It makes more sense if you think of const as "read-only". Volatile just means the compiler can't make the assumption that the compiler is the only thing that can modify the variable. A const volatile variable can return different results when read different times.

[–] [email protected] 10 points 8 months ago* (last edited 8 months ago) (8 children)

I thought of it more in terms of changing constants (by casting the const away). AFAIK when it's not volatile, the compiler can place it into read-only data segment or make it a part of some other data, etc. So, technically, changing a const volatile would be less of a UB compared to changing a regular const (?)

[–] Scoopta 66 points 8 months ago (1 children)

const volatile is used a lot when doing HW programming. Const will prevent your code from editing it and volatile prevents the compiler from making assumptions. For example reading from a read only MMIO region. Hardware might change the value hence volatile but you can't because it's read only so marking it as const allows the compiler to catch it instead of allowing you to try and fail.

[–] [email protected] 27 points 8 months ago (1 children)

I will not tell my kids regular scary stories. I will tell them about embedded systems

[–] [email protected] 22 points 8 months ago* (last edited 8 months ago) (2 children)

When you program embedded you'll also dereference NULL pointers at some point.

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Some platforms can have something interesting at memory address 0x0 (it's often NULL in C).

[–] Scoopta 14 points 8 months ago

In amd64/x86 kernel space you can dereference null as well. My hobby kernel keeps critical kernel structures there XD.

[–] [email protected] 2 points 8 months ago* (last edited 8 months ago)

I was thinking about telling them how in embedded systems it's a good practice to allocate the memory by hand, having in mind the backlog, but yours will come first

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