coreos-go-utils: new eclass for Go related utilities

This eclass adopts parts of coreos-go.eclass and the dev-lang/go
ebuilds, providing functionality useful to both types of builds.

sdk_container/src/third_party/coreos-overlay/app-emulation/containerd/containerd-0.2.3.ebuild

@@ -32,7 +32,7 @@ RDEPEND="app-emulation/runc
 S=${WORKDIR}/${P}/src/${EGO_PN}
 
 src_compile() {
-	export GOARCH=$(go_get_arch)
+	export GOARCH=$(go_arch)
 	export CGO_ENABLED=1
 	export CC=$(tc-getCC)
 	export CXX=$(tc-getCXX)

sdk_container/src/third_party/coreos-overlay/app-emulation/runc/runc-1.0.0_rc1_p20160615-r1.ebuild

@@ -34,7 +34,7 @@ src_prepare() {
 
 src_compile() {
 	# fix up cross-compiling variables
-	export GOARCH=$(go_get_arch)
+	export GOARCH=$(go_arch)
 	export CGO_ENABLED=1
 	export CC=$(tc-getCC)
 	export CXX=$(tc-getCXX)

sdk_container/src/third_party/coreos-overlay/eclass/coreos-go-utils.eclass

@@ -0,0 +1,116 @@
+# Copyright 2016 CoreOS, Inc.
+# Distributed under the terms of the GNU General Public License v2
+# $Header: $
+
+# @ECLASS: coreos-go-utils.eclass
+# @BLURB: Utility functions for Go
+# @DESCRIPTION:
+# A utility eclass for functions needed when building both Go itself
+# and packages that depend on it. It does not set any metadata.
+
+case "${EAPI:-0}" in
+	5|6) ;;
+	*) die "Unsupported EAPI=${EAPI} for ${ECLASS}"
+esac
+
+inherit flag-o-matic toolchain-funcs
+
+# @FUNCTION: go_arch
+# @USAGE: [chost]
+# @DESCRIPTION:
+# export GOARCH=$(go_arch $CHOST)
+go_arch() {
+	# By chance most portage arch names match Go
+	local portage_arch=$(tc-arch "${1:-${CHOST}}")
+	local endian=$(tc-endian "${1:-${CHOST}}")
+	case "${portage_arch}" in
+		x86)	echo 386;;
+		x64-*)	echo amd64;;
+		ppc64)
+			[[ "${endian}" = big ]] && echo ppc64 || echo ppc64le ;;
+		*)	echo "${portage_arch}";;
+	esac
+}
+
+# @FUNCTION: go_arm
+# @USAGE: [chost]
+# @DESCRIPTION:
+# export GOARM=$(go_arm $CHOST)
+go_arm() {
+	case "${1:-${CHOST}}" in
+		armv5*)	echo 5;;
+		armv6*)	echo 6;;
+		armv7*)	echo 7;;
+		*)
+			die "unknown GOARM for ${1:-${CHOST}}"
+			;;
+	esac
+}
+
+# @FUNCTION: go_os
+# @USAGE: [chost]
+# @DESCRIPTION:
+# export GOOS=$(go_os $CHOST)
+go_os() {
+	case "${1:-${CHOST}}" in
+		*-linux*)	echo linux;;
+		*-darwin*)	echo darwin;;
+		*-freebsd*)	echo freebsd;;
+		*-netbsd*)	echo netbsd;;
+		*-openbsd*)	echo openbsd;;
+		*-solaris*)	echo solaris;;
+		*-cygwin*|*-interix*|*-winnt*)
+			echo windows
+			;;
+		*)
+			die "unknown GOOS for ${1:-${CHOST}}"
+			;;
+	esac
+}
+
+# @FUNCTION: go_export
+# @USAGE: [chost]
+# @DESCRIPTION:
+# Export GOARCH, GOOS, GOARM, CC, CXX, and CGO_* environment variables.
+go_export() {
+	export GOARCH=$(go_arch "$@")
+	export GOOS=$(go_os "$@")
+	if [[ "${GOARCH}" == "arm" ]]; then
+		export GOARM=$(go_arm "$@")
+	fi
+
+	# Go's 6l linker does not support PIE, disable so cgo binaries
+	# which use 6l+gcc for linking can be built correctly.
+	if gcc-specs-pie; then
+		append-ldflags -nopie
+	fi
+
+	export CC=$(tc-getCC)
+	export CXX=$(tc-getCXX)
+	export CGO_ENABLED=${CGO_ENABLED:-1}
+	export CGO_CFLAGS="${CFLAGS}"
+	export CGO_CPPFLAGS="${CPPFLAGS}"
+	export CGO_CXXFLAGS="${CXXFLAGS}"
+	export CGO_LDFLAGS="${LDFLAGS}"
+}
+
+# @FUNCTION: go_tuple
+# @USAGE: [chost]
+# @DESCRIPTION:
+# The uniqe string defining a Go target, as used in directory names.
+# e.g. linux_amd64 for x86_64-pc-linux-gnu
+go_tuple()
+{
+	echo "$(go_os $@)_$(go_arch $@)"
+}
+
+# @FUNCTION: go_cross_compile
+# @USAGE: [chost]
+# @DESCRIPTION:
+# Check if Go consideres compiling for $CHOST as cross-compilation.
+# Since Go's target tuples are smaller than GCC's Go may not consider
+# itself as a cross-compiler even if the GCC it is using for cgo is.
+go_cross_compile()
+{
+	[[ $(go_tuple ${CBUILD:-${CHOST}}) != $(go_tuple $@) ]]
+}

