Re: Error while copying a large file in pg_rewind

On Thu, Jul 6, 2017 at 4:18 PM, Kuntal Ghosh <kuntalghosh(dot)2007(at)gmail(dot)com> wrote:
> On Wed, Jul 5, 2017 at 9:35 AM, Michael Paquier
> <michael(dot)paquier(at)gmail(dot)com> wrote:
>> On Tue, Jul 4, 2017 at 4:41 PM, Kuntal Ghosh <kuntalghosh(dot)2007(at)gmail(dot)com> wrote:
>>> I've not yet started the patch and it may take some time for me to
>>> understand and write
>>> the patch in a correct way. Since, you've almost written the patch,
>>> IMHO, please go ahead
>>> and submit the patch. I'll happily review and test it. :-)
>>>
>>> Thanks for the notes.
>>
>> OK, thanks. Here you go.
>>
> Thanks for the patch. It looks good and it solves the existing issues.
>
> But, I'm little concerned/doubt regarding the following part of the code.
> +/*
> + * Converts an int64 from network byte order to native format.
> + */
> +static int64
> +pg_recvint64(int64 value)
> +{
> + union
> + {
> + int64 i64;
> + uint32 i32[2];
> + } swap;
> + int64 result;
> +
> + swap.i64 = value;
> +
> + result = (uint32) ntohl(swap.i32[0]);
> + result <<= 32;
> + result |= (uint32) ntohl(swap.i32[1]);
> +
> + return result;
> +}
> Does this always work correctly irrespective of the endianess of the
> underlying system?

I think this will have problem, we may need to do like

union
{
int64 i64;
uint8 i8[8];
} swap;

....
and reverse complete array if byte order is changed

or we can use something like "be64toh"

>
>
> --
> Thanks & Regards,
> Kuntal Ghosh
> EnterpriseDB: http://www.enterprisedb.com
>
>
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--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com