Ian is correct: These numbers are a Cap'n Proto encoding of your schema
file, which includes names, so they will always change when you modify the
file. But, that doesn't mean there's any incompatibility.

-Kenton

On Wed, Feb 21, 2018 at 10:39 AM, <[email protected]> wrote:

> Per capnp "evolving your schema" we tried changing the name of a struct
> but keeping its id the same e.g. changing this:
>
> struct MyMessageList {
>   mList @0: List(MyMessage);
> }
>
> struct MyMessage {
>   field0 @0: Int32;
> }
>
> to this:
>
> struct MyMessageList {
>   mList @0: List(DeprectedMyMessage);
> }
>
> struct DeprectedMyMessage @0xd4201303ceef0b19 {
>   field0 @0: Int32;
> }
>
>
> We found that the generated header files were the same (modulo the name
> change), but that the data section in the c++ files had changed values,
> which was worrisome. For example:
>
> static const ::capnp::_::AlignedData<58> b_b23f9d28332a82cf = {
>                        |    static const ::capnp::_::AlignedData<59>
> b_b23f9d28332a82cf = {
> static const ::capnp::_::AlignedData<58> b_b23f9d28332a82cf = {
>                        |    static const ::capnp::_::AlignedData<59>
> b_b23f9d28332a82cf = {
>  {   0,   0,   0,   0,   5,   0,   6,   0,
>                               {   0,   0,   0,   0,   5,   0,   6,   0,
>    207, 130,  42,  51,  40, 157,  63, 178,
>                                 207, 130,  42,  51,  40, 157,  63, 178,
>     50,   0,   0,   0,   2,   0,   0,   0,
>                        |         60,   0,   0,   0,   2,   0,   0,   0,
>    171, 205,  79,  88, 213, 104,  54, 210,
>                                 171, 205,  79,  88, 213, 104,  54, 210,
>      0,   0,   0,   0,   0,   0,   0,   0,
>                                   0,   0,   0,   0,   0,   0,   0,   0,
>      0,   0,   0,   0,   0,   0,   0,   0,
>                                   0,   0,   0,   0,   0,   0,   0,   0,
>     21,   0,   0,   0,  50,   2,   0,   0,
>                        |         21,   0,   0,   0, 130,   2,   0,   0,
>     53,   0,   0,   0,   7,   0,   0,   0,
>                        |         57,   0,   0,   0,   7,   0,   0,   0,
>      0,   0,   0,   0,   0,   0,   0,   0,
>                                   0,   0,   0,   0,   0,   0,   0,   0,
>     49,   0,   0,   0, 175,   0,   0,   0,
>                        |         53,   0,   0,   0, 175,   0,   0,   0,
>
> Is it expected that the data section would change in this way? Does it
> affect the serialization / deserialization in a safe or unsafe way? What is
> the data section encoding anyway?
>
>
>
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