What's the Wackiest Coding Hack You've Ever Seen?

xkcd.com/221/

There's the classic fast inverse square root:

float Q_rsqrt( float number )
{
    long i;
    float x2, y;
    const float threehalfs = 1.5F;

    x2 = number * 0.5F;
    y  = number;
    i  = * ( long * ) &y;                       // evil floating point bit level hacking
    i  = 0x5f3759df - ( i >> 1 );               // what the fuck? 
    y  = * ( float * ) &i;
    y  = y * ( threehalfs - ( x2 * y * y ) );   // 1st iteration
//  y  = y * ( threehalfs - ( x2 * y * y ) );   // 2nd iteration, this can be removed

    return y;
}

And here's something I wrote myself:

let x={},s=(S,A=30,T='black,red,green,yellow,blue,magenta,cyan,white'.split`,`)=>T.map((a,i)=>x[a+S]=t=>`\x1b[${i+A}m${t}\x1b[0m`)&&s;s('')('Bg',40)('BrBg',100)('Br',90)('',0,'reset,bold,dim,italic,underline,blink,,reverse,hide,strike'.split`,`);export default x

It's been a while since I wrote this so it took me a hot minute to understand it :P
It's a little terminal color library I golfed, called planckcolors

#define private public
#include <SomeClassWithPrivateMembers.h>

For those who are not familiar with C++, the #define private public say that "Starting from now, each time you see “private” word, replace it with “public”.

Meaning, you can now access private members of following class.
I had to do this to workaround an uninitialized private variable in a 3rd part, leading to a crash.
Definitely an anti-pattern and doesn't work every time (create some low level binary incompatibilities).

If by whacky, you mean bad:

switch(true)

It was the source of a bug, but the developer put it back when I fixed it to if else. 🤷

The FizzBuzz code challenge, where developers are asked to write a program that prints the numbers from 1 to 100. But for multiples of three, the program should print Fizz instead of the number, and for multiples of five, it should print Buzz. For numbers that are multiples of both three and five, the program should print FizzBuzz. This challenge has led to some creative solutions, including one developer who wrote the entire program in one line of code using a ternary operator.

I honestly don't remember where, but I saw some code that used an array of function pointers, like

logTrue = () => console.log("It's true");
logFalse = () => console.log("It's false");
var foo = [logFalse, logTrue]
foo[+true]() //Chrome doesn't convert directly from true to 1, so have to do this to convert it.
/// "It's true"

Probably the classic clear fix

.background { background: background}

Valid css and functioning too.

In typescript, you can use require() to work around a circular dependency error.

I've always been in awe of Duff's Device
Duff's Device(Wikipedia)