That's intentional; IOW the "most code" that is unable to handle OOM conditions are written that way.
You can write code that handles OOM conditions gracefully, but that way of writing code is the default only in C. In every other language you need to go off the beaten path to gracefully handle OOM conditions.
It's possible. But very very few projects do.
What are you talking about? Every allocation must be checked at the point of allocation, which is "the default"
If you write non-idiomatically, then sure, in other languages you can jump through a couple of hoops and check every allocation, but that's not the default.
The default in C is to return an error when allocation fails.
The default in C++, Rust, etc is to throw an exception. The idiomatic way in C++, etc is to not handle that exception.
C doesn't force you to check the allocation at all. The default behavior is to simply invoke undefined behavior the first time you use the returned allocation if it failed.
In practice I've found most people write their own wrappers around malloc that at least crash - for example: https://docs.gtk.org/glib/memory.html
PS. The current default in rust to print something and then abort the program, not panic (i.e. not throw an exception). Though the standard library reserves the right to change that to a panic in the future.
No one ever claimed it did; I said, and still do, that the in C, at any rate, the default is to check the returned value from memory allocations.
And, that is true.
The default in other language is not to recover.
> No one ever claimed it did;
You specifically said
> Every allocation must be checked at the point of allocation
...
> the default is to check the returned value from memory allocations.
Default has a meaning, and it's what happens if you don't explicitly choose to do something else.
In libc - this is to invoke undefined behavior if the user uses the allocation.
In glib - the library that underpins half the linux desktop - this is to crash. This is an approach I've seen elsewhere as well to the point where I'm comfortable calling it "default" in the sense that people change their default behavior to it.
Nowhere that I've ever seen, in C, is it to make the user handle the error. I assume there are projects with santizers that do do that, I haven't worked on them, and they certainly don't make up the majority.
It also has the meaning of doing the common thing: https://www.merriam-webster.com/dictionary/default
> : a selection made usually automatically or without active consideration
See that "without active consideration" there? The default usage of malloc includes, whether you want to acknowledge it or not, checking the returned value.
C doesn't have anything done automatically, so I am wondering why you would choose to think that by "default" one would mean that something automatically gets done.
"Ubiquitous" is a different word than default, checking the return code of malloc isn't even that. As an example - I've been having some issues with pipewire recently (unrelated) and happen to know it uses an unwrapped malloc. And it doesn't reliably check the return code. For example: https://github.com/PipeWire/pipewire/blob/6ed964546586e809f7...
And again, this isn't cherry picked, this is just "the last popular open source C code base I've looked at". This is the common case in C. Either you wrap malloc to crash, or you just accept undefined behavior if malloc fails. It is the rare project that doesn't do one of those two.
Right. But this is what you initially responded to:
> You can write code that handles OOM conditions gracefully, but that way of writing code is the default only in C.
How did you get from "That way" to thinking I claimed that C, by default, handles allocation failures?
> As an example - I've been having some issues with pipewire recently (unrelated) and happen to know it uses an unwrapped malloc.
Correct. That does not mean that the default way of writing allocation in C is anything other than what I said.
Do programmers make mistakes? Sure. But that's not what asked - what was asked is how do you handle memory errors gracefully, and I pointed out that, in idiomatic C, handling memory errors gracefully is the default way of handling memory errors.
That is not the case for other languages.
I think you might want to reread the line you quoted directly above this,
That way of writing code, i.e. "write[ing] code that handles OOM conditions gracefully" "is the default [...] in C".
This is what I am saying is not the case. The default in C is undefined behavior (libc) or crashing (a significant fraction of projects allocator wrappers). Not "handling OOM gracefully" - i.e. handling OOM errors.
I am reading exactly what I said:
> You can write code that handles OOM conditions gracefully, but that way of writing code is the default only in C.
How is it possible to read that as anything other than "That Way Of Writing Code Is The Default Way In C"?
Are you saying that checking the result of malloc (and others) is not the default way of allocating memory?
In C - yes. I've said that repeatedly now...
> In C - yes. I've said that repeatedly now...
Well, that's just not true. The instances of unchecked allocations are both few and far between, *and* treated as bugs when reported :-/
Maybe you should program in a language for a little bit before forming an opinion on it :-/
For good reason. Most C software is not designed to run in a situation where malloc might fail.
I, unlike you, have provided evidence of this by pointing to major pieces of the linux desktop that do not do so.
because of OS-level overcommit, which is nearly always a good thing
It doesn't matter about the language you are writing in, because your OS can tell you that the allocation succeeded, but when you come to use it, only then do you find out that the memory isn't there.
It's a place where windows legitimately is better than linux.
Sure, but ... what does that have to do with this thread? Using `mmap` is not the same as using `malloc` and friends.
If you turn off overcommit, malloc will return NULL on failure to allocate. If you specifically request mmap to ignore overcommit, and it does, why are you surprised?
You misunderstand, you specifically request mmap to ignore overcommit, and it doesn't, not does.
What it has to do with this thread is it makes turning off overcommit on linux an exceptionally unpalatable option because it makes a lot of correct software incorrect in an unfixable manner.
It may not be as simple as "that's our policy". I worked at one place (embedded C++ code, 2018) that simply reset the device every 24h because they never managed to track down all the leaks.
Finding memory leaks in C++ is a non-trivial and time-consuming task. It gets easier if your project doesn't use exceptions, but it's still very difficult.
Was not available for that specific device, but even with Valgrind and similar tools, you are still going to run into weird destructor issues with inheritance.
There are many possible combinations of virtual, non-virtual, base-class, derived-class, constructors and destructors; some of them will indeed cause a memory leak, and are allowed to by the standard.
I love these folklore comments. Post an example.
In Zig you must handle it. Even if handling means "don't care, panic", you have to spell that out.
No, this is wishful thinking. While plenty of programs out the are in the business of maintaining caches that could be optimistically evicted in order to proceed in low-memory situations, the vast majority of programs are not caching anything. If they're out of memory, they just can't proceed.