From: Tom Lane <tgl@sss.pgh.pa.us>
To: pgsql-hackers@lists.postgresql.org
Subject: Silencing the remaining clang 15 warnings
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Date: Mon, 19 Sep 2022 15:20:43 -0400
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While working on the -Wdeprecated-non-prototype fixups discussed
nearby, I saw that clang 15.0 produces a few other new warnings
(which are also visible in the buildfarm).  Pursuant to our
usual policy that we should suppress warnings on compilers likely
to be used for development, here's a patch to silence them.

There are three groups of these:

* With %pure-parser, Bison makes the "yynerrs" variable local
instead of static, and then if you don't use it clang notices
that it's set but never read.  There doesn't seem to be a way
to persuade Bison not to emit the variable at all, so here I've
just added "(void) yynerrs;" to the topmost production of each
affected grammar.  If anyone has a nicer idea, let's hear it.

* xlog.c's AdvanceXLInsertBuffer has a local variable "npages"
that is only read in the "#ifdef WAL_DEBUG" stanza at the
bottom.  Here I've done the rather ugly and brute-force thing
of wrapping all the variable's references in "#ifdef WAL_DEBUG".
(I tried marking it PG_USED_FOR_ASSERTS_ONLY, but oddly that
did not silence the warning.)  I kind of wonder how useful this
function's WAL_DEBUG output is --- maybe just dropping that
altogether would be better?

* array_typanalyze.c's compute_array_stats counts the number
of null arrays in the column, but then does nothing with the
result.  AFAICS this is redundant with what std_compute_stats
will do, so I just removed the variable.

Any thoughts?

			regards, tom lane


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diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transa=
m/xlog.c
index 81d339d57d..2651bcaa76 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -1785,7 +1785,9 @@ AdvanceXLInsertBuffer(XLogRecPtr upto, TimeLineID tl=
i, bool opportunistic)
 	XLogRecPtr	NewPageEndPtr =3D InvalidXLogRecPtr;
 	XLogRecPtr	NewPageBeginPtr;
 	XLogPageHeader NewPage;
+#ifdef WAL_DEBUG
 	int			npages =3D 0;
+#endif
 =

 	LWLockAcquire(WALBufMappingLock, LW_EXCLUSIVE);
 =

@@ -1928,7 +1930,9 @@ AdvanceXLInsertBuffer(XLogRecPtr upto, TimeLineID tl=
i, bool opportunistic)
 =

 		XLogCtl->InitializedUpTo =3D NewPageEndPtr;
 =

+#ifdef WAL_DEBUG
 		npages++;
+#endif
 	}
 	LWLockRelease(WALBufMappingLock);
 =

diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 82f03fc9c9..c6ec694ceb 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -864,6 +864,7 @@ parse_toplevel:
 			stmtmulti
 			{
 				pg_yyget_extra(yyscanner)->parsetree =3D $1;
+				(void) yynerrs;		/* suppress compiler warning */
 			}
 			| MODE_TYPE_NAME Typename
 			{
diff --git a/src/backend/utils/adt/array_typanalyze.c b/src/backend/utils/=
adt/array_typanalyze.c
index 1964cedd93..2360c680ac 100644
--- a/src/backend/utils/adt/array_typanalyze.c
+++ b/src/backend/utils/adt/array_typanalyze.c
@@ -218,7 +218,6 @@ compute_array_stats(VacAttrStats *stats, AnalyzeAttrFe=
tchFunc fetchfunc,
 {
 	ArrayAnalyzeExtraData *extra_data;
 	int			num_mcelem;
-	int			null_cnt =3D 0;
 	int			null_elem_cnt =3D 0;
 	int			analyzed_rows =3D 0;
 =

@@ -320,8 +319,7 @@ compute_array_stats(VacAttrStats *stats, AnalyzeAttrFe=
tchFunc fetchfunc,
 		value =3D fetchfunc(stats, array_no, &isnull);
 		if (isnull)
 		{
-			/* array is null, just count that */
-			null_cnt++;
+			/* ignore arrays that are null overall */
 			continue;
 		}
 =

diff --git a/src/backend/utils/adt/jsonpath_gram.y b/src/backend/utils/adt=
/jsonpath_gram.y
index 7e28853a57..2a56629cc3 100644
--- a/src/backend/utils/adt/jsonpath_gram.y
+++ b/src/backend/utils/adt/jsonpath_gram.y
@@ -113,6 +113,7 @@ result:
 										*result =3D palloc(sizeof(JsonPathParseResult));
 										(*result)->expr =3D $2;
 										(*result)->lax =3D $1;
+										(void) yynerrs;
 									}
 	| /* EMPTY */					{ *result =3D NULL; }
 	;
diff --git a/src/bin/pgbench/exprparse.y b/src/bin/pgbench/exprparse.y
index ade2ecdaab..f6387d4a3c 100644
--- a/src/bin/pgbench/exprparse.y
+++ b/src/bin/pgbench/exprparse.y
@@ -80,7 +80,10 @@ static PgBenchExpr *make_case(yyscan_t yyscanner, PgBen=
chExprList *when_then_lis
 =

 %%
 =

-result: expr				{ expr_parse_result =3D $1; }
+result: expr				{
+								expr_parse_result =3D $1;
+								(void) yynerrs; /* suppress compiler warning */
+							}
 =

 elist:						{ $$ =3D NULL; }
 	| expr					{ $$ =3D make_elist($1, NULL); }

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