From: Tom Lane <tgl@sss.pgh.pa.us>
To: Thomas Munro <thomas.munro@gmail.com>
cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: Warning in geqo_main.c from clang 13
In-reply-to: <85872.1637723874@sss.pgh.pa.us>
References: <CA+hUKGLTSZQwES8VNPmWO9AO0wSeLt36OCPDAZTccT1h7Q7kTQ@mail.gmail.com> <85872.1637723874@sss.pgh.pa.us>
Comments: In-reply-to Tom Lane <tgl@sss.pgh.pa.us>
	message dated "Tue, 23 Nov 2021 22:17:54 -0500"
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Date: Sat, 22 Jan 2022 17:34:16 -0500
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I wrote:
> Thomas Munro <thomas.munro@gmail.com> writes:
>> Clang 13 on my machine and peripatus (but not Apple clang 13 on eg
>> sifika, I'm still confused about Apple's versioning but I think that's
>> really llvm 12-based) warns:
>> geqo_main.c:86:8: warning: variable 'edge_failures' set but not used
>> [-Wunused-but-set-variable]
>> Here's one way to silence it.

> I'm kind of inclined to just drop the edge_failures recording/logging
> altogether, rather than make that rats-nest of #ifdefs even worse.
> It's not like anyone has cared about that number in the last decade
> or two.

We're starting to see more buildfarm animals producing this warning,
so I took another look, and thought of a slightly less invasive way to
silence it.  I confirmed this works with clang 13.0.0 on Fedora 35.

			regards, tom lane


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diff --git a/src/backend/optimizer/geqo/geqo_main.c b/src/backend/optimize=
r/geqo/geqo_main.c
index 333a26a695..68ed74325c 100644
--- a/src/backend/optimizer/geqo/geqo_main.c
+++ b/src/backend/optimizer/geqo/geqo_main.c
@@ -227,12 +227,17 @@ geqo(PlannerInfo *root, int number_of_rels, List *in=
itial_rels)
 	}
 =

 =

-#if defined(ERX) && defined(GEQO_DEBUG)
+#if defined(ERX)
+#if defined(GEQO_DEBUG)
 	if (edge_failures !=3D 0)
 		elog(LOG, "[GEQO] failures: %d, average: %d",
 			 edge_failures, (int) number_generations / edge_failures);
 	else
 		elog(LOG, "[GEQO] no edge failures detected");
+#else
+	/* suppress variable-set-but-not-used warnings from some compilers */
+	(void) edge_failures;
+#endif
 #endif
 =

 #if defined(CX) && defined(GEQO_DEBUG)

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