Is Using Uninitialized Local Variables a Reliable Way to Generate Random Numbers in C ?

Unveiling the Truths: Is Uninitialized Local Variable a Blazing Random Number Generator?

While uninitialized local variables in C are notorious for Undefined Behavior (UB), some claim they offer a rapid path to random numbers, particularly when employed for visual aesthetics. However, before delving into this possibility, it's crucial to emphasize that relying on UB is akin to playing with fire.

Reading from an uninitialized register on x86[-64] architectures can indeed produce unpredictable results, giving the illusion of randomness. However, there are glaring drawbacks to this approach:

1. Unpredictable Randomness:
The data retrieved from an uninitialized register largely depends on previous stack contents, which might exhibit patterns or even contain sensitive information. Therefore, the resulting "randomness" is far from reliable.

2. Danger Lurks:
UB is a slippery slope where compilers can unleash unpredictable consequences. The compiler might insert malicious code or even alter your codebase's behavior in unforeseen ways.

3. Performance Trap:
Contrary to intuitive reasoning, uninitialized variables don't necessarily enhance performance. Modern compilers employ sophisticated optimizations that render "random" values from uninitialized variables as inefficient as dedicated random number generators.

In comparison to the proposed "random" approach, the built-in rand() function is far superior in terms of speed, reliability, and predictability. It guarantees true randomness by utilizing a pseudo-random number generator.

Therefore, indulging in UB for "randomness" is a reckless gamble. Stick to proven methods like rand() and shield your codebase from the menacing grip of Undefined Behavior.

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