“NUL”字符（“\0”）字节是分隔的还是分配给带有字符串的字符数组？

Question

If i define a string:

   char array[5] = {"hello"};

Is the NUL character (\0) byte "hidden" added to "array[5]", so that the array is not contained of 5 bytes in memory, it is contained of 6 bytes?

OR does the NUL character byte lie "separated" from "array[5]" in memory only after the last element of the char-array, but not directly assigned to "array[5]"?

If i would put this:

  i = strlen(array);
  printf("The Amount of bytes preserved for array: %d",i);

What would be the result for the amount of bytes preserved for array[5]?

Does the "NUL" character ("\0") byte lie separated after the last element of char-array in the memory or is it assigned to that char-array?

Answer 1

Does the "NUL" character ("\0") byte lie separated after the last element of char-array in the memory or is it assigned to that char-array?

No. Neither answer is correct. See below for details.

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Answer for C:

If you write your code like that, with an explicit size that is too small for the terminator, array will have exactly 5 elements and there will be no NUL character.

strlen(array) has undefined behavior because array is not a string (it has no terminator). char array[5] = {"hello"}; is equivalent to char array[5] = {'h', 'e', 'l', 'l', 'o'}; .

On the other hand, if you write

char array[] = "hello";

it is equivalent to

char array[6] = {'h', 'e', 'l', 'l', 'o', '\0'};

and strlen will report 5 .

The relevant part of the C standard is:

An array of character type may be initialized by a character string literal, optionally enclosed in braces. Successive characters of the character string literal ( including the terminating null character if there is room or if the array is of unknown size) initialize the elements of the array.

(Emphasis mine.)

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Answer for C++:

Your code is invalid. [dcl.init.string] states:

There shall not be more initializers than there are array elements. [ Example:

 char cv[4] = "asdf"; // error

is ill-formed since there is no space for the implied trailing '\0' . — end example ]

Answer 2

In C++, char array[5] = {"hello"} is of six bytes. But you have assigned five bytes only. Therefore, the array declaration is incorrect.

Alternatively, this works: char array[6] = {"hello"} .