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341 points dochtman | 1 comments | 16 Mar 25 19:35 UTC | HN request time: 0.226s | source

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YZF ◴[16 Mar 25 20:12 UTC] No.43381858[source]▶

I found out I already know Rust:

        unsafe {
            let x_tmp0 = _mm_clmulepi64_si128(xmm_crc0, crc_fold, 0x10);
            xmm_crc0 = _mm_clmulepi64_si128(xmm_crc0, crc_fold, 0x01);
            xmm_crc1 = _mm_xor_si128(xmm_crc1, x_tmp0);
            xmm_crc1 = _mm_xor_si128(xmm_crc1, xmm_crc0);

Kidding aside, I thought the purpose of Rust was for safety but the keyword unsafe is sprinkled liberally throughout this library. At what point does it really stop mattering if this is C or Rust?

Presumably with inline assembly both languages can emit what is effectively the same machine code. Is the Rust compiler a better optimizing compiler than C compilers?

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1. atoav ◴[17 Mar 25 08:02 UTC] No.43386151[source]▶

>>43381858 #

There are certain optimizations you can only make with unsafe, because the borrow checker is smart, but not all-knowing. There have been countless discussions how unsafe isn't the ideal name. It should be more like in the meaning of trust the programmer that they checked this manually.

That being said, most rust programs don't ever need to use unsafe directly. If you go very low level or tune for prrformance it might become useful however.

Or if you're lazy and just want to stop the borrow checker from saving your ass.

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Zlib-rs is faster than C