3.1 Size and Alignment of Atomic C Types
The following
table shows the atomic data types and how they are represented. Alignment
(align columns) is in bytes.
Table 7 Size and alignment of atomic C types
|
|
|
|
|
|
|
|
|
|
Integral
|
|
|
|
|
|
|
|
|
|
_Atomic _Bool
|
1
|
1
|
1
|
1
|
1
|
1
|
1
|
1
|
|
_Atomic char
_Atomic signed char
|
1
|
1
|
1
|
1
|
1
|
1
|
1
|
1
|
|
_Atomic unsigned char
|
1
|
1
|
1
|
1
|
1
|
1
|
1
|
1
|
|
_Atomic short
_Atomic signed short
|
2
|
2
|
2
|
2
|
2
|
2
|
2
|
2
|
|
_Atomic unsigned short
|
2
|
2
|
2
|
2
|
2
|
2
|
2
|
2
|
|
_Atomic int
_Atomic signed int
_Atomic enum
|
4
|
4
|
4
|
4
|
4
|
4
|
4
|
4
|
|
_Atomic unsigned int
|
4
|
4
|
4
|
4
|
4
|
4
|
4
|
4
|
|
_Atomic long
_Atomic signed long
_Atomic unsigned long
|
8
|
8
|
4
|
4
|
8
|
8
|
4
|
4
|
|
_Atomic long long
_Atomic signed long long
_Atomic unsigned long long
|
8
|
8
|
8
|
8
|
8
|
8
|
8
|
8
|
|
Pointer
|
|
|
|
|
|
|
|
|
|
any-type _Atomic *
_Atomic( any-type (*) () )
|
8
|
8
|
4
|
4
|
8
|
8
|
4
|
4
|
|
Floating-Point
|
|
|
|
|
|
|
|
|
|
_Atomic float
|
4
|
4
|
4
|
4
|
4
|
4
|
4
|
4
|
|
_Atomic double
|
8
|
8
|
8
|
8
|
8
|
8
|
8
|
8
|
|
_Atomic long double
|
16
|
16
|
12
|
4
|
16
|
16
|
16
|
8
|
|
Complex
|
|
|
|
|
|
|
|
|
|
_Atomic float _Complex
|
8
|
8
|
8
|
8
|
8
|
8
|
8
|
8
|
|
_Atomic double _Complex
|
16
|
16
|
16
|
16
|
16
|
16
|
16
|
8
|
|
_Atomic long double _Complex
|
32
|
16
|
24
|
4
|
32
|
16
|
32
|
8
|
|
Imaginary
|
|
|
|
|
|
|
|
|
|
_Atomic float _Imaginary
|
4
|
4
|
4
|
4
|
4
|
4
|
4
|
4
|
|
_Atomic double _Imaginary
|
8
|
8
|
8
|
8
|
8
|
8
|
8
|
8
|
|
_Atomic long double _Imaginary
|
16
|
16
|
12
|
4
|
16
|
16
|
16
|
8
|
|
struct (selective examples)
|
|
|
|
|
|
|
|
|
|
_Atomic struct {char a[2];}
|
2
|
2
|
2
|
2
|
2
|
2
|
2
|
2
|
|
_Atomic struct {short a[2];}
|
4
|
4
|
4
|
4
|
4
|
4
|
4
|
4
|
|
_Atomic struct {int a[2];}
|
8
|
8
|
8
|
8
|
8
|
8
|
8
|
8
|
|
_Atomic struct {char a[16];}
|
16
|
16
|
16
|
16
|
16
|
16
|
16
|
8
|
|
The general alignment rule for atomic struct types is: if the size
of the struct type is one of 2, 4, 8 or 16 and the alignment of the
corresponding non-atomic type is smaller than the size, then the alignment of the atomic
struct type is increased to match the size.
Atomic types are not permitted for bit-fields.