I understand it's tradeoffs and we all have real-world limitations to contend with -- but again, of all the corners that could be cut that's exactly the one I didn't imagine they would.
Nasty.
One of them was unburdened by any thought of freeing stuff, and relied entirely on the application exiting for cleanup. This was very convenient to work with, and never ended up posing an issue.
Another used a series of allocation arenas, where certain arenas would be cleared at certain points in the compiler pipeline. This made for both speedy alloc/freeing and avoided leaks, since you weren't at risk of "forgetting" a data structure. It was also a major headache to keep track of exactly what the longest lifetime of a long-lived datastructure might be, and to pick an arena that won't be cleared in the meantime. Unfortunately the programs compiled with this compiler were large enough that we certainly couldn't have gotten away with just leaking memory; we sometimes OOMed as-is!
The third used standard C++ memory management. This compiler was quite simple, and the vast majority of its data used stack-based lifetimes. For a more complex compiler this would've become a headache.
I think that all of these compilers chose the correct allocation strategy for what they were doing. "Good practices" aren't as universal as we might like to believe, they depend entirely on the context in which a tool is designed to operate. And yes, we can guard to some extent against that context changing, but for the most part that's why we keep getting paid.
I was taught -- including at the start of my career when I used exclusively C/C++ (about 18.5y ago) -- to take care of all resources I was using and not rely on runtimes.
I understand and appreciate different usages but to me doing a proper cleanup was the sane default for most programmers. And that's all what I was saying.
Obviously, as one digs deeper in a specialised area where more and more efficiency is demanded then they have to reach for tools that most of us wouldn't normally. That's quite normal and was always interesting for me to read about.
I don't think it's even that uncommon. I believe some HFT firms run Java with a huge amount of RAM and GC disabled, and get around it by just rebooting the software occasionally.
To me writing software like that is fair game, I don't see the point in being dogmatic about "how things should be done".
For specialised apps and servers it's of course a perfectly good practice.
I recall reading somewhere, years ago, that some OSes couldn't be relied upon to release unfreed memory when a process terminated. In those contexts, fastidious freeing would be important even in short-lived processes.
In my own C code I tend to free everything so that I get a clean trace from Valgrind and don't risk masking legitimate bugs, but I typically write long-running daemons.
But still, in a world where languages and runtimes are also judged by their ability to run in lambda/serverless setups, I'd think this practice will start being obsolete, wouldn't you think?
(What I mean is that I imagine that any serverless function that runs in severely constrained and measured environments like the AWS Lambda would gain a significant edge over the competition if it did an eager cleanup. Should allow more of them to work in parallel?)
Because a language server needs to do a lot of the same work as a compiler.
This is an eventual hope for rustc. For now, the latest language server and it share a bunch of libraries, but language servers are effectively compiler frontends.
The leak to watch out for is reduced to the persisted data (eg in S3) between executions
I suppose, judging by the downvotes, that some find that perspective naive so I'll just cut it here because no productive discussion is happening. :(
You only need to care when you're at risk of OOM'ing during runtime. If you're generating too much garbage, you either need to start cleaning up after yourself, or you need to generate less of it -- but it doesn't matter which choice you take from the perspective of the OS or the server-less function.
The only reason I can think of for server-less to impact the validity of this pattern is from it's lower memory capacity -- but otherwise it's the same constraints. And anyways, it's probably not nice to generate a few GB of garbage even if the user has the space
And how many millions of iterations have been done successfully in that "awful" system?
The very fact that you never imagined it I think says a lot.
As I acknowledged in other comments of mine downthread, I understand that different situations require different tradeoffs. It's just that forgoing memory deallocation wasn't one of them in my head.