0024023: Revamp the OCCT Handle -- plugin

Definition of PLUGINFACTORY function changed to return Standard_Transient* instead of Handle(Standard_Transient), which cannot be returned by C-style function.
Default implementation of PLUGINFACTORY() instantiated by macro PLUGIN() is corrected accordingly.
Methods Factory() in persistence packages are made returning const & to handle; this is to reflect the fact that returned handle should point to existing object (usually statically allocated) rather than new one.

src/BinDrivers/BinDrivers.cdl

@@ -33,6 +33,7 @@ is
     class DocumentRetrievalDriver;
 
     Factory (theGUID : GUID from Standard) returns Transient from Standard;
+    ---C++: return const &
 
     AttributeDrivers (MsgDrv : MessageDriver from CDM)
     	returns ADriverTable from BinMDF;

src/BinDrivers/BinDrivers.cxx

@@ -34,7 +34,7 @@ static Standard_GUID BinRetrievalDriver("03a56836-8269-11d5-aab2-0050044b1af1");
 //function : Factory
 //purpose  : PLUGIN FACTORY
 //=======================================================================
-Handle(Standard_Transient) BinDrivers::Factory(const Standard_GUID& theGUID)
+const Handle(Standard_Transient)& BinDrivers::Factory(const Standard_GUID& theGUID)
 {
   if (theGUID == BinStorageDriver)
   {
@@ -57,7 +57,8 @@ Handle(Standard_Transient) BinDrivers::Factory(const Standard_GUID& theGUID)
   }
 
   Standard_Failure::Raise ("BinDrivers : unknown GUID");
-  return NULL;
+  static Handle(Standard_Transient) aNullHandle;
+  return aNullHandle;
 }
 
 //=======================================================================
@@ -90,7 +91,4 @@ TCollection_AsciiString BinDrivers::StorageVersion()
   return BinLDrivers::StorageVersion();
 }
 
-#ifdef _MSC_VER
-#pragma warning(disable:4190) /* disable warning on C++ type returned by C function; should be OK for C++ usage */
-#endif
 PLUGIN(BinDrivers)

src/BinLDrivers/BinLDrivers.cdl

@@ -35,6 +35,7 @@ is
     imported VectorOfDocumentSection;
 
     Factory (theGUID : GUID from Standard) returns Transient from Standard;
+    ---C++: return const &
 
     AttributeDrivers (MsgDrv : MessageDriver from CDM)
         returns ADriverTable from BinMDF;

src/BinLDrivers/BinLDrivers.cxx

@@ -32,7 +32,7 @@ static Standard_GUID BinLRetrievalDriver("13a56836-8269-11d5-aab2-0050044b1af1")
 //function : Factory
 //purpose  : PLUGIN FACTORY
 //=======================================================================
-Handle(Standard_Transient) BinLDrivers::Factory(const Standard_GUID& theGUID)
+const Handle(Standard_Transient)& BinLDrivers::Factory(const Standard_GUID& theGUID)
 {
   if (theGUID == BinLStorageDriver)
   {
@@ -55,7 +55,8 @@ Handle(Standard_Transient) BinLDrivers::Factory(const Standard_GUID& theGUID)
   }
 
   Standard_Failure::Raise ("BinLDrivers : unknown GUID");
-  return NULL;
+  static Handle(Standard_Transient) aNullHandle;
+  return aNullHandle;
 }
 
 //=======================================================================
@@ -89,7 +90,4 @@ TCollection_AsciiString BinLDrivers::StorageVersion()
   return aVersionStr;
 }
 
-#ifdef _MSC_VER
-#pragma warning(disable:4190) /* disable warning on C++ type returned by C function; should be OK for C++ usage */
-#endif
 PLUGIN(BinLDrivers)

src/BinTObjDrivers/BinTObjDrivers.cxx

@@ -30,7 +30,7 @@
 static Standard_GUID BinStorageDriver  ("f78ff4a2-a779-11d5-aab4-0050044b1af1");
 static Standard_GUID BinRetrievalDriver("f78ff4a3-a779-11d5-aab4-0050044b1af1");
 
-Handle(Standard_Transient) BinTObjDrivers::Factory(const Standard_GUID& aGUID)
+const Handle(Standard_Transient)& BinTObjDrivers::Factory(const Standard_GUID& aGUID)
 {
   if(aGUID == BinStorageDriver)
   {
@@ -69,7 +69,4 @@ void BinTObjDrivers::AddDrivers (const Handle(BinMDF_ADriverTable)& aDriverTable
   aDriverTable -> AddDriver (new BinTObjDrivers_IntSparseArrayDriver (aMsgDrv));
 }
 
