// local C.
	if l, ok := sel.X.(*ast.Ident); !ok || l.Name != "C" {
		return
	}
	if context == ctxAssign2 {
		context = ctxExpr
	}
	if context == ctxEmbedType {
		error_(sel.Pos(), "cannot embed C type")
	}
	goname := sel.Sel.Name
	if goname == "errno" {
		error_(sel.Pos(), "cannot refer to errno directly; see documentation")
		return
	}
	if goname == "_CMalloc" {

NUL byte.

As Go doesn't have support for C's union type in the general case,
C's union types are represented as a Go byte array with the same length.

Go structs cannot embed fields with C types.

Go code cannot refer to zero-sized fields that occur at the end of
non-empty C structs. To get the address of such a field (which is the

}
</pre>

<p>
An interface type <code>T</code> may not embed itself
or any interface type that embeds <code>T</code>, recursively.
</p>

<pre>
// illegal: Bad cannot embed itself
type Bad interface {
	Bad
}

// illegal: Bad1 cannot embed itself using Bad2
type Bad1 interface {
	Bad2
}
type Bad2 interface {
	Bad1
}
</pre>

	f Float                 // illegal
}
</pre>

<p>
An interface type <code>T</code> may not embed a type element
that is, contains, or embeds <code>T</code>, directly or indirectly.
</p>

<pre>
// illegal: Bad may not embed itself
type Bad interface {
	Bad
}

// illegal: Bad1 may not embed itself using Bad2
type Bad1 interface {
	Bad2
}
type Bad2 interface {
	Bad1
}

			// flag to disable the warning. Yes, really good diagnostics, clang.
			"-Wno-unknown-warning-option",
			"-Wno-unneeded-internal-declaration",
			"-Wno-unused-function",
			"-Qunused-arguments",
			// Clang embeds prototypes for some builtin functions,
			// like malloc and calloc, but all size_t parameters are
			// incorrectly typed unsigned long. We work around that
			// by disabling the builtin functions (this is safe as