[v9,1/8] rustc: new virtual package

The compiler for the Rust programming language is called rustc.

There is only one reference implementation for it, based on LLVM, from
the Rust project [1]. It can generate code for various architectures so
it can be labeled as a cross-compiler. But, as for GCC, building it
from source takes time.

So it would be sensible to have at least one package which provides it
as a pre-built version, fetched from the upstream project. Later another
package can be added, to build it from source code.

In addition to the compiler, the standard library for the host and/or
the target should also be fetched/built.

So, add a virtual package named rustc to enable support for multiple
providers.

Currently, only the host variant will be available to allow the user to
cross-compile Rust programs for the target.

[1] http://rust-lang.org

Signed-off-by: Eric Le Bihan <eric.le.bihan.dev@free.fr>
---
 package/Config.in.host       |  1 +
 package/rustc/Config.in.host | 17 +++++++++++++++++
 package/rustc/rustc.mk       | 31 +++++++++++++++++++++++++++++++
 3 files changed, 49 insertions(+)
 create mode 100644 package/rustc/Config.in.host
 create mode 100644 package/rustc/rustc.mk

Hello,

On Thu, 28 Dec 2017 16:51:39 +0100, Eric Le Bihan wrote:

> diff --git a/package/rustc/Config.in.host b/package/rustc/Config.in.host
> new file mode 100644
> index 0000000000..16c95fa0b4
> --- /dev/null
> +++ b/package/rustc/Config.in.host
> @@ -0,0 +1,17 @@
> +config BR2_PACKAGE_HOST_RUSTC_ARCH_SUPPORTS
> +	bool
> +	default y
> +	depends on BR2_HOSTARCH = "x86_64" || BR2_HOSTARCH = "x86"
> +	depends on BR2_i386 || BR2_x86_64 \
> +		|| BR2_arm  || BR2_aarch64 \
> +		|| BR2_powerpc  || BR2_powerpc64 \
> +		|| BR2_mips || BR2_mipsel || BR2_mips64 || BR2_mips64el

This would be more readable as:

	default y if BR2_aarch64
	default y if BR2_arm && !BR2_ARM_CPU_ARMV4 && !BR2_ARM_CPU_ARMV5
	default y if BR2_i386
	default y if ...
	default y if BR2_mips || BR2_mipsel
	default y if (BR2_mips64 || BR2_mips64el) && BR2_MIPS_NABI64
	default y if BR2_x86_64

> +	depends on !BR2_ARM_CPU_ARMV4 && !BR2_ARM_CPU_ARMV5
> +	depends on !BR2_MIPS_NABI32
> +	depends on BR2_TOOLCHAIN_USES_GLIBC

Since it's weird for a host package to have a target architecture
dependency and target C library dependency, it would be good to have a
comment that explains this. I assume it's because of the Rust standard
library, so something like:

	# The pre-built Rust standard library is only available for the
	# following architectures/ABIs, and is built against glibc.

> diff --git a/package/rustc/rustc.mk b/package/rustc/rustc.mk
> new file mode 100644
> index 0000000000..4163a44bc1
> --- /dev/null
> +++ b/package/rustc/rustc.mk
> @@ -0,0 +1,31 @@
> +################################################################################
> +#
> +# rustc
> +#
> +################################################################################
> +
> +RUST_ARCH := $(call qstrip,$(BR2_ARCH))
> +
> +ifeq ($(BR2_ARM_CPU_ARMV7A),y)
> +RUST_ARCH := armv7
> +endif
> +
> +ifeq ($(BR2_ARM_EABI),y)
> +RUST_ABI := eabi
> +else ifeq ($(BR2_ARM_EABIHF),y)
> +RUST_ABI := eabihf
> +else ifeq ($(BR2_mips64)$(BR2_mips64el),y)
> +RUST_ABI := abi64
> +endif

Perhaps this could be defined in the Config.in file as well ?

config BR2_PACKAGE_HOST_RUSTC_ARCH
	string
	default "armv7" 	if BR2_ARM_CPU_ARMV7A
	default BR2_ARCH 	if !BR2_ARM_CPU_ARMV7A

config BR2_PACKAGE_HOST_RUSTC_ABI
	string
	default "eabi" 		if BR2_ARM_EABI
	default "eabihf" 	if BR2_ARM_EABIHF
	default "abi64" 	if BR2_MIPS_NABI64

> +RUST_TARGET_NAME := $(RUST_ARCH)-unknown-linux-gnu$(RUST_ABI)

Why are you using := in this file instead of = ?

