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Comment by nneonneo | Hacker News Reader

Neat hack! One minor improvement suggestion: if you seed the RNG with `__DATE__` (or a hash of that string), then you can replicate the one-puzzle-a-day experience with no need for an externally-supplied seed variable.

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Good point! I wanted to be able to modify SEED in order to test that everything was fine with multiple words, using __DATE__ didn't come to mind :)

    #ifndef SEED
    #define SEED __DATE__
    #endif

Wondering what happens if you allocate a chunk of uninitialized memory inside a constexpr? Could this be used for a quick constexpr RNG seed?

You simply can't. The constexpr environment won't let you have uninitialized variables/memory anywhere. It won't let you access dangling/out-of-bounds pointers either, overflow two-complement types, etc.

Accessing uninitialized objects is undefined behaviour, which traps in the constexpr context.

A very neat thing of constexpr is that it does not have undefined behaviour ; any thing that would cause UB at run-time is flagged as a compile error. Every variable must be fully initialized.

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