Re: [PATCH] ident authentication fails on kFreeBSD/x86-64 due to wrong struct size

I wrote:
> Martin Pitt <mpitt@debian.org> writes:
>> /* Compute size without padding */
>> -    char        cmsgmem[ALIGN(sizeof(struct cmsghdr)) + ALIGN(sizeof(Cred))];    /* for NetBSD */
>> +    char        cmsgmem[ALIGN(sizeof(struct cmsghdr)) + sizeof(Cred)];    /* for NetBSD */

> Hm.  That code's been like that for a very long time (since 2001
> according to the git history...).  How much confidence can we have
> that this change won't result in breakage on other flavors of *BSD?

BTW, I wonder whether the real bug isn't on the libpq side instead.
I notice that its idea of the cmsgmem size is not like the backend's:

#ifdef HAVE_STRUCT_CMSGCRED
    /* Prevent padding */
    char        cmsgmem[sizeof(struct cmsghdr) + sizeof(struct cmsgcred)];

This corresponds to the original coding in the backend, but not to what
the code looks like now.  The subsequent whacking around of the backend
cmsgmem declaration was documented as fixing problems on NetBSD and then
OpenBSD.  If it's true as per the libpq comment that only FreeBSD needs
the client-side cmsgmem buffer, this might not have gotten retested.

            regards, tom lane