Make cast function from circle to polygon error safe

Previously, the function casting type circle to type polygon could not
be made error safe, because it is an SQL language function.

This refactors it as a C/internal function, by sharing code with the
C/internal function that the SQL function previously wrapped, and soft
error support is added.

Author: jian he <jian.universality@gmail.com>
Reviewed-by: Amul Sul <sulamul@gmail.com>
Reviewed-by: Corey Huinker <corey.huinker@gmail.com>
Discussion: Discussion: https://www.postgresql.org/message-id/flat/CADkLM%3Dfv1JfY4Ufa-jcwwNbjQixNViskQ8jZu3Tz_p656i_4hQ%40mail.gmail.com

src/backend/catalog/system_functions.sql

@@ -99,12 +99,6 @@ CREATE OR REPLACE FUNCTION path_contain_pt(path, point)
  IMMUTABLE PARALLEL SAFE STRICT COST 1
 RETURN on_ppath($2, $1);
 
-CREATE OR REPLACE FUNCTION polygon(circle)
- RETURNS polygon
- LANGUAGE sql
- IMMUTABLE PARALLEL SAFE STRICT COST 1
-RETURN polygon(12, $1);
-
 CREATE OR REPLACE FUNCTION age(timestamptz)
  RETURNS interval
  LANGUAGE sql

src/backend/utils/adt/geo_ops.c

@@ -125,6 +125,7 @@ static float8 circle_ar(CIRCLE *circle);
 
 /* Routines for polygons */
 static void make_bound_box(POLYGON *poly);
+static POLYGON *circle_poly_internal(int32 npts, const CIRCLE *circle, FunctionCallInfo fcinfo);
 static void poly_to_circle(CIRCLE *result, POLYGON *poly, Node *escontext);
 static bool lseg_inside_poly(Point *a, Point *b, POLYGON *poly, int start);
 static bool poly_contain_poly(POLYGON *contains_poly, POLYGON *contained_poly);
@@ -5317,11 +5318,9 @@ fail:
 }
 
 
-Datum
-circle_poly(PG_FUNCTION_ARGS)
+static POLYGON *
+circle_poly_internal(int32 npts, const CIRCLE *circle, FunctionCallInfo fcinfo)
 {
-	int32		npts = PG_GETARG_INT32(0);
-	CIRCLE	   *circle = PG_GETARG_CIRCLE_P(1);
 	POLYGON    *poly;
 	int			base_size,
 				size;
@@ -5330,12 +5329,12 @@ circle_poly(PG_FUNCTION_ARGS)
 	float8		anglestep;
 
 	if (FPzero(circle->radius))
-		ereport(ERROR,
+		ereturn(fcinfo->context, NULL,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 				 errmsg("cannot convert circle with radius zero to polygon")));
 
 	if (npts < 2)
-		ereport(ERROR,
+		ereturn(fcinfo->context, NULL,
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 				 errmsg("must request at least 2 points")));
 
@@ -5344,7 +5343,7 @@ circle_poly(PG_FUNCTION_ARGS)
 
 	/* Check for integer overflow */
 	if (base_size / npts != sizeof(poly->p[0]) || size <= base_size)
-		ereport(ERROR,
+		ereturn(fcinfo->context, NULL,
 				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
 				 errmsg("too many points requested")));
 
@@ -5356,17 +5355,51 @@ circle_poly(PG_FUNCTION_ARGS)
 
 	for (i = 0; i < npts; i++)
 	{
-		angle = float8_mul(anglestep, i);
+		float8		temp;
 
-		poly->p[i].x = float8_mi(circle->center.x,
-								 float8_mul(circle->radius, cos(angle)));
-		poly->p[i].y = float8_pl(circle->center.y,
-								 float8_mul(circle->radius, sin(angle)));
+		angle = float8_mul_safe(anglestep, i, fcinfo->context);
+		if (SOFT_ERROR_OCCURRED(fcinfo->context))
+			return NULL;
+
+		temp = float8_mul_safe(circle->radius, cos(angle), fcinfo->context);
+		if (SOFT_ERROR_OCCURRED(fcinfo->context))
+			return NULL;
+
+		poly->p[i].x = float8_mi_safe(circle->center.x, temp, fcinfo->context);
+		if (SOFT_ERROR_OCCURRED(fcinfo->context))
+			return NULL;
+
+		temp = float8_mul_safe(circle->radius, sin(angle), fcinfo->context);
+		if (SOFT_ERROR_OCCURRED(fcinfo->context))
+			return NULL;
+
+		poly->p[i].y = float8_pl_safe(circle->center.y, temp, fcinfo->context);
+		if (SOFT_ERROR_OCCURRED(fcinfo->context))
+			return NULL;
 	}
 
 	make_bound_box(poly);
 
-	PG_RETURN_POLYGON_P(poly);
+	return poly;
+}
+
+Datum
+circle_poly(PG_FUNCTION_ARGS)
+{
+	int32		npts = PG_GETARG_INT32(0);
+	CIRCLE	   *circle = PG_GETARG_CIRCLE_P(1);
+
+	PG_RETURN_POLYGON_P(circle_poly_internal(npts, circle, fcinfo));
+}
+
+/* convert circle to 12-vertex polygon */
+Datum
+circle_to_poly(PG_FUNCTION_ARGS)
+{
+	int32		npts = 12;
+	CIRCLE	   *circle = PG_GETARG_CIRCLE_P(0);
+
+	PG_RETURN_POLYGON_P(circle_poly_internal(npts, circle, fcinfo));
 }
 
 /*

src/include/catalog/catversion.h

@@ -57,6 +57,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	202603241
+#define CATALOG_VERSION_NO	202603301
 
 #endif

src/include/catalog/pg_proc.dat

@@ -3390,8 +3390,8 @@
   proname => 'center', prorettype => 'point', proargtypes => 'circle',
   prosrc => 'circle_center' },
 { oid => '1544', descr => 'convert circle to 12-vertex polygon',
-  proname => 'polygon', prolang => 'sql', prorettype => 'polygon',
-  proargtypes => 'circle', prosrc => 'see system_functions.sql' },
+  proname => 'polygon', prorettype => 'polygon',
+  proargtypes => 'circle', prosrc => 'circle_to_poly' },
 { oid => '1545', descr => 'number of points',
   proname => 'npoints', prorettype => 'int4', proargtypes => 'path',
   prosrc => 'path_npoints' },