Keith Thompson Keith-S-Thompson

This is a CVS demo script for this question posted by Paul Bunch on Stack Overflow.

The cvs annotate command prints a message on standard error of the form:

Annotations for hello.txt
***************

The questioner is trying to redirect that message when invoking cvs annotate from a Perl script. I have so far been unable to reproduce the problem. I ask Paul Bunch to try running this script on his own system.

This is a simplified test case for this question on Stack Overflow.

I believe I've found a bug in the implementation of the "==" operator for pointers in both gcc and clang.

pointer_equality_bug.c is a demonstration of the bug.

Quoting N1570 6.5.9p6:

Two pointers compare equal if and only if both are null pointers,

This small C++ program demonstrates an apparent optimization bug in g++.

It's based on a question on Stack Overflow: Does C++ allow an optimizing compiler to ignore side effects on the for-condition?. (I'm reasonably sure the answer in this case is no.)

Demo for clang bug (demonstrated with version 3.4)
Based on this question on Stack Overflow.

===

It turns out that this isn't a bug; see Jens Gustedt's answer to the question.

One hash

Two hashes

Three hashes

Four hashes

Five hashes

korn.c is the "Best One Liner" winner of the 1987 International Obfuscated C Code Contest, by David Korn (yes, the author of the Korn Shell).

korn.hint, as the name implies, offers some hints.

A commenter on Stack Overflow asked for some clarification. I didn't want to post spoilers on the site, so I'm posting them here instead. If you haven't already (and if you're familiar with the rules of C) I encourage you to study the program for a while first.

=====

Here's the code:

	#include <stdio.h>
	#include <stdint.h>
	int main(void) {

	int64_t u = 0;
	int i;

	for(i=0;i<44;i++)
	u \|= (uint64_t)1 << i;

	/*
	* In response to http://stackoverflow.com/a/22918463/827263
	* "In C you can't declare variables/functions (in same scope) with the same name more than once."
	*/

	#include <stdio.h>

	void yes_you_can(void);
	void yes_you_can(void);
	void yes_you_can(void);

	/*
	* Test program based on code in the Wikipedia POSIX Threads
	* article, https://en.wikipedia.org/wiki/POSIX_Threads.
	*
	* Demo for http://stackoverflow.com/q/19128948/827263
	*/
	#include <pthread.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <assert.h>