eclass/cros-rust.eclass - third_party/overlays/chromiumos-overlay - Git at Google

 # Copyright 2018 The Chromium OS Authors. All rights reserved.
 # Distributed under the terms of the GNU General Public License v2

 # @ECLASS: cros-rust.eclass
 # @MAINTAINER:
 # The Chromium OS Authors <chromium-os-dev@chromium.org>
 # @BUGREPORTS:
 # Please report bugs via https://crbug.com/new (with component "Tools>ChromeOS-Toolchain")
 # @VCSURL: https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/master/eclass/@ECLASS@
 # @BLURB: Eclass for fetching, building, and installing Rust packages.

 if [[ -z ${_ECLASS_CROS_RUST} ]]; then
 _ECLASS_CROS_RUST="1"

 # Check for EAPI 6+.
 case "${EAPI:-0}" in
 [012345]) die "unsupported EAPI (${EAPI}) in eclass (${ECLASS})" ;;
 esac

 # @ECLASS-VARIABLE: CROS_RUST_EMPTY_CRATE
 # @PRE_INHERIT
 # @DESCRIPTION:
 # Indicates that this package is an empty crate for satisfying cargo's
 # requirements but will not actually be used during compile time.  Used by
 # dev-dependencies or crates like winapi.
 : "${CROS_RUST_EMPTY_CRATE:=}"

 # @ECLASS-VARIABLE: CROS_RUST_EMPTY_CRATE_FEATURES
 # @PRE_INHERIT
 # @DESCRIPTION:
 # Array of Cargo features emitted into the Cargo.toml of an empty crate. Allows
 # downstream crates to depend on this crate with the given features enabled.
 if [[ ! -v CROS_RUST_EMPTY_CRATE_FEATURES ]]; then
 	CROS_RUST_EMPTY_CRATE_FEATURES=()
 fi

 # @ECLASS-VARIABLE: CROS_RUST_OVERFLOW_CHECKS
 # @PRE_INHERIT
 # @DESCRIPTION:
 # Enable integer overflow checks for this package.  Packages that wish to
 # disable integer overflow checks should set this value to 0.  Integer overflow
 # checks are always enabled when the cros-debug flag is set.
 : "${CROS_RUST_OVERFLOW_CHECKS:=1}"

 # @ECLASS-VARIABLE: CROS_RUST_REMOVE_DEV_DEPS
 # @PRE_INHERIT
 # @DESCRIPTION:
 # Removes all the dev-dependencies from the Cargo.toml. This can break circular
 # dependencies and help minimize how many dependent packages need to be added.
 : "${CROS_RUST_REMOVE_DEV_DEPS:=}"

 inherit toolchain-funcs cros-debug cros-sanitizers

 IUSE="asan fuzzer lsan +lto msan test tsan ubsan"
 REQUIRED_USE="?? ( asan lsan msan tsan )"

 EXPORT_FUNCTIONS src_unpack src_prepare src_configure src_install

 DEPEND="
 	>=virtual/rust-1.28.0:=
 	>=dev-util/cargo-0.29.0
 "

 ECARGO_HOME="${WORKDIR}/cargo_home"
 CROS_RUST_REGISTRY_DIR="/usr/lib/cros_rust_registry"

 # Ignore odr violations in unit tests in asan builds
 # (https://github.com/rust-lang/rust/issues/41807).
 ASAN_OPTIONS="detect_odr_violation=0"

 # @FUNCTION: cargo_src_unpack
 # @DESCRIPTION:
 # Unpacks the package
 cros-rust_src_unpack() {
 	debug-print-function ${FUNCNAME} "$@"

 	local archive
 	for archive in ${A}; do
 		case "${archive}" in
 			*.crate)
 				ebegin "Unpacking ${archive}"

 				ln -s "${DISTDIR}/${archive}" "${archive}.tar"
 				unpack "./${archive}.tar"
 				rm "${archive}.tar"

 				eend $?
 				;;
 			*)
 				unpack "${archive}"
 				;;
 		esac
 	done

 	if [[ "${CROS_RUST_EMPTY_CRATE}" == "1" ]]; then
 		# Generate an empty Cargo.toml and src/lib.rs for this crate.
 		mkdir -p "${S}/src"
 		cat <<- EOF >> "${S}/Cargo.toml"
 		[package]
 		name = "${PN}"
 		version = "${PV}"
 		authors = ["The Chromium OS Authors"]

