	# Use a lock file around a command if possible.
	# Print a message if the lock isn't immediately entered,
	# and block until it is.
	function fx-try-locked {
	if [[ -z "${_FX_LOCK_FILE}" ]]; then
	fx-error "fx internal error: attempt to run locked command before fx-config-read"
	exit 1
	fi
	if ! command -v shlock >/dev/null; then
	# Can't lock! Fall back to unlocked operation.
	fx-exit-on-failure "$@"
	elif shlock -f "${_FX_LOCK_FILE}" -p $$; then
	# This will cause a deadlock if any subcommand calls back to fx build,
	# because shlock isn't reentrant by forked processes.
	fx-cmd-locked "$@"
	else
	echo "Locked by ${_FX_LOCK_FILE}..."
	while ! shlock -f "${_FX_LOCK_FILE}" -p $$; do sleep .1; done
	fx-cmd-locked "$@"
	fi
	}

	function fx-cmd-locked {
	if [[ -z "${_FX_LOCK_FILE}" ]]; then
	fx-error "fx internal error: attempt to run locked command before fx-config-read"
	exit 1
	fi
	# Exit trap to clean up lock file
	trap "[[ -n \"${_FX_LOCK_FILE}\" ]] && rm -f \"${_FX_LOCK_FILE}\"" EXIT
	fx-exit-on-failure "$@"
	}

	function fx-exit-on-failure {
	"$@" \|\| exit $?
	}

	# Massage a ninja command line to add default -j and/or -l switches.
	# Note this takes the ninja command itself as first argument.
	# This can be used both to run ninja directly or to run a wrapper script.
	function fx-run-ninja {
	# Separate the command from the arguments so we can prepend default -j/-l
	# switch arguments. They need to come before the user's arguments in case
	# those include -- or something else that makes following arguments not be
	# handled as normal switches.
	local cmd="$1"
	shift

	local args=()
	local have_load=false
	local have_jobs=false
	while [[ $# -gt 0 ]]; do
	case "$1" in
	-l) have_load=true ;;
	-j) have_jobs=true ;;
	esac
	args+=("$1")
	shift
	done

	if ! $have_load; then
	if [[ "$(uname -s)" == "Darwin" ]]; then
	# Load level on Darwin is quite different from that of Linux, wherein a
	# load level of 1 per CPU is not necessarily a prohibitive load level. An
	# unscientific study of build side effects suggests that cpus*20 is a
	# reasonable value to prevent catastrophic load (i.e. user can not kill
	# the build, can not lock the screen, etc).
	local cpus="$(fx-cpu-count)"
	args=("-l" $((cpus * 20)) "${args[@]}")
	fi
	fi

	if ! $have_jobs; then
	local concurrency="$(fx-choose-build-concurrency)"
	# macOS in particular has a low default for number of open file descriptors
	# per process, which is prohibitive for higher job counts. Here we raise
	# the number of allowed file descriptors per process if it appears to be
	# low in order to avoid failures due to the limit. See `getrlimit(2)` for
	# more information.
	local min_limit=$((concurrency * 2))
	if [[ $(ulimit -n) -lt "${min_limit}" ]]; then
	ulimit -n "${min_limit}"
	fi
	args=("-j" "${concurrency}" "${args[@]}")
	fi

	# TERM is passed for the pretty ninja UI
	# PATH is passed as some tools are referenced via $PATH due to platform differences.
	# TMPDIR is passed for Goma on macOS. TMPDIR must be set, or unset, not
	# empty. Some Dart build tools have been observed writing into source paths
	# when TMPDIR="" - it is deliberately unquoted and using the ${+} expansion
	# expression).
	fx-try-locked env -i TERM="${TERM}" PATH="${PATH}" \
	${NINJA_STATUS+"NINJA_STATUS=${NINJA_STATUS}"} \
	${TMPDIR+"TMPDIR=$TMPDIR"} \
	"$cmd" "${args[@]}"
	}