Zig in Depth: FixedBufferAllocator

NOTE: This series only covers Zig 0.11.0! Help me create more content like this!
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Zig offers a wide range of allocators that provide different strategies for memory management. The FixedBufferAllocator provides an easy and convenient way to use code that requires an allocator while providing a fixed-size stack-allocated and fast backing store to put the data into. In this episode you'll learn how to use the FixedBufferAllocator and see when it's the best option versus other allocator types.
The code: codeberg.org/d...
Relevant Links:
- ziglang.org/do...
- ziglang.org/do...

[@bjorn2625]

Are you able to explain the logic behind .init’in an allocator and then having to get to the actual allocator by calling .allocator(). Why not have the mother struct be the real allocator?

[@dudethebuilder]

Actually, there's a video further down the playlist that explains how Interfaces can be implemented in Zig. The method explained in that video is precisely the one used by the standard library Allocator interface. In brief, the struct that you call init on is an implementing struct, but only by calling its allocator method do you obtain the actual implementation of the Allocator interface for that struct type. Sounds confusing but when you watch that video you'll see why this is.

[@bjorn2625]

@@dudethebuilder great thank you, I shall look forward to that. It smells a bit like dependency injection, but still can’t wrap my head around it completely.

[@kyp0717]

Thank you!

[@vryder]

Is FixedBufferAllocator alloc thread safe?

[@dudethebuilder]

No, but you can wrap any allocator with a std.heap.ThreadSafeAllocator to make it thread safe: var tsa = std.heap.ThreadSafeAllocator{ .child = fba.allocator() }; const allocator = tsa.allocator();

[@vryder]

@@dudethebuilder Nice, thanks for the info!

[@RobertVoogdgeert]

Running zig 0.12.0-dev.1836+dd189a354 I get errors in every exercise in which tests are used. Also this one Build Summary: 2/5 steps succeeded; 1 failed test transitive failure ├─ run test cached │ └─ zig test Debug native cached 57ms MaxRSS:13M └─ run test transitive failure └─ zig test Debug native failure Is this because I start out with zig init, which creates the zig.build, zig.build.zon, etc. (which I all leave untouched)? Zig run main.zig runs fine, but zig build test always runs into errors. Any idea what might cause this?

[@dudethebuilder]

I'm pretty sure it has to be changes between Zig 0.11.0 and the version you're running. A lot of changes have already been merged into the 0.12 development branch (master) so it wouldn't surprise me that something in the testing framework has changed. That's why I'm sticking to Zig 0.11 stable for the entire course because it would have been too much of a moving target to try it with 0.12 master.