How to handle nested structs when converting C headers?

In the following snippet i'm currently converting, how would you convert the nested typed union and structures? Would you declare them separately then use their types in the Tcl_Obj struct? or is there a nice way in D to nest them like C?

typedef struct Tcl_Obj {
    int refCount;		/* When 0 the object will be freed. */
    char *bytes;		/* This points to the first byte of the
				 * object's string representation. The array
				 * must be followed by a null byte (i.e., at
				 * offset length) but may also contain
				 * embedded null characters. The array's
				 * storage is allocated by ckalloc. NULL means
				 * the string rep is invalid and must be
				 * regenerated from the internal rep.  Clients
				 * should use Tcl_GetStringFromObj or
				 * Tcl_GetString to get a pointer to the byte
				 * array as a readonly value. */
    int length;			/* The number of bytes at *bytes, not
				 * including the terminating null. */
    Tcl_ObjType *typePtr;	/* Denotes the object's type. Always
				 * corresponds to the type of the object's
				 * internal rep. NULL indicates the object has
				 * no internal rep (has no type). */
    union {			/* The internal representation: */
	long longValue;		/*   - an long integer value. */
	double doubleValue;	/*   - a double-precision floating value. */
	VOID *otherValuePtr;	/*   - another, type-specific value. */
	Tcl_WideInt wideValue;	/*   - a long long value. */
	struct {		/*   - internal rep as two pointers. */
	    VOID *ptr1;
	    VOID *ptr2;
	} twoPtrValue;
	struct {		/*   - internal rep as a wide int, tightly
				 *     packed fields. */
	    VOID *ptr;		/* Pointer to digits. */
	    unsigned long value;/* Alloc, used, and signum packed into a
				 * single word. */
	} ptrAndLongRep;
    } internalRep;
} Tcl_Obj;

On Wednesday, 11 December 2013 at 22:45:35 UTC, Gary Willoughby wrote:
> How to handle nested structs when converting C headers?

Nested structs and unions like in your example are supported in D too, same syntax, same effect.

On Wednesday, 11 December 2013 at 22:54:04 UTC, Adam D. Ruppe wrote:
> Nested structs and unions like in your example are supported in D too, same syntax, same effect.

Actually, no, not quite the same syntax, I didn't notice the name at the end of the C one (in D, the anonymous nested structs and unions are supported).

But almost the same then: make them a nested type with a name after the struct or union keyword then the member. So

    struct TwoPtrValue {                /*   - internal rep as two pointers. */
            VOID *ptr1;
            VOID *ptr2;
        }
     TwoPtrValue twoPtrValue;

that's how I'd do it

Adam D. Ruppe:

> Nested structs and unions like in your example are supported in D too, same syntax, same effect.

But don't forget to add to use "static struct" instad of "struct".

Bye,
bearophile

On Wednesday, 11 December 2013 at 23:12:39 UTC, bearophile wrote:
> Adam D. Ruppe:
>
>> Nested structs and unions like in your example are supported in D too, same syntax, same effect.
>
> But don't forget to add to use "static struct" instad of "struct".
>
> Bye,
> bearophile

Have you got an example because i always get:

tcl.d(713): Error: no identifier for declarator twoPtrValue
tcl.d(718): Error: no identifier for declarator ptrAndLongRep
tcl.d(719): Error: no identifier for declarator internalRep

On Wednesday, 11 December 2013 at 23:27:57 UTC, Gary Willoughby wrote:
> On Wednesday, 11 December 2013 at 23:12:39 UTC, bearophile wrote:
>> Adam D. Ruppe:
>>
>>> Nested structs and unions like in your example are supported in D too, same syntax, same effect.
>>
>> But don't forget to add to use "static struct" instad of "struct".
>>
>> Bye,
>> bearophile
>
> Have you got an example because i always get:
>
> tcl.d(713): Error: no identifier for declarator twoPtrValue
> tcl.d(718): Error: no identifier for declarator ptrAndLongRep
> tcl.d(719): Error: no identifier for declarator internalRep

Like this perhaps:

struct Tcl_Obj
{
    int refCount;
    char* bytes;
    int length;
    Tcl_ObjType* typePtr;

    static union internalRep
	{
		c_long longValue;
		double doubleValue;
		void* otherValuePtr;
		Tcl_WideInt wideValue;

		static struct twoPtrValue
		{
			void* ptr1;
			void* ptr2;
		}

		static struct ptrAndLongRep
		{
			void* ptr;
			c_ulong value;
		}
    }
}

Gary Willoughby:

> Have you got an example because i always get:
>
> tcl.d(713): Error: no identifier for declarator twoPtrValue
> tcl.d(718): Error: no identifier for declarator ptrAndLongRep
> tcl.d(719): Error: no identifier for declarator internalRep

In D you can't define a struct/union and use it to define an instance on the fly. You have to split definition and use in two parts.

Bye,
bearophile

On Wednesday, 11 December 2013 at 23:35:04 UTC, Gary Willoughby wrote:
>     static union internalRep


try

static union InternalRep { /* note the capital letter */
  /* snip */
}
InternalRep internalRep;; // still need a decl

On Wednesday, 11 December 2013 at 23:36:11 UTC, bearophile wrote:
> In D you can't define a struct/union and use it to define an instance on the fly.

Well, you can if it is anonymous.

struct Foo {
    union {
        struct { ubyte a; ubyte b; }
        ubyte[2] arr;
    }
}

That works in D, and it makes foo.a == arr[0] and foo.b == arr[1];

Adam D. Ruppe:

> Well, you can if it is anonymous.
>
> struct Foo {
>     union {
>         struct { ubyte a; ubyte b; }
>         ubyte[2] arr;
>     }
> }
>
> That works in D, and it makes foo.a == arr[0] and foo.b == arr[1];

Right :-) I like D structs.

Bye,
bearophile