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Lines without a '\ 0' char?

If by mistake I define a char array without "\ 0" as its last character, what happens then? I ask this because I noticed that if I try to iterate over the while (cnt! = '\ 0') array, where cnt is the int variable used as the index for the array and at the same time print the cnt values ​​to monitor what happens , the iteration stops at the last character + 2. Additional characters are, of course, random, but I can’t understand why it should stop after 2. When does the compiler automatically insert the character '\ 0'? Links to related documentation will be appreciated.

To clarify, I will give an example. Say the array "str" ​​contains the word doh (without "\ 0"). Printing the cnt variable in each loop would give me this DOH + or doh ^ etc.

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EDIT (undefined behavior)

Access to array elements outside the bounds of the array is undefined behavior.
Calling string functions with anything other than string C is undefined behavior.
Do not do that!

Line C is a sequence of bytes ending with a '\0'(a NUL terminator). All bytes must belong to the same object.

In any case, you see a coincidence!

But it can happen like this:

                        ,------------------ garbage
                        | ,---------------- str[cnt] (when cnt == 4, no bounds-checking)
memory ----> [...|d|o|h|*|0|0|0|4|...]
                  |   |   \_____/  -------- cnt (big-endian, properly 4-byte aligned)
                  \___/  ------------------ str
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