From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
cc: pgsql-hackers@postgresql.org, Nikita Glukhov <n.gluhov@postgrespro.ru>,
        Andrew Dunstan <andrew@dunslane.net>,
        David Rowley <dgrowleyml@gmail.com>
Subject: Re: PG 15 (and to a smaller degree 14) regression due to ExprEvalStep
 size
In-reply-to: <1014296.1655422634@sss.pgh.pa.us>
References: <20220616233130.rparivafipt6doj3@alap3.anarazel.de>
 <1014296.1655422634@sss.pgh.pa.us>
Comments: In-reply-to Tom Lane <tgl@sss.pgh.pa.us>
	message dated "Thu, 16 Jun 2022 19:37:14 -0400"
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Date: Wed, 22 Feb 2023 16:34:44 -0500
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I wrote:
> Andres Freund <andres@anarazel.de> writes:
>> Maybe it's worth sticking a StaticAssert() for the struct size
>> somewhere.

> Indeed.  I thought we had one already.

>> I'm a bit wary about that being too noisy, there are some machines with
>> odd alignment requirements. Perhaps worth restricting the assertion to
>> x86-64 + armv8 or such?

> I'd put it in first and only reconsider if it shows unfixable problems.

Now that we've got the sizeof(ExprEvalStep) under control, shouldn't
we do the attached?

			regards, tom lane


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Content-Description: check-sizeof-ExprEvalStep.patch

diff --git a/src/include/executor/execExpr.h b/src/include/executor/execExpr.h
index 86e1ac1e65..06c3adc0a1 100644
--- a/src/include/executor/execExpr.h
+++ b/src/include/executor/execExpr.h
@@ -669,6 +669,10 @@ typedef struct ExprEvalStep
 	}			d;
 } ExprEvalStep;
 
+/* Enforce the size rule given in the comment above */
+StaticAssertDecl(sizeof(ExprEvalStep) <= 64,
+				 "size of ExprEvalStep exceeds 64 bytes");
+
 
 /* Non-inline data for container operations */
 typedef struct SubscriptingRefState

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