I think you should reconsider the actual problem, if you do not understand it.

The fact that rustc is backwards compatible is great, sure. But it does not solve the problem of distributors.

Say you have libfoo-1.0 that uses rust and cargo 1.2 . A distributor that now releases their linux version and wants to ship libfoo-1.0 must consider the requirements for supporting it. This support usually outlives the upstream support.

If libfoo-1.0 uses C, for instance, it is highly likely that a distributor can backport any security-relevant changes from libfoo-1.1, 1.2, and later into 1.0.

In the case of rust there are two uncertainties creeping in: One is the highly dynamic nature of cargo dependencies. libfoo might depend on a myriad of crates transitively and rust simply is too young to provide any experience in how long they will be available or supported. And no, it is generally not a good idea to update to new feature releases for security updates. This is something that stable distributions explicitly try to avoid.

So our distributor now must consider if changes in libfoo-1.2 pulled in changes via cargo that cannot be easily backported because they are feature releases or have a dependency on a newer version of rust.

The second problem is the compiler itself. Any change in libfoo-1.2 might require a newer version of rust. It is great that they want to be backwards compatible but now our distributor must consider upgrading a substantial piece of software during the support period (and testing the backwards compatibility, of course) just to backport a security fix.

Please don't get me wrong, I really like rust and I think these problems can be solved. But I also like stable software and all these languages with their package repositories seem to simply ignore everything that's older than one or two years. If rust wants to become a new C, which I would very much like, it needs to demonstrate a certain stability.

I think you are missing the fact that the solutions are already in place for all of this.

> One is the highly dynamic nature of cargo dependencies. libfoo might depend on a myriad of crates transitively and rust simply is too young to provide any experience in how long they will be available or supported. And no, it is generally not a good idea to update to new feature releases for security updates. This is something that stable distributions explicitly try to avoid.

crates.io is designed so that dependencies put up on it remain available forever, and that the only other cargo related dependencies also have to be hosted on crates.io - solving the availability problem.

Of course if you're trying to backport a security fix to an old version of a transitive dependency that (like the non-transitive dependency) is no longer supported, you do have to make that backport. Once you make that backport it's easy to update the version of the transitive dependency with a [patch] section in the top level Cargo.toml.

> The second problem is the compiler itself. Any change in libfoo-1.2 might require a newer version of rust.

This is already mitigated in multiple ways. As discussed before, people do make sure to support old versions of compilers, you don't need to have a compiler on your target platform anyways. But moreover, the amount new language features make backporting difficult is dwarfed by the amount that internal library changes do.

What I don't really like in cargo is its' overcentralized and author-centric approach. What if some of your dependencies relies on the crate, which author doesn't support anymore and doesn't even accept patches? You will basically have to maintain a fork either with a different name (because you can't push it to crates.io) or have a patched version which you also can't push and have to manually update every Cargo.toml of every dependency in your project to use your fork. And what if you have not only one Rust project in your complex system? You will have to update or vendor everything. This is a real maintenance hell.

While in C/C++ I can just build a fork as dynamic library and put it to the system image or to the own package manager repo.

I mean for sure Cargo is great for small hobby projects, but for the big complicated enterprise projects it's not really suitable. Even Google doesn't use Cargo in Fuchsia and vendors everything.

I'm not entirely thrilled with the cargo solutions here, but when I compare them to the options in other languages I think they're adequate.

If you're making a small change, you use a [patch] section in the Cargo.toml for your workspace if you're using one, or the Cargo.toml for your binary/.so/.a if you're not, and it will cause your entire dependency tree to use your forked library. You don't need to fork the entire ecosystem as you suggest.

The [patch] works at the "workspace" level (and you generally should stick your entire complex system under one workspace), so if you use that feature properly for your "complex system" (keeping everything under one workspace), it is a one line change to replace the dependency for your entire system. If you use multiple, well, one per workspace that produces a binary/.so/.a.

Also, for big enterprise projects, I would assume you would use a private registry in the first place, which is apparently well supported (though I haven't used it). That's how the enterprise places I work at have dealt with python dependencies for instance (I haven't used rust in a enterprise).

I can sort of understand people trying to maintain LTS linux distros complaining that for their purposes this is a bit of a pain compared to C style shared libraries (because they need to modify a lot of rust workspaces)... but to be honest I think that's a question of their package management tooling not rust's. Rust provided the tools they need to make their custom tooling work. As a user the number of times shared libraries have caused me pain makes me think that this static linking is the superior method of packaging.

When I started programming, static linking was the only way of packaging software in mainstream computing, if it was so superior we wouldn't have moved away from it.

Also although we are talking about open source here, in many OSes, and enterprises, distribution of binary libraries is a very important subject, which cargo doesn't allow for.

> Any change in libfoo-1.2 might require a newer version of rust.

In theory perhaps. But in theory this could happen with C or C++ too. In practice, security patches try to be minimal.

Sure, if you're several versions behind you might have more work to do. But you knew you were gonna own that problem when you decided to lag behind.