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The operator sizeof produces the required memory storage space of its operand when the code is compiled. The operand is written following the keyword sizeof and may be the symbol of a storage space, e.g., a variable, an expression, or a type name. Parentheses for the operand are optional, except when specifying a type name.
In C++, complex arithmetic can be performed using the complex number class, but the two methods are not code-compatible. (The standards since C++11 require binary compatibility, however.) [16] Variable length arrays. This feature leads to possibly non-compile time sizeof operator. [17]
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.
The initial proposal to the C++ standards committee outlined a combination of the two variants; the operator would return a reference type only if the declared type of the expression included a reference. To emphasize that the deduced type would reflect the "declared type" of the expression, the operator was proposed to be named decltype. [2]
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.
This is a list of operators in the C and C++ programming languages.. All listed operators are in C++ and lacking indication otherwise, in C as well. Some tables include a "In C" column that indicates whether an operator is also in C. Note that C does not support operator overloading.
Although function pointers in C and C++ can be implemented as simple addresses, so that typically sizeof(Fx)==sizeof(void *), member pointers in C++ are sometimes implemented as "fat pointers", typically two or three times the size of a simple function pointer, in order to deal with virtual methods and virtual inheritance [citation needed].
In C++03, a class or struct must follow a number of rules for it to be considered a plain old data ... In C++03, the sizeof operator can be used on types and objects ...