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From: Bertrand Drouvot <[email protected]>
To: Michael Paquier <[email protected]>
Cc: Anthonin Bonnefoy <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Subject: Re: Fix uninitialized xl_running_xacts padding
Date: Fri, 13 Feb 2026 10:08:32 +0000
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <CAO6_Xqoxp7C+y0L==xZXH5V=9PjpBx4T9vJYs87EbxFp_9nwOA@mail.gmail.com>
	<[email protected]>

Hi,

On Fri, Feb 13, 2026 at 06:50:08PM +0900, Michael Paquier wrote:
> On Fri, Feb 13, 2026 at 10:39:14AM +0100, Anthonin Bonnefoy wrote:
> > The 3 bytes of padding after subxid_overflow were left uninitialized,
> > leading to the random 'ca ce 9b' data being written in the WAL. The
> > attached patch fixes the issue by zeroing the xl_running_xacts
> > structure in LogCurrentRunningXacts using MemSet.
> 
> This uninitialized padding exists for as long as this code exists,
> down to efc16ea52067.  No objection here to clean up that on HEAD.

It's not as important as when a struct which is used as an hash key has padding
bytes uninitialized (and byte comparisons are done on the key) but I'm also
+1 to make it "cleaner".

Regards,

-- 
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com

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