Remove variable length arrays

VLAs aren't supported by Visual Studio.

- Remove all existing instances of VLAs.
- Add a flag, -Werror=vla, which makes gcc refuse to compile if we add
  VLAs in the future.

configure

@@ -661,6 +661,7 @@ infodir
 docdir
 oldincludedir
 includedir
+runstatedir
 localstatedir
 sharedstatedir
 sysconfdir
@@ -737,6 +738,7 @@ datadir='${datarootdir}'
 sysconfdir='${prefix}/etc'
 sharedstatedir='${prefix}/com'
 localstatedir='${prefix}/var'
+runstatedir='${localstatedir}/run'
 includedir='${prefix}/include'
 oldincludedir='/usr/include'
 docdir='${datarootdir}/doc/${PACKAGE_TARNAME}'
@@ -989,6 +991,15 @@ do
   | -silent | --silent | --silen | --sile | --sil)
     silent=yes ;;
 
+  -runstatedir | --runstatedir | --runstatedi | --runstated \
+  | --runstate | --runstat | --runsta | --runst | --runs \
+  | --run | --ru | --r)
+    ac_prev=runstatedir ;;
+  -runstatedir=* | --runstatedir=* | --runstatedi=* | --runstated=* \
+  | --runstate=* | --runstat=* | --runsta=* | --runst=* | --runs=* \
+  | --run=* | --ru=* | --r=*)
+    runstatedir=$ac_optarg ;;
+
   -sbindir | --sbindir | --sbindi | --sbind | --sbin | --sbi | --sb)
     ac_prev=sbindir ;;
   -sbindir=* | --sbindir=* | --sbindi=* | --sbind=* | --sbin=* \
@@ -1126,7 +1137,7 @@ fi
 for ac_var in	exec_prefix prefix bindir sbindir libexecdir datarootdir \
 		datadir sysconfdir sharedstatedir localstatedir includedir \
 		oldincludedir docdir infodir htmldir dvidir pdfdir psdir \
-		libdir localedir mandir
+		libdir localedir mandir runstatedir
 do
   eval ac_val=\$$ac_var
   # Remove trailing slashes.
@@ -1279,6 +1290,7 @@ Fine tuning of the installation directories:
   --sysconfdir=DIR        read-only single-machine data [PREFIX/etc]
   --sharedstatedir=DIR    modifiable architecture-independent data [PREFIX/com]
   --localstatedir=DIR     modifiable single-machine data [PREFIX/var]
+  --runstatedir=DIR       modifiable per-process data [LOCALSTATEDIR/run]
   --libdir=DIR            object code libraries [EPREFIX/lib]
   --includedir=DIR        C header files [PREFIX/include]
   --oldincludedir=DIR     C header files for non-gcc [/usr/include]
@@ -4007,6 +4019,41 @@ if test x"$citusac_cv_prog_cc_cflags__Wmissing_prototypes" = x"yes"; then
   CITUS_CFLAGS="$CITUS_CFLAGS -Wmissing-prototypes"
 fi
 
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $CC supports -Werror=vla" >&5
+$as_echo_n "checking whether $CC supports -Werror=vla... " >&6; }
+if ${citusac_cv_prog_cc_cflags__Werror_vla+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  citusac_save_CFLAGS=$CFLAGS
+CFLAGS="$citusac_save_CFLAGS -Werror=vla"
+ac_save_c_werror_flag=$ac_c_werror_flag
+ac_c_werror_flag=yes
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  citusac_cv_prog_cc_cflags__Werror_vla=yes
+else
+  citusac_cv_prog_cc_cflags__Werror_vla=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+ac_c_werror_flag=$ac_save_c_werror_flag
+CFLAGS="$citusac_save_CFLAGS"
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $citusac_cv_prog_cc_cflags__Werror_vla" >&5
+$as_echo "$citusac_cv_prog_cc_cflags__Werror_vla" >&6; }
+if test x"$citusac_cv_prog_cc_cflags__Werror_vla" = x"yes"; then
+  CITUS_CFLAGS="$CITUS_CFLAGS -Werror=vla"
+fi
+  # visual studio does not support these
 