sdk_container/src/third_party/coreos-overlay/eclass/coreos-go.eclass

@@ -9,26 +9,15 @@
 # @DESCRIPTION:
 # Name of the Go package unpacked to ${S}, this is required.
 
-[[ ${EAPI} != "5" ]] && die "${ECLASS}: Only EAPI=5 is supported"
+case "${EAPI:-0}" in
+	5|6) ;;
+	*) die "Unsupported EAPI=${EAPI} for ${ECLASS}"
+esac
 
-inherit flag-o-matic multiprocessing toolchain-funcs
+inherit coreos-go-utils multiprocessing
 
 DEPEND="dev-lang/go:="
 
-# @FUNCTION: go_get_arch
-# @USAGE: export GOARCH=$(go_get_arch)
-go_get_arch() {
-	# By chance most portage arch names match Go
-	local portage_arch=$(tc-arch ${CHOST})
-	case "${portage_arch}" in
-		x86)	echo 386;;
-		x64-*)	echo amd64;;
-		ppc64)
-			[[ "$(tc-endian)" = big ]] && echo ppc64 || echo ppc64le ;;
-		*)	echo "${portage_arch}";;
-	esac
-}
-
 # @FUNCTION: go_build
 # @USAGE: <package-name> [<binary-name>]
 go_build() {
@@ -55,7 +44,7 @@ go_build() {
 coreos-go_src_prepare() {
 	debug-print-function ${FUNCNAME} "$@"
 
-	export GOARCH=$(go_get_arch)
+	go_export
 	export GOPATH="${WORKDIR}/gopath"
 	export GOBIN="${GOPATH}/bin"
 
@@ -68,19 +57,6 @@ coreos-go_src_prepare() {
 	local package_path="${GOPATH}/src/${COREOS_GO_PACKAGE}"
 	mkdir -p "${package_path%/*}" || die "${ECLASS}: bad path: ${package_path%/*}"
 	ln -sT "${S}" "${package_path}" || die "${ECLASS}: bad path: ${S}"
-
-	# Go's 6l linker does not support PIE, disable so cgo binaries
-	# which use 6l+gcc for linking can be built correctly.
-	if gcc-specs-pie; then
-		append-ldflags -nopie
-	fi
-
-	export CC=$(tc-getCC)
-	export CGO_ENABLED=${CGO_ENABLED:-1}
-	export CGO_CFLAGS="${CFLAGS}"
-	export CGO_CPPFLAGS="${CPPFLAGS}"
-	export CGO_CXXFLAGS="${CXXFLAGS}"
-	export CGO_LDFLAGS="${LDFLAGS}"
 }
 
 coreos-go_src_compile() {