←back to thread

Why is the Rust compiler so slow?

(sharnoff.io)
302 points Bogdanp | 3 comments | 26 Jun 25 19:29 UTC | HN request time: 0.423s | source
Show context
taylorallred ◴[26 Jun 25 20:29 UTC] No.44390996[source]▶
So there's this guy you may have heard of called Ryan Fleury who makes the RAD debugger for Epic. The whole thing is made with 278k lines of C and is built as a unity build (all the code is included into one file that is compiled as a single translation unit). On a decent windows machine it takes 1.5 seconds to do a clean compile. This seems like a clear case-study that compilation can be incredibly fast and makes me wonder why other languages like Rust and Swift can't just do something similar to achieve similar speeds.
replies(18): >>44391046 #>>44391066 #>>44391100 #>>44391170 #>>44391214 #>>44391359 #>>44391671 #>>44391740 #>>44393057 #>>44393294 #>>44393629 #>>44394710 #>>44395044 #>>44395135 #>>44395226 #>>44395485 #>>44396044 #>>44401496 #
lordofgibbons ◴[26 Jun 25 20:39 UTC] No.44391100[source]▶
The more your compiler does for you at build time, the longer it will take to build, it's that simple.

Go has sub-second build times even on massive code-bases. Why? because it doesn't do a lot at build time. It has a simple module system, (relatively) simple type system, and leaves a whole bunch of stuff be handled by the GC at runtime. It's great for its intended use case.

When you have things like macros, advanced type systems, and want robustness guarantees at build time.. then you have to pay for that.

replies(9): >>44391549 #>>44391582 #>>44391630 #>>44391910 #>>44394240 #>>44395833 #>>44397304 #>>44401934 #>>44402705 #
1. jstanley ◴[27 Jun 25 11:14 UTC] No.44395833[source]▶
> Go has sub-second build times even on massive code-bases.

Unless you use sqlite, in which case your build takes a million years.

replies(2): >>44396492 #>>44399849 #
2. Groxx ◴[27 Jun 25 13:03 UTC] No.44396492[source]▶
Yeah, I deal with multiple Go projects that take a couple minutes to link the final binary, much less build all the intermediates.

Compilation speed depends on what you do with a language. "Fast" is not an absolute, and for most people it depends heavily on community habits. Rust habits tend to favor extreme optimizability and/or extreme compile-time guarantees, and that's obviously going to be slower than simpler code.

3. infogulch ◴[27 Jun 25 20:11 UTC] No.44399849[source]▶
Try https://github.com/ncruces/go-sqlite3 it runs sqlite in WASM with wazero, a pure Go WASM runtime, so it builds without any CGo required. Most of the benchmarks are within a few % of the performance of mattn/go-sqlite3.