 		[features]
 		EOF

 		if [[ "$(declare -p CROS_RUST_EMPTY_CRATE_FEATURES 2> /dev/null)" != "declare -a"* ]]; then
 			eerror "CROS_RUST_EMPTY_CRATE_FEATURES must be an array"
 			die
 		fi

 		local feature
 		for feature in "${CROS_RUST_EMPTY_CRATE_FEATURES[@]}"; do
 			echo "${feature} = []" >> "${S}/Cargo.toml"
 		done

 		touch "${S}/src/lib.rs"
 	fi

 	# Set up the cargo config.
 	mkdir -p "${ECARGO_HOME}"

 	cat <<- EOF > "${ECARGO_HOME}/config"
 	[source.chromeos]
 	directory = "${SYSROOT}/${CROS_RUST_REGISTRY_DIR}"

 	[source.crates-io]
 	replace-with = "chromeos"
 	local-registry = "/nonexistent"

 	[target.${CHOST}]
 	linker = "$(tc-getCC)"
 	EOF

 	# When the target environment is different from the host environment,
 	# add a setting for the target environment.
 	if tc-is-cross-compiler; then
 		cat <<- EOF >> "${ECARGO_HOME}/config"

 		[target.${CBUILD}]
 		linker = "$(tc-getBUILD_CC)"
 		EOF
 	fi
 }

 # @FUNCTION: cros-rust_src_prepare
 # @DESCRIPTION:
 # Prepares the src. This function supports "# provided by ebuild" macro and
 # "# ignored by ebuild" macro for replacing and removing path dependencies
 # with ones provided by their ebuild in Cargo.toml
 # and Cargo.toml will be modified in place. If the macro is used in
 # ${S}/Cargo.toml, CROS_WORKON_OUTOFTREE_BUILD can't be set to 1 in its ebuild.
 cros-rust_src_prepare() {
 	if grep -q "# provided by ebuild" "${S}/Cargo.toml"; then
 		if [[ "${CROS_WORKON_OUTOFTREE_BUILD}" == 1 ]]; then
 			die 'CROS_WORKON_OUTOFTREE_BUILD=1 must not be set when using' \
 				'`provided by ebuild`'
 		fi

 		# Replace path dependencies with ones provided by their ebuild.
 		#
 		# For local developer builds, we want Cargo.toml to contain path
 		# dependencies on sibling crates within the same repository or elsewhere
 		# in the Chrome OS source tree. This enables developers to run `cargo
 		# build` and have dependencies resolve correctly to their locally
 		# checked out code.
 		#
 		# At the same time, some crates contained within the crosvm repository
 		# have their own ebuild independent of the crosvm ebuild so that they
 		# are usable from outside of crosvm. Ebuilds of downstream crates won't
 		# be able to depend on these crates by path dependency because that
 		# violates the build sandbox. We perform a sed replacement to eliminate
 		# the path dependency during ebuild of the downstream crates.
 		#
 		# The sed command says: in any line containing `# provided by ebuild`,
 		# please replace `path = "..."` with `version = "*"`. The intended usage
 		# is like this:
 		#
 		#     [dependencies]
 		#     data_model = { path = "../data_model" }  # provided by ebuild
 		#
 		sed -i \
 			'/# provided by ebuild$/ s/path = "[^"]*"/version = "*"/' \
 			"${S}/Cargo.toml" || die
 	fi

 	if grep -q "# ignored by ebuild" "${S}/Cargo.toml"; then
 		if [[ "${CROS_WORKON_OUTOFTREE_BUILD}" == 1 ]]; then
 			die 'CROS_WORKON_OUTOFTREE_BUILD=1 must not be set when using' \
 				'`ignored by ebuild`'
 		fi
 		# Emerge ignores "out-of-sandbox" [patch.crates-io] lines in
 		# Cargo.toml.
 		sed -i \
 			'/# ignored by ebuild/d' \
 			"${S}/Cargo.toml" || die
 	fi

 	# Remove lines that start with "[dev-dependencies." until a line is found that
 	# starts with "[" but not "[dev-d".
 	#
 	# The sed script is of the form '/A/,/B/{/B/!d}'.
 	# The first part '/A/,/B/' includes lines that match /A/ and following lines
 	# until a line matches the second pattern /B/ inclusive. The last part,
 	# {/B/!d} deletes included lines that don't match /B/.
 	#
 	# The first pattern /^\[dev-dependencies\./ is fairly easy to understand. it
 	# matches any line that begins with "[dev-dependencies." The second pattern
 	# would ideally be /^[/ which would match any line that starts with "[".
 	# unfortunately that also matches the first pattern so the range would always
 	# be one line. To avoid this problem the second pattern approximates a check
 	# to make sure the first pattern isn't matched. It does so by testing to see
 	# if the string that follows the "[" doesn't match "dev-d". This is
 	# accomplished by matching strings that don't begin with "d", or begin with
 	# "d" but don't begin with "de", or begin with "de" but don't begin with
 	# "dev", ... or begin with "dev-" but don't begin with "dev-d".
 	if [[ "${CROS_RUST_REMOVE_DEV_DEPS}" == 1 ]]; then
 		local neg_pattern='/^\[($|[^d]|d($|[^e]|e($|[^v]|v($|[^-]|-($|[^d])))))/'
 		sed -i -E \
 			"/^\\[dev-dependencies\\./,${neg_pattern}{${neg_pattern}!d}" \
 			"${S}/Cargo.toml" || die
 	fi

