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Vlang Update (#165)
* Vlang Update * Update vlang-update-2020-06-17.markdown * Update nix.yml
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@ -14,6 +14,3 @@ jobs:
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nix-build docker.nix
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docker load -i result
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docker tag xena/christinewebsite:latest xena/christinewebsite:$(echo $GITHUB_SHA | head -c7)
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- run: |
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nix-env -if ./nix/dhall-yaml.nix
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dhall-to-yaml-ng --omit-empty --file site.dhall
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@ -1,8 +1,8 @@
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---
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title: V is for Vaporware
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date: 2019-06-23
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series: v
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tags:
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- v
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- rant
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---
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@ -1,8 +1,8 @@
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---
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title: "V is for Vvork in Progress"
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date: 2020-01-03
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series: v
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tags:
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- v
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- constructive-criticism
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---
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@ -0,0 +1,260 @@
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---
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title: V Update - June 2020
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date: 2020-06-17
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series: v
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---
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# V Update - June 2020
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Every so often I like to check in on the [V Programming Language][vlang]. It's been
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about six months since [my last post](https://christine.website/blog/v-vvork-in-progress-2020-01-03),
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so I thought I'd take another look at it and see what progress has been done in six
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months.
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[vlang]: https://vlang.io
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Last time I checked, V 0.2 was slated for release in December 2019. It is currently
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June 2020, and the latest release (at time of writing) is [0.1.27][vrelease0127].
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## Feature Update
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Interestingly, the V author seems to have walked back one of their original
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listed features of V and now has an [abstract syntax tree][ast] for representing the
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grammar of the language. They still claim that functions are "pure" by default, but
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allow functions to perform print statements while still being "pure". Printing data
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to standard out is an impure side effect, but if you constrain the definition of
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"side effects" to only include mutability of memory, this could be fine.
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[vrelease0127]: https://github.com/vlang/v/releases/tag/0.1.27
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[ast]: https://github.com/vlang/v/commit/093a025ebfe4f0957d5d69ad4ddcdc905a6d7b81#diff-5adb689a65970037f7f0ced3d4b9e800
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The next stable release 0.2 seems to be planned for June 2020 (according to the readme);
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and according to the todo list in the repo, memory management seems to be one of the
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things that will be finished. V is also apparently in alpha, but will also apparently
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jump from alpha directly to stable?
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## Build
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Testing V is a bit more difficult for me now as its build process is incompatible
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with my Linux tower's [NixOS](https://nixos.org/nixos) install (I tend to try and
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package all the programs I use for testing this stuff so it is easier to reproduce
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my environment on other machines). The V scripts also do not work on my NixOS tower
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because it doesn't have a `/usr/local/bin`. The correct way to make a shell script
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cross-platform is to use the following header:
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```sh
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#!/usr/bin/env v
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```
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This makes the `env` program search for the V binary in your `$PATH`, and will
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function correctly on all platforms.
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The Makefile in the V source tree seems to do
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network calls, specifically a `git clone`. Remember that this is on the front page
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of the website:
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> V can be bootstrapped in under a second by compiling its code translated to C with a simple
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>
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> `cc v.c`
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>
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> No libraries or dependencies needed.
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Git is a dependency, which means perl is a dependency, which means a shell is a
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dependency, which means glibc is a dependency, which means that a lot of other
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things (including posix threads) are also dependencies. Pedantically, you could even
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go as far as saying that you could count the Linux kernel, the processor being used
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and the like as dependencies, but that's a bit out of scope for this.
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## Memory Management
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> V doesn't use garbage collection or reference counting. The compiler cleans
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> everything up during compilation. If your V program compiles, it's guaranteed
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> that it's going to be leak free.
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Amusingly, the documentation still claims that memory management is both a work in
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progress and has perfect accuracy for cleaning up things at compile time. Let's run
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my favorite test, the "how much ram do you leak compiling hello world" test. Last
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it leaked `4,600,383` bytes (or about 4.6 megabytes) and before that it leaked
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`3,861,785` bytes (or about 3.9 megabytes). This time:
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```
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$ valgrind ./v hello.v
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==5413== Memcheck, a memory error detector
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==5413== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
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==5413== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info
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==5413== Command: ./v hello.v
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==5413==
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==5413==
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==5413== HEAP SUMMARY:
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==5413== in use at exit: 7,232,779 bytes in 163,690 blocks
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==5413== total heap usage: 182,696 allocs, 19,006 frees, 11,309,504 bytes allocated
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==5413==
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==5413== LEAK SUMMARY:
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==5413== definitely lost: 2,673,351 bytes in 85,739 blocks
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==5413== indirectly lost: 4,265,809 bytes in 77,711 blocks
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==5413== possibly lost: 256,000 bytes in 1 blocks
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==5413== still reachable: 37,619 bytes in 239 blocks
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==5413== suppressed: 0 bytes in 0 blocks
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==5413== Rerun with --leak-check=full to see details of leaked memory
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==5413==
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==5413== For counts of detected and suppressed errors, rerun with: -v
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==5413== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
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```
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It seems that the memory managment really is a work in progress. This increase in
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leakage means that the compiler building itself now creates `30,409,141` bytes of
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leaked ram (which if i recall is actually a remarkable improvement).
