显式定义变量地址（在Go中）

Question

Simplified Question:

Is it practical for a programmer to keep track of the addresses of variables, so that a variable's address can be used as a point of data on that variable?

Original Question:

I am attempting to wrap my head around how variables are stored and referenced by address using pointers in Go.

As a general principal, is it ever useful to assign a variable's address directly? I can imagine a situation in which data could be encoded in the physical (virtual) address of a variable, and not necessarily the value of that variable.

For instance, the 1000th customer has made a 500 dollars of purchases. Could I store an interger at location 1000 with a value of 500?

I know that the common way to do something like this is with an array, where the variable at position 999 corresponds to the 1000th customer, but my question is not about arrays, it's about assigning addresses directly.

Suppose I'm dealing with billions of objects. Is there an easy way to use the address as part of the data on the object, and the value stored at that location as different data?

for instance, an int at address 135851851904 holds a value of 46876, 135851851905 holds 123498761, etc. I imagine at this point an array or slice would be far too large to be efficient.

Incidentally, if my question due to a misunderstanding, is there a resource someone can provide which explains the topic in deep, but understandable detail? I have been unable to find a good resource on the subject that really explains the details.

Answer 1

is it ever useful to assign a variable's address directly?

You can use the unsafe package to achieve that but the idea is that you don't do it unless you have a concrete and otherwise unsolvable use-case that requires it.

Could I store an interger at location 1000 with a value of 500?

As mentioned before it is possible but choosing an arbitrary address won't get you far because it may not even be mapped. If you write to such a location you'll get a access violation (and your program will crash). If you happen to hit a valid address number you'll likely be overwriting other data that your program needs to run.

Is there an easy way to use the address as part of the data on the object, and the value stored at that location as different data?

In general no.

If you managed to build some kind of algebraic structure closed under the operations by which your own pointer-arithmetic is defined in a finite set of addresses which you can guarantee to always be a valid virtual memory segment then yes but it defeats the purpose of using a garbage collected language. Additionally it would be hell to read such a program.