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Topic: Obfuscated code (Read 19765 times) |
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-D-
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The code isn't so obfuscated when it's written like PROPER code....
#include <stdio.h>
#define _ F-->00 || F-OO--;
void F_OO();
long F=00,OO=00;
void main()
{
F_OO();
printf("%1.3f\n", 4.0*-F/OO/OO);
}
void F_OO()
{
...
}
This is pretty much the first 3 lines expanded.
The #define is a macro that defines the _ character. But it is only expanded for cases where the _ isn't used in a label (such as it is used in F_OO ).
F_OO is actually a function that uses long drawn out operation on F and OO to make them become -202 and -16 respectively.
4 * -202 / -16 / -16 = 3.156 which is what is printed out. The 4. in the given code is really 4.0. the - sign is actually a unary minus making the -202 into 202, it doesn't do a subtraction. It wouldn't have been as obfuscated if it had been written -4.*F/OO/OO see?
So, the code calls the F_00 function to change the values of F and OO, then prints out some math mangling of those values.
The last thing that makes this code more complicated is that they didn't declare their return types for F_OO or main and attempted to assume then as void (which is invalid, proper C would default them to integers). I'll ignore errors associated with not declaring includes or function prototypes and assume those were just not put in the excerpt.
-D-
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anton
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Since 4.*-F/OO/OO results in an approximation of Pi, we get:
Pi = -4F/OO2
Pi*(OO/2)2 = -F
It makes sense to assume that OO is the diameter of a circle, and F is its area (negative). The circle is actually the one "drawn" in the function F_OO(). Later, I will replace F with a and OO with d.
Let's see what happens in the F_OO function. Each line consists of "_" followed by a string of "-_". Each "_" is replaced with "a-->0 || a-d--;" which means following:
- Subtract one from a. (a--)
- If, before the subtraction, a was negative then perform "a-d--", since the operator || executes its right part only when the left part is false. The meaningful action here is only "d--"; that is, subtract one from d.
The underscore in each "-_" is replaced with the same thing; the only difference is the initial minus sign. Now -a is compared with zero; since -a is always positive, the second part never gets executed.
And now we get the full picture: each of "_" and "-_" decreases a by one; thus, a contains the negative area of the circle. In addition, each initial "_" decreases d by one - in the end d becomes equal to the negative height of the circle, which is the same as its diameter.
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Paul
Newbie
Posts: 1
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Re: Obfuscated code
« Reply #2 on: Apr 6th, 2013, 10:07pm » |
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People keep showing fractions of pi.You all need to realise pi is a whole number and the rest of the numbers are the fractions.Point then nonpoint.The nonpoint should be a whole number?Ok,seems right doesn't it?
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