Comment by timschmidt
8 hours ago
> The facts that these exist and the programmer has to always be consciously be aware of it
This is what separates a systems programming language suitable for OS and embedded development from managed languages, which are not.
The complexity ultimately stems from unavoidable details of the hardware. Languages which do not offer similar representations will be incapable of making full use of the underlying hardware, including writing certain projects like bootloaders, firmwares, OSes, etc. Rust is pretty close to state-of-the-art in terms of providing reasonable abstractions over the hardware.
It sounds to me like you're used to managed languages with a runtime which are great for certain applications, but unable to be specific enough about memory layout, how data is formatted in memory, etc. for some tasks. Those choices were made for you by the language runtime's authors and necessarily limit the language's applicability to some problems. Rust, C++, and other systems programming languages don't have such limitations, but require you to understand more of the complexity of what the system is actually doing.
Any language which provides adequate representations for taking full advantage of the hardware is going to be on a similar order of complexity as Rust, C++, or other systems programming languages, because the hardware is complex. Managed languages can be nice for introducing folks to programming, precisely because much of the complexity is hidden in the runtime, but that can be a double edged sword when it comes time to approach a systems level task.
Instead of wishing the language didn't offer those representations, it may be more productive to ask why C++ and Rust converged on such similar ones. Exploration of that question will be enlightening.
None of these have anything to do to do with memory layout or how data is formatted in the memory. You are arguing a different point than the one being discussed here.
These are fundamentally hacks around the compiler’s inability to understand ownership and lifetimes, at least the way Rust (and C++) are designed.
These exist in Rust because otherwise you would have to use unsafe blocks all the time to write any reasonable code.
Safe threading seems like fully exploiting hardware features to me. That's the biggest thing smart pointers and Rc, Arc, and Cell types enable. Perhaps I could have been clearer.
The comment about memory layout was an additional point that dealing with hardware requires that you format, align, and position information in memory as the hardware expects, which requires either exposing those details, or encoding them in a runtime.
Safe threading sounds great, as long as the language gets out of my way when I absolutely do not care about safe threading.
I write compilers (and have contributed to the Rust compiler!), and there has been approximately zero times in twenty or so years that thread safety has been a concern.
6 replies →
There should be no such difference. The bigger problem is that OS's enforce this duality when in fact there should only be application level software and an absolutely tiny core to handle IPC and scheduling. This then allows you to enforce the boundaries between various bits far more strictly.
The kernel, the memory manager and device drivers, the language runtimes for managed languages; would these not be written in "systems" languages? Essential complexity can only be rearranged, not removed. Nothing changes the fact that every interface between hardware and software needs to be bridged.
On a different note: why should the kernel even handle IPC or scheduling? Those take the basic capabilities of context switching, timer management, and memory management. Even "core functionality" can be a context switch (or a few) away; is a syscall not just a message to a system server? Only the most basic form of communication is necessary to delegate arbitrary functionality, so a true microkernel should only introduce that as an abstraction. Everything else either follows from the hardware or is left to the whims of software.
> The kernel, the memory manager and device drivers, the language runtimes for managed languages; would these not be written in "systems" languages?
The kernel and memory manager: probably yes, the device drivers: not necessarily, the language runtimes for managed languages: not necessarily.
> On a different note: why should the kernel even handle IPC or scheduling?
Because any other solution will quickly run into chicken-and-the-egg style problems.
> Those take the basic capabilities of context switching, timer management, and memory management.
Yes. But only one timer, the rest should be free to use by other applications.
> Even "core functionality" can be a context switch (or a few) away; is a syscall not just a message to a system server?
No. A syscall is usually defined as a call to a ring one level in from the one where you currently are. But lots of things that are syscalls right now do not necessarily have to be.
> Only the most basic form of communication is necessary to delegate arbitrary functionality, so a true microkernel should only introduce that as an abstraction.
Indeed. And they do.
> Everything else either follows from the hardware or is left to the whims of software.
A lot of the stuff that 'follows from the hardware' can be dealt with at the application level.
It seems like you think that some shadowy cabal somewhere decided to differentiate systems languages from managed languages and keep them divided. That is not the case. The distinction describes how the language has been implemented, which is based on the choices of the language authors alone, and is usually down to practical considerations about how to implement the thing at all.
Saying "There should be no such difference." is a bit like saying bicycles should be allowed on the highway and semi trucks should be accepted on walking paths. The difference is inherent in the thing. A result of how they were built. And what they can and can't accomplish as a result.
> It seems like you think that some shadowy cabal somewhere decided to differentiate systems languages from managed languages and keep them divided. That is not the case.
You could have made that point without the strawman, and what a ridiculous thing to say anyway.
> The distinction describes how the language has been implemented, which is based on the choices of the language authors alone, and is usually down to practical considerations about how to implement the thing at all.
That is so obvious I do not understand what point you are trying to make here.
> Saying "There should be no such difference." is a bit like saying bicycles should be allowed on the highway and semi trucks should be accepted on walking paths. The difference is inherent in the thing. A result of how they were built. And what they can and can't accomplish as a result.
No, the error is yours: you are interpreting my sentence in a way that is blatantly wrong and then argue with the outcome. I'm not saying that there shouldn't be 'trucks or bicycles' in terms of programming languages. What I'm saying is that the boundary between where you use a 'systems programming language' and where you use an 'application programming language' is artificial and that we are using too much of the former in a place where we probably should be using the latter.