Make earthdistance use version-0 calling convention if not USE_FLOAT8_BYVAL,

and version-1 if USE_FLOAT8_BYVAL.  This might seem a bit pointless, but the
idea is to have at least one regression test that will fail if we ever
accidentally break version-0 functions that return float8.  However, they're
already broken, or at least hopelessly unportable, in the USE_FLOAT8_BYVAL
case.

Per a recent suggestion from Greg Stark.

contrib/earthdistance/earthdistance.c

-/* $PostgreSQL: pgsql/contrib/earthdistance/earthdistance.c,v 1.14 2008/04/20 01:05:52 tgl Exp $ */
+/* $PostgreSQL: pgsql/contrib/earthdistance/earthdistance.c,v 1.15 2008/04/21 01:11:43 tgl Exp $ */
 
 #include "postgres.h"
 
@@ -17,10 +17,6 @@ PG_MODULE_MAGIC;
 static const double EARTH_RADIUS = 3958.747716;
 static const double TWO_PI = 2.0 * M_PI;
 
-PG_FUNCTION_INFO_V1(geo_distance);
-
-Datum		geo_distance(PG_FUNCTION_ARGS);
-
 
 /******************************************************
  *
@@ -37,26 +33,22 @@ degtorad(double degrees)
 	return (degrees / 360.0) * TWO_PI;
 }
 
-
 /******************************************************
  *
- * geo_distance - distance between points
+ * geo_distance_internal - distance between points
  *
  * args:
  *	 a pair of points - for each point,
  *	   x-coordinate is longitude in degrees west of Greenwich
  *	   y-coordinate is latitude in degrees above equator
  *
- * returns: float8
+ * returns: double
  *	 distance between the points in miles on earth's surface
  ******************************************************/
 
-Datum
-geo_distance(PG_FUNCTION_ARGS)
+static double
+geo_distance_internal(Point *pt1, Point *pt2)
 {
-	Point	   *pt1 = PG_GETARG_POINT_P(0);
-	Point	   *pt2 = PG_GETARG_POINT_P(1);
-	float8		result;
 	double		long1,
 				lat1,
 				long2,
@@ -81,7 +73,57 @@ geo_distance(PG_FUNCTION_ARGS)
 			cos(lat1) * cos(lat2) * sin(longdiff / 2.) * sin(longdiff / 2.));
 	if (sino > 1.)
 		sino = 1.;
-	result = 2. * EARTH_RADIUS * asin(sino);
 
+	return 2. * EARTH_RADIUS * asin(sino);
+}
+
+
+/******************************************************
+ *
+ * geo_distance - distance between points
+ *
+ * args:
+ *	 a pair of points - for each point,
+ *	   x-coordinate is longitude in degrees west of Greenwich
+ *	   y-coordinate is latitude in degrees above equator
+ *
+ * returns: float8
+ *	 distance between the points in miles on earth's surface
+ *
+ * If float8 is passed-by-value, the oldstyle version-0 calling convention
+ * is unportable, so we use version-1.  However, if it's passed-by-reference,
+ * continue to use oldstyle.  This is just because we'd like earthdistance
+ * to serve as a canary for any unintentional breakage of version-0 functions
+ * with float8 results.
+ ******************************************************/
+
+#ifdef USE_FLOAT8_BYVAL
+
+Datum		geo_distance(PG_FUNCTION_ARGS);
+PG_FUNCTION_INFO_V1(geo_distance);
+
+Datum
+geo_distance(PG_FUNCTION_ARGS)
+{
+	Point	   *pt1 = PG_GETARG_POINT_P(0);
+	Point	   *pt2 = PG_GETARG_POINT_P(1);
+	float8		result;
+
+	result = geo_distance_internal(pt1, pt2);
 	PG_RETURN_FLOAT8(result);
 }
+
+#else /* !USE_FLOAT8_BYVAL */
+
+double	   *geo_distance(Point *pt1, Point *pt2);
+
+double *
+geo_distance(Point *pt1, Point *pt2)
+{
+	double	   *resultp = palloc(sizeof(double));
+
+	*resultp = geo_distance_internal(pt1, pt2);
+	return resultp;
+}
+
+#endif /* USE_FLOAT8_BYVAL */