Re: [RFC][PATCH 1/2] Create initial kernel ABI header infrastructure

[Kyle Moffett]

On Mar 26, 2006, at 10:38:59, Martin Mares wrote:
> > It _is_ fragile, but for a number of POSIX-defined structs that's  
> > actually the only way to do it without duplicating the data  
> > structure in entirety, unless the GCC people can implement a  
> > "typedef struct foo struct bar;"
>
> Actually, something like that can be achieved using anonymous  
> structure members:
>
> struct xxx {
> 	struct yyy;
> };

Oh, if only that worked.  Actually, what happens is the "struct yyy;"  
declaration inside of struct xxx looks just like "struct yyy;" out in  
the middle of some random header file.  It predeclares the existence  
of a struct yyy and does nothing else.

For instance, the following sample program:
  struct foo {
  	int a;
  	int b;
  };

  struct bar {
  	struct foo;
  };

  int main()
  {
  	struct foo myfoo = { .a = 1, .b = 2 };
  	struct bar mybar = { .a = 1, .b = 2 };
  	return 0;
  }

Compiled like this:
  gcc mytest.c -o mytest

Generates these errors:
  mytest.c:7: warning: declaration does not declare anything
  mytest.c: In function `main':
  mytest.c:12: error: unknown field `a' specified in initializer
  mytest.c:12: warning: excess elements in struct initializer
  mytest.c:12: warning: (near initialization for `mybar')
  mytest.c:12: error: unknown field `b' specified in initializer
  mytest.c:12: warning: excess elements in struct initializer
  mytest.c:12: warning: (near initialization for `mybar')

Cheers,
Kyle Moffett

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