Avoid casting void * function arguments

In many cases, the cast would silently drop a const qualifier.  To
fix, drop the unnecessary cast and let the compiler check the types
and qualifiers.  Add const to read-only local variables, preserving
the const qualifiers from the function signatures.

Co-authored-by: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Co-authored-by: Peter Eisentraut <peter@eisentraut.org>
Discussion: https://postgr.es/m/aUQHy/MmWq7c97wK%40ip-10-97-1-34.eu-west-3.compute.internal

src/backend/access/brin/brin_minmax_multi.c

@@ -857,8 +857,8 @@ brin_range_deserialize(int maxvalues, SerializedRanges *serialized)
 static int
 compare_expanded_ranges(const void *a, const void *b, void *arg)
 {
-	ExpandedRange *ra = (ExpandedRange *) a;
-	ExpandedRange *rb = (ExpandedRange *) b;
+	const ExpandedRange *ra = a;
+	const ExpandedRange *rb = b;
 	Datum		r;
 
 	compare_context *cxt = (compare_context *) arg;
@@ -895,8 +895,8 @@ compare_expanded_ranges(const void *a, const void *b, void *arg)
 static int
 compare_values(const void *a, const void *b, void *arg)
 {
-	Datum	   *da = (Datum *) a;
-	Datum	   *db = (Datum *) b;
+	const Datum *da = a;
+	const Datum *db = b;
 	Datum		r;
 
 	compare_context *cxt = (compare_context *) arg;
@@ -1304,8 +1304,8 @@ merge_overlapping_ranges(FmgrInfo *cmp, Oid colloid,
 static int
 compare_distances(const void *a, const void *b)
 {
-	DistanceValue *da = (DistanceValue *) a;
-	DistanceValue *db = (DistanceValue *) b;
+	const DistanceValue *da = a;
+	const DistanceValue *db = b;
 
 	if (da->value < db->value)
 		return 1;

src/backend/access/common/heaptuple.c

@@ -103,7 +103,7 @@ static HTAB *missing_cache = NULL;
 static uint32
 missing_hash(const void *key, Size keysize)
 {
-	const missing_cache_key *entry = (missing_cache_key *) key;
+	const missing_cache_key *entry = key;
 
 	return hash_bytes((const unsigned char *) DatumGetPointer(entry->value), entry->len);
 }
@@ -111,8 +111,8 @@ missing_hash(const void *key, Size keysize)
 static int
 missing_match(const void *key1, const void *key2, Size keysize)
 {
-	const missing_cache_key *entry1 = (missing_cache_key *) key1;
-	const missing_cache_key *entry2 = (missing_cache_key *) key2;
+	const missing_cache_key *entry1 = key1;
+	const missing_cache_key *entry2 = key2;
 
 	if (entry1->len != entry2->len)
 		return entry1->len > entry2->len ? 1 : -1;

src/backend/access/heap/pruneheap.c

@@ -2021,8 +2021,8 @@ heap_log_freeze_eq(xlhp_freeze_plan *plan, HeapTupleFreeze *frz)
 static int
 heap_log_freeze_cmp(const void *arg1, const void *arg2)
 {
-	HeapTupleFreeze *frz1 = (HeapTupleFreeze *) arg1;
-	HeapTupleFreeze *frz2 = (HeapTupleFreeze *) arg2;
+	const HeapTupleFreeze *frz1 = arg1;
+	const HeapTupleFreeze *frz2 = arg2;
 
 	if (frz1->xmax < frz2->xmax)
 		return -1;

src/backend/access/nbtree/nbtpage.c

@@ -1462,8 +1462,8 @@ _bt_delitems_update(BTVacuumPosting *updatable, int nupdatable,
 static int
 _bt_delitems_cmp(const void *a, const void *b)
 {
-	TM_IndexDelete *indexdelete1 = (TM_IndexDelete *) a;
-	TM_IndexDelete *indexdelete2 = (TM_IndexDelete *) b;
+	const TM_IndexDelete *indexdelete1 = a;
+	const TM_IndexDelete *indexdelete2 = b;
 
