Re: Move allocation size overflow handling to MemoryContextAllocExtended()?

From: Michael Paquier <michael(dot)paquier(at)gmail(dot)com>
To: Andres Freund <andres(at)anarazel(dot)de>
Cc: PostgreSQL mailing lists <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Move allocation size overflow handling to MemoryContextAllocExtended()?
Date: 2016-10-05 00:38:15
Message-ID: CAB7nPqSTnj_6nFz=diYt7WciMSv4Dw=GF8T-4ffNXbH0QK2imw@mail.gmail.com
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On Wed, Oct 5, 2016 at 8:56 AM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> That made me wonder if it's not actually a mistake for
> MemoryContextAllocExtended() size parameter to be declared
> Size/size_t. That prevents it from detecting such overflows, forcing
> code like the above on callsites.
>
> Comments?

The existing interface of MemoryContextAlloc do not care much about
anything except Size, so I'd just give the responsability to the
caller to do checks like queue != (Size) queue when queue is a uint64
for example. And I can see that your patch is using uint32 for
SH_TYPE->size.
--
Michael

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