 #
 # --enable-coverage enables generation of code coverage metrics with gcov

configure.in

@@ -163,6 +163,7 @@ CITUSAC_PROG_CC_CFLAGS_OPT([-Wendif-labels])
 CITUSAC_PROG_CC_CFLAGS_OPT([-Wmissing-format-attribute])
 CITUSAC_PROG_CC_CFLAGS_OPT([-Wmissing-declarations])
 CITUSAC_PROG_CC_CFLAGS_OPT([-Wmissing-prototypes])
+CITUSAC_PROG_CC_CFLAGS_OPT([-Werror=vla])  # visual studio does not support these
 
 #
 # --enable-coverage enables generation of code coverage metrics with gcov

src/backend/distributed/connection/remote_commands.c

@@ -744,11 +744,16 @@ WaitForAllConnections(List *connectionList, bool raiseInterrupts)
 	int connectionIndex = 0;
 	ListCell *connectionCell = NULL;
 
-	MultiConnection *allConnections[totalConnectionCount];
-	WaitEvent events[totalConnectionCount];
-	bool connectionReady[totalConnectionCount];
+	MultiConnection *allConnections[REMOTE_MAX_CONNECTIONS];
+	WaitEvent events[REMOTE_MAX_CONNECTIONS];
+	bool connectionReady[REMOTE_MAX_CONNECTIONS];
 	WaitEventSet *waitEventSet = NULL;
 
+	if (totalConnectionCount > REMOTE_MAX_CONNECTIONS)
+	{
+		ereport(ERROR, (errmsg("too many connections")));
+	}
+
 	/* convert connection list to an array such that we can move items around */
 	foreach(connectionCell, connectionList)
 	{

src/backend/distributed/master/master_metadata_utility.c

@@ -637,7 +637,7 @@ NodeGroupHasShardPlacements(uint32 groupId, bool onlyConsiderActivePlacements)
 
 	HeapTuple heapTuple = NULL;
 	SysScanDesc scanDescriptor = NULL;
-	ScanKeyData scanKey[scanKeyCount];
+	ScanKeyData scanKey[2];
 
 	Relation pgPlacement = heap_open(DistPlacementRelationId(),
 									 AccessShareLock);
@@ -1097,7 +1097,7 @@ DeleteShardPlacementRow(uint64 placementId)
 	Relation pgDistPlacement = NULL;
 	SysScanDesc scanDescriptor = NULL;
 	const int scanKeyCount = 1;
-	ScanKeyData scanKey[scanKeyCount];
+	ScanKeyData scanKey[1];
 	bool indexOK = true;
 	HeapTuple heapTuple = NULL;
 	TupleDesc tupleDescriptor = NULL;

src/backend/distributed/metadata/metadata_sync.c

@@ -813,11 +813,10 @@ static void
 MarkNodeHasMetadata(char *nodeName, int32 nodePort, bool hasMetadata)
 {
 	const bool indexOK = false;
-	const int scanKeyCount = 2;
 
 	Relation pgDistNode = NULL;
 	TupleDesc tupleDescriptor = NULL;
-	ScanKeyData scanKey[scanKeyCount];
+	ScanKeyData scanKey[2];
 	SysScanDesc scanDescriptor = NULL;
 	HeapTuple heapTuple = NULL;
 	Datum values[Natts_pg_dist_node];
@@ -833,7 +832,7 @@ MarkNodeHasMetadata(char *nodeName, int32 nodePort, bool hasMetadata)
 				BTEqualStrategyNumber, F_INT4EQ, Int32GetDatum(nodePort));
 
 	scanDescriptor = systable_beginscan(pgDistNode, InvalidOid, indexOK,
-										NULL, scanKeyCount, scanKey);
+										NULL, 2, scanKey);
 
 	heapTuple = systable_getnext(scanDescriptor);
 	if (!HeapTupleIsValid(heapTuple))

src/backend/distributed/test/distributed_deadlock_detection.c

@@ -49,9 +49,8 @@ get_adjacency_list_wait_graph(PG_FUNCTION_ARGS)
 	HASH_SEQ_STATUS status;
 	TransactionNode *transactionNode = NULL;
 
-	const int attributeCount = 2;
-	Datum values[attributeCount];
-	bool isNulls[attributeCount];
+	Datum values[2];
+	bool isNulls[2];
 
 	CheckCitusVersion(ERROR);
 

src/backend/distributed/transaction/backend_data.c

@@ -133,9 +133,8 @@ get_current_transaction_id(PG_FUNCTION_ARGS)
 	TupleDesc tupleDescriptor = NULL;
 	HeapTuple heapTuple = NULL;
 