 	Assert(indexdelete1->id != indexdelete2->id);
 

src/backend/access/nbtree/nbtpreprocesskeys.c

@@ -1792,8 +1792,8 @@ _bt_unmark_keys(IndexScanDesc scan, int *keyDataMap)
 static int
 _bt_reorder_array_cmp(const void *a, const void *b)
 {
-	BTArrayKeyInfo *arraya = (BTArrayKeyInfo *) a;
-	BTArrayKeyInfo *arrayb = (BTArrayKeyInfo *) b;
+	const BTArrayKeyInfo *arraya = a;
+	const BTArrayKeyInfo *arrayb = b;
 
 	return pg_cmp_s32(arraya->scan_key, arrayb->scan_key);
 }

src/backend/access/nbtree/nbtsplitloc.c

@@ -594,8 +594,8 @@ _bt_deltasortsplits(FindSplitData *state, double fillfactormult,
 static int
 _bt_splitcmp(const void *arg1, const void *arg2)
 {
-	SplitPoint *split1 = (SplitPoint *) arg1;
-	SplitPoint *split2 = (SplitPoint *) arg2;
+	const SplitPoint *split1 = arg1;
+	const SplitPoint *split2 = arg2;
 
 	return pg_cmp_s16(split1->curdelta, split2->curdelta);
 }

src/backend/access/spgist/spgkdtreeproc.c

@@ -84,8 +84,8 @@ typedef struct SortedPoint
 static int
 x_cmp(const void *a, const void *b)
 {
-	SortedPoint *pa = (SortedPoint *) a;
-	SortedPoint *pb = (SortedPoint *) b;
+	const SortedPoint *pa = a;
+	const SortedPoint *pb = b;
 
 	if (pa->p->x == pb->p->x)
 		return 0;
@@ -95,8 +95,8 @@ x_cmp(const void *a, const void *b)
 static int
 y_cmp(const void *a, const void *b)
 {
-	SortedPoint *pa = (SortedPoint *) a;
-	SortedPoint *pb = (SortedPoint *) b;
+	const SortedPoint *pa = a;
+	const SortedPoint *pb = b;
 
 	if (pa->p->y == pb->p->y)
 		return 0;

src/backend/statistics/extended_stats.c

@@ -862,8 +862,8 @@ int
 multi_sort_compare(const void *a, const void *b, void *arg)
 {
 	MultiSortSupport mss = (MultiSortSupport) arg;
-	SortItem   *ia = (SortItem *) a;
-	SortItem   *ib = (SortItem *) b;
+	const SortItem *ia = a;
+	const SortItem *ib = b;
 	int			i;
 
 	for (i = 0; i < mss->ndims; i++)

src/backend/statistics/mcv.c

@@ -402,8 +402,8 @@ count_distinct_groups(int numrows, SortItem *items, MultiSortSupport mss)
 static int
 compare_sort_item_count(const void *a, const void *b, void *arg)
 {
-	SortItem   *ia = (SortItem *) a;
-	SortItem   *ib = (SortItem *) b;
+	const SortItem *ia = a;
+	const SortItem *ib = b;
 
 	if (ia->count == ib->count)
 		return 0;
@@ -465,8 +465,8 @@ static int
 sort_item_compare(const void *a, const void *b, void *arg)
 {
 	SortSupport ssup = (SortSupport) arg;
-	SortItem   *ia = (SortItem *) a;
-	SortItem   *ib = (SortItem *) b;
+	const SortItem *ia = a;
+	const SortItem *ib = b;
 
 	return ApplySortComparator(ia->values[0], ia->isnull[0],
 							   ib->values[0], ib->isnull[0],

src/backend/tsearch/spell.c

@@ -210,8 +210,8 @@ cmpspellaffix(const void *s1, const void *s2)
 static int
 cmpcmdflag(const void *f1, const void *f2)
 {
-	CompoundAffixFlag *fv1 = (CompoundAffixFlag *) f1,
-			   *fv2 = (CompoundAffixFlag *) f2;
+	const CompoundAffixFlag *fv1 = f1;
+	const CompoundAffixFlag *fv2 = f2;
 
