Quiet warnings about casts of function types

It is easy enough to stop casting _PgObject_pureVirtualCalled
to incompatible function types, as it makes modern compilers
suspicious, and was only done in three places anyway.

Author: jcflack

pljava-so/src/main/c/PgObject.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2004-2020 Tada AB and other contributors, as listed below.
+ * Copyright (c) 2004-2023 Tada AB and other contributors, as listed below.
  *
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the The BSD 3-Clause License
@@ -66,11 +66,6 @@ const char* PgObjectClass_getName(PgObjectClass self)
 	return self->name;
 }
 
-void _PgObject_pureVirtualCalled(PgObject object)
-{
-	ereport(ERROR, (errmsg("Pure virtual method called")));
-}
-
 char* PgObject_getClassName(jclass cls)
 {
 	jstring jstr;

pljava-so/src/main/c/type/Type.c

@@ -1029,6 +1029,31 @@ void Type_initialize(void)
 	initializeTypeBridges();
 }
 
+static Type unimplementedTypeObtainer(Oid typeId);
+static jvalue unimplementedDatumCoercer(Type, Datum);
+static Datum unimplementedObjectCoercer(Type, jobject);
+
+static Type unimplementedTypeObtainer(Oid typeId)
+{
+	ereport(ERROR,
+		(errmsg("no type obtainer registered for type oid %ud", typeId)));
+	pg_unreachable();
+}
+
+static jvalue unimplementedDatumCoercer(Type t, Datum d)
+{
+	ereport(ERROR,
+		(errmsg("no datum coercer registered for type oid %ud", t->typeId)));
+	pg_unreachable();
+}
+
+static Datum unimplementedObjectCoercer(Type t, jobject o)
+{
+	ereport(ERROR,
+		(errmsg("no object coercer registered for type oid %ud", t->typeId)));
+	pg_unreachable();
+}
+
 /*
  * Abstract Type constructor
  */
@@ -1047,8 +1072,8 @@ TypeClass TypeClass_alloc2(
 	self->javaTypeName    = "";
 	self->javaClass       = 0;
 	self->canReplaceType  = _Type_canReplaceType;
-	self->coerceDatum     = (DatumCoercer)_PgObject_pureVirtualCalled;
-	self->coerceObject    = (ObjectCoercer)_PgObject_pureVirtualCalled;
+	self->coerceDatum     = unimplementedDatumCoercer;
+	self->coerceObject    = unimplementedObjectCoercer;
 	self->createArrayType = _Type_createArrayType;
 	self->invoke          = _Type_invoke;
 	self->getSRFCollector = _Type_getSRFCollector;
@@ -1137,9 +1162,7 @@ static void _registerType(
 
 void Type_registerType(const char* javaTypeName, Type type)
 {
-	_registerType(
-		type->typeId, javaTypeName, type,
-		(TypeObtainer)_PgObject_pureVirtualCalled);
+	_registerType(type->typeId, javaTypeName, type, unimplementedTypeObtainer);
 }
 
 void Type_registerType2(

pljava-so/src/main/include/pljava/PgObject_priv.h

@@ -1,10 +1,14 @@
 /*
- * Copyright (c) 2004, 2005, 2006 TADA AB - Taby Sweden
- * Distributed under the terms shown in the file COPYRIGHT
- * found in the root folder of this project or at
- * http://eng.tada.se/osprojects/COPYRIGHT.html
+ * Copyright (c) 2004-2023 Tada AB and other contributors, as listed below.
  *
- * @author Thomas Hallgren
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the The BSD 3-Clause License
+ * which accompanies this distribution, and is available at
+ * http://opensource.org/licenses/BSD-3-Clause
+ *
+ * Contributors:
+ *   Tada AB
+ *   Chapman Flack
  */
 #ifndef __pljava_PgObject_priv_h
 #define __pljava_PgObject_priv_h
@@ -54,12 +58,6 @@ struct PgObject_
 	PgObjectClass m_class;
 };
 
-/*
- * Internal bogus. Someone forgot to replace a function
- * pointer somewhere.
- */
-extern void _PgObject_pureVirtualCalled(PgObject self);
-
 /*
  * Throw an exception indicating that wanted member could not be
  * found.