Best regards,

Thomas

Hi!

On 17-12-28 17:27:49, Thomas Petazzoni wrote:
> Hello,
>
> On Thu, 28 Dec 2017 16:51:39 +0100, Eric Le Bihan wrote:
>
> > diff --git a/package/rustc/Config.in.host b/package/rustc/Config.in.host
> > new file mode 100644
> > index 0000000000..16c95fa0b4
> > --- /dev/null
> > +++ b/package/rustc/Config.in.host
> > @@ -0,0 +1,17 @@
> > +config BR2_PACKAGE_HOST_RUSTC_ARCH_SUPPORTS
> > +	bool
> > +	default y
> > +	depends on BR2_HOSTARCH = "x86_64" || BR2_HOSTARCH = "x86"
> > +	depends on BR2_i386 || BR2_x86_64 \
> > +		|| BR2_arm  || BR2_aarch64 \
> > +		|| BR2_powerpc  || BR2_powerpc64 \
> > +		|| BR2_mips || BR2_mipsel || BR2_mips64 || BR2_mips64el
>
> This would be more readable as:
>
> 	default y if BR2_aarch64
> 	default y if BR2_arm && !BR2_ARM_CPU_ARMV4 && !BR2_ARM_CPU_ARMV5
> 	default y if BR2_i386
> 	default y if ...
> 	default y if BR2_mips || BR2_mipsel
> 	default y if (BR2_mips64 || BR2_mips64el) && BR2_MIPS_NABI64
> 	default y if BR2_x86_64
>

OK.

> > +	depends on !BR2_ARM_CPU_ARMV4 && !BR2_ARM_CPU_ARMV5
> > +	depends on !BR2_MIPS_NABI32
> > +	depends on BR2_TOOLCHAIN_USES_GLIBC
>
> Since it's weird for a host package to have a target architecture
> dependency and target C library dependency, it would be good to have a
> comment that explains this. I assume it's because of the Rust standard
> library, so something like:
>
> 	# The pre-built Rust standard library is only available for the
> 	# following architectures/ABIs, and is built against glibc.

OK.

> > diff --git a/package/rustc/rustc.mk b/package/rustc/rustc.mk
> > new file mode 100644
> > index 0000000000..4163a44bc1
> > --- /dev/null
> > +++ b/package/rustc/rustc.mk
> > @@ -0,0 +1,31 @@
> > +################################################################################
> > +#
> > +# rustc
> > +#
> > +################################################################################
> > +
> > +RUST_ARCH := $(call qstrip,$(BR2_ARCH))
> > +
> > +ifeq ($(BR2_ARM_CPU_ARMV7A),y)
> > +RUST_ARCH := armv7
> > +endif
> > +
> > +ifeq ($(BR2_ARM_EABI),y)
> > +RUST_ABI := eabi
> > +else ifeq ($(BR2_ARM_EABIHF),y)
> > +RUST_ABI := eabihf
> > +else ifeq ($(BR2_mips64)$(BR2_mips64el),y)
> > +RUST_ABI := abi64
> > +endif
>
> Perhaps this could be defined in the Config.in file as well ?
>
> config BR2_PACKAGE_HOST_RUSTC_ARCH
> 	string
> 	default "armv7" 	if BR2_ARM_CPU_ARMV7A
> 	default BR2_ARCH 	if !BR2_ARM_CPU_ARMV7A
>
> config BR2_PACKAGE_HOST_RUSTC_ABI
> 	string
> 	default "eabi" 		if BR2_ARM_EABI
> 	default "eabihf" 	if BR2_ARM_EABIHF
> 	default "abi64" 	if BR2_MIPS_NABI64

OK.

> > +RUST_TARGET_NAME := $(RUST_ARCH)-unknown-linux-gnu$(RUST_ABI)
>
> Why are you using := in this file instead of = ?

A long time ago, I ran into an error about $(RUST_TARGET_NAME) not being
defined, hence the simply expanded variable. I'll check this again.

Regards,

--
ELB