 	Assert(fv1->flagMode == fv2->flagMode);
 

src/backend/utils/adt/rangetypes_gist.c

@@ -1729,9 +1729,9 @@ get_gist_range_class(RangeType *range)
 static int
 single_bound_cmp(const void *a, const void *b, void *arg)
 {
-	SingleBoundSortItem *i1 = (SingleBoundSortItem *) a;
-	SingleBoundSortItem *i2 = (SingleBoundSortItem *) b;
-	TypeCacheEntry *typcache = (TypeCacheEntry *) arg;
+	const SingleBoundSortItem *i1 = a;
+	const SingleBoundSortItem *i2 = b;
+	TypeCacheEntry *typcache = arg;
 
 	return range_cmp_bounds(typcache, &i1->bound, &i2->bound);
 }
@@ -1742,9 +1742,9 @@ single_bound_cmp(const void *a, const void *b, void *arg)
 static int
 interval_cmp_lower(const void *a, const void *b, void *arg)
 {
-	NonEmptyRange *i1 = (NonEmptyRange *) a;
-	NonEmptyRange *i2 = (NonEmptyRange *) b;
-	TypeCacheEntry *typcache = (TypeCacheEntry *) arg;
+	const NonEmptyRange *i1 = a;
+	const NonEmptyRange *i2 = b;
+	TypeCacheEntry *typcache = arg;
 
 	return range_cmp_bounds(typcache, &i1->lower, &i2->lower);
 }
@@ -1755,9 +1755,9 @@ interval_cmp_lower(const void *a, const void *b, void *arg)
 static int
 interval_cmp_upper(const void *a, const void *b, void *arg)
 {
-	NonEmptyRange *i1 = (NonEmptyRange *) a;
-	NonEmptyRange *i2 = (NonEmptyRange *) b;
-	TypeCacheEntry *typcache = (TypeCacheEntry *) arg;
+	const NonEmptyRange *i1 = a;
+	const NonEmptyRange *i2 = b;
+	TypeCacheEntry *typcache = arg;
 
 	return range_cmp_bounds(typcache, &i1->upper, &i2->upper);
 }

src/backend/utils/adt/rangetypes_spgist.c

@@ -185,9 +185,9 @@ spg_range_quad_choose(PG_FUNCTION_ARGS)
 static int
 bound_cmp(const void *a, const void *b, void *arg)
 {
-	RangeBound *ba = (RangeBound *) a;
-	RangeBound *bb = (RangeBound *) b;
-	TypeCacheEntry *typcache = (TypeCacheEntry *) arg;
+	const RangeBound *ba = a;
+	const RangeBound *bb = b;
+	TypeCacheEntry *typcache = arg;
 
 	return range_cmp_bounds(typcache, ba, bb);
 }

src/backend/utils/adt/rangetypes_typanalyze.c

@@ -111,9 +111,9 @@ float8_qsort_cmp(const void *a1, const void *a2, void *arg)
 static int
 range_bound_qsort_cmp(const void *a1, const void *a2, void *arg)
 {
-	RangeBound *b1 = (RangeBound *) a1;
-	RangeBound *b2 = (RangeBound *) a2;
-	TypeCacheEntry *typcache = (TypeCacheEntry *) arg;
+	const RangeBound *b1 = a1;
+	const RangeBound *b2 = a2;
+	TypeCacheEntry *typcache = arg;
 
 	return range_cmp_bounds(typcache, b1, b2);
 }

src/backend/utils/cache/typcache.c

@@ -235,8 +235,8 @@ shared_record_table_compare(const void *a, const void *b, size_t size,
 							void *arg)
 {
 	dsa_area   *area = (dsa_area *) arg;
-	SharedRecordTableKey *k1 = (SharedRecordTableKey *) a;
-	SharedRecordTableKey *k2 = (SharedRecordTableKey *) b;
+	const SharedRecordTableKey *k1 = a;
+	const SharedRecordTableKey *k2 = b;
 	TupleDesc	t1;
 	TupleDesc	t2;
 
