Re: Are padding bits always zero?

[Honey via Digitalmars-d-learn]

On Saturday, 24 June 2017 at 12:41:47 UTC, Steven Schveighoffer 
wrote:
Any padding bits between fields should be 0 as long as the 
struct is initialized (i.e. as long as you don't do Struct s = 
void).

Padding bits after the fields I assume would be 0, but I don't 
know if this is defined. It's possible the compiler doesn't 
consider those bits to be part of the struct, and just there 
for alignment.

There is no spec for this, but I know that when the compiler 
has to fill gaps with something it chooses 0.

Thanks. Your answer has generated more questions. ;-)

Let's say, I have a struct S of size n with m bits of padding at 
the end. How can I find m?

Is it possible to provide a facility Pad such that for any struct 
T, Pad!T is a struct that mimics T but contains explicit instead 
of implicit padding? E.g.

struct Foo
{
   ubyte b;
   double d;
   int i;
}

struct Pad!Foo
{
   ubyte b;
   ubyte[7] __padding_0;
   double d;
   int i;
   ubyte[4] __padding_1;
}