>I don't understand; errno is (*__errno()) so it should compile.

try this:

    % cat finkle.c
    #include <errno.h>
    struct foo {
	    int errno; /* this is a *STRUCT MEMBER* */
    };      
    % cc finkle.c
    finkle.c:3: field `__errno' declared as a function

and wonder about the various merits of separate name spaces and
pre-processors.

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