How is the STL vector typically implemented? It has a raw char [] repository, which sometimes changes by a certain coefficient, and then causes a new placement when the pushed_back element (a very interesting grammatical form that I should mention), linguists should study such forms of verbs as pushed_back :) < w> And then there are alignment requirements. So the natural question is, how can I name a new placement on char [] and make sure that the alignment requirements are met. So I searched the 2003 C ++ standard for the word “alignment” and found the following:
Paragraph 3.9 Paragraph 5
Object types have alignment requirements (3.9.1, 3.9.2). Alignment of the full type of an object is an integer value defined by the implementation, representing the number of bytes; an object is allocated at an address that meets the requirements for aligning its object type.
Clause 5.3.4 Clause 10:
The new expression passes the amount of space requested by the allocation function as the first argument of type std :: size_t. This argument must be at least the size of the object to be created; it can be larger than the size of the created object only if the object is an array. For char and unsigned char arrays, the difference between the result of the new expression and the address returned by the distribution function must be a multiple of the strictest alignment requirement (3.9) of any type of object whose size is no larger than the size of the created array. [Note. Since it is assumed that the distribution functions return pointers to the store that are properly aligned for objects of any type, this restriction on the service data of the distribution of the array allows you to use the general idiom of allocating arrays of characters,in which objects of other types will subsequently be placed. ]
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1:
X, sizeof (X) == n , X n - ( " - " ).
1: , , 1.
Statement2: 1 , , 5000000 , 5000000, , char , .
Question2: , 1000 500 ( , - 2 )? ?