Fix inappropriate uses of PG_GETARG_UINT32()

The chr() function used PG_GETARG_UINT32() even though the argument is
declared as (signed) integer.  As a result, you can pass negative
arguments to this function and it internally interprets them as
positive.  Ultimately ends up being harmless, but it seems wrong, so
fix this and rearrange the internal error checking a bit to
accommodate this.

Another case was in the documentation, where example code used
PG_GETARG_UINT32() with an argument declared as signed integer.

Reviewed-by: Nathan Bossart <bossartn@amazon.com>
Discussion: https://www.postgresql.org/message-id/flat/7e43869b-d412-8f81-30a3-809783edc9a3%40enterprisedb.com

Author: petere

doc/src/sgml/xfunc.sgml

@@ -3193,7 +3193,7 @@ retcomposite(PG_FUNCTION_ARGS)
         oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
 
         /* total number of tuples to be returned */
-        funcctx->max_calls = PG_GETARG_UINT32(0);
+        funcctx->max_calls = PG_GETARG_INT32(0);
 
         /* Build a tuple descriptor for our result type */
         if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)

src/backend/utils/adt/oracle_compat.c

@@ -999,10 +999,26 @@ ascii(PG_FUNCTION_ARGS)
 Datum
 chr			(PG_FUNCTION_ARGS)
 {
-	uint32		cvalue = PG_GETARG_UINT32(0);
+	int32		arg = PG_GETARG_INT32(0);
+	uint32		cvalue;
 	text	   *result;
 	int			encoding = GetDatabaseEncoding();
 
+	/*
+	 * Error out on arguments that make no sense or that we can't validly
+	 * represent in the encoding.
+	 */
+	if (arg < 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("character number must be positive")));
+	else if (arg == 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+				 errmsg("null character not permitted")));
+
+	cvalue = arg;
+
 	if (encoding == PG_UTF8 && cvalue > 127)
 	{
 		/* for Unicode we treat the argument as a code point */
@@ -1017,7 +1033,7 @@ chr			(PG_FUNCTION_ARGS)
 		if (cvalue > 0x0010ffff)
 			ereport(ERROR,
 					(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
-					 errmsg("requested character too large for encoding: %d",
+					 errmsg("requested character too large for encoding: %u",
 							cvalue)));
 
 		if (cvalue > 0xffff)
@@ -1058,28 +1074,19 @@ chr			(PG_FUNCTION_ARGS)
 		if (!pg_utf8_islegal(wch, bytes))
 			ereport(ERROR,
 					(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
-					 errmsg("requested character not valid for encoding: %d",
+					 errmsg("requested character not valid for encoding: %u",
 							cvalue)));
 	}
 	else
 	{
 		bool		is_mb;
 
-		/*
-		 * Error out on arguments that make no sense or that we can't validly
-		 * represent in the encoding.
-		 */
-		if (cvalue == 0)
-			ereport(ERROR,
-					(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
-					 errmsg("null character not permitted")));
-
 		is_mb = pg_encoding_max_length(encoding) > 1;
 
 		if ((is_mb && (cvalue > 127)) || (!is_mb && (cvalue > 255)))
 			ereport(ERROR,
 					(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
-					 errmsg("requested character too large for encoding: %d",
+					 errmsg("requested character too large for encoding: %u",
 							cvalue)));
 
 		result = (text *) palloc(VARHDRSZ + 1);