Add support for ISO C11 unnamed structure/union fields to dtrace

[marcel]

Summary

Recurse the members of the unnamed structure/union fields and
insert them in the outer structure, effectivy flattening the
hierarchy.

[markj]

Hm, this discards information. For instance, when pretty-printing an mbuf with DTrace, the first few fields are shown to be in a union:

7  36863                   ip_input:entry struct mbuf {
    union  {
        struct mbuf *m_next = 0
        struct m_slist = {
            struct mbuf *sle_next = 0
        }
        struct m_stailq = {
            struct mbuf *stqe_next = 0
        }
    }

I attempted to handle anonymous structs/unions to some extent with r305055. Where are you seeing problems?

[marcel]

I'm seeing this with a slightly older 11-stable. I see that r305055 has been MFC'd as r313129 on 2017-02-02. which means the fix is not present on the system I see it in. Both my up-to-date -current and -stable systems seem to work (see example below). So it looks the problem was already fixed!

example:
sudo dtrace -n fbt:kernel:ip_input:entry'{@len = quantize(args[0]->m_pkthdr.len);}'

[marcel]

Already fixed.

[markj]

In D9857#203687, @marcel wrote:

I'm seeing this with a slightly older 11-stable. I see that r305055 has been MFC'd as r313129 on 2017-02-02. which means the fix is not present on the system I see it in. Both my up-to-date -current and -stable systems seem to work (see example below). So it looks the problem was already fixed!

Sorry for the delayed MFC. Glad to hear that it fixes your problem though.