custom rust versions are not supported

[hgy59]

As discussed in #6123 (comment) it is not possible yet, to have a specific rust version (i.e. 1.77.2, 1.78, nightly, ...) for a specific cross package.

A solution is now required, since /cross/fd_8.7.0 fails to build for hi3535 arch with rust >= 1.79.

[th0ma7]

I don't believe this is the issue... The installer tries by default to install a newer version of the rust toolchain using the minimal version needed.... in this case version 1.81 so it looks for a 1.81.0-armv7l-unknown-linux-gnueabi. Such version no longer exists for armv7l since 1.77.2.

Interestingly I do have a locally compiled and accessible 1.82.0-armv7l-unknown-linux-gnueabi but it doesn't even try to use it.

The solution is probably to find a way to override this behavior to avoid the cargo call:

  ==> Cargo install rust package fd (rustc +1.81.0-armv7l-unknown-linux-gnueabi -vV)
error: toolchain '1.81.0-armv7l-unknown-linux-gnueabi' is not installable
```
So it enforces using the version already available along with using the rust armv7l build from #6364.

[hgy59]

I don't believe this is the issue... The installer tries by default to install a newer version of the rust toolchain using the minimal version needed.... in this case version 1.81 so it looks for a 1.81.0-armv7l-unknown-linux-gnueabi. Such version no longer exists for armv7l since 1.77.2.

But when I clean the syno-hi3535-6.2.4 toolchain and build a package for hi3535-6.2.4 it installs the toolchain and rustc is version 1.83.0

===>  Installing rustc toolchain for syno-hi3535
===>  - rustup installation PATH: /spksrc/distrib/rustup
===>  - cargo installation PATH: /spksrc/distrib/cargo
===>  - default PATH: /spksrc/distrib/cargo/bin:/scripts:/usr/local/bin:/usr/bin:/bin:/usr/games
===>  curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --no-modify-path
info: downloading installer
warning: it looks like you have an existing installation of Rust at:
warning: /spksrc/distrib/cargo/bin
warning: It is recommended that rustup be the primary Rust installation.
warning: Otherwise you may have confusion unless you are careful with your PATH
warning: If you are sure that you want both rustup and your already installed Rust
warning: then please reply `y' or `yes' or set RUSTUP_INIT_SKIP_PATH_CHECK to yes
warning: or pass `-y' to ignore all ignorable checks.
error: cannot install while Rust is installed
warning: continuing (because the -y flag is set and the error is ignorable)
error: $HOME differs from euid-obtained home directory: you may be using sudo
error: $HOME directory: /home
error: euid-obtained home directory: /home/user
info: profile set to 'default'
info: default host triple is x86_64-unknown-linux-gnu
warning: Updating existing toolchain, profile choice will be ignored
info: syncing channel updates for 'stable-x86_64-unknown-linux-gnu'
info: default toolchain set to 'stable-x86_64-unknown-linux-gnu'

  stable-x86_64-unknown-linux-gnu unchanged - rustc 1.83.0 (90b35a623 2024-11-26)


Rust is installed now. Great!

To get started you need Cargo's bin directory (/spksrc/distrib/cargo/bin) in
your PATH
environment variable. This has not been done automatically.

To configure your current shell, you need to source
the corresponding env file under /spksrc/distrib/cargo.

This is usually done by running one of the following (note the leading DOT):
. "/spksrc/distrib/cargo/env"            # For sh/bash/zsh/ash/dash/pdksh
source "/spksrc/distrib/cargo/env.fish"  # For fish
env make --no-print-directory rust_toml > /spksrc/toolchain/syno-hi3535-6.2.4/work/hi3535.toml 2>/dev/null;
===>  rustup toolchain install stable
info: syncing channel updates for 'stable-x86_64-unknown-linux-gnu'

  stable-x86_64-unknown-linux-gnu unchanged - rustc 1.83.0 (90b35a623 2024-11-26)

info: checking for self-update
===>  rustup default stable
info: using existing install for 'stable-x86_64-unknown-linux-gnu'
info: default toolchain set to 'stable-x86_64-unknown-linux-gnu'

  stable-x86_64-unknown-linux-gnu unchanged - rustc 1.83.0 (90b35a623 2024-11-26)

