Silencing the remaining clang 15 warnings - Mailing list pgsql-hackers

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

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/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 tli, bool opportunistic)
     XLogRecPtr    NewPageEndPtr = InvalidXLogRecPtr;
     XLogRecPtr    NewPageBeginPtr;
     XLogPageHeader NewPage;
+#ifdef WAL_DEBUG
     int            npages = 0;
+#endif

     LWLockAcquire(WALBufMappingLock, LW_EXCLUSIVE);

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

         XLogCtl->InitializedUpTo = 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 = $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, 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
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 = 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
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, 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); }