Process variadic arguments consistently in json functions

json_build_object and json_build_array and the jsonb equivalents did not
correctly process explicit VARIADIC arguments. They are modified to use
the new extract_variadic_args() utility function which abstracts away
the details of the call method.

Michael Paquier, reviewed by Tom Lane and Dmitry Dolgov.

Backpatch to 9.5 for the jsonb fixes and 9.4 for the json fixes, as
that's where they originated.

1 files changed, 24 insertions, 60 deletions

diff --git a/src/backend/utils/adt/json.c b/src/backend/utils/adt/json.c
index 1ddb42b4d08..baf1178995c 100644
--- a/src/backend/utils/adt/json.c
+++ b/src/backend/utils/adt/json.c
@@ -17,6 +17,7 @@
 #include "access/transam.h"
 #include "catalog/pg_type.h"
 #include "executor/spi.h"
+#include "funcapi.h"
 #include "lib/stringinfo.h"
 #include "libpq/pqformat.h"
 #include "mb/pg_wchar.h"
@@ -2111,10 +2112,17 @@ json_build_object(PG_FUNCTION_ARGS)
 {
 	int			nargs = PG_NARGS();
 	int			i;
-	Datum		arg;
 	const char *sep = "";
 	StringInfo	result;
-	Oid			val_type;
+	Datum	   *args;
+	bool	   *nulls;
+	Oid		   *types;
+
+	/* fetch argument values to build the object */
+	nargs = extract_variadic_args(fcinfo, 0, false, &args, &types, &nulls);
+
+	if (nargs < 0)
+		PG_RETURN_NULL();
 
 	if (nargs % 2 != 0)
 		ereport(ERROR,
@@ -2128,52 +2136,22 @@ json_build_object(PG_FUNCTION_ARGS)
 
 	for (i = 0; i < nargs; i += 2)
 	{
-		/*
-		 * Note: since json_build_object() is declared as taking type "any",
-		 * the parser will not do any type conversion on unknown-type literals
-		 * (that is, undecorated strings or NULLs).  Such values will arrive
-		 * here as type UNKNOWN, which fortunately does not matter to us,
-		 * since unknownout() works fine.
-		 */
 		appendStringInfoString(result, sep);
 		sep = ", ";
 
 		/* process key */
-		val_type = get_fn_expr_argtype(fcinfo->flinfo, i);
-
-		if (val_type == InvalidOid)
-			ereport(ERROR,
-					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-					 errmsg("could not determine data type for argument %d",
-							i + 1)));
-
-		if (PG_ARGISNULL(i))
+		if (nulls[i])
 			ereport(ERROR,
 					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 					 errmsg("argument %d cannot be null", i + 1),
 					 errhint("Object keys should be text.")));
 
-		arg = PG_GETARG_DATUM(i);
-
-		add_json(arg, false, result, val_type, true);
+		add_json(args[i], false, result, types[i], true);
 
 		appendStringInfoString(result, " : ");
 
 		/* process value */
-		val_type = get_fn_expr_argtype(fcinfo->flinfo, i + 1);
-
-		if (val_type == InvalidOid)
-			ereport(ERROR,
-					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-					 errmsg("could not determine data type for argument %d",
-							i + 2)));
-
-		if (PG_ARGISNULL(i + 1))
-			arg = (Datum) 0;
-		else
-			arg = PG_GETARG_DATUM(i + 1);
-
-		add_json(arg, PG_ARGISNULL(i + 1), result, val_type, false);
+		add_json(args[i + 1], nulls[i + 1], result, types[i + 1], false);
 	}
 
 	appendStringInfoChar(result, '}');
@@ -2196,12 +2174,19 @@ json_build_object_noargs(PG_FUNCTION_ARGS)
 Datum
 json_build_array(PG_FUNCTION_ARGS)
 {
-	int			nargs = PG_NARGS();
+	int			nargs;
 	int			i;
-	Datum		arg;
 	const char *sep = "";
 	StringInfo	result;
-	Oid			val_type;
+	Datum	   *args;
+	bool	   *nulls;
+	Oid		   *types;
+
+	/* fetch argument values to build the array */
+	nargs = extract_variadic_args(fcinfo, 0, false, &args, &types, &nulls);
+
+	if (nargs < 0)
+		PG_RETURN_NULL();
 
 	result = makeStringInfo();
 
@@ -2209,30 +2194,9 @@ json_build_array(PG_FUNCTION_ARGS)
 
 	for (i = 0; i < nargs; i++)
 	{
-		/*
-		 * Note: since json_build_array() is declared as taking type "any",
-		 * the parser will not do any type conversion on unknown-type literals
-		 * (that is, undecorated strings or NULLs).  Such values will arrive
-		 * here as type UNKNOWN, which fortunately does not matter to us,
-		 * since unknownout() works fine.
-		 */
 		appendStringInfoString(result, sep);
 		sep = ", ";
-
-		val_type = get_fn_expr_argtype(fcinfo->flinfo, i);
-
-		if (val_type == InvalidOid)
-			ereport(ERROR,
-					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-					 errmsg("could not determine data type for argument %d",
-							i + 1)));
-
-		if (PG_ARGISNULL(i))
-			arg = (Datum) 0;
-		else
-			arg = PG_GETARG_DATUM(i);
-
-		add_json(arg, PG_ARGISNULL(i), result, val_type, false);
+		add_json(args[i], nulls[i], result, types[i], false);
 	}
 
 	appendStringInfoChar(result, ']');