-#ifdef _MSC_VER
-#pragma warning(disable:4190) /* disable warning on C++ type returned by C function; should be OK for C++ usage */
-#endif
 PLUGIN(BinTObjDrivers)

src/BinTObjDrivers/BinTObjDrivers.hxx

@@ -30,7 +30,7 @@ class BinTObjDrivers
  public:
   // ---------- PUBLIC METHODS ----------
 
-  Standard_EXPORT static Handle(Standard_Transient) Factory
+  Standard_EXPORT static const Handle(Standard_Transient)& Factory
                         (const Standard_GUID& aGUID);
   // Returns a driver corresponding to <aGUID>. Used for plugin.
 

src/BinXCAFDrivers/BinXCAFDrivers.cdl

@@ -25,6 +25,7 @@ is
     class DocumentRetrievalDriver;
 
     Factory (theGUID : GUID from Standard) returns Transient from Standard;
+    ---C++: return const &
 
     AttributeDrivers (MsgDrv : MessageDriver from CDM)
     	returns ADriverTable from BinMDF;

src/BinXCAFDrivers/BinXCAFDrivers.cxx

@@ -29,7 +29,7 @@ static Standard_GUID BinXCAFRetrievalDriver("a78ff497-a779-11d5-aab4-0050044b1af
 //function :
 //purpose  : 
 //=======================================================================
-Handle(Standard_Transient) BinXCAFDrivers::Factory(const Standard_GUID& theGUID) {
+const Handle(Standard_Transient)& BinXCAFDrivers::Factory(const Standard_GUID& theGUID) {
 
   if (theGUID == BinXCAFStorageDriver)
   {
@@ -53,7 +53,8 @@ Handle(Standard_Transient) BinXCAFDrivers::Factory(const Standard_GUID& theGUID)
 
 
   Standard_Failure::Raise ("XCAFBinDrivers : unknown GUID");
-  return NULL;
+  static Handle(Standard_Transient) aNullHandle;
+  return aNullHandle;
 }
 
 //=======================================================================
@@ -70,7 +71,4 @@ Handle(BinMDF_ADriverTable) BinXCAFDrivers::AttributeDrivers(const Handle(CDM_Me
   return aTable;
 }
 
-#ifdef _MSC_VER
-#pragma warning(disable:4190) /* disable warning on C++ type returned by C function; should be OK for C++ usage */
-#endif
 PLUGIN(BinXCAFDrivers)

src/FWOSDriver/FWOSDriver.cdl

@@ -26,4 +26,6 @@ is
     Factory(aGUID: GUID from Standard)
     returns Transient from Standard;
     ---Purpose: returns a DriverFactory.
+    ---C++: return const&
+
 end FWOSDriver;

src/FWOSDriver/FWOSDriver.cxx

@@ -19,13 +19,9 @@
 
 #include <Plugin_Macro.hxx>
 
-#ifdef _MSC_VER
-#pragma warning(disable:4190) /* disable warning on C++ type returned by C function; should be OK for C++ usage */
-#endif
-
 PLUGIN(FWOSDriver)
 
-Handle(Standard_Transient) FWOSDriver::Factory(const Standard_GUID& /*aGUID*/) {
+const Handle(Standard_Transient)& FWOSDriver::Factory(const Standard_GUID& /*aGUID*/) {
   static Handle(FWOSDriver_DriverFactory) f;
   if(f.IsNull()) f = new FWOSDriver_DriverFactory;
   return f;

src/Plugin/Plugin.cxx

@@ -94,8 +94,8 @@ Handle(Standard_Transient) Plugin::Load (const Standard_GUID& aGUID,
   else
     f = theMapOfFunctions(pid);
   
-  Handle(Standard_Transient) (*fp) (const Standard_GUID&) = NULL;
+  Standard_Transient* (*fp) (const Standard_GUID&) = NULL;
-  fp = (Handle(Standard_Transient) (*)(const Standard_GUID&)) f;
+  fp = (Standard_Transient* (*)(const Standard_GUID&)) f;
   Handle(Standard_Transient) theServiceFactory = (*fp) (aGUID);
   return theServiceFactory;
   

src/Plugin/Plugin_Macro.hxx

@@ -17,11 +17,11 @@
 #ifndef _Plugin_Macro_HeaderFile
 #define _Plugin_Macro_HeaderFile
 
