John Carmack on Mutable Variables

Re:John Carmack on Mutable Variables by tialaramex on Friday October 31, 2025 @06:52PM (#45777589)

That's not a constant, that's an immutable variable which is why your diagnostic said it was read-only.

   const int x = 2;
   int *p = &x;
   *p = 3; // Now x is 3

And since I paid for the place where I'm writing this with cash earned writing C a decade or so ago, I think we can rule out "unfamiliar with C" as a symptom.

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Re:John Carmack on Mutable Variables by tredre3 on Saturday November 01, 2025 @09:52PM (#45787212)

Now x is 3 but you also get a compiler warning telling you not to do that.

In my opinion it's a bit disingenuous to argue that it isn't a const just because you can ignore the compiler and shoot yourself in the foot. If you listen to the compiler, it is reflected in the assembly that it is a constant value the same as #define x 2.

Is Rust better at enforcing guarantees? Of course. Is `const` in C `const` if you don't ignore compiler warnings and errors? Also of course.

> And since I paid for the place where I'm writing this with cash earned writing C a decade or so ago

Ditto!

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