assignment by index or field doesn't work in C++

Question

static struct inet_protosw inetsw_array[] =
{
    [0] = { /* assignment by index */
      .type =       SOCK_STREAM, /* assignment by field */
      .protocol =   IPPROTO_TCP,
      .prot =       &tcp_prot,
      .ops =        &inet_stream_ops,
      .no_check =   0,
      .flags =      INET_PROTOSW_PERMANENT |
              INET_PROTOSW_ICSK,
    },
}

The above code works in C, but not in C++. I think the 2 methods are really nice. How C++ remove it?

PS: It seems field assignment can be accomplished by: type: SOCK_STREAM

More on this, http://stackoverflow.com/questions/4900739/why-are-designated-initializers-not-implemented-in-g — jweyrich, Sep 08 '11 at 02:43

score 4 · Answer 1 · answered Sep 08 '11 at 02:36

4

C and C++ are different languages. This code sample uses object initialization features that exist in C and do not exist in C++.

It's not that "C++ removed it", it's that it was not part of C back when C++ branched from it.

answered Sep 08 '11 at 02:36

Cubbi

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Yes. These 2 features are added in new version gcc – pengguang001 Sep 08 '11 at 02:56

Roland Illig · Accepted Answer · 2011-09-08T03:35:53.863

0

If I remember correctly the [0] and .type initialization designators have been introduced by ISO C99, and since the C++ standard came out in 1998, it didn't incorporate these features.

And also in C++11 it is not possible. The relevant section in the standard is 8.5.1 Aggregates, and all the examples in that section are without designators.

edited Sep 08 '11 at 03:35

answered Sep 08 '11 at 02:38

Roland Illig

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assignment by index or field doesn't work in C++

2 Answers2