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However, `hello world` seems to leak again:
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```
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$ valgrind ./hello
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==13258== Memcheck, a memory error detector
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==13258== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
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==13258== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info
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==13258== Command: ./hello
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==13258==
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hello world
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==13258==
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==13258== HEAP SUMMARY:
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==13258== in use at exit: 12,144 bytes in 14 blocks
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==13258== total heap usage: 15 allocs, 1 frees, 13,168 bytes allocated
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==13258==
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==13258== LEAK SUMMARY:
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==13258== definitely lost: 0 bytes in 0 blocks
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==13258== indirectly lost: 0 bytes in 0 blocks
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==13258== possibly lost: 0 bytes in 0 blocks
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==13258== still reachable: 12,144 bytes in 14 blocks
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==13258== suppressed: 0 bytes in 0 blocks
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==13258== Rerun with --leak-check=full to see details of leaked memory
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==13258==
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==13258== For counts of detected and suppressed errors, rerun with: -v
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==13258== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
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```
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I'm not entirely sure how this happened, but here is the output of
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`v -keepc hello.v`: https://git.io/Jfdsu.
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## Doom
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The [Doom](https://github.com/vlang/doom) translation project still has one file
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translated (and apparently it breaks sound effects but not music).
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## 1.2 Million Lines of Code
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Let's re-run the artificial as heck 1.2 million lines of code benchmark from the
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last post:
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```
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$ bash -c 'time ~/code/v/v main.v'
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real 7m54.847s
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user 7m32.860s
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sys 0m14.212s
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```
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This is a major improvement! It's cut at least 2 minutes off of the build time for
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this incredibly contrived benchmark! Let's see how big the generated binary is:
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```
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$ du -hs ./main
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179M ./main
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```
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This is identical to how big it was last time. Let's see how much ram it leaks:
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```
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$ valgrind ./main
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==11773== Memcheck, a memory error detector
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==11773== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
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==11773== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info
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==11773== Command: ./main
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==11773==
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hello, 1 1!
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<snipped>
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==11773==
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==11773== HEAP SUMMARY:
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==11773== in use at exit: 12,144 bytes in 14 blocks
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==11773== total heap usage: 15 allocs, 1 frees, 13,168 bytes allocated
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==11773==
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==11773== LEAK SUMMARY:
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==11773== definitely lost: 0 bytes in 0 blocks
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==11773== indirectly lost: 0 bytes in 0 blocks
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==11773== possibly lost: 0 bytes in 0 blocks
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==11773== still reachable: 12,144 bytes in 14 blocks
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==11773== suppressed: 0 bytes in 0 blocks
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==11773== Rerun with --leak-check=full to see details of leaked memory
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==11773==
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==11773== For counts of detected and suppressed errors, rerun with: -v
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==11773== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
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```
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About what I expected.
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## Concurrency
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A common problem that shows up when writing multi-threaded code are
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[race conditions][races]. Effectively, race conditions are when two bits of code try
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to do the same thing at the same time on the same block of memory. This leads to
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undefined behavior, which is bad because it can corrupt or crash programs.
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[races]: https://en.wikipedia.org/wiki/Race_condition
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As an example, consider this program `raceanint.v`:
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```
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fn main() {
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foo := [ 1 ]
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go add(mut foo)
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go add(mut foo)
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for {}
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}
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fn add(mut foo []int) {
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for {
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foo[0] = foo[0] + 1
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}
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}
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```
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In theory, this should have two threads infinitely trying to increment `foo[0]`,
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which will eventually result in `foo[0]` getting corrupted by two threads trying to
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do the same thing at the same time (given the tight loops invovled).
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However, I can't get this to build:
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```
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==================
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/home/cadey/.cache/v/raceanint.tmp.c: In function ‘add_thread_wrapper’:
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/home/cadey/.cache/v/raceanint.tmp.c:1209:6: error: incompatible type for argument 1 of ‘add’
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add(arg->arg1);
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^~~
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/home/cadey/.cache/v/raceanint.tmp.c:1198:13: note: expected ‘array_int * {aka struct array *}’ but argument is of type ‘array_int {aka struct array}’
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static void add(array_int* foo);
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^~~
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/home/cadey/.cache/v/raceanint.tmp.c: In function ‘strconv__v_sprintf’:
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/home/cadey/.cache/v/raceanint.tmp.c:3611:7: warning: variable ‘th_separator’ set but not used [-Wunused-but-set-variable]
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bool th_separator = false;
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^~~~~~~~~~~~
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/home/cadey/.cache/v/raceanint.tmp.c: In function ‘print_backtrace_skipping_top_frames_linux’:
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...
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==================
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(Use `v -cg` to print the entire error message)
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builder error:
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==================
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C error. This should never happen.
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If you were not working with C interop, please raise an issue on GitHub:
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https://github.com/vlang/v/issues/new/choose
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```
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Like I said before, I also cannot file new issues about this. So if you are willing
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to help me out, please open an issue about this.
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---
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Overall, V looks like it is making about as much progress as I had figured it would.
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I wish the team luck in their work!
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