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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