alignof operator (since C++11)

Queries alignment requirements of a type.

[edit] Syntax

Returns a value of type std::size_t .

[edit] Explanation

Returns the alignment, in bytes, required for any instance of the type indicated by type-id, which is either complete object type, an array type whose element type is complete, or a reference type to one of those types.

If the type is reference type, the operator returns the alignment of referenced type; if the type is array type, alignment requirement of the element type is returned.

[edit] Notes

See alignment for the meaning and properties of the value returned by alignof.

[edit] Keywords

alignof

[edit] Example

#include <iostream>
 
struct Foo
{
 int i;
 float f;
 char c;
};
 
// Note: alignas(alignof(long double)) below can be
// simplified to alignas(long double) if desired.
struct alignas(alignof(long double)) Foo2
{
 // put your definition here
}; 
 
struct Empty {};
 
struct alignas(64) Empty64 {};
 
#define SHOW(expr) std::cout << #expr << " = " << (expr) << '\n'
 
int main()
{
 SHOW(alignof(char));
 SHOW(alignof(int*));
 SHOW(alignof(Foo));
 SHOW(alignof(Foo2));
 SHOW(alignof(Empty));
 SHOW(alignof(Empty64));
}

alignof(char) = 1
alignof(int*) = 8
alignof(Foo) = 4
alignof(Foo2) = 16
alignof(Empty) = 1
alignof(Empty64) = 64

[edit] Defect reports

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

[edit] References

[edit] See also

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