Fix string truncation to be multibyte-aware in text_name and bpchar_name.

Previously, casts to name could generate invalidly-encoded results.

Also, make these functions match namein() more exactly, by consistently
using palloc0() instead of ad-hoc zeroing code.

Back-patch to all supported branches.

Karl Schnaitter and Tom Lane

Author: tglsfdc

src/backend/utils/adt/name.c

@@ -46,13 +46,17 @@ Datum
 namein(PG_FUNCTION_ARGS)
 {
 	char	   *s = PG_GETARG_CSTRING(0);
-	NameData   *result;
+	Name		result;
 	int			len;
 
 	len = strlen(s);
-	len = pg_mbcliplen(s, len, NAMEDATALEN - 1);
 
-	result = (NameData *) palloc0(NAMEDATALEN);
+	/* Truncate oversize input */
+	if (len >= NAMEDATALEN)
+		len = pg_mbcliplen(s, len, NAMEDATALEN - 1);
+
+	/* We use palloc0 here to ensure result is zero-padded */
+	result = (Name) palloc0(NAMEDATALEN);
 	memcpy(NameStr(*result), s, len);
 
 	PG_RETURN_NAME(result);

src/backend/utils/adt/varchar.c

@@ -372,9 +372,9 @@ bpchar_name(PG_FUNCTION_ARGS)
 	len = VARSIZE_ANY_EXHDR(s);
 	s_data = VARDATA_ANY(s);
 
-	/* Truncate to max length for a Name */
+	/* Truncate oversize input */
 	if (len >= NAMEDATALEN)
-		len = NAMEDATALEN - 1;
+		len = pg_mbcliplen(s_data, len, NAMEDATALEN - 1);
 
 	/* Remove trailing blanks */
 	while (len > 0)
@@ -384,16 +384,10 @@ bpchar_name(PG_FUNCTION_ARGS)
 		len--;
 	}
 
-	result = (NameData *) palloc(NAMEDATALEN);
+	/* We use palloc0 here to ensure result is zero-padded */
+	result = (Name) palloc0(NAMEDATALEN);
 	memcpy(NameStr(*result), s_data, len);
 
-	/* Now null pad to full length... */
-	while (len < NAMEDATALEN)
-	{
-		*(NameStr(*result) + len) = '\0';
-		len++;
-	}
-
 	PG_RETURN_NAME(result);
 }
 

src/backend/utils/adt/varlena.c

@@ -2256,18 +2256,12 @@ text_name(PG_FUNCTION_ARGS)
 
 	/* Truncate oversize input */
 	if (len >= NAMEDATALEN)
-		len = NAMEDATALEN - 1;
+		len = pg_mbcliplen(VARDATA_ANY(s), len, NAMEDATALEN - 1);
 
-	result = (Name) palloc(NAMEDATALEN);
+	/* We use palloc0 here to ensure result is zero-padded */
+	result = (Name) palloc0(NAMEDATALEN);
 	memcpy(NameStr(*result), VARDATA_ANY(s), len);
 
-	/* now null pad to full length... */
-	while (len < NAMEDATALEN)
-	{
-		*(NameStr(*result) + len) = '\0';
-		len++;
-	}
-
 	PG_RETURN_NAME(result);
 }