What's the meaning of "block is entered recursively"?

Question

I asked a question on reddit. The question was literally Why does the starting point of a lifetime of an automatic object(which doesn't have VLA) precede a scope of an object?
And I got the answer which can be the example of my question.

Code

#include <stdio.h>

int main(void) {
    int i = 0;
back:
    printf("i = %d", i);
    int j;
    if (i < 5) {
        if (i == 0)
            j = 0;
        j += i;
        printf(", j = %d\n", j);
        i++;
        goto back;
    }
    printf("\n");
}

Output

i = 0, j = 0
i = 1, j = 1
i = 2, j = 3
i = 3, j = 6
i = 4, j = 10
i = 5

But someone said "The value of j becomes indeterminate when its declaration is reached, ..." because of C17 6.2.4p6(with my bold)

For such an object that does not have a variable length array type, its lifetime extends from entry into the block with which it is associated until execution of that block ends in any way. (Entering an enclosed block or calling a function suspends, but does not end, execution of the current block.) If the block is entered recursively, a new instance of the object is created each time. The initial value of the object is indeterminate. If an initialization is specified for the object, it is performed each time the declaration or compound literal is reached in the execution of the block; otherwise, the value becomes indeterminate each time the declaration is reached.

Just going to a label in current block differs from repeating an entire associated block in a recursive function or an iterative statement. In this point of view, I don't think j is not affected by the rule(but it's just my thought).

By the way, I think there is a contradiction irrespective of which way we think.
- If int j; isn't created anew in each sequence, it is a redefinition.
- If int j; is created anew in each sequence, j shall have a garbage value from second sequence. But the output is shown as if the value of 'j' is retained.

I read quoted part of documentation over and over, but couldn't understand it. What am I missing?

Answer 1

The part that is important is later:

If an initialization is specified for the object, [...]; otherwise, the value becomes indeterminate each time the declaration is reached.

Each time int j is reached, the value of j becomes indeterminate. j retaining the previous value is also an example of garbage value, as that can be any value. If your code depends on that value, that means the behavior of your code is not defined.

If the block is entered recursively, a new instance of the object is created each time

A "block" is generally something that starts with a { and ends with a }. That paragraph is for recursive function.

void func()
{ // block start
    int a; // new instance of object created each time, even recursively
    func(); // enter the block recursively
} // block end

There is one block in your code created with int main(void) { and another block in your code is the one after if (i < 5) {. That if (i < 5) { block is not entered recursively, it's entered, then leaved, then entered again, then leaved again.

If int j; isn't created anew in each sequence, it is a redefinition.

Quoting that quote:

For such an object [object with automatic storage duration, see previous point in standard] that does not have a variable length array type, its lifetime extends from entry into the block with which it is associated until execution of that block ends in any way.

The lifetime of the object identified by j starts at entry into the block, so I would argue it's not "created anew".

int main(void) { // lifetime of "object j" starts here
                 // but you can't access it, no identifier is associated with it
back:;
    int j; // the identifier `j` is associated with "object j"
           // the value of the object associated with `j` is indeterminate
           // _each time_ execution flow gets here
    goto back;
} // lifetime of "object j" ends here (or at `return`)
  // scope of identifier `j` also ends here