shafik

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

FrankHB

FAQ

包含若干待定整理内容。

待补充

const/常量表达式(constant expression) 的联系和不同。

参考：

alexpana

Various 'features' of C++ that show the hacky / inconsistent way in which the language was constructed. This is a work in progress, and currently contains some of the reasons I can remember why I've given up on C++. If you want to contribute, leave your favourite "hack" in the comments.

1. (in)Visibility: C++ allows changing the access modifier of a virtual function in the derived class. Not only does C++ have no notion of interfaces, it actually allows subclasses to hide methods declared public in the superclass.

2. Operator over-overloading: One of the increment operators takes a dummy int parameter in order to allow overloading. Can you tell which without googling? (hint: its postfix).

3. Exception unspecifiers: C++ has two types of exception specifiers: throw() and nothrow. The first is deprecated (because 'we screwed up, sorry, let's forget about this terrible mess'). The second one guarantees it's contract by terminating the application when violated. That's because functions declared

non

What is the appeal of dynamically-typed languages?

Kris Nuttycombe asks:

I genuinely wish I understood the appeal of unityped languages better. Can someone who really knows both well-typed and unityped explain?

I think the terms well-typed and unityped are a bit of question-begging here (you might as well say good-typed versus bad-typed), so instead I will say statically-typed and dynamically-typed.

I'm going to approach this article using Scala to stand-in for static typing and Python for dynamic typing. I feel like I am credibly proficient both languages: I don't currently write a lot of Python, but I still have affection for the language, and have probably written hundreds of thousands of lines of Python code over the years.

hirataya

// -*- coding: utf-8 -*-
// ==UserScript==
// @name        They are all 17 years old
// @author	HIRATA Yasuyuki <yasu@asuka.net>
// @namespace	http://yasu.asuka.net/
// @version	1.1.0
// @include	http://www.google.tld/search?*
// @include	https://www.google.tld/search?*
// @released	2013-04-23
// @updated     2013-04-30

asabaylus

Anchors in Markdown

To create an anchor to a heading in github flavored markdown. Add - characters between each word in the heading and wrap the value in parens (#some-markdown-heading) so your link should look like so:

[create an anchor](#anchors-in-markdown)