Comment by yellowapple
5 years ago
To clarify, it's up to the function being called; the convention set by Zig's standard library is that if a function needs to allocate memory, then the allocator (specifically, a struct of function pointers to an allocator's implementations of realloc and shrink) should be one of the function's arguments.
There is of course nothing stopping a function from ignoring this and using the C global allocator if need be (or, as I've done in some experiments, using a C library's custom allocator - in my case that of SQLite).
(EDIT: from what I understand, there's technically nothing stopping C from using this sort of strategy, either; a struct of function pointers ain't exactly exotic. It's just a matter of libraries being written with that convention in mind, which doesn't seem to be very common.)
Oh so it has, in fact, the same caveat as Rust's scheme.
Edit: I guess the difference is that Zig doesn't have years of not supporting it, making the ecosystem more prone to support it.
In a large complex application you are going to want to use the same allocator everywhere, or close to everywhere, and almost all functions may allocate memory directly or indirectly, in which case this Zig convention will require most every function to have a useless parameter. That sounds enraging.
It's common to use multiple allocators in some domains; game developers often use a bump allocator[0] which is reset at the end of every frame.
[0] https://twitter.com/SebAaltonen/status/1080235671883841541
Thanks, that's a good counterexample.
A large complex application seems like exactly the kind of environment where being stuck with a single allocator would be enraging. I personally like the idea of being able to give each component of a large system its own fixed chunk of memory (and an allocator over that chunk), such that if one component goes crazy with memory consumption it's isolated to that component instead of choking out the whole system.
That makes a little bit of sense if by "component" you mean not a software component but a unit of work users care about (e.g. a document).
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