 	default
 }

 # @FUNCTION: cros-rust_src_configure
 # @DESCRIPTION:
 # Configures the source and exports any environment variables needed during the
 # build.
 cros-rust_src_configure() {
 	sanitizers-setup-env

 	export CARGO_TARGET_DIR="${WORKDIR}"
 	export CARGO_HOME="${ECARGO_HOME}"
 	export HOST="${CBUILD}"
 	export HOST_CC="$(tc-getBUILD_CC)"
 	# PKG_CONFIG_ALLOW_CROSS is required by pkg-config.
 	# https://github.com/rust-lang/pkg-config-rs/issues/41.
 	# Since cargo will overwrites $HOST with "" when building pkg-config, we
 	# need to set it regardless of the value of tc-is-cross-compiler here.
 	export PKG_CONFIG_ALLOW_CROSS=1
 	export TARGET="${CHOST}"
 	export TARGET_CC="$(tc-getCC)"

 	# There is a memory leak in libbacktrace:
 	# https://github.com/rust-lang/rust/issues/59125
 	cros-rust_use_sanitizers || export RUST_BACKTRACE=1

 	# We want debug info even in release builds.
 	local rustflags=(
 		-Cdebuginfo=2
 		-Copt-level=3
 	)

 	use lto && rustflags+=( -Clto )

 	# We don't want to abort during tests.
 	use test || rustflags+=( -Cpanic=abort )

 	if use cros-debug || [[ "${CROS_RUST_OVERFLOW_CHECKS}" == "1" ]]; then
 		rustflags+=( -Coverflow-checks=on )
 	fi

 	use cros-debug && rustflags+=( -Cdebug-assertions=on )

 	use asan && rustflags+=( -Csanitizer=address )
 	use lsan && rustflags+=( -Csanitizer=leak )
 	use msan && rustflags+=( -Csanitizer=memory )
 	use tsan && rustflags+=( -Csanitizer=thread )
 	use ubsan && rustflags+=( -Clink-arg=-fsanitize=undefined )

 	if use fuzzer; then
 		rustflags+=(
 			--cfg fuzzing
 			-Cpasses=sancov
 			-Cllvm-args=-sanitizer-coverage-level=4
 			-Cllvm-args=-sanitizer-coverage-inline-8bit-counters
 			-Cllvm-args=-sanitizer-coverage-trace-compares
 			-Cllvm-args=-sanitizer-coverage-pc-table
 			-Cllvm-args=-sanitizer-coverage-trace-divs
 			-Cllvm-args=-sanitizer-coverage-trace-geps
 			-Cllvm-args=-sanitizer-coverage-prune-blocks=0
 		)
 	fi

 	export RUSTFLAGS="${rustflags[*]}"
 }

 # @FUNCTION: cros-rust_use_sanitizers
 # @DESCRIPTION:
 # Checks whether sanitizers are being used.
 cros-rust_use_sanitizers() {
 	use_sanitizers || use lsan
 }

 # @FUNCTION: ecargo
 # @USAGE: <args to cargo>
 # @DESCRIPTION:
 # Call cargo with the specified command line options.
 ecargo() {
 	debug-print-function ${FUNCNAME} "$@"

 	# The cargo developers have decided to make it as painful as possible to
 	# use cargo inside another build system.  So there is no way to tell
 	# cargo to just not write this lock file.  Instead we have to bend over
 	# backwards to accommodate cargo.
 	addwrite Cargo.lock
 	rm -f Cargo.lock

 	cargo -v "$@" || die

 	# Now remove any Cargo.lock files that cargo pointlessly created.
 	rm -f Cargo.lock
 }

 # @FUNCTION: ecargo_build
 # @USAGE: <args to cargo build>
 # @DESCRIPTION:
 # Call `cargo build` with the specified command line options.
 ecargo_build() {
 	ecargo build --target="${CHOST}" --release "$@"
 }

