The address of a statically allocated variable is fixed at the time the program begins running, and cannot be changed. The storage space is reserved, and usually initialized, when the program is loaded and begins execution. Statically allocated variables are allocated in the, , or section. In a high level language, storage space for a variable can be allocated in one of three ways: statically, dynamically, and automatically. Typical memory layout for a program with a 32-bit address space. Golden Rule 3: The size of a structure cannot depend on its context.įigure 1.7. Adding padding or trailing bytes only when simple is used as a component of a structure or of an array would make its size ambiguous. It is worth noting that the size of operator must always yield the same value when applied to a type. Removing any of the padding or trailing bytes would make B improperly aligned in some cases (try to lay out vect if simple has no trailing bytes). In all cases, B retains an offset that is a multiple of 2. For BUS16, the same code fragment would yield a natural boundary of 2 and a size of 8 for simple. In all instances of structure simple, B retains an offset that is a multiple of 4. By following the Golden Rules, the compiler guarantees that B is properly aligned in every possible case, as shown by the memory layouts for structure simple, array vect, and structure outer. The most demanding member in simple is the integer B, whose natural boundary is 4 on BUS32. On BUS32, the natural boundary for simple is 4, which means its size must be 12. For example, AAAA represents a 4-byte structure member.Ĭurly braces surround an unpacked structure. The letter is repeated to show how many bytes the member occupies (one letter per byte). Uppercase letters denote a nonbit structure member.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |