void pointer to struct pointer cast

What you say is all good but I'm having a similar problem casting (elegantly) a common pointer at runtime.

I have a common kernel which uses various dll's to implement a particular sub-system determined at runtime. Each sub-system requires a different data structure; the pointer to which must be stored at the kernel level to be within scope at runtime when I malloc() the required structure space.

I therefore want a generic (void*) pointer in the kernel. I do not want to use a specific typedef as this requires the sub-system data structure to be defined in an include that the kernel has access to (this is really my problem).

I am trying to make each sub-system (dll) self contained so wish to keep all the data definitions with the sub-system (i.e. not available to the kernel at build time).

So what I require is a way to declare a pointer (presumably 'void') and then assign it a structure type at runtime so I don't need to cast each access to the structure.

Doesn't seem a big ask but I can't see anyway around not using your

(struct*)ptr->a

syntax but this will be very messy for the many hundreds of references I'm making to the structure members.

Any other ideas?

What you say is all good but I'm having a similar problem casting (elegantly) a common pointer at runtime.

I have a common kernel which uses various dll's to implement a particular sub-system determined at runtime. Each sub-system requires a different data structure; the pointer to which must be stored at the kernel level to be within scope at runtime when I malloc() the required structure space.

I therefore want a generic (void*) pointer in the kernel. I do not want to use a specific typedef as this requires the sub-system data structure to be defined in an include that the kernel has access to (this is really my problem).

I am trying to make each sub-system (dll) self contained so wish to keep all the data definitions with the sub-system (i.e. not available to the kernel at build time).

So what I require is a way to declare a pointer (presumably 'void') and then assign it a structure type at runtime so I don't need to cast each access to the structure.

Doesn't seem a big ask but I can't see anyway around not using your

(struct*)ptr->a

syntax but this will be very messy for the many hundreds of references I'm making to the structure members.

Any other ideas?

But it is!

Types are purely a compile-time, source thing - they have no meaning at runtime to the actual CPU!

How about #define-ing a macro...?

You have 2 conflicting goals.
The kernel accessing data, and you not wanting to have an understanding of what it is accessing because it is in a DLL. If the Kernel merely needs to pass the data (pointer) I suppose this works.

Erstwhile making a macro is likely the 'cleanest' route.
IE

typedef struct insect
{
 float value;
 char *name;
 uint32_t count;
}
insect;

#define INSECT(VPTR) ((insect *)(VPTR))
#define INSECT_VALUE(VPTR) INSECT(VPTR)->value
#define INSECT_NAME(VPTR)  INSECT(VPTR)->name
#define INSECT_COUNT(VPTR) INSECT(VPTR)->count

etc

"I therefore want a generic (void*) pointer in the kernel. ...

So what I require is a way to declare a pointer (presumably 'void') and then assign it a structure type at runtime so I don't need to cast each access to the structure."

Is there a reason that each subsystem can't simply assign the 'void*' to its own subsystem-specific structure pointer and use that? No casting required.

Note that C and C++ differs a bit for void* pointers.