Thanks to ilproxyil for correcting the last bit here and answering the last part of your question: Although this is a slightly different example, it shows that the `*` does not result in a conversion of lvalue to rvalue, and since the expression is the immediate operand of `&` expecting an lvalue, then the behavior is defined. Even if it is legal, why deviate from the convention? Array + 5 is anyway shorter and in my opinion more readable. 27) An array without elements is _____. A) legal in C++ B) illegal in C++ C) automatically deploys an element with a value of zero D) automatically provides a value — the null terminator E) None of these elements 6) If you use the same ____, you can create relationships between the data stored in two or more arrays. A) Name of table B) Data C) Index D) Arguments E) None of this Here is what the standard has to say on the subject: 25) A(n) _____ can be used to specify the starting values of an array. A) Initialization list B) Table name C) Index D) Element E) None of them According to the gcc documentation for C++, &array[5] is legal. In C++ and C, you can safely address the item beyond the end of an array – you get a valid pointer. Therefore, &array[5] is a legal expression. Edit: Oh, now I see that you`re not really asking if holding a pointer to this address is legal, but if exactly this way of getting the pointer is legal. I will now turn the floor over to the other respondents.
A post-fixed expression followed by a bracketed expression [] is an index label of an element of an array object. The definition of the index operator [] is that E1[E2] is the same as (*(E1)+(E2))). Due to the conversion rules that apply to the binary operator +, E1[E2] is the 2nd element of E1 (counting from zero) if E1 is an array object (equivalent to a pointer to the initial element of an array object) and E2 is an integer. array[5] is not a qualified identifier, as far as I can say (the list is on p. 87); The next one appears to be the identifier, but while array is an identifier, array[5] is not. It is not a lvalue because „A lvalue refers to an object or function“. (p. 76). array[5] is obviously not a function and is not guaranteed to refer to a valid object (since array + 5 comes after the last array element assigned).
Edit: By the way, the end() iterator for STL containers is usually implemented this way (as a pointer to a single past-end), so that`s pretty good evidence that the practice is legal. I don`t think it`s illegal, but I think &array`s behavior[5] is not defined. Which seems to me to imply that yes, you can legally dereference it, but the result of reading or writing to the place is not specified. An address constant expression is a pointer to a lvalue. The pointer is explicitly created using the Unary &. or with an array expression (4.2) . Kind. The index operator []. can be used when creating an address constant expression, but the value of an object should not be called using these operators. If the index operator is used, one of its operands must be an integral constant expression.
Your example is legal, but only because you don`t use an out-of-bounds pointer. As long as there is no out-of-bounds pointer dereferencing, the operation is fully covered by the standard and the entire behavior is defined. From my reading, the above is completely legal. The second argument presented below is: * is the dereferencing operator. And although it is a commonly used term to describe the „*“ operator; This term is deliberately avoided in the standard, as the term „de-indexing“ is not well defined in terms of language and meaning for the underlying material. At this point, you have an indefinite behavior because the expression ((E1)+(E2)) did not actually point to an object, and the norm indicates what the result should be unless it is. Note: It is legal to add to get one beyond the table (p. 113): It seems to me that &array[5] is legally C++ since it is a constant expression of address. 30) What is the last legal clue that can be used with the following table? 29) It is ____ to pass an argument to a function that contains a single array element, such as numbers[3]. A) illegal in C++ B) legal in C++ C) not recommended by the ANSI committee D) no good programming practice E) None of these elements 3) To access an array element, use the name of the array and ____ of the element. A) Data type B) index C) Name D) Value E) None of this Of course, this is for the + operator.
To be sure, here`s what the standard says about the array index: I believe it`s legal, and it depends on the conversion of „lvalue into rvalue.“ The last line of Core Issue 232 is as follows: The U.S. Supreme Court has agreed to hear an offer from President Biden`s administration to reinstate a federal law that criminalizes encouraging illegal immigration after it was struck down by a lower court as a violation of free speech. nbcnews.to/3UFhLnG U.S. Supreme Court is reviewing prohibition on promoting illegal immigration reut.rs/3W4vaXl 12) An element of a two-dimensional array is denoted by ____ followed by ___. A) the name of the table, the column number of the element B) the row subscript of the element, the column subscript of the element C) a comma, a semicolon D) the line subscript of the element, the name of the table E) None of them show an example of: A) Standard arguments B) an invalid array declaration C) an invalid array initialization D) implicit size of the array E) None of these cases If your example is NOT a general case, but a specific one, so it`s allowed. You can legally, AFAIK, move one beyond the allocated memory block. However, this does not work for a generic case, that is, when you try to access elements farther from 1 from the end of an array. Note that the standard explicitly allows pointers to point to an element beyond the end of the array unless they are not referenced. In versions 6.5.2.1 and 6.5.3.2, the expression is &array[5] &*(array + 5), which is equivalent to (array+5), indicating a term beyond the end of the array.