dupuy

Markdown and reStructuredText

GitHub supports several lightweight markup languages for documentation; the most popular ones (generally, not just at GitHub) are Markdown and reStructuredText. Markdown is sometimes considered easier to use, and is often preferred when the purpose is simply to generate HTML. On the other hand, reStructuredText is more extensible and powerful, with native support (not just embedded HTML) for tables, as well as things like automatic generation of tables of contents.

darcyparker

damphat

#! /bin/bash
# Description: show dependency tree
# Author: damphat

if [ $# != 1 ]; then
	echo 'Usage: apt-rdepends-tree <package>'
	echo 'Required packages: apt-rdepends'
	exit 1  
fi

shizmob

#!/bin/sh
downpomf="https://a.pomf.cat/"
uppomf="https://pomf.cat/upload.php"

if test $# -lt 1 ; then
    echo "Usage: `basename $0` FILE [FILE...]"
    exit 1
fi

set=

sr105

#! /bin/bash
# Description: show dependency tree
# Author: damphat

if [ $# -lt 1 ]; then
	echo 'Usage: apt-rdepends-tree [-r] <package>'
	echo 'Required packages: apt-rdepends'
	exit 1  
fi

detomon

SSE Intrinsic Cheat Sheet (SSE3)

Load and Store

__m128 _mm_load_ps (float * a)
{

rygorous

Why do compilers even bother with exploiting undefinedness signed overflow? And what are those
mysterious cases where it helps?

A lot of people (myself included) are against transforms that aggressively exploit undefined behavior, but
I think it's useful to know what compiler writers are accomplishing by this.

TL;DR: C doesn't work very well if int!=register width, but (for backwards compat) int is 32-bit on all
major 64-bit targets, and this causes quite hairy problems for code generation and optimization in some
fairly common cases. The signed overflow UB exploitation is an attempt to work around this.

KodrAus

Profiling performance

Using perf:

$ perf record -g binary
$ perf script | stackcollapse-perf.pl | rust-unmangle | flamegraph.pl > flame.svg

NOTE: See @GabrielMajeri's comments below about the -g option.

tomaka

Let's take the first example from the Rust generators RFC:

#[async]
fn print_lines() -> io::Result<()> {
    let addr = "127.0.0.1:8080".parse().unwrap();
    let tcp = await!(TcpStream::connect(&addr))?;
    ...
}

rygorous

why doesn't radfft support AVX on PC?

So there's two separate issues here: using instructions added in AVX and using 256-bit wide vectors. The former turns out to be much easier than the latter for our use case.

Problem number 1 was that you positively need to put AVX code in a separate file with different compiler settings (/arch:AVX for VC++, -mavx for GCC/Clang) that make all SSE code emitted also use VEX encoding, and at the time radfft was written there was no way in CDep to set compiler flags for just one file, just for the overall build.

[There's the GCC "target" annotations on individual funcs, which in principle fix this, but I ran into nasty problems with this for several compiler versions, and VC++ has no equivalent, so we're not currently using that and just sticking with different compilation units.]

The other issue is to do with CPU power management.