Re: Out-of-memory error reports in libpq

I wrote:
> Andres Freund <andres(at)anarazel(dot)de> writes:
>> Hm. It seems we should be able to guarantee that the recovery path can print
>> something, at least in the PGconn case. Is it perhaps worth pre-sizing
>> PGConn->errorMessage so it'd fit an error like this?
>> But perhaps that's more effort than it's worth.

> Yeah. I considered changing things so that oom_buffer contains
> "out of memory\n" rather than an empty string, but I'm afraid
> that that's making unsupportable assumptions about what PQExpBuffers
> are used for.

Actually, wait a minute. There are only a couple of places that ever
read out the value of conn->errorMessage, so let's make those places
responsible for dealing with OOM scenarios. That leads to a nicely
small patch, as attached, and it looks to me like it makes us quite
bulletproof against such scenarios.

It might still be worth doing the "pqReportOOM" changes to save a
few bytes of code space, but I'm less excited about that now.

regards, tom lane