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1 line
12 KiB
JavaScript
1 line
12 KiB
JavaScript
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"use strict";(self.webpackChunkspeice_io=self.webpackChunkspeice_io||[]).push([["9437"],{4217:function(e,n,t){t.r(n),t.d(n,{assets:function(){return l},contentTitle:function(){return r},default:function(){return d},frontMatter:function(){return s},metadata:function(){return a},toc:function(){return c}});var a=t(6954),o=t(5893),i=t(65);let s={slug:"2018/12/allocation-safety",title:"QADAPT - debug_assert! for allocations",date:new Date("2018-12-15T12:00:00.000Z"),authors:["bspeice"],tags:[]},r=void 0,l={authorsImageUrls:[void 0]},c=[{value:"Why an Allocator?",id:"why-an-allocator",level:2},{value:"Example 1",id:"example-1",level:3},{value:"Example 2",id:"example-2",level:3},{value:"Example 3",id:"example-3",level:3},{value:"Blowing Things Up",id:"blowing-things-up",level:2},{value:"Using a procedural macro",id:"using-a-procedural-macro",level:3},{value:"Using a regular macro",id:"using-a-regular-macro",level:3},{value:"Using function calls",id:"using-function-calls",level:3},{value:"Caveats",id:"caveats",level:3},{value:"Conclusion",id:"conclusion",level:2}];function h(e){let n={a:"a",blockquote:"blockquote",code:"code",em:"em",h2:"h2",h3:"h3",img:"img",li:"li",ol:"ol",p:"p",pre:"pre",strong:"strong",...(0,i.a)(),...e.components};return(0,o.jsxs)(o.Fragment,{children:[(0,o.jsx)(n.p,{children:"I think it's part of the human condition to ignore perfectly good advice when it comes our way. A\nbit over a month ago, I was dispensing sage wisdom for the ages:"}),"\n",(0,o.jsxs)(n.blockquote,{children:["\n",(0,o.jsxs)(n.p,{children:["I had a really great idea: build a custom allocator that allows you to track your own allocations.\nI gave it a shot, but learned very quickly: ",(0,o.jsx)(n.strong,{children:"never write your own allocator."})]}),"\n",(0,o.jsxs)(n.p,{children:["-- ",(0,o.jsx)(n.a,{href:"/2018/10/case-study-optimization",children:"me"})]}),"\n"]}),"\n",(0,o.jsx)(n.p,{children:"I proceeded to ignore it, because we never really learn from our mistakes."}),"\n",(0,o.jsx)(n.p,{children:"There's another part of the human condition that derives joy from seeing things explode."}),"\n",(0,o.jsx)("center",{children:(0,o.jsx)(n.p,{children:(0,o.jsx)(n.img,{alt:"Explosions",src:t(7537).Z+"",width:"400",height:"280"})})}),"\n",(0,o.jsxs)(n.p,{children:["And ",(0,o.jsx)(n.em,{children:"that's"})," the part I'm going to focus on."]}),"\n",(0,o.jsx)(n.h2,{id:"why-an-allocator",children:"Why an Allocator?"}),"\n",(0,o.jsx)(n.p,{children:"So why, after complaining about allocators, would I still want to write one? There are three reasons\nfor that:"}),"\n",(0,o.jsxs)(n.ol,{children:["\n",(0,o.jsx)(n.li,{children:"Allocation/dropping is slow"}),"\n",(0,o.jsx)(n.li,{children:"It's difficult to know exactly when Rust will allocate or drop, especially when using code that\nyou did not write"}),"\n",(0,o.jsx)(n.li,{children:"I want automated tools to verify behavior, instead of inspecting by hand"}),"\n"]}),"\n",(0,o.jsxs)(n.p,{children:["When I say \"slow,\" it's important to define the terms. If you're writing web applications, you'll\nspend orders of magnitude more time waiting for the database than you will the allocator. However,\nthere's still plenty of code where micro- or nano-seconds matter; think\n",(0,o.jsx)(n.a,{href:"https://www.youtube.com/watch?v=NH1Tta7purM",children:"finance"}),",\n",(0,o.jsx)(n.a,{href:"https://www.reddit.com/r/rust/comments/9hg7yj/synthesizer_progress_update/e6c291f",children:"real-time audio"}),",\n",(0,o.jsx)(n.a,{href:"https://polysync.io/blog/session-types-for-hearty-codecs/",children:"self-driving cars"}),", and\n",(0,o.jsx)(n.a,{href:"https://carllerche.github.io/bytes/bytes/index.html",children:"networking"}),". In these situations it's simply\nunacceptable for you to spend time doing things that are not your program, and waiting on the\nallocator is not cool."]}),"\n",(0,o.jsxs)(n.p,{children:["As I continue to learn Rust, it's difficult for me to predict where exactly allocations will happen.\nSo, I propose we play a quick trivia game: ",(0,o.jsx)(n.strong,{children:"Does this code invoke the
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