Question

I am a bit confused about Memory address alingment for union.

typedef union { 
               char state[x];
               char encode[4];
               int index;
} Location;

We use several alignment rule while writing code, ex:

int      4 bit alignment
double   4 bit for linux
char *   4 bit for linux

“how that union will be aligned”
For those conditions;
If

   x < 4      ?
   x = 4      ?
   x > 4      ?

platform linux
assembly x86 64 bit

NOTE: If you have better opinion, feel free when improve that question

Answer 1

I’m a bit confused as to what your actual question is 🙂

But, if you’re asking how that union will be aligned, a union has to follow two relevant rules here.

1. All items must start at the start of the union.
2. The union as a whole must have the alignment of its strictest component.

In other words, it’s likely that the int is the driving force here in terms of alignment

The value of x is irrelevant here if the alignment of a single char is one. It’s not the whole array that needs to be aligned, just each element of it.