Often for dsp type stuff you'd blow out the stack for the size of a time series or image buffer. I typically preallocate when the size is known and reuse. Is yhere a good way to do that statically.

In Rust? Simplest thing is to declare an array as a static. Mutable statics do require unsafe, because it's inherently not threadsafe, but if you wanted to stay away from that directly, just depends on what kinds of tradeoffs you're interested in making.

I didn't realize who I was replying to! But yes in rust. I have messed with mutable statics with a mutex and maybeuinit mostly for exporting stuff as a cdylib that has mutable state, and found I lose some of what I love about rust. So I heap allocate once and do borrows for each stage in my pipeline (SDR stuff). Sometimes a stage copies to cuda device mem, or back, or doesn't and just carries a device pointer through behind an abstraction. Is there a good reason to avoid preallocation on the heap?

I thought we were talking about a situation with no heap! If you have that luxury, heck yeah just call malloc.

That's not always viable. Allowing heap allocation only at init is pretty common in embedded. Read config to get sizes, allocate at startup, never call free().

I don't understand what you mean by "That's not always viable." You can either call malloc, or you can't. If you can only call it at startup, only call it at startup. Every project has different requirements, and Rust will let you satisfy any of them.

I believe first Warcraft game used the same technique in C, IIRC.

Seems to have worked. But it would be a mess to use only stack and static memory for today's large applications.

Absolutely, it’s a pain in the butt. But sometimes it’s what you have to do.