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

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

[Mike Gilbert]

---
 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 ${CHOST} in
+		*-aix*)     system=aix ;;
+		*-cygwin*)  system=cygwin ;;
+		*-darwin*)  system=darwin ;;
+		*-freebsd*) system=freebsd ;;
+		*-linux*)   system=linux ;;
+		*-solaris*) system=sunos ;;
+	esac
+
+	local cpu_family=$(tc-arch)
+	case ${cpu_family} in
+		amd64) cpu_family=x86_64 ;;
+		arm64) cpu_family=aarch64 ;;
+	esac
+
+	# This may require adjustment based on CFLAGS
+	local cpu=${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 "${T}"/meson.crossfile
-#		)
-#	fi
+	# Both meson(1) and _meson_create_cross_file need these
+	tc-export AR CC CXX STRIP
+
+	if tc-is-cross-compiler; then
+		_meson_create_cross_file || die "unable to write meson cross file"
+		mesonargs+=(
+			--cross-file "${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[@]}")
-- 
2.13.0

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

[Michał Górny]

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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

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

[Mike Gilbert]

On Mon, May 29, 2017 at 5:06 PM, Michał Górny <mgorny@gentoo.org> wrote:
> On pon, 2017-05-29 at 16:58 -0400, Mike Gilbert wrote:
>> +     # 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?

Good question.

The 'system' property controls some built-in logic in meson itself
(mainly for MS Windows), and may be referenced by project files as
'host_machine.system()'. Setting it to 'unknown' may cause failures
for projects that actually look at it.

However, I think most projects would work without having this set to a
known value.

>> +     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?

Yes, it corrects two obvious deviations from uname -m on Linux. x86 is
ok since that is what meson expects/generates for i?86.

I'm not sure what you mean by "assert for all correct"; if you mean
check for all valid values for cpu_family, such a list does not exist.

Similar to 'system' this property may or may not be used depending on
the project. Defaulting to "unknown" should be fine in many cases. I
don't think we need to fail.

>> +     # 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.

Makes sense. I'll revise this to "local -x CC=$(tc-getCC)", etc.

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

[Mike Gilbert]

This has been pushed.