Memory model - cppreference.com (original) (raw)

Defines the semantics of computer memory storage for the purpose of the C++ abstract machine.

The memory available to a C++ program is one or more contiguous sequences of bytes. Each byte in memory has a unique address.

[edit] Byte

A byte is the smallest addressable unit of memory. It is defined as a contiguous sequence of bits, large enough to hold

• the value of any UTF-8 code unit (256 distinct values) and of

Similar to C, C++ supports bytes of sizes 8 bits and greater.

The types char, unsigned char, and signed char use one byte for both storage and value representation. The number of bits in a byte is accessible as CHAR_BIT or std::numeric_limits<unsigned char>::digits.

[edit] Memory location

A memory location is the storage occupied by the object representation of either an object of scalar type that is not a bit-field, or the largest contiguous sequence of bit-fields of non-zero length.

Note: Various features of the language, such as references and virtual functions, might involve additional memory locations that are not accessible to programs but are managed by the implementation.

struct S { char a; // memory location #1 int b : 5; // memory location #2 int c : 11, // memory location #2 (continued) : 0, d : 8; // memory location #3 struct { int ee : 8; // memory location #4 } e; } obj; // The object “obj” consists of 4 separate memory locations

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

[edit] See also