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

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
index b4f629f4a8f8be5e9624716bcd1b9bc0cc1664f8..998befd2cbb7eb99fd79fd519e0ece0e87b49a48 100644 (file)
--- 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
index eb0430fe98f623e6dc80ca2afc641f61d68d83d9..e02812467227749723d4628f09a119d4fd8840f4 100644 (file)
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -1785,7 +1785,7 @@ 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
index 82f03fc9c93f5ac21e3900737ca5a8b69699b7a2..c6ec694cebca04354bafb3f347aaca91adc89b8c 100644 (file)
--- 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 1964cedd93ff6890889f5c452bae12ecb03aa631..2360c680ac896e82ede0f9ea456a53ac0790b4bc 100644 (file)
--- 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 7e28853a57f65573453325e7205971bea968b9c6..2a56629cc3a12855140fc8e9dbf1380ac974a7c9 100644 (file)
--- 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 ade2ecdaab89c3728015ba26420744f12bbe8e83..f6387d4a3cbeb08639faf95ed89fdd942b03e423 100644 (file)
--- 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); }