 # @FUNCTION: ecargo_build_fuzzer
 # @DESCRIPTION:
 # Call `cargo build` with fuzzing options enabled.
 ecargo_build_fuzzer() {
 	local fuzzer_libdir="$(dirname "$($(tc-getCC) -print-libgcc-file-name)")"
 	local fuzzer_arch="${ARCH}"
 	if [[ "${ARCH}" == "amd64" ]]; then
 		fuzzer_arch="x86_64"
 	fi

 	local link_args=(
 		-Clink-arg="-L${fuzzer_libdir}"
 		-Clink-arg="-lclang_rt.fuzzer-${fuzzer_arch}"
 		-Clink-arg="-lc++"
 		-Clink-arg="-Wl,-export-dynamic"
 	)

 	# The `rustc` subcommand for cargo allows us to set some extra flags for
 	# the current package without setting them for all `rustc` invocations.
 	# On the other hand the flags in the RUSTFLAGS environment variable are set
 	# for all `rustc` invocations.
 	ecargo rustc --target="${CHOST}" --release "$@" -- "${link_args[@]}"
 }

 # @FUNCTION: ecargo_test
 # @USAGE: <args to cargo test>
 # @DESCRIPTION:
 # Call `cargo test` with the specified command line options.
 ecargo_test() {
 	ecargo test --target="${CHOST}" --target-dir "target/ecargo-test" --release "$@"
 }

 # @FUNCTION: cros-rust_publish
 # @USAGE: [crate name] [crate version]
 # @DESCRIPTION:
 # Publish a library crate to the local registry.  Should only be called from
 # within a src_install() function.
 cros-rust_publish() {
 	debug-print-function ${FUNCNAME} "$@"

 	local name="${1:-${PN}}"
 	local version="${2:-${PV}}"

 	# Create the .crate file.
 	ecargo package --allow-dirty --no-metadata --no-verify || die

 	# Unpack the crate we just created into the directory registry.
 	local crate="${CARGO_TARGET_DIR}/package/${name}-${version}.crate"

 	mkdir -p "${D}/${CROS_RUST_REGISTRY_DIR}"
 	pushd "${D}/${CROS_RUST_REGISTRY_DIR}" > /dev/null
 	tar xf "${crate}" || die

 	# Calculate the sha256sum since cargo will want this later.
 	local shasum="$(sha256sum ${crate} | cut -d ' ' -f 1)"
 	local dir="${name}-${version}"
 	local checksum="${T}/${name}-${version}-checksum.json"

 	# Calculate the sha256 hashes of all the files in the crate.
 	local files=( $(find "${dir}" -type f) )

 	[[ "${#files[@]}" == "0" ]] && die "Could not find crate files for ${name}"

 	# Now start filling out the checksum file.
 	printf '{\n\t"package": "%s",\n\t"files": {\n' "${shasum}" > "${checksum}"
 	local idx=0
 	local f
 	for f in "${files[@]}"; do
 		shasum="$(sha256sum ${f} | cut -d ' ' -f 1)"
 		printf '\t\t"%s": "%s"' "${f#${dir}/}" "${shasum}" >> "${checksum}"

 		# The json parser is unnecessarily strict about not allowing
 		# commas on the last line so we have to track this ourselves.
 		idx="$((idx+1))"
 		if [[ "${idx}" == "${#files[@]}" ]]; then
 			printf '\n' >> "${checksum}"
 		else
 			printf ',\n' >> "${checksum}"
 		fi
 	done
 	printf "\t}\n}\n" >> "${checksum}"
 	popd > /dev/null

 	insinto "${CROS_RUST_REGISTRY_DIR}/${name}-${version}"
 	newins "${checksum}" .cargo-checksum.json

 	# We want the Cargo.toml.orig file to be world readable.
 	fperms 0644 "${CROS_RUST_REGISTRY_DIR}/${name}-${version}/Cargo.toml.orig"
 }

 # @FUNCTION: cros-rust_get_build_dir
 # @DESCRIPTION:
 # Return the path to the directory where build artifacts are available.
 cros-rust_get_build_dir() {
 	echo "${CARGO_TARGET_DIR}/${CHOST}/release"
 }

 cros-rust_src_install() {
 	debug-print-function ${FUNCNAME} "$@"

 	cros-rust_publish
 }

 # @FUNCTION: cros-rust_get_crate_version
 # @USAGE: <path to crate>
 # @DESCRIPTION:
 # Returns the version for a crate by finding the first 'version =' line in the
 # Cargo.toml in the crate.
 cros-rust_get_crate_version() {
 	local crate="${1:-${S}}"
 	[[ $# -gt 1 ]] && die "${FUNCNAME}: incorrect number of arguments"
 	awk '/^version = / { print $3 }' "${crate}/Cargo.toml" | head -n1 | tr -d '"'
 }

 fi
	# Copyright 2018 The Chromium OS Authors. All rights reserved.
	# Distributed under the terms of the GNU General Public License v2

