[gentoo-dev] [PATCH] eclass/go-env.eclass: add helper to set compile env

[James Le Cuirot <chewi@gentoo.org>]

From: Thilo Fromm <thilo.alexander@gmail.com>

This change adds a helper function to explicitly set CC, CXX, and
GOARCH, and carrying over CFLAGS, LDFLAGS and friends to CGO
equivalents, to provide a minimal sane compile environment for Go.
It enables Go builds to play nice with crossdev's wrappers for
emerge/ebuild etc. Previously, Go ebuilds emitted binaries for the host
architecture.

For example, when running on an x86_64 host:
   emerge-aarch64-cross-linux-gnu foo
will now correctly emerge Go package "foo" for aarch64 instead of
x86_64.

The eclass provides a single helper function
    go-env_set_compile_environment()
intended to be called by other Go eclasses in an early build stage.
Ebuilds may also explicitly call this function.

Calls to this function from _src_prepare in go-module.eclass,
golang-vcs-snapshot.eclass, and golang-vcs.eclass have also been added
to un-break cross-compilation of existing Go packages.

Signed-off-by: Thilo Fromm <thilo.alexander@gmail.com>
Closes: https://github.com/gentoo/gentoo/pull/33539
Signed-off-by: James Le Cuirot <chewi@gentoo.org>
---
 eclass/go-env.eclass              | 48 +++++++++++++++++++++++++++++++
 eclass/go-module.eclass           |  5 +++-
 eclass/golang-vcs-snapshot.eclass |  5 +++-
 eclass/golang-vcs.eclass          |  5 +++-
 4 files changed, 60 insertions(+), 3 deletions(-)
 create mode 100644 eclass/go-env.eclass

See the GitHub link for earlier discussion. This still doesn't work for cross-prefix
builds, unless you set CGO_ENABLED=1, but fixing that involves different code and can
be done later.

diff --git a/eclass/go-env.eclass b/eclass/go-env.eclass
new file mode 100644
index 000000000000..0b4d44658a07
--- /dev/null
+++ b/eclass/go-env.eclass
@@ -0,0 +1,48 @@
+# Copyright 2023 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+# @ECLASS: go-env.eclass
+# @MAINTAINER:
+# Flatcar Maintainers <infra@flatcar.org>
+# @AUTHOR:
+# Flatcar Maintainers <infra@flatcar.org>
+# @BLURB: Helper eclass for setting the Go compile environment. Required for cross-compiling.
+# @DESCRIPTION:
+# This eclass includes a helper function for setting the compile environment for Go ebuilds.
+# Intended to be called by other Go eclasses in an early build stage, e.g. src_unpack.
+
+if [[ -z ${_GO_ENV_ECLASS} ]]; then
+_GO_ENV_ECLASS=1
+
+inherit toolchain-funcs
+
+# @FUNCTION: go-env_set_compile_environment
+# @DESCRIPTION:
+# Set up basic compile environment: CC, CXX, and GOARCH.
+# Also carry over CFLAGS, LDFLAGS and friends.
+# Required for cross-compiling with crossdev.
+# If not set, host defaults will be used and the resulting binaries are host arch.
+# (e.g. "emerge-aarch64-cross-linux-gnu foo" run on x86_64 will emerge "foo" for x86_64
+#  instead of aarch64)
+go-env_set_compile_environment() {
+	local arch=$(tc-arch "${CHOST}}")
+	case "${arch}" in
+		x86)	GOARCH="386" ;;
+		x64-*)	GOARCH="amd64" ;;
+		ppc64)  if [[ "$(tc-endian "${${CHOST}}")" = "big" ]] ; then
+					GOARCH="ppc64"
+				else
+					GOARCH="ppc64le"
+				fi ;;
+			*)	GOARCH="${arch}" ;;
+	esac
+
+	tc-export CC CXX
+	export GOARCH
+	export CGO_CFLAGS="${CGO_CFLAGS:-$CFLAGS}"
+	export CGO_CPPFLAGS="${CGO_CPPFLAGS:-$CPPFLAGS}"
+	export CGO_CXXFLAGS="${CGO_CXXFLAGS:-$CXXFLAGS}"
+	export CGO_LDFLAGS="${CGO_LDFLAGS:-$LDFLAGS}"
+}
+
+fi
diff --git a/eclass/go-module.eclass b/eclass/go-module.eclass
index 6c58d7f26f07..701d36e012e2 100644
--- a/eclass/go-module.eclass
+++ b/eclass/go-module.eclass
@@ -68,7 +68,7 @@ esac
 if [[ -z ${_GO_MODULE_ECLASS} ]]; then
 _GO_MODULE_ECLASS=1

