[Go] Size and alignment guarantees (SPEC)

Reference:
https://golang.org/ref/spec#Size_and_alignment_guarantees


Numeric types:
A numeric type represents sets of integer or floating-point values. 

The predeclared architecture-independent numeric types are:

• uint8       the set of all unsigned  8-bit integers (0 to 255)
• uint16      the set of all unsigned 16-bit integers (0 to 65535)
• uint32      the set of all unsigned 32-bit integers (0 to 4294967295)
• uint64      the set of all unsigned 64-bit integers (0 to 18446744073709551615)
• int8        the set of all signed  8-bit integers (-128 to 127)
• int16       the set of all signed 16-bit integers (-32768 to 32767)
• int32       the set of all signed 32-bit integers (-2147483648 to 2147483647)
• int64       the set of all signed 64-bit integers (-9223372036854775808 to 9223372036854775807)
• float32     the set of all IEEE-754 32-bit floating-point numbers
• float64     the set of all IEEE-754 64-bit floating-point numbers
• complex64   the set of all complex numbers with float32 real and imaginary parts
• complex128  the set of all complex numbers with float64 real and imaginary parts
• byte        alias for uint8
• rune        alias for int32

For the numeric types, the following sizes are guaranteed:

type                                 size in bytes

byte, uint8, int8              1

uint16, int16                   2

uint32, int32, float32      4

uint64, int64, float64, complex64     8

complex128                    16

The following minimal alignment properties are guaranteed:

• For a variable x of any type: unsafe.Alignof(x) is at least 1.
• For a variable x of struct type: unsafe.Alignof(x) is the largest of all the values unsafe.Alignof(x.f) for each field f of x, but at least 1.
• For a variable x of array type: unsafe.Alignof(x) is the same as the alignment of a variable of the array's element type.
• A struct or array type has size zero if it contains no fields (or elements, respectively) that have a size greater than zero. Two distinct zero-size variables may have the same address in memory.