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Feature request for "friendship" of pointers in "C"


Hi, the following scenario has a "definition hole" in the "C" language

code example:

-------------------------
struct base {
  ...
};

struct A {
  struct base obj;
  ...
} aObj;

struct B {
  struct base obj;
  ...
} bObj;

void method_base (struct base * hdl, ...);

method_base(&aObj, ...)
method_base(&bObj, ...)
------------------------

- a POINTER to "A" is also a valid POINTER to "base"

- a POINTER to "B" is also a valid POINTER to "base"

- a POINTER to "base" is NOT a valid POINTER to "A" and "B"

I require a solution for this problem WITHOUT forced pointer cast
code and without "void* and type-check" inflation.

The following solutions are acceptable:

1. "gcc" discover by its own that "base" is a "friend" of "A" and "B".
2. add a "frienddef" keyword like "typedef" using:
     typedef struct base * baseP;
     typedef struct A    * aP;
     typedef struct P    * bP;
     frienddef baseP aP;
     frienddef baseP bP;
3. add a #PRAGMA to enable/disable this feature
4. add a "gcc" api to easy extend "GCC" without being FORCED
   to "hack" the core.

thanks for your help


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