Re: [PATCH] build: Check for cargo when building rust language

[Arthur Cohen <arthur.cohen@embecosm.com>]

Hi Rainer!

On 4/17/24 10:13, Rainer Orth wrote:
> Andrew Pinski <pinskia@gmail.com> writes:
> 
>> On Mon, Apr 8, 2024 at 9:39 AM <pierre-emmanuel.patry@embecosm.com> wrote:
>>>
>>> From: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>
>>>
>>> Hello,
>>>
>>> The rust frontend requires cargo to build some of it's components,
>>> it's presence was not checked during configuration.
>>
>> WHY did this go in right before the release of GCC 14?
>> I don't get why this is considered temporary and it goes in right
>> before a release.
>> That seems broken to me.
> 
> two more questions about this:
> 
> Right now, the new cargo configure test disable rust on all of my
> targets (Solaris, Linux, Darwin) which didn't have it installed.  Before
> (as recent as last Friday), I could successfully build and test
> crab1/rust on all of them without cargo in sight.  So I wonder if the
> patch isn't premature.

We already have components depending on Rust libraries in our 
development repository, so this patch is important to ensure errors are 
emitted early during the configure phase rather than later at build 
time. I don't think this is premature, considering that your targets 
would fail to build the Rust frontend next time we upstream commits, 
which should happen this week or early next week.

> Besides, while there are packaged versions of cargo for Solaris 11.4 and
> Linux, Darwin hasn't anything (not checked Homebrew or similar yet).
> What's worse, rustup only supports macOS 10.12 and up, while I'm still
> regularly testing 10.7 and 10.11.  I don't really feel like building
> rust from source here (if it works at all).  This hasn't been an issue
> for any other languages that require additional tools for bootstrapping
> (like Ada or D): there are versions of GNAT around that still support
> those old Darwin releases, and I could use the C++ version of GDC in GCC
> 11.

Sorry, I'm not too familiar with the Rust situation on macOS. I am 
reading that starting from Rust version 1.74, the minimum macOS version 
required is indeed 10.12, released in 2016 I believe?

We currently depend on Rust version 1.72, so you should be able to 
install it on macOS 10.11. Maybe with rustup? You can try something like 
the following:

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y 
--default-toolchain=1.72.0;

which is the default installation method for Rustup, with version 1.72 
of the language specified. I'm not able to test this, sorry, but I'm 
very interested in knowing if it works. I think you can also install 
Rust using Homebrew, but again I am not able to test this and apologize.

The goal is to reduce that Rust version further soon anyway - we are 
going to target Rust version 1.49, released 3 years ago, as that is the 
version that gccrs aims to compile. This will bring us closer to 
compiling our dependencies with our own frontend.

> At the very least, the Rust situation needs to be documented clearly.

I'd love to work on this - what sort of documentation do you have in 
mind? Do you mean something like the online GCC documentation or an 
in-tree file? Let me know what you'd like me to add and I'll be happy to 
do so.

> 
> 	Rainer
> 

Kindly,

Arthur