Question

Anonymous structs have been added in the C11 standard, so

typedef struct { 
    struct {int a, b};
    int c; 
} abc_struct;

is valid and standard. Is it also within the standard to use a typedef in place of the full struct declaration? E.g.:

typedef struct { 
    int a, b;
} ab_struct;

typedef struct { 
    ab_struct;
    int c; 
} abc_struct;

The GCC documentation says that this is a Plan 9 extension, but then it works in the
few compilers I’ve tried (including GCC…). By my reading of the standard itself,
I think it’s OK, but this is the sort of close reading that’s easy to screw up.

Answer 1

This was apparently asked in a question to the C committee by Joseph S. Myers of the gcc team. And the answer is no, it is not valid in C11.

See the answer here:

http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1549.pdf

And Myers’s comment:

This week’s London WG14 meeting agreed to disallow the use of typedefs in declaring anonymous structure and union fields, as per N1549.

source http://gcc.gnu.org/ml/gcc-patches/2011-03/msg01151.html

The question was asked in SC22WG15.12205 see 5.28 SC22WG14.12205, Anonymous Structures (N1425) in http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1490.pdf