Identifying Rust’s collect::<Vec>() memory leak footgun

Over the weekend, I was working on a personal Rust project when I ran into an excessive memory usage problem. After an evening of trial and error, I found a workaround to fix the memory usage, but I still didn’t understand how the issue was even possible, so I then spent another evening digging th...

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Hasnain says:

“This was a surprising and annoying bug to investigate, but at least I learned a lot about Rust in the process. I had no idea that the standard library was doing this kind of optimization under the hood (and since this is code-based, it happens even in debug builds). It’s also an illustration of how an optimization in one place can lead to bugs downstream by violating programmers’ expectations.

Anyway, I hope that writing about my experience can help other people avoid this footgun in the future, or at least teach people something interesting about Rust.”

Posted on 2024-01-18T16:48:23+0000