API change to PVSupport, likely unused though

Author: anjohnson

documentation/RELEASE_NOTES.md

@@ -2,6 +2,16 @@
 
 This document summarizes the changes to the module between releases.
 
+## Release 4.7.2 (UNRELEASED)
+
+* The virtual `init()` method of `class PVSupport` has been made un-virtual, and the base-class
+  implementation always returns `false` as it should not be used. The `ControlSupport` and
+  `ScalarAlarmSupport` derived classes already provided their own implementations but needed
+  different method arguments, so a virtual base-class method couldn't be used anyway.
+  Those derived classes don't appear to be used internally at all, although they were being
+  used in Marty Kraimer's exampleCPP repository which is no longer maintained or recommended
+  for use anyway.
+
 ## Release 4.7.1 (EPICS 7.0.8, Dec 2023)
 
 * Added data distributor plugin which can be used for distributing data between 

src/pv/controlSupport.h

@@ -35,19 +35,18 @@ class epicsShareClass ControlSupport :
      */
     virtual ~ControlSupport();
     /**
-     * @brief Connects to contol fields.
+     * @brief Connects to control fields.
      *
      * @param pvValue The field to support.
      * @param pvSupport Support specific fields.
      * @return <b>true</b> for success and <b>false</b> for failure.
      */
-    virtual bool init(
+    bool init(
         epics::pvData::PVFieldPtr const & pvValue,
         epics::pvData::PVFieldPtr const & pvSupport);
     /**
      * @brief Honors control fields.
      *
-     *
      * @return Returns true is any fields were modified; otherwise false.
      */
     virtual bool process();

src/pv/pvSupport.h

@@ -38,17 +38,17 @@ class epicsShareClass PVSupport
      */
     virtual ~PVSupport(){}
     /**
-     * @brief Optional  initialization method.
+     * @brief Required initialization method.
      *
-     * Called after PVRecord is created but before record is installed into PVDatabase.
+     * Implementation classes must define an init() method that must be
+     * explicitly called by PVRecord classes that use them to provide
+     * references to the specific fields to be supported. Different support
+     * will may different fields, so a virtual method cannot be defined in
+     * this base class to support them, hence this method always fails.
      *
-     * @param pvValue The field to support.
-     * @param pvSupport Support specific fields.
      * @return <b>true</b> for success and <b>false</b> for failure.
      */
-    virtual bool init(
-        epics::pvData::PVFieldPtr const & pvValue,
-        epics::pvData::PVFieldPtr const & pvSupport) {return true;}
+    bool init() {return false;}
     /**
      *  @brief Optional method for derived class.
      *

src/pv/scalarAlarmSupport.h

@@ -45,7 +45,7 @@ class epicsShareClass ScalarAlarmSupport :
      * @param pvSupport Support specific fields.
      * @return <b>true</b> for success and <b>false</b> for failure.
      */
-    virtual bool init(
+    bool init(
         epics::pvData::PVFieldPtr const & pvValue,
         epics::pvData::PVStructurePtr const & pvAlarm,
         epics::pvData::PVFieldPtr const & pvSupport);