Revert workarounds for -Wmissing-braces false positives on old GCC

We have collected several instances of a workaround for GCC bug 53119,
which caused false-positive compiler warnings.  This bug has long been
fixed, but was still seen on the buildfarm, most recently on lapwing
with gcc (Debian 4.7.2-5).  (The GCC bug tracker mentions that a fix
was backported to 4.7.4 and 4.8.3.)

That compiler no longer runs warning-free since commit 6fdd5d9563, so
we don't need to keep these workarounds.  And furthermore, the
consensus appears to be that we don't want to keep supporting that era
of platform anymore at all.

This reverts the following commits:

d937904cce
506428d091
b449afb582
6392f2a096
bad0763a4d
5e0c761d0a

and makes a few similar fixes to newer code.

Discussion: https://www.postgresql.org/message-id/flat/e170d61f-01ab-4cf9-ab68-91cd1fac62c5%40eisentraut.org
Discussion: https://www.postgresql.org/message-id/flat/CA%2BTgmoYEAm-KKZibAP3hSqbTFTjUd47XtVcf3xSFDpyecXX9uQ%40mail.gmail.com

contrib/pg_prewarm/autoprewarm.c

@@ -798,12 +798,11 @@ apw_detach_shmem(int code, Datum arg)
 static void
 apw_start_leader_worker(void)
 {
-	BackgroundWorker worker;
+	BackgroundWorker worker = {0};
 	BackgroundWorkerHandle *handle;
 	BgwHandleStatus status;
 	pid_t		pid;
 
-	MemSet(&worker, 0, sizeof(BackgroundWorker));
 	worker.bgw_flags = BGWORKER_SHMEM_ACCESS;
 	worker.bgw_start_time = BgWorkerStart_ConsistentState;
 	strcpy(worker.bgw_library_name, "pg_prewarm");
@@ -840,10 +839,9 @@ apw_start_leader_worker(void)
 static void
 apw_start_database_worker(void)
 {
-	BackgroundWorker worker;
+	BackgroundWorker worker = {0};
 	BackgroundWorkerHandle *handle;
 
-	MemSet(&worker, 0, sizeof(BackgroundWorker));
 	worker.bgw_flags =
 		BGWORKER_SHMEM_ACCESS | BGWORKER_BACKEND_DATABASE_CONNECTION;
 	worker.bgw_start_time = BgWorkerStart_ConsistentState;

contrib/postgres_fdw/postgres_fdw.c

@@ -3333,7 +3333,7 @@ estimate_path_cost_size(PlannerInfo *root,
 		{
 			RelOptInfo *outerrel = fpinfo->outerrel;
 			PgFdwRelationInfo *ofpinfo;
-			AggClauseCosts aggcosts;
+			AggClauseCosts aggcosts = {0};
 			double		input_rows;
 			int			numGroupCols;
 			double		numGroups = 1;
@@ -3357,7 +3357,6 @@ estimate_path_cost_size(PlannerInfo *root,
 			input_rows = ofpinfo->rows;
 
 			/* Collect statistics about aggregates for estimating costs. */
-			MemSet(&aggcosts, 0, sizeof(AggClauseCosts));
 			if (root->parse->hasAggs)
 			{
 				get_agg_clause_costs(root, AGGSPLIT_SIMPLE, &aggcosts);

src/backend/optimizer/path/costsize.c

@@ -2690,13 +2690,12 @@ cost_agg(Path *path, PlannerInfo *root,
 	double		output_tuples;
 	Cost		startup_cost;
 	Cost		total_cost;
-	AggClauseCosts dummy_aggcosts;
+	const AggClauseCosts dummy_aggcosts = {0};
 
 	/* Use all-zero per-aggregate costs if NULL is passed */
 	if (aggcosts == NULL)
 	{
 		Assert(aggstrategy == AGG_HASHED);
-		MemSet(&dummy_aggcosts, 0, sizeof(AggClauseCosts));
 		aggcosts = &dummy_aggcosts;
 	}
 

src/backend/storage/smgr/bulk_write.c

@@ -46,7 +46,7 @@
 
 #define MAX_PENDING_WRITES XLR_MAX_BLOCK_ID
 
-static const PGIOAlignedBlock zero_buffer = {{0}};	/* worth BLCKSZ */
+static const PGIOAlignedBlock zero_buffer = {0};	/* worth BLCKSZ */
 
 typedef struct PendingWrite
 {

src/bin/pg_waldump/rmgrdesc.c

@@ -41,8 +41,8 @@ static const RmgrDescData RmgrDescTable[RM_N_BUILTIN_IDS] = {
 
 #define CUSTOM_NUMERIC_NAME_LEN sizeof("custom###")
 
-static char CustomNumericNames[RM_N_CUSTOM_IDS][CUSTOM_NUMERIC_NAME_LEN] = {{0}};
-static RmgrDescData CustomRmgrDesc[RM_N_CUSTOM_IDS] = {{0}};
+static char CustomNumericNames[RM_N_CUSTOM_IDS][CUSTOM_NUMERIC_NAME_LEN] = {0};
+static RmgrDescData CustomRmgrDesc[RM_N_CUSTOM_IDS] = {0};
 static bool CustomRmgrDescInitialized = false;
 
