Replace remaining StrNCpy() by strlcpy()

They are equivalent, except that StrNCpy() zero-fills the entire
destination buffer instead of providing just one trailing zero.  For
all but a tiny number of callers, that's just overhead rather than
being desirable.

Remove StrNCpy() as it is now unused.

In some cases, namestrcpy() is the more appropriate function to use.
While we're here, simplify the API of namestrcpy(): Remove the return
value, don't check for NULL input.  Nothing was using that anyway.
Also, remove a few unused name-related functions.

Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/flat/44f5e198-36f6-6cdb-7fa9-60e34784daae%402ndquadrant.com

Author: petere

contrib/pgcrypto/crypt-des.c

@@ -720,7 +720,7 @@ px_crypt_des(const char *key, const char *setting)
 			if (des_setkey((char *) keybuf))
 				return NULL;
 		}
-		StrNCpy(output, setting, 10);
+		strlcpy(output, setting, 10);
 
 		/*
 		 * Double check that we weren't given a short setting. If we were, the

src/backend/access/transam/slru.c

@@ -252,7 +252,7 @@ SimpleLruInit(SlruCtl ctl, const char *name, int nslots, int nlsns,
 	 */
 	ctl->shared = shared;
 	ctl->do_fsync = true;		/* default behavior */
-	StrNCpy(ctl->Dir, subdir, sizeof(ctl->Dir));
+	strlcpy(ctl->Dir, subdir, sizeof(ctl->Dir));
 }
 
 /*

src/backend/access/transam/xlogarchive.c

@@ -323,7 +323,7 @@ ExecuteRecoveryCommand(const char *command, const char *commandName, bool failOn
 				case 'r':
 					/* %r: filename of last restartpoint */
 					sp++;
-					StrNCpy(dp, lastRestartPointFname, endp - dp);
+					strlcpy(dp, lastRestartPointFname, endp - dp);
 					dp += strlen(dp);
 					break;
 				case '%':

src/backend/catalog/pg_constraint.c

@@ -484,7 +484,7 @@ ChooseConstraintName(const char *name1, const char *name2,
 	conDesc = table_open(ConstraintRelationId, AccessShareLock);
 
 	/* try the unmodified label first */
-	StrNCpy(modlabel, label, sizeof(modlabel));
+	strlcpy(modlabel, label, sizeof(modlabel));
 
 	for (;;)
 	{

src/backend/commands/indexcmds.c

@@ -2246,7 +2246,7 @@ ChooseRelationName(const char *name1, const char *name2,
 	char		modlabel[NAMEDATALEN];
 
 	/* try the unmodified label first */
-	StrNCpy(modlabel, label, sizeof(modlabel));
+	strlcpy(modlabel, label, sizeof(modlabel));
 
 	for (;;)
 	{

src/backend/commands/statscmds.c

@@ -681,7 +681,7 @@ ChooseExtendedStatisticName(const char *name1, const char *name2,
 	char		modlabel[NAMEDATALEN];
 
 	/* try the unmodified label first */
-	StrNCpy(modlabel, label, sizeof(modlabel));
+	strlcpy(modlabel, label, sizeof(modlabel));
 
 	for (;;)
 	{

src/backend/commands/tablecmds.c

@@ -606,7 +606,7 @@ DefineRelation(CreateStmt *stmt, char relkind, Oid ownerId,
 	 * Truncate relname to appropriate length (probably a waste of time, as
 	 * parser should have done this already).
 	 */
-	StrNCpy(relname, stmt->relation->relname, NAMEDATALEN);
+	strlcpy(relname, stmt->relation->relname, NAMEDATALEN);
 
 	/*
 	 * Check consistency of arguments

src/backend/postmaster/pgstat.c

@@ -4367,7 +4367,7 @@ pgstat_send_archiver(const char *xlog, bool failed)
 	 */
 	pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_ARCHIVER);
 	msg.m_failed = failed;
-	StrNCpy(msg.m_xlog, xlog, sizeof(msg.m_xlog));
+	strlcpy(msg.m_xlog, xlog, sizeof(msg.m_xlog));
 	msg.m_timestamp = GetCurrentTimestamp();
 	pgstat_send(&msg, sizeof(msg));
 }

src/backend/replication/logical/logical.c

@@ -39,6 +39,7 @@
 #include "replication/snapbuild.h"
 #include "storage/proc.h"
 #include "storage/procarray.h"
+#include "utils/builtins.h"
 #include "utils/memutils.h"
 
 /* data for errcontext callback */
@@ -288,6 +289,7 @@ CreateInitDecodingContext(const char *plugin,
 {
 	TransactionId xmin_horizon = InvalidTransactionId;
 	ReplicationSlot *slot;
+	NameData	plugin_name;
 	LogicalDecodingContext *ctx;
 	MemoryContext old_context;
 
@@ -319,9 +321,14 @@ CreateInitDecodingContext(const char *plugin,
 				(errcode(ERRCODE_ACTIVE_SQL_TRANSACTION),
 				 errmsg("cannot create logical replication slot in transaction that has performed writes")));
 
-	/* register output plugin name with slot */
+	/*
+	 * Register output plugin name with slot.  We need the mutex to avoid
+	 * concurrent reading of a partially copied string.  But we don't want any
+	 * complicated code while holding a spinlock, so do namestrcpy() outside.
+	 */
+	namestrcpy(&plugin_name, plugin);
 	SpinLockAcquire(&slot->mutex);
-	StrNCpy(NameStr(slot->data.plugin), plugin, NAMEDATALEN);
+	slot->data.plugin = plugin_name;
 	SpinLockRelease(&slot->mutex);
 
 	if (XLogRecPtrIsInvalid(restart_lsn))

src/backend/replication/slot.c

@@ -275,7 +275,7 @@ ReplicationSlotCreate(const char *name, bool db_specific,
 
 	/* first initialize persistent data */
 	memset(&slot->data, 0, sizeof(ReplicationSlotPersistentData));
-	StrNCpy(NameStr(slot->data.name), name, NAMEDATALEN);
+	namestrcpy(&slot->data.name, name);
 	slot->data.database = db_specific ? MyDatabaseId : InvalidOid;
 	slot->data.persistency = persistency;