From: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: Thomas Munro <thomas.munro@gmail.com>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: using explicit_bzero
Date: Mon, 22 Jul 2019 20:17:17 +0200
Message-ID: <2751372e-e443-479a-0403-c414eae8e14e@2ndquadrant.com> (raw)
In-Reply-To: <25152.1563403539@sss.pgh.pa.us>
References: <20190717211931.GA906@alvherre.pgsql>
<25152.1563403539@sss.pgh.pa.us>
On 2019-07-18 00:45, Tom Lane wrote:
> Alvaro Herrera <alvherre@2ndquadrant.com> writes:
>> On 2019-Jul-11, Thomas Munro wrote:
>>> Following a trail of crumbs beginning at OpenSSH's fallback
>>> implementation of this[1], I learned that C11 has standardised
>>> memset_s[2] for this purpose. Macs have memset_s but no
>>> explicit_bzero. FreeBSD has both. I wonder if it'd be better to make
>>> memset_s the function we use in our code, considering its standard
>>> blessing and therefore likelihood of being available on every system
>>> eventually.
>
>> Sounds like a future-proof way would be to implement memset_s in
>> src/port if absent from the OS (using explicit_bzero and other tricks),
>> and use that.
>
> +1 for using the C11-standard name, even if that's not anywhere
> in the real world yet.
ISTM that a problem is that you cannot implement a replacement
memset_s() as a wrapper around explicit_bzero(), unless you also want to
implement the bound checking stuff. (The "s"/safe in this family of
functions refers to the bound checking, not the cannot-be-optimized-away
property.) The other way around it is easier.
Also, the "s" family of functions appears to be a quagmire of
controversy and incompatibility, so it's perhaps better to stay away
from it for the time being.
--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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To: pgsql-hackers@postgresql.org
Cc: peter.eisentraut@2ndquadrant.com, tgl@sss.pgh.pa.us, alvherre@2ndquadrant.com, thomas.munro@gmail.com
Subject: Re: using explicit_bzero
In-Reply-To: <2751372e-e443-479a-0403-c414eae8e14e@2ndquadrant.com>
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