-inherit multiprocessing toolchain-funcs
+inherit multiprocessing toolchain-funcs go-env

 if [[ ! ${GO_OPTIONAL} ]]; then
 	BDEPEND=">=dev-lang/go-1.18"
@@ -363,6 +363,7 @@ go-module_setup_proxy() {
 #    local go proxy.  This mode is deprecated.
 # 2. Otherwise, if EGO_VENDOR is set, bail out, as this functionality was removed.
 # 3. Otherwise, call 'ego mod verify' and then do a normal unpack.
+# Set compile env via go-env.
 go-module_src_unpack() {
 	if use amd64 || use arm || use arm64 ||
 		( use ppc64 && [[ $(tc-endian) == "little" ]] ) || use s390 || use x86; then
@@ -386,6 +387,8 @@ go-module_src_unpack() {
 			${nf} ego mod verify
 		fi
 	fi
+
+	go-env_set_compile_environment
 }

 # @FUNCTION: _go-module_src_unpack_gosum
diff --git a/eclass/golang-vcs-snapshot.eclass b/eclass/golang-vcs-snapshot.eclass
index 9c199bbbd8c5..d34b8a6e913d 100644
--- a/eclass/golang-vcs-snapshot.eclass
+++ b/eclass/golang-vcs-snapshot.eclass
@@ -52,7 +52,7 @@ esac
 if [[ -z ${_GOLANG_VCS_SNAPSHOT_ECLASS} ]]; then
 _GOLANG_VCS_SNAPSHOT_ECLASS=1

-inherit golang-base
+inherit golang-base go-env

 # @ECLASS_VARIABLE: EGO_VENDOR
 # @DESCRIPTION:
@@ -92,6 +92,7 @@ _golang-vcs-snapshot_dovendor() {
 # @FUNCTION: golang-vcs-snapshot_src_unpack
 # @DESCRIPTION:
 # Extract the first archive from ${A} to the appropriate location for GOPATH.
+# Set compile env via go-env.
 golang-vcs-snapshot_src_unpack() {
 	local lib vendor_path x
 	ego_pn_check
@@ -117,6 +118,8 @@ golang-vcs-snapshot_src_unpack() {
 			fi
 		done
 	fi
+
+	go-env_set_compile_environment
 }

 fi
diff --git a/eclass/golang-vcs.eclass b/eclass/golang-vcs.eclass
index 7558db4776cb..6f7a837bc15f 100644
--- a/eclass/golang-vcs.eclass
+++ b/eclass/golang-vcs.eclass
@@ -20,7 +20,7 @@ esac
 if [[ -z ${_GOLANG_VCS_ECLASS} ]]; then
 _GOLANG_VCS_ECLASS=1

-inherit estack golang-base
+inherit estack golang-base go-env

 PROPERTIES+=" live"

@@ -63,6 +63,7 @@ PROPERTIES+=" live"
 # @INTERNAL
 # @DESCRIPTION:
 # Create EGO_STORE_DIR if necessary.
+# Set compile env via go-env.
 _golang-vcs_env_setup() {
 	debug-print-function ${FUNCNAME} "$@"

@@ -84,6 +85,8 @@ _golang-vcs_env_setup() {
 	mkdir -p "${WORKDIR}/${P}/src" ||
 		die "${ECLASS}: unable to create ${WORKDIR}/${P}"
 	return 0
+
+	go-env_set_compile_environment
 }

 # @FUNCTION: _golang-vcs_fetch
--
2.41.0