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sizeof is a unary operator in the programming languages C and C++. It generates the storage size of an expression or a data type , measured in the number of char -sized units. Consequently, the construct sizeof (char) is guaranteed to be 1 .
The operator sizeof yields a value of the type size_t. The maximum size of size_t is provided via SIZE_MAX, a macro constant which is defined in the <stdint.h> header (cstdint header in C++). size_t is guaranteed to be at least 16 bits wide. Additionally, POSIX includes ssize_t, which is a signed integer type of the same width as size_t.
All logical operators exist in C and C++ and can be overloaded in C++, albeit the overloading of the logical AND and logical OR is discouraged, because as overloaded operators they behave as ordinary function calls, which means that both of their operands are evaluated, so they lose their well-used and expected short-circuit evaluation property ...
The C and C++ programming languages are closely related but have many significant differences. C++ began as a fork of an early, pre-standardized C, and was designed to be mostly source-and-link compatible with C compilers of the time.
The sizeof operator on such a struct gives the size of the structure as if the flexible array member were empty. This may include padding added to accommodate the flexible member; the compiler is also free to re-use such padding as part of the array itself.
It should be noted that, since sizeof is a compile-time operation, it is impossible to use sizeof to determine the size of an array if it cannot be evaluated at compile time. That's incorrect since C99 introduces variable-length arrays. In that case, the size of the array can only be evaluated at run-time, and sizeof() will be evaluated at runtime.
The C and C++ syntax given above is the canonical one used in all the textbooks - but it's difficult to read and explain. Even the above typedef examples use this syntax. However, every C and C++ compiler supports a more clear and concise mechanism to declare function pointers: use typedef , but don't store the pointer as part of the definition.
In 1989, C++ 2.0 was released, followed by the updated second edition of The C++ Programming Language in 1991. [32] New features in 2.0 included multiple inheritance, abstract classes, static member functions, const member functions, and protected members. In 1990, The Annotated C++ Reference Manual was published. This work became the basis for ...