info: note that the toolchain 'stable-x86_64-unknown-linux-gnu' is currently in use (directory override for '/spksrc/toolchain/syno-hi3535-6.2.4')
===>  rustup target add armv7-unknown-linux-gnueabi
rustup override set stable
info: override toolchain for '/spksrc/toolchain/syno-hi3535-6.2.4' set to 'stable-x86_64-unknown-linux-gnu'
rustup target add armv7-unknown-linux-gnueabi
info: component 'rust-std' for target 'armv7-unknown-linux-gnueabi' is up to date
rustup show
Default host: x86_64-unknown-linux-gnu
rustup home:  /spksrc/distrib/rustup

installed toolchains
--------------------

stable-x86_64-unknown-linux-gnu (default)
1.77.2-x86_64-unknown-linux-gnu
1.82.0-powerpc-unknown-linux-gnuspe
1.54-x86_64-unknown-linux-gnu
1.63-x86_64-unknown-linux-gnu
1.64-x86_64-unknown-linux-gnu
qoriq
stage2-powerpc-unknown-linux-gnuspe

installed targets for active toolchain
--------------------------------------

aarch64-unknown-linux-gnu
armv5te-unknown-linux-gnueabi
armv7-unknown-linux-gnueabi
armv7-unknown-linux-gnueabihf
i686-unknown-linux-gnu
powerpc-unknown-linux-gnu
x86_64-unknown-linux-gnu

active toolchain
----------------

stable-x86_64-unknown-linux-gnu (directory override for '/spksrc/toolchain/syno-hi3535-6.2.4')
rustc 1.83.0 (90b35a623 2024-11-26)

And when building cross/bat for hi3535 is uses rustc 1.83.0 with --target armv7-unknown-linux-gnueabi:

===>  Extracting for bat
tar -xzpf /spksrc/cross/bat/../../distrib/bat-0.24.0.tar.gz -C /spksrc/cross/bat/work-hi3535-6.2.4
===>  Patching for bat
===>  Configuring for bat
===>  - Configure ARGS:
===>  - Install prefix: /usr/local/bat
===>  Compiling for bat
===>  Installing for bat
find /spksrc/cross/bat/work-hi3535-6.2.4/install//usr/local/bat/ \! -type d -printf '%P\n' | sed 's?^target/??g' | sort > /spksrc/cross/bat/work-hi3535-6.2.4/bat.plist.tmp
  ==> Cargo install rust package bat (rustc +stable -vV)
rustc 1.83.0 (90b35a623 2024-11-26)
binary: rustc
commit-hash: 90b35a6239c3d8bdabc530a6a0816f7ff89a0aaf
commit-date: 2024-11-26
host: x86_64-unknown-linux-gnu
release: 1.83.0
LLVM version: 19.1.1
cargo +stable install --path /spksrc/cross/bat/work-hi3535-6.2.4/bat-0.24.0 --root /spksrc/cross/bat/work-hi3535-6.2.4/install/usr/local/bat --target armv7-unknown-linux-gnueabi
  Installing bat v0.24.0 (/spksrc/cross/bat/work-hi3535-6.2.4/bat-0.24.0)
    Updating crates.io index

I think the mismatch is armv7l-unknown-linux-gnueabi vs. armv7-unknown-linux-gnueabi vs. armv7-unknown-linux-gnueabihf

IMHO we do need armv7l-*-gnueabi but armv7-*-gnueabi and the difference between ARMv7L and ARMv7 is gnueabi vs gnueabihf and not armv7l vs. armv7.

IMPORTANT NOTE:
ARMv7L does not mean armv7l.

All DSM 32bit arm archs have uname -m = armv7l (ARMv7_ARCHS and I guess ARMv7L_ARCHS too).

[th0ma7]

I think the mismatch is armv7l-unknown-linux-gnueabi vs. armv7-unknown-linux-gnueabi vs. armv7-unknown-linux-gnueabihf

Indeed, that could well be it... in spksrc.cross-rust-env.mk we have:

ifeq ($(findstring $(RUST_ARCH), $(ARMv7_ARCHS)),$(RUST_ARCH))
RUST_TARGET = armv7-unknown-linux-gnueabihf
endif
ifeq ($(findstring $(RUST_ARCH), $(ARMv7L_ARCHS)),$(RUST_ARCH))
RUST_TARGET = armv7-unknown-linux-gnueabi
endif

So from fd error, should hi3535 be using armv7-unknown-linux-gnueabi instead?

===>  Installing for fd
find /home/spksrc/rust-arm/spksrc/cross/fd_8.7.0/work-hi3535-6.2.4/install//usr/local/fd/ \! -type d -printf '%P\n' | sed 's?^target/??g' | sort > /home/spksrc/rust-arm/spksrc/cross/fd_8.7.0/work-hi3535-6.2.4/fd.plist.tmp
  ==> Cargo install rust package fd (rustc +1.81.0-armv7l-unknown-linux-gnueabi -vV)
error: toolchain '1.81.0-armv7l-unknown-linux-gnueabi' is not installable

IMHO we do need armv7l-*-gnueabi but armv7-*-gnueabi and the difference between ARMv7L and ARMv7 is gnueabi vs gnueabihf and not armv7l vs. armv7.

IMPORTANT NOTE: ARMv7L does not mean armv7l.

All DSM 32bit arm archs have uname -m = armv7l (ARMv7_ARCHS and I guess ARMv7L_ARCHS too).

EDIT: and armv7l-unknown-linux-gnueabi does not exists https://rust-lang.github.io/rustup-components-history/