	# @ECLASS: cros-rust.eclass
	# @MAINTAINER:
	# The Chromium OS Authors <chromium-os-dev@chromium.org>
	# @BUGREPORTS:
	# Please report bugs via https://crbug.com/new (with component "Tools>ChromeOS-Toolchain")
	# @VCSURL: https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/master/eclass/@ECLASS@
	# @BLURB: Eclass for fetching, building, and installing Rust packages.

	if [[ -z ${_ECLASS_CROS_RUST} ]]; then
	_ECLASS_CROS_RUST="1"

	# Check for EAPI 6+.
	case "${EAPI:-0}" in
	[012345]) die "unsupported EAPI (${EAPI}) in eclass (${ECLASS})" ;;
	esac

	# @ECLASS-VARIABLE: CROS_RUST_EMPTY_CRATE
	# @PRE_INHERIT
	# @DESCRIPTION:
	# Indicates that this package is an empty crate for satisfying cargo's
	# requirements but will not actually be used during compile time. Used by
	# dev-dependencies or crates like winapi.
	: "${CROS_RUST_EMPTY_CRATE:=}"

	# @ECLASS-VARIABLE: CROS_RUST_EMPTY_CRATE_FEATURES
	# @PRE_INHERIT
	# @DESCRIPTION:
	# Array of Cargo features emitted into the Cargo.toml of an empty crate. Allows
	# downstream crates to depend on this crate with the given features enabled.
	if [[ ! -v CROS_RUST_EMPTY_CRATE_FEATURES ]]; then
	CROS_RUST_EMPTY_CRATE_FEATURES=()
	fi

	# @ECLASS-VARIABLE: CROS_RUST_OVERFLOW_CHECKS
	# @PRE_INHERIT
	# @DESCRIPTION:
	# Enable integer overflow checks for this package. Packages that wish to
	# disable integer overflow checks should set this value to 0. Integer overflow
	# checks are always enabled when the cros-debug flag is set.
	: "${CROS_RUST_OVERFLOW_CHECKS:=1}"

	# @ECLASS-VARIABLE: CROS_RUST_REMOVE_DEV_DEPS
	# @PRE_INHERIT
	# @DESCRIPTION:
	# Removes all the dev-dependencies from the Cargo.toml. This can break circular
	# dependencies and help minimize how many dependent packages need to be added.
	: "${CROS_RUST_REMOVE_DEV_DEPS:=}"

	inherit toolchain-funcs cros-debug cros-sanitizers

	IUSE="asan fuzzer lsan +lto msan test tsan ubsan"
	REQUIRED_USE="?? ( asan lsan msan tsan )"

	EXPORT_FUNCTIONS src_unpack src_prepare src_configure src_install

	DEPEND="
	>=virtual/rust-1.28.0:=
	>=dev-util/cargo-0.29.0
	"

	ECARGO_HOME="${WORKDIR}/cargo_home"
	CROS_RUST_REGISTRY_DIR="/usr/lib/cros_rust_registry"

	# Ignore odr violations in unit tests in asan builds
	# (https://github.com/rust-lang/rust/issues/41807).
	ASAN_OPTIONS="detect_odr_violation=0"

	# @FUNCTION: cargo_src_unpack
	# @DESCRIPTION:
	# Unpacks the package
	cros-rust_src_unpack() {
	debug-print-function ${FUNCNAME} "$@"

	local archive
	for archive in ${A}; do
	case "${archive}" in
	*.crate)
	ebegin "Unpacking ${archive}"

	ln -s "${DISTDIR}/${archive}" "${archive}.tar"
	unpack "./${archive}.tar"
	rm "${archive}.tar"

	eend $?
	;;
	*)
	unpack "${archive}"
	;;
	esac
	done

	if [[ "${CROS_RUST_EMPTY_CRATE}" == "1" ]]; then
	# Generate an empty Cargo.toml and src/lib.rs for this crate.
	mkdir -p "${S}/src"
	cat <<- EOF >> "${S}/Cargo.toml"
	[package]
	name = "${PN}"
	version = "${PV}"
	authors = ["The Chromium OS Authors"]

