From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
cc: pgsql-hackers@postgresql.org
Subject: Re: Make stack depth check work with asan's use-after-return
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Comments: In-reply-to Andres Freund <andres@anarazel.de>
	message dated "Wed, 27 May 2026 09:23:13 -0400"
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Date: Wed, 27 May 2026 09:54:51 -0400
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Andres Freund <andres@anarazel.de> writes:
> The reason for that breakage is that with the stack-use-after-return log=
ic,
> stack variables are moved to heap allocations, to allow to detect refere=
nces
> to the memory at a later time. That breaks our stack-depth check, which =
is why
> we had to disable detect_stack_use_after_return in CI. Luckily
> __builtin_frame_address() works correctly, even under asan, so use that.
> I think we should backpatch this. I'd be worried about using
> __builtin_frame_address(), but we already do, for the base address of th=
e
> stack.

+1.  It was a little weird that we adopted __builtin_frame_address()
to measure the location of the stack bottom but not the stack top.
So I think this is good cleanup even if ASAN weren't forcing it.

I might write the comments a bit differently, in particular I suggest
changing

- 	 * Compute distance from reference point to my local variables
+ 	 * Compute distance from reference point to my stack frame

			regards, tom lane