Re: [gentoo-dev] [PATCH] meson.eclass: implement basic cross-compiler support

[Michał Górny]

On pon, 2017-05-29 at 16:58 -0400, Mike Gilbert wrote:
> ---
>  eclass/meson.eclass | 74 +++++++++++++++++++++++++++++++++++++++++------------
>  1 file changed, 57 insertions(+), 17 deletions(-)
>
> diff --git a/eclass/meson.eclass b/eclass/meson.eclass
> index 758e4180ba7a..0fdb1d848973 100644
> --- a/eclass/meson.eclass
> +++ b/eclass/meson.eclass
> @@ -39,8 +39,7 @@ esac
>
>  if [[ -z ${_MESON_ECLASS} ]]; then
>
> -# FIXME: We will need to inherit toolchain-funcs as well to support crossdev.
> -inherit ninja-utils
> +inherit ninja-utils toolchain-funcs
>
>  fi
>
> @@ -71,17 +70,52 @@ DEPEND=">=dev-util/meson-0.39.1
>  # Optional meson arguments as Bash array; this should be defined before
>  # calling meson_src_configure.
>
> -# Create a cross file for meson
> -# fixme: This function should write a cross file as described at the
> -# following url.
> -# http://mesonbuild.com/Cross-compilation.html
> -# _meson_create_cross_file() {
> -#	touch "${T}"/meson.crossfile
> -# }
> +# @FUNCTION: _meson_create_cross_file
> +# @INTERNAL
> +# @DESCRIPTION:
> +# Creates a cross file. meson uses this to define settings for
> +# cross-compilers. This function is called from meson_src_configure.
> +_meson_create_cross_file() {
> +	# Reference: http://mesonbuild.com/Cross-compilation.html
> +
> +	# system roughly corresponds to uname -s (lowercase)
> +	local system=unknown
> +	case ${CHOST} in
> +		*-aix*)     system=aix ;;
> +		*-cygwin*)  system=cygwin ;;
> +		*-darwin*)  system=darwin ;;
> +		*-freebsd*) system=freebsd ;;
> +		*-linux*)   system=linux ;;
> +		*-solaris*) system=sunos ;;

Don't you want to die on unknown system? Or is it likely to work anyway?

> +	esac
> +
> +	local cpu_family=$(tc-arch)
> +	case ${cpu_family} in
> +		amd64) cpu_family=x86_64 ;;
> +		arm64) cpu_family=aarch64 ;;

That's purely mapping from known-wrong values, correct? Maybe it'd be
reasonable to assert for all correct too, and fail on unknown?

> +	esac
> +
> +	# This may require adjustment based on CFLAGS
> +	local cpu=${CHOST%%-*}
> +
> +	cat > "${T}/meson.${CHOST}" <<-EOF
> +	[binaries]
> +	ar = '${AR}'
> +	c = '${CC}'
> +	cpp = '${CXX}'
> +	strip = '${STRIP}'
> +
> +	[host_machine]
> +	system = '${system}'
> +	cpu_family = '${cpu_family}'
> +	cpu = '${cpu}'
> +	endian = '$(tc-endian)'
> +	EOF
> +}
>
>  # @FUNCTION: meson_src_configure
>  # @DESCRIPTION:
> -# This is the meson_src_configure function
> +# This is the meson_src_configure function.
>  meson_src_configure() {
>  	debug-print-function ${FUNCNAME} "$@"
>
> @@ -94,13 +128,19 @@ meson_src_configure() {
>  		--sysconfdir "${EPREFIX}/etc"
>  		)
>
> -# fixme: uncomment this for crossdev support
> -#	if tc-is-cross-compiler; then
> -#		_meson_create_cross_file || die "unable to write meson cross file"
> -#		mesonargs+=(
> -#			--cross-file "${T}"/meson.crossfile
> -#		)
> -#	fi
> +	# Both meson(1) and _meson_create_cross_file need these
> +	tc-export AR CC CXX STRIP

Wouldn't it be reasonable to make them local first anyway? I would try
to avoid polluting the environment.

> +
> +	if tc-is-cross-compiler; then
> +		_meson_create_cross_file || die "unable to write meson cross file"
> +		mesonargs+=(
> +			--cross-file "${T}"/meson.${CHOST}
> +		)
> +		# In cross mode, meson uses CC/CXX as the "build" compilers
> +		local -x AR=$(tc-getBUILD_AR)
> +		local -x CC=$(tc-getBUILD_CC)
> +		local -x CXX=$(tc-getBUILD_CXX)
> +	fi
>
>  	# Append additional arguments from ebuild
>  	mesonargs+=("${emesonargs[@]}")

-- 
Best regards,
Michał Górny