	[features]
	EOF

	if [[ "$(declare -p CROS_RUST_EMPTY_CRATE_FEATURES 2> /dev/null)" != "declare -a"* ]]; then
	eerror "CROS_RUST_EMPTY_CRATE_FEATURES must be an array"
	die
	fi

	local feature
	for feature in "${CROS_RUST_EMPTY_CRATE_FEATURES[@]}"; do
	echo "${feature} = []" >> "${S}/Cargo.toml"
	done

	touch "${S}/src/lib.rs"
	fi

	# Set up the cargo config.
	mkdir -p "${ECARGO_HOME}"

	cat <<- EOF > "${ECARGO_HOME}/config"
	[source.chromeos]
	directory = "${SYSROOT}/${CROS_RUST_REGISTRY_DIR}"

	[source.crates-io]
	replace-with = "chromeos"
	local-registry = "/nonexistent"

	[target.${CHOST}]
	linker = "$(tc-getCC)"
	EOF

	# When the target environment is different from the host environment,
	# add a setting for the target environment.
	if tc-is-cross-compiler; then
	cat <<- EOF >> "${ECARGO_HOME}/config"

	[target.${CBUILD}]
	linker = "$(tc-getBUILD_CC)"
	EOF
	fi
	}

	# @FUNCTION: cros-rust_src_prepare
	# @DESCRIPTION:
	# Prepares the src. This function supports "# provided by ebuild" macro and
	# "# ignored by ebuild" macro for replacing and removing path dependencies
	# with ones provided by their ebuild in Cargo.toml
	# and Cargo.toml will be modified in place. If the macro is used in
	# ${S}/Cargo.toml, CROS_WORKON_OUTOFTREE_BUILD can't be set to 1 in its ebuild.
	cros-rust_src_prepare() {
	if grep -q "# provided by ebuild" "${S}/Cargo.toml"; then
	if [[ "${CROS_WORKON_OUTOFTREE_BUILD}" == 1 ]]; then
	die 'CROS_WORKON_OUTOFTREE_BUILD=1 must not be set when using' \
	'`provided by ebuild`'
	fi

	# Replace path dependencies with ones provided by their ebuild.
	#
	# For local developer builds, we want Cargo.toml to contain path
	# dependencies on sibling crates within the same repository or elsewhere
	# in the Chrome OS source tree. This enables developers to run `cargo
	# build` and have dependencies resolve correctly to their locally
	# checked out code.
	#
	# At the same time, some crates contained within the crosvm repository
	# have their own ebuild independent of the crosvm ebuild so that they
	# are usable from outside of crosvm. Ebuilds of downstream crates won't
	# be able to depend on these crates by path dependency because that
	# violates the build sandbox. We perform a sed replacement to eliminate
	# the path dependency during ebuild of the downstream crates.
	#
	# The sed command says: in any line containing `# provided by ebuild`,
	# please replace `path = "..."` with `version = "*"`. The intended usage
	# is like this:
	#
	# [dependencies]
	# data_model = { path = "../data_model" } # provided by ebuild
	#
	sed -i \
	'/# provided by ebuild$/ s/path = "[^"]"/version = ""/' \
	"${S}/Cargo.toml" \|\| die
	fi

	if grep -q "# ignored by ebuild" "${S}/Cargo.toml"; then
	if [[ "${CROS_WORKON_OUTOFTREE_BUILD}" == 1 ]]; then
	die 'CROS_WORKON_OUTOFTREE_BUILD=1 must not be set when using' \
	'`ignored by ebuild`'
	fi
	# Emerge ignores "out-of-sandbox" [patch.crates-io] lines in
	# Cargo.toml.
	sed -i \
	'/# ignored by ebuild/d' \
	"${S}/Cargo.toml" \|\| die
	fi

	# Remove lines that start with "[dev-dependencies." until a line is found that
	# starts with "[" but not "[dev-d".
	#
	# The sed script is of the form '/A/,/B/{/B/!d}'.
	# The first part '/A/,/B/' includes lines that match /A/ and following lines
	# until a line matches the second pattern /B/ inclusive. The last part,
	# {/B/!d} deletes included lines that don't match /B/.
	#
	# The first pattern /^\[dev-dependencies\./ is fairly easy to understand. it
	# matches any line that begins with "[dev-dependencies." The second pattern
	# would ideally be /^[/ which would match any line that starts with "[".
	# unfortunately that also matches the first pattern so the range would always
	# be one line. To avoid this problem the second pattern approximates a check
	# to make sure the first pattern isn't matched. It does so by testing to see
	# if the string that follows the "[" doesn't match "dev-d". This is
	# accomplished by matching strings that don't begin with "d", or begin with
	# "d" but don't begin with "de", or begin with "de" but don't begin with
	# "dev", ... or begin with "dev-" but don't begin with "dev-d".
	if [[ "${CROS_RUST_REMOVE_DEV_DEPS}" == 1 ]]; then
	local neg_pattern='/^\[($\|[^d]\|d($\|[^e]\|e($\|[^v]\|v($\|[^-]\|-($\|[^d])))))/'
	sed -i -E \
	"/^\\[dev-dependencies\\./,${neg_pattern}{${neg_pattern}!d}" \
	"${S}/Cargo.toml" \|\| die
	fi

