danielhenrymantilla

The curious case of the rustfmt-induced lifetime error

Consider the following snippet, which compiles fine:

trait Tr {}

struct A(Option<Box<dyn Tr>>);

impl A {

danielhenrymantilla

Liveness and lifetime-using drop glue

Rules of liveness: about the "discard point"

1. with no drop glue, no "library" code gets executed, so a fortiori, no lifetimes/borrows/w/e are used/dereferenced, so it would be sound for lifetimes of the discardee to be dangling here.

   ⇒ No need for liveness to extend to this point

2. with drop glue:

   1. either the drop glue does somehow refer to that lifetime,

danielhenrymantilla

Understanding the role of SONAME in dynamic linkage and dynamic loading

Note that this is a Linux-specific feature.

The primary role of SONAME

Say we are a library libfoo.so.3.5, and some dependent binary artifact is being linked against us.

• Note that this dependent binary artifact may well be a final executable, à la ./main;

danielhenrymantilla

use ::polonius_the_crab::prelude::*;

struct DummyStream {
    buffer: Vec<u8>,
    frame_count: u32,
}

impl DummyStream {
    fn new(width: usize, height: usize) -> Self {
        Self {

danielhenrymantilla

# http://www.graphviz.org/content/cluster

digraph G {
    graph [fontname = "courier"];
    node [fontname = "courier", shape=box];
    edge [fontname = "courier"];

    compound=true;
    
    subgraph cluster_a {

danielhenrymantilla

digraph __crate__ {
subgraph cluster_Mir_0_10 {
    graph [fontname="Courier, monospace"];
    node [fontname="Courier, monospace"];
    edge [fontname="Courier, monospace"];
    // label=<fn main() -&gt; ()<br align="left"/>let mut _1: std::string::String;<br align="left"/>let mut _2: DropGlue&lt;&amp;mut std::string::String&gt;;<br align="left"/>let mut _3: &amp;mut std::string::String;<br align="left"/>let mut _4: *mut std::string::String;<br align="left"/>let _5: ();<br align="left"/>debug _2 =&gt; _2;<br align="left"/>debug _1 =&gt; _1;<br align="left"/>>;
    bb0__0_10 [shape="none", label=<<table border="0" cellborder="1" cellspacing="0"><tr><td bgcolor="gray" align="center" colspan="1">0</td></tr><tr><td align="left" balign="left">StorageLive(_1)<br/></td></tr><tr><td align="left">_1 = String::new()</td></tr></table>>];
    bb1__0_10 [shape="none", label=<<table border="0" cellborder="1" cellspacing="0"><tr><td bgcolor="gray" align="center" colspan="1">1</td></tr><tr><td align="left" balign="left">Sto

danielhenrymantilla

[These posts have been extracted from this Discord conversation, so as not to require readers to use their Discord account to read it 😔]

Question

HI!

Question and idea about narrowing lifetime of mutable references.

In rust code when developing finite state machines, behaviour trees and other algorithms we often need to pass around Context on which these algorithms will work.

danielhenrymantilla

MSRV Policy

The MSRV (Minimum Supported Rust [toolchain] Version) policy of my crates for a [semver-compatible bump] is the following:

stable - 9

More precisely:

• Patch[^patch] bump ⇒ same MSRV

danielhenrymantilla

How to Resize an Image in Github README.md (i.e. Github Flavored Markdown)

Percentage:

<img src="https://user-images.githubusercontent.com/16319829/81180309-2b51f000-8fee-11ea-8a78-ddfe8c3412a7.png" width=50% height=50%>

Pixels:

<img src="https://user-images.githubusercontent.com/16319829/81180309-2b51f000-8fee-11ea-8a78-ddfe8c3412a7.png" width="150" height="280">

danielhenrymantilla

Question

how can I convert an array to a vec without cloning the values

Technically-correct answer

Make a Vec of references:

array.iter_mut().collect::<Vec<_>>();