Rustaceans at the border [LWN.net]

Rustaceans at the border

Posted Apr 16, 2022 1:00 UTC (Sat) by nybble41 (subscriber, #55106)
In reply to: Rustaceans at the border by Hello71
Parent article: Rustaceans at the border

> unix linkers have pruned unnecessary object files from the final link for basically as long as unix has existed

Yes, but Rust goes farther. It doesn't just prune unused object files as a whole but individual functions, global data, trait implementations, and even code paths, taking advantage of static analysis across module boundaries. The closest equivalent in C would be link-time optimization, which is relatively new and not enabled by default.

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Rustaceans at the border

Posted Apr 16, 2022 11:26 UTC (Sat) by smurf (subscriber, #17840) [Link] (1 responses)

Any C compiler worth its salt already can put each function into its own section, which the linker then skips if it's not referenced. This scheme has been supported by gcc/ld since, umm, whenever. It's hardly as comprehensive as LTO but gets the job done well enough for the kernel and, frankly, most other codebases that aren't heavily obfuscated C++.

Rustaceans at the border

Posted Apr 17, 2022 2:48 UTC (Sun) by willy (subscriber, #9762) [Link]

You might want to check whether CONFIG_LD_DEAD_CODE_DATA_ELIMINATION is set in your kernel before making such confident assertions.