Suppress variable-set-but-not-used warnings from clang 15.

tglsfdc · tglsfdc · commit b7d9b0c2667e · 2022-09-20T12:04:37.000-04:00
clang 15+ will issue a set-but-not-used warning when the only use of a variable is in autoincrements (e.g., "foo++;"). That's perfectly sensible, but it detects a few more cases that we'd not noticed before. Silence the warnings with our usual methods, such as PG_USED_FOR_ASSERTS_ONLY, or in one case by actually removing a useless variable. One thing that we can't nicely get rid of is that with %pure-parser, Bison emits "yynerrs" as a local variable that falls foul of this warning. To silence those, I inserted "(void) yynerrs;" in the top-level productions of affected grammars. Per recently-established project policy, this is a candidate for back-patching into out-of-support branches: it suppresses annoying compiler warnings but changes no behavior. Hence, back-patch to 9.5, which is as far as these patches go without issues. (A preliminary check shows that the prior branches need some other set-but-not-used cleanups too, so I'll leave them for another day.) Discussion: https://postgr.es/m/514615.1663615243@sss.pgh.pa.us
diff --git a/src/backend/access/gist/gistxlog.c b/src/backend/access/gist/gistxlog.c
@@ -81,7 +81,7 @@ gistRedoPageUpdateRecord(XLogReaderState *record)
 		char	   *begin;
 		char	   *data;
 		Size		datalen;
-		int			ninserted = 0;
+		int			ninserted PG_USED_FOR_ASSERTS_ONLY = 0;
 
 		data = begin = XLogRecGetBlockData(record, 0, &datalen);
 
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
@@ -1778,7 +1778,7 @@ AdvanceXLInsertBuffer(XLogRecPtr upto, TimeLineID tli, bool opportunistic)
 	XLogRecPtr	NewPageEndPtr = InvalidXLogRecPtr;
 	XLogRecPtr	NewPageBeginPtr;
 	XLogPageHeader NewPage;
-	int			npages = 0;
+	int			npages pg_attribute_unused() = 0;
 
 	LWLockAcquire(WALBufMappingLock, LW_EXCLUSIVE);
 
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
@@ -859,6 +859,7 @@ parse_toplevel:
 			stmtmulti
 			{
 				pg_yyget_extra(yyscanner)->parsetree = $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
@@ -218,7 +218,6 @@ compute_array_stats(VacAttrStats *stats, AnalyzeAttrFetchFunc fetchfunc,
 {
 	ArrayAnalyzeExtraData *extra_data;
 	int			num_mcelem;
-	int			null_cnt = 0;
 	int			null_elem_cnt = 0;
 	int			analyzed_rows = 0;
 
@@ -320,8 +319,7 @@ compute_array_stats(VacAttrStats *stats, AnalyzeAttrFetchFunc fetchfunc,
 		value = 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
@@ -131,6 +131,7 @@ result:
 										*result = palloc(sizeof(JsonPathParseResult));
 										(*result)->expr = $2;
 										(*result)->lax = $1;
+										(void) yynerrs;
 									}
 	| /* EMPTY */					{ *result = NULL; }
 	;
diff --git a/src/bin/pgbench/exprparse.y b/src/bin/pgbench/exprparse.y
@@ -80,7 +80,10 @@ static PgBenchExpr *make_case(yyscan_t yyscanner, PgBenchExprList *when_then_lis
 
 %%
 
-result: expr				{ expr_parse_result = $1; }
+result: expr				{
+								expr_parse_result = $1;
+								(void) yynerrs; /* suppress compiler warning */
+							}
 
 elist:						{ $$ = NULL; }
 	| expr					{ $$ = make_elist($1, NULL); }

Original file line number	Diff line number	Diff line change
`@@ -859,6 +859,7 @@ parse_toplevel:`
`859`	`859`	`stmtmulti`
`860`	`860`	`{`
`861`	`861`	`pg_yyget_extra(yyscanner)->parsetree = $1;`
	`862`	`+ (void) yynerrs; /* suppress compiler warning */`
`862`	`863`	`}`
`863`	`864`	`\| MODE_TYPE_NAME Typename`
`864`	`865`	`{`
Original file line number	Diff line number	Diff line change
`@@ -218,7 +218,6 @@ compute_array_stats(VacAttrStats *stats, AnalyzeAttrFetchFunc fetchfunc,`
`218`	`218`	`{`
`219`	`219`	`ArrayAnalyzeExtraData *extra_data;`
`220`	`220`	`int num_mcelem;`
`221`		`- int null_cnt = 0;`
`222`	`221`	`int null_elem_cnt = 0;`
`223`	`222`	`int analyzed_rows = 0;`
`224`	`223`
`@@ -320,8 +319,7 @@ compute_array_stats(VacAttrStats *stats, AnalyzeAttrFetchFunc fetchfunc,`
`320`	`319`	`value = fetchfunc(stats, array_no, &isnull);`
`321`	`320`	`if (isnull)`
`322`	`321`	`{`
`323`		`- /* array is null, just count that */`
`324`		`- null_cnt++;`
	`322`	`+ /* ignore arrays that are null overall */`
`325`	`323`	`continue;`
`326`	`324`	`}`
`327`	`325`
Original file line number	Diff line number	Diff line change
`@@ -131,6 +131,7 @@ result:`
`131`	`131`	`*result = palloc(sizeof(JsonPathParseResult));`
`132`	`132`	`(*result)->expr = $2;`
`133`	`133`	`(*result)->lax = $1;`
	`134`	`+ (void) yynerrs;`
`134`	`135`	`}`
`135`	`136`	`\| /* EMPTY / { result = NULL; }`
`136`	`137`	`;`