@@ -259,8 +259,8 @@ shared_record_table_compare(const void *a, const void *b, size_t size,
 static uint32
 shared_record_table_hash(const void *a, size_t size, void *arg)
 {
-	dsa_area   *area = (dsa_area *) arg;
-	SharedRecordTableKey *k = (SharedRecordTableKey *) a;
+	dsa_area   *area = arg;
+	const SharedRecordTableKey *k = a;
 	TupleDesc	t;
 
 	if (k->shared)
@@ -2013,7 +2013,7 @@ lookup_rowtype_tupdesc_domain(Oid type_id, int32 typmod, bool noError)
 static uint32
 record_type_typmod_hash(const void *data, size_t size)
 {
-	RecordCacheEntry *entry = (RecordCacheEntry *) data;
+	const RecordCacheEntry *entry = data;
 
 	return hashRowType(entry->tupdesc);
 }
@@ -2024,8 +2024,8 @@ record_type_typmod_hash(const void *data, size_t size)
 static int
 record_type_typmod_compare(const void *a, const void *b, size_t size)
 {
-	RecordCacheEntry *left = (RecordCacheEntry *) a;
-	RecordCacheEntry *right = (RecordCacheEntry *) b;
+	const RecordCacheEntry *left = a;
+	const RecordCacheEntry *right = b;
 
 	return equalRowTypes(left->tupdesc, right->tupdesc) ? 0 : 1;
 }

src/bin/pg_dump/pg_dump.c

@@ -11102,7 +11102,7 @@ fetchAttributeStats(Archive *fout)
 static char *
 dumpRelationStats_dumper(Archive *fout, const void *userArg, const TocEntry *te)
 {
-	const RelStatsInfo *rsinfo = (RelStatsInfo *) userArg;
+	const RelStatsInfo *rsinfo = userArg;
 	static PGresult *res;
 	static int	rownum;
 	PQExpBuffer query;

src/test/modules/injection_points/injection_points.c

@@ -189,7 +189,7 @@ injection_init_shmem(void)
  * otherwise.
  */
 static bool
-injection_point_allowed(InjectionPointCondition *condition)
+injection_point_allowed(const InjectionPointCondition *condition)
 {
 	bool		result = true;
 
@@ -232,8 +232,8 @@ injection_points_cleanup(int code, Datum arg)
 void
 injection_error(const char *name, const void *private_data, void *arg)
 {
-	InjectionPointCondition *condition = (InjectionPointCondition *) private_data;
-	char	   *argstr = (char *) arg;
+	const InjectionPointCondition *condition = private_data;
+	char	   *argstr = arg;
 
 	if (!injection_point_allowed(condition))
 		return;
@@ -248,8 +248,8 @@ injection_error(const char *name, const void *private_data, void *arg)
 void
 injection_notice(const char *name, const void *private_data, void *arg)
 {
-	InjectionPointCondition *condition = (InjectionPointCondition *) private_data;
-	char	   *argstr = (char *) arg;
+	const InjectionPointCondition *condition = private_data;
+	char	   *argstr = arg;
 
 	if (!injection_point_allowed(condition))
 		return;
@@ -268,7 +268,7 @@ injection_wait(const char *name, const void *private_data, void *arg)
 	uint32		old_wait_counts = 0;
 	int			index = -1;
 	uint32		injection_wait_event = 0;
-	InjectionPointCondition *condition = (InjectionPointCondition *) private_data;
+	const InjectionPointCondition *condition = private_data;
 
 	if (inj_state == NULL)
 		injection_init_shmem();