Re: [Buildroot] [PATCH v3 3/3] package/go: use host compiler when go-bootstrap unsupported

[Thomas Petazzoni via buildroot <buildroot@buildroot.org>]

Hello Christian,

On Tue, 14 Feb 2023 23:32:56 -0800
Christian Stewart via buildroot <buildroot@buildroot.org> wrote:

> The process for "bootstrapping" the Go compiler in Buildroot is:
> 
> 1. Compile a C/C++ cross-compiler (gcc) as the host toolchain.

I find "host toolchain" confusing here. I generally understand "host
toolchain" as "native toolchain".

> diff --git a/package/go/go.mk b/package/go/go.mk
> index 4db703a301..68f6d9e36b 100644
> --- a/package/go/go.mk
> +++ b/package/go/go.mk
> @@ -12,7 +12,6 @@ GO_LICENSE = BSD-3-Clause
>  GO_LICENSE_FILES = LICENSE
>  GO_CPE_ID_VENDOR = golang
>  
> -HOST_GO_DEPENDENCIES = host-go-bootstrap-stage2
>  HOST_GO_GOPATH = $(HOST_DIR)/share/go-path
>  HOST_GO_HOST_CACHE = $(HOST_DIR)/share/host-go-cache
>  HOST_GO_ROOT = $(HOST_DIR)/lib/go
> @@ -109,6 +108,11 @@ else # !BR2_PACKAGE_HOST_GO_TARGET_ARCH_SUPPORTS
>  HOST_GO_CGO_ENABLED = 1
>  endif # BR2_PACKAGE_HOST_GO_TARGET_ARCH_SUPPORTS
>  
> +ifeq ($(HOST_GO_CGO_ENABLED),1)
> +# For cgo support the toolchain needs to be available.
> +HOST_GO_DEPENDENCIES += toolchain
> +endif

Why is this added as part of this commit? It seems completely
unrelated. And in fact, shouldn't this be the correct thing to do
instead of what PATCH 1/3 is doing with the toolchain dependency added
on host-go-bootstrap-stage2 ?

> diff --git a/support/dependencies/dependencies.sh b/support/dependencies/dependencies.sh
> index 4353e9585e..943c7d0daf 100755
> --- a/support/dependencies/dependencies.sh
> +++ b/support/dependencies/dependencies.sh
> @@ -217,6 +217,10 @@ if grep -q ^BR2_NEEDS_HOST_UTF8_LOCALE=y $BR2_CONFIG ; then
>  	fi
>  fi
>  
> +if grep -q ^BR2_NEEDS_HOST_GO=y $BR2_CONFIG ; then
> +	check_prog_host "go"
> +fi

I think this is missing a version check on go: you need at least go
1.17.x to be able to build a go >= 1.20. The check as written here does
not check the go version.

Also, I am wondering if we couldn't improve things a bit and use an
already installed (and sufficiently recent) Go compiler to save on
building host-go-bootstrap-stage{1,2} even on architectures where the
full bootstrap build is supported.

We would have the following cases:

 - Architecture supported by bootstrap-stage{1,2}

   - If system-provided Go is available and recent enough => use it and skip bootstrap
   - If not, do bootstrapping

 - Architecture not supported by bootstrap-stage{1,2}

   - If system-provided Go is available and recent enough => use it
   - If not, should not happen due to check

It is of course not mandatory to implement this right now. It would be
a nice to have, but not a must have for sure.

Best regards,

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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