POD

[Walter Bright]

On 12/29/2006 5:41 AM, Aleksey S. Skidan wrote:
> I just wonder if there's such a thing as POD type in D? I have failed to find
> one. The extern(C) struct seems not to be the thing because it is hardwired to
> the ABI.
>

D's definition of POD:

/***************************************
  * Return true if struct is POD (Plain Old Data).
  * This is defined as:
  *      not nested
  *      no postblits, constructors, destructors, or assignment operators
  *      no fields with with any of those
  * The idea being these are compatible with C structs.
  *
  * Note that D struct constructors can mean POD, since there is always default
  * construction with no ctor, but that interferes with OPstrpar which wants it
  * on the stack in memory, not in registers.
  */
bool StructDeclaration::isPOD()
{
     if (isnested || cpctor || postblit || ctor || dtor)
         return false;

     /* Recursively check any fields have a constructor.
      * We should cache the results of this.
      */
     for (size_t i = 0; i < fields.dim; i++)
     {
         Dsymbol *s = fields[i];
         VarDeclaration *v = s->isVarDeclaration();
         assert(v && v->storage_class & STCfield);
         if (v->storage_class & STCref)
             continue;
         Type *tv = v->type->toBasetype();
         while (tv->ty == Tsarray)
         {   TypeSArray *ta = (TypeSArray *)tv;
             tv = tv->nextOf()->toBasetype();
         }
         if (tv->ty == Tstruct)
         {   TypeStruct *ts = (TypeStruct *)tv;
             StructDeclaration *sd = ts->sym;
             if (!sd->isPOD())
                 return false;
         }
     }
     return true;
}