 /*

src/bin/pgbench/pgbench.c

@@ -2279,15 +2279,10 @@ evalStandardFunc(CState *st,
 {
 	/* evaluate all function arguments */
 	int			nargs = 0;
+	PgBenchValue vargs[MAX_FARGS] = {0};
 	PgBenchExprLink *l = args;
 	bool		has_null = false;
 
-	/*
-	 * This value is double braced to workaround GCC bug 53119, which seems to
-	 * exist at least on gcc (Debian 4.7.2-5) 4.7.2, 32-bit.
-	 */
-	PgBenchValue vargs[MAX_FARGS] = {{0}};
-
 	for (nargs = 0; nargs < MAX_FARGS && l != NULL; nargs++, l = l->next)
 	{
 		if (!evaluateExpr(st, l->expr, &vargs[nargs]))

src/common/blkreftable.c

@@ -265,7 +265,7 @@ BlockRefTableSetLimitBlock(BlockRefTable *brtab,
 						   BlockNumber limit_block)
 {
 	BlockRefTableEntry *brtentry;
-	BlockRefTableKey key = {{0}};	/* make sure any padding is zero */
+	BlockRefTableKey key = {0}; /* make sure any padding is zero */
 	bool		found;
 
 	memcpy(&key.rlocator, rlocator, sizeof(RelFileLocator));
@@ -300,7 +300,7 @@ BlockRefTableMarkBlockModified(BlockRefTable *brtab,
 							   BlockNumber blknum)
 {
 	BlockRefTableEntry *brtentry;
-	BlockRefTableKey key = {{0}};	/* make sure any padding is zero */
+	BlockRefTableKey key = {0}; /* make sure any padding is zero */
 	bool		found;
 #ifndef FRONTEND
 	MemoryContext oldcontext = MemoryContextSwitchTo(brtab->mcxt);
@@ -340,7 +340,7 @@ BlockRefTableEntry *
 BlockRefTableGetEntry(BlockRefTable *brtab, const RelFileLocator *rlocator,
 					  ForkNumber forknum, BlockNumber *limit_block)
 {
-	BlockRefTableKey key = {{0}};	/* make sure any padding is zero */
+	BlockRefTableKey key = {0}; /* make sure any padding is zero */
 	BlockRefTableEntry *entry;
 
 	Assert(limit_block != NULL);
@@ -521,7 +521,7 @@ WriteBlockRefTable(BlockRefTable *brtab,
 		for (i = 0; i < brtab->hash->members; ++i)
 		{
 			BlockRefTableSerializedEntry *sentry = &sdata[i];
-			BlockRefTableKey key = {{0}};	/* make sure any padding is zero */
+			BlockRefTableKey key = {0}; /* make sure any padding is zero */
 			unsigned	j;
 
 			/* Write the serialized entry itself. */
@@ -616,7 +616,7 @@ BlockRefTableReaderNextRelation(BlockRefTableReader *reader,
 								BlockNumber *limit_block)
 {
 	BlockRefTableSerializedEntry sentry;
-	BlockRefTableSerializedEntry zentry = {{0}};
+	BlockRefTableSerializedEntry zentry = {0};
 
 	/*
 	 * Sanity check: caller must read all blocks from all chunks before moving
@@ -1291,7 +1291,7 @@ BlockRefTableWrite(BlockRefTableBuffer *buffer, void *data, int length)
 static void
 BlockRefTableFileTerminate(BlockRefTableBuffer *buffer)
 {
-	BlockRefTableSerializedEntry zentry = {{0}};
+	BlockRefTableSerializedEntry zentry = {0};
 	pg_crc32c	crc;
 
 	/* Write a sentinel indicating that there are no more entries. */

src/common/file_utils.c

@@ -687,7 +687,7 @@ pg_pwritev_with_retry(int fd, const struct iovec *iov, int iovcnt, off_t offset)
 ssize_t
 pg_pwrite_zeros(int fd, size_t size, off_t offset)
 {
-	static const PGIOAlignedBlock zbuffer = {{0}};	/* worth BLCKSZ */
+	static const PGIOAlignedBlock zbuffer = {0};	/* worth BLCKSZ */
 	void	   *zerobuf_addr = unconstify(PGIOAlignedBlock *, &zbuffer)->data;
 	struct iovec iov[PG_IOV_MAX];
 	size_t		remaining_size = size;

src/interfaces/libpq/fe-auth-oauth-curl.c

@@ -1232,7 +1232,7 @@ register_socket(CURL *curl, curl_socket_t socket, int what, void *ctx,
 #endif
 #ifdef HAVE_SYS_EVENT_H
 	struct async_ctx *actx = ctx;
-	struct kevent ev[2] = {{0}};
+	struct kevent ev[2] = {0};
 	struct kevent ev_out[2];
 	struct timespec timeout = {0};
 	int			nev = 0;