Frédéric Brière fbriere

What is the Strict Aliasing Rule and Why do we care?

(OR Type Punning, Undefined Behavior and Alignment, Oh My!)

What is strict aliasing? First we will describe what is aliasing and then we can learn what being strict about it means.

In C and C++ aliasing has to do with what expression types we are allowed to access stored values through. In both C and C++ the standard specifies which expression types are allowed to alias which types. The compiler and optimizer are allowed to assume we follow the aliasing rules strictly, hence the term strict aliasing rule. If we attempt to access a value using a type not allowed it is classified as undefined behavior(UB). Once we have undefined behavior all bets are off, the results of our program are no longer reliable.

Unfortunately with strict aliasing violations, we will often obtain the results we expect, leaving the possibility the a future version of a compiler with a new optimization will break code we th

Tails - The Amnesic Incognito Live System - is a live operating system that "aims at preserving your privacy and anonymity." It is a Linux Debian distribution configured to follow several security measures including sending all internet traffic through the Tor network.

These are the steps I followed for setting up Tails. Tails provides a utility for setting up persistence, this utility only works when running a Tails installation created from within Tails using the Tails Installer. After consistently getting an "Operation System Not Found" message on my computer when trying to run the Tails installed by the Tails Installer, some research lead me to find out it was possible to set up persistence manually. This turned out to provide greater flexibility, as now I am able to keep my persistent partition on a USB drive and my Tails installation on a disk.

Locate the section for your github remote in the .git/config file. It looks like this:

[remote "origin"]
	fetch = +refs/heads/*:refs/remotes/origin/*
	url = [email protected]:joyent/node.git

Now add the line fetch = +refs/pull/*/head:refs/remotes/origin/pr/* to this section. Obviously, change the github url to match your project's URL. It ends up looking like this:

	#!/usr/bin/perl
	# from http://stackoverflow.com/questions/298314/find-files-in-git-repo-over-x-megabytes-that-dont-exist-in-head
	use 5.008;
	use strict;
	use Memoize;

	sub usage { die "usage: git-large-blob <size[b\|k\|m]> [<git-log arguments ...>]\n" }

	@ARGV or usage();
	my ( $max_size, $unit ) = ( shift =~ /^(\d+)([bkm]?)\z/ ) ? ( $1, $2 ) : usage();