+//! Macro implementing C-style interface function to get factory object from the dynamically loaded library
 #define PLUGIN(name) \
-extern "C" {Standard_EXPORT Handle(Standard_Transient) PLUGINFACTORY(const Standard_GUID&);} \
+extern "C" Standard_EXPORT Standard_Transient* PLUGINFACTORY(const Standard_GUID& aGUID) { \
-Handle(Standard_Transient) PLUGINFACTORY(const Standard_GUID& aGUID) { \
+   return const_cast<Standard_Transient*>(name::Factory(aGUID).get()); \
-   return name::Factory(aGUID);}\
+}
-\
 					
 
 #endif

src/XmlDrivers/XmlDrivers.cdl

@@ -32,6 +32,7 @@ is
     class DocumentRetrievalDriver;
 
     Factory (theGUID : GUID from Standard) returns Transient from Standard;
+    ---C++: return const &
 
     AttributeDrivers (theMsgDriver: MessageDriver from CDM)
         returns ADriverTable from XmlMDF;

src/XmlDrivers/XmlDrivers.cxx

@@ -40,7 +40,7 @@ static Standard_GUID XmlRetrievalDriver("03a56822-8269-11d5-aab2-0050044b1af1");
 //function : Factory
 //purpose  : PLUGIN FACTORY
 //=======================================================================
-Handle(Standard_Transient) XmlDrivers::Factory(const Standard_GUID& theGUID)
+const Handle(Standard_Transient)& XmlDrivers::Factory(const Standard_GUID& theGUID)
 {
   if (theGUID == XmlStorageDriver)
   {
@@ -64,7 +64,8 @@ Handle(Standard_Transient) XmlDrivers::Factory(const Standard_GUID& theGUID)
   }
  
   Standard_Failure::Raise ("XmlDrivers : unknown GUID");
-  return NULL;
+  static Handle(Standard_Transient) aNullHandle;
+  return aNullHandle;
 }
 
 //=======================================================================
@@ -87,9 +88,5 @@ Handle(XmlMDF_ADriverTable) XmlDrivers::AttributeDrivers
   return aTable;
 }
 
-#ifdef _MSC_VER
-#pragma warning(disable:4190) /* disable warning on C++ type returned by C function; should be OK for C++ usage */
-#endif
-
 // Declare entry point PLUGINFACTORY
 PLUGIN(XmlDrivers)

src/XmlLDrivers/XmlLDrivers.cdl

@@ -35,6 +35,7 @@ is
     imported SequenceOfNamespaceDef;
 
     Factory (theGUID : GUID from Standard) returns Transient from Standard;
+    ---C++: return const &
 
     CreationDate returns AsciiString from TCollection;
 

src/XmlLDrivers/XmlLDrivers.cxx

@@ -36,7 +36,7 @@ static Standard_GUID XmlLRetrievalDriver("13a56822-8269-11d5-aab2-0050044b1af1")
 //function : Factory
 //purpose  : PLUGIN FACTORY
 //=======================================================================
-Handle(Standard_Transient) XmlLDrivers::Factory(const Standard_GUID& theGUID)
+const Handle(Standard_Transient)& XmlLDrivers::Factory(const Standard_GUID& theGUID)
 {
   if (theGUID == XmlLStorageDriver)
   {
@@ -60,7 +60,8 @@ Handle(Standard_Transient) XmlLDrivers::Factory(const Standard_GUID& theGUID)
   }
  
   Standard_Failure::Raise ("XmlLDrivers : unknown GUID");
-  return NULL;
+  static Handle(Standard_Transient) aNullHandle;
+  return aNullHandle;
 }
 
 #define SLENGTH 80
@@ -121,9 +122,5 @@ TCollection_AsciiString XmlLDrivers::StorageVersion()
   return aVersionStr;
 }
 
-#ifdef _MSC_VER
-#pragma warning(disable:4190) /* disable warning on C++ type returned by C function; should be OK for C++ usage */
-#endif
-
 // Declare entry point PLUGINFACTORY
 PLUGIN(XmlLDrivers)

src/XmlTObjDrivers/XmlTObjDrivers.cxx

@@ -31,7 +31,7 @