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sizeof cannot be used in C preprocessor expressions, such as #if, because it is an element of the programming language, not of the preprocessor syntax, which has no data types. The following example in C++ uses the operator sizeof with variadic templates.
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].
For example, += and -= are often called plus equal(s) and minus equal(s), instead of the more verbose "assignment by addition" and "assignment by subtraction". The binding of operators in C and C++ is specified (in the corresponding Standards) by a factored language grammar, rather than a precedence table. This creates some subtle conflicts.
Both of these types are defined in the <stddef.h> header (cstddef in C++). size_t is an unsigned integer type used to represent the size of any object (including arrays) in the particular implementation. The operator sizeof yields a value of the type size_t.
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.
C++, however, requires that if a function with external linkage is declared inline in any translation unit then it must be so declared (and therefore also defined) in every translation unit where it is used, and that all the definitions of that function be identical, following the ODR. Static inline functions behave identically in C and C++.
In the C++ programming language, decltype is a keyword used to query the type of an expression.Introduced in C++11, its primary intended use is in generic programming, where it is often difficult, or even impossible, to express types that depend on template parameters.
The A::max_size() member function returns the largest number of objects of type T that could be expected to be successfully allocated by an invocation of A::allocate; the value returned is typically A::size_type(-1) / sizeof(T). [14] Also, the A::address member function returns an A::pointer denoting the address of an object, given an A::reference.