	default
	}

	# @FUNCTION: cros-rust_src_configure
	# @DESCRIPTION:
	# Configures the source and exports any environment variables needed during the
	# build.
	cros-rust_src_configure() {
	sanitizers-setup-env

	export CARGO_TARGET_DIR="${WORKDIR}"
	export CARGO_HOME="${ECARGO_HOME}"
	export HOST="${CBUILD}"
	export HOST_CC="$(tc-getBUILD_CC)"
	# PKG_CONFIG_ALLOW_CROSS is required by pkg-config.
	# https://github.com/rust-lang/pkg-config-rs/issues/41.
	# Since cargo will overwrites $HOST with "" when building pkg-config, we
	# need to set it regardless of the value of tc-is-cross-compiler here.
	export PKG_CONFIG_ALLOW_CROSS=1
	export TARGET="${CHOST}"
	export TARGET_CC="$(tc-getCC)"

	# There is a memory leak in libbacktrace:
	# https://github.com/rust-lang/rust/issues/59125
	cros-rust_use_sanitizers \|\| export RUST_BACKTRACE=1

	# We want debug info even in release builds.
	local rustflags=(
	-Cdebuginfo=2
	-Copt-level=3
	)

	use lto && rustflags+=( -Clto )

	# We don't want to abort during tests.
	use test \|\| rustflags+=( -Cpanic=abort )

	if use cros-debug \|\| [[ "${CROS_RUST_OVERFLOW_CHECKS}" == "1" ]]; then
	rustflags+=( -Coverflow-checks=on )
	fi

	use cros-debug && rustflags+=( -Cdebug-assertions=on )

	use asan && rustflags+=( -Csanitizer=address )
	use lsan && rustflags+=( -Csanitizer=leak )
	use msan && rustflags+=( -Csanitizer=memory )
	use tsan && rustflags+=( -Csanitizer=thread )
	use ubsan && rustflags+=( -Clink-arg=-fsanitize=undefined )

	if use fuzzer; then
	rustflags+=(
	--cfg fuzzing
	-Cpasses=sancov
	-Cllvm-args=-sanitizer-coverage-level=4
	-Cllvm-args=-sanitizer-coverage-inline-8bit-counters
	-Cllvm-args=-sanitizer-coverage-trace-compares
	-Cllvm-args=-sanitizer-coverage-pc-table
	-Cllvm-args=-sanitizer-coverage-trace-divs
	-Cllvm-args=-sanitizer-coverage-trace-geps
	-Cllvm-args=-sanitizer-coverage-prune-blocks=0
	)
	fi

	export RUSTFLAGS="${rustflags[*]}"
	}

	# @FUNCTION: cros-rust_use_sanitizers
	# @DESCRIPTION:
	# Checks whether sanitizers are being used.
	cros-rust_use_sanitizers() {
	use_sanitizers \|\| use lsan
	}

	# @FUNCTION: ecargo
	# @USAGE: <args to cargo>
	# @DESCRIPTION:
	# Call cargo with the specified command line options.
	ecargo() {
	debug-print-function ${FUNCNAME} "$@"

	# The cargo developers have decided to make it as painful as possible to
	# use cargo inside another build system. So there is no way to tell
	# cargo to just not write this lock file. Instead we have to bend over
	# backwards to accommodate cargo.
	addwrite Cargo.lock
	rm -f Cargo.lock

	cargo -v "$@" \|\| die

	# Now remove any Cargo.lock files that cargo pointlessly created.
	rm -f Cargo.lock
	}

	# @FUNCTION: ecargo_build
	# @USAGE: <args to cargo build>
	# @DESCRIPTION:
	# Call `cargo build` with the specified command line options.
	ecargo_build() {
	ecargo build --target="${CHOST}" --release "$@"
	}