-	const int attributeCount = 5;
-	Datum values[attributeCount];
-	bool isNulls[attributeCount];
+	Datum values[5];
+	bool isNulls[5];
 
 	DistributedTransactionId *distributedTransctionId = NULL;
 
@@ -196,9 +195,8 @@ get_all_active_transactions(PG_FUNCTION_ARGS)
 
 	int backendIndex = 0;
 
-	const int attributeCount = 5;
-	Datum values[attributeCount];
-	bool isNulls[attributeCount];
+	Datum values[5];
+	bool isNulls[5];
 
 	CheckCitusVersion(ERROR);
 

src/backend/distributed/utils/colocation_utils.c

@@ -457,7 +457,7 @@ ColocationId(int shardCount, int replicationFactor, Oid distributionColumnType)
 	HeapTuple colocationTuple = NULL;
 	SysScanDesc scanDescriptor;
 	const int scanKeyCount = 3;
-	ScanKeyData scanKey[scanKeyCount];
+	ScanKeyData scanKey[3];
 	bool indexOK = true;
 
 	Relation pgDistColocation = heap_open(DistColocationRelationId(), AccessShareLock);
@@ -660,7 +660,7 @@ UpdateRelationColocationGroup(Oid distributedRelationId, uint32 colocationId)
 	bool shouldSyncMetadata = false;
 	bool indexOK = true;
 	int scanKeyCount = 1;
-	ScanKeyData scanKey[scanKeyCount];
+	ScanKeyData scanKey[1];
 	Datum values[Natts_pg_dist_partition];
 	bool isNull[Natts_pg_dist_partition];
 	bool replace[Natts_pg_dist_partition];
@@ -1052,7 +1052,7 @@ DeleteColocationGroup(uint32 colocationId)
 	Relation pgDistColocation = NULL;
 	SysScanDesc scanDescriptor = NULL;
 	int scanKeyCount = 1;
-	ScanKeyData scanKey[scanKeyCount];
+	ScanKeyData scanKey[1];
 	bool indexOK = false;
 	HeapTuple heapTuple = NULL;
 

src/backend/distributed/utils/metadata_cache.c

@@ -273,7 +273,7 @@ IsDistributedTableViaCatalog(Oid relationId)
 	HeapTuple partitionTuple = NULL;
 	SysScanDesc scanDescriptor = NULL;
 	const int scanKeyCount = 1;
-	ScanKeyData scanKey[scanKeyCount];
+	ScanKeyData scanKey[1];
 	bool indexOK = true;
 
 	Relation pgDistPartition = heap_open(DistPartitionRelationId(), AccessShareLock);

src/backend/distributed/utils/node_metadata.c

@@ -1044,7 +1044,7 @@ GetNodeTuple(char *nodeName, int32 nodePort)
 	const int scanKeyCount = 2;
 	const bool indexOK = false;
 
-	ScanKeyData scanKey[scanKeyCount];
+	ScanKeyData scanKey[2];
 	SysScanDesc scanDescriptor = NULL;
 	HeapTuple heapTuple = NULL;
 	HeapTuple nodeTuple = NULL;
@@ -1289,7 +1289,7 @@ DeleteNodeRow(char *nodeName, int32 nodePort)
 
 	HeapTuple heapTuple = NULL;
 	SysScanDesc heapScan = NULL;
-	ScanKeyData scanKey[scanKeyCount];
+	ScanKeyData scanKey[2];
 
 	Relation pgDistNode = heap_open(DistNodeRelationId(), RowExclusiveLock);
 

src/include/distributed/metadata_sync.h

@@ -56,5 +56,4 @@ extern void CreateTableMetadataOnWorkers(Oid relationId);
 	"shardlength = EXCLUDED.shardlength, " \
 	"groupid = EXCLUDED.groupid"
 
-
 #endif /* METADATA_SYNC_H */

src/include/distributed/remote_commands.h

@@ -17,6 +17,8 @@
 #define QUERY_SEND_FAILED 1
 #define RESPONSE_NOT_OKAY 2
 
+#define REMOTE_MAX_CONNECTIONS 1024
+
 struct pg_result; /* target of the PGresult typedef */
 
 /* GUC, determining whether statements sent to remote nodes are logged */