	# @FUNCTION: ecargo_build_fuzzer
	# @DESCRIPTION:
	# Call `cargo build` with fuzzing options enabled.
	ecargo_build_fuzzer() {
	local fuzzer_libdir="$(dirname "$($(tc-getCC) -print-libgcc-file-name)")"
	local fuzzer_arch="${ARCH}"
	if [[ "${ARCH}" == "amd64" ]]; then
	fuzzer_arch="x86_64"
	fi

	local link_args=(
	-Clink-arg="-L${fuzzer_libdir}"
	-Clink-arg="-lclang_rt.fuzzer-${fuzzer_arch}"
	-Clink-arg="-lc++"
	-Clink-arg="-Wl,-export-dynamic"
	)

	# The `rustc` subcommand for cargo allows us to set some extra flags for
	# the current package without setting them for all `rustc` invocations.
	# On the other hand the flags in the RUSTFLAGS environment variable are set
	# for all `rustc` invocations.
	ecargo rustc --target="${CHOST}" --release "$@" -- "${link_args[@]}"
	}

	# @FUNCTION: ecargo_test
	# @USAGE: <args to cargo test>
	# @DESCRIPTION:
	# Call `cargo test` with the specified command line options.
	ecargo_test() {
	ecargo test --target="${CHOST}" --target-dir "target/ecargo-test" --release "$@"
	}

	# @FUNCTION: cros-rust_publish
	# @USAGE: [crate name] [crate version]
	# @DESCRIPTION:
	# Publish a library crate to the local registry. Should only be called from
	# within a src_install() function.
	cros-rust_publish() {
	debug-print-function ${FUNCNAME} "$@"

	local name="${1:-${PN}}"
	local version="${2:-${PV}}"

	# Create the .crate file.
	ecargo package --allow-dirty --no-metadata --no-verify \|\| die

	# Unpack the crate we just created into the directory registry.
	local crate="${CARGO_TARGET_DIR}/package/${name}-${version}.crate"

	mkdir -p "${D}/${CROS_RUST_REGISTRY_DIR}"
	pushd "${D}/${CROS_RUST_REGISTRY_DIR}" > /dev/null
	tar xf "${crate}" \|\| die

	# Calculate the sha256sum since cargo will want this later.
	local shasum="$(sha256sum ${crate} \| cut -d ' ' -f 1)"
	local dir="${name}-${version}"
	local checksum="${T}/${name}-${version}-checksum.json"

	# Calculate the sha256 hashes of all the files in the crate.
	local files=( $(find "${dir}" -type f) )

	[[ "${#files[@]}" == "0" ]] && die "Could not find crate files for ${name}"

	# Now start filling out the checksum file.
	printf '{\n\t"package": "%s",\n\t"files": {\n' "${shasum}" > "${checksum}"
	local idx=0
	local f
	for f in "${files[@]}"; do
	shasum="$(sha256sum ${f} \| cut -d ' ' -f 1)"
	printf '\t\t"%s": "%s"' "${f#${dir}/}" "${shasum}" >> "${checksum}"

	# The json parser is unnecessarily strict about not allowing
	# commas on the last line so we have to track this ourselves.
	idx="$((idx+1))"
	if [[ "${idx}" == "${#files[@]}" ]]; then
	printf '\n' >> "${checksum}"
	else
	printf ',\n' >> "${checksum}"
	fi
	done
	printf "\t}\n}\n" >> "${checksum}"
	popd > /dev/null

	insinto "${CROS_RUST_REGISTRY_DIR}/${name}-${version}"
	newins "${checksum}" .cargo-checksum.json

	# We want the Cargo.toml.orig file to be world readable.
	fperms 0644 "${CROS_RUST_REGISTRY_DIR}/${name}-${version}/Cargo.toml.orig"
	}

	# @FUNCTION: cros-rust_get_build_dir
	# @DESCRIPTION:
	# Return the path to the directory where build artifacts are available.
	cros-rust_get_build_dir() {
	echo "${CARGO_TARGET_DIR}/${CHOST}/release"
	}

	cros-rust_src_install() {
	debug-print-function ${FUNCNAME} "$@"

	cros-rust_publish
	}

	# @FUNCTION: cros-rust_get_crate_version
	# @USAGE: <path to crate>
	# @DESCRIPTION:
	# Returns the version for a crate by finding the first 'version =' line in the
	# Cargo.toml in the crate.
	cros-rust_get_crate_version() {
	local crate="${1:-${S}}"
	[[ $# -gt 1 ]] && die "${FUNCNAME}: incorrect number of arguments"
	awk '/^version = / { print $3 }' "${crate}/Cargo.toml" \| head -n1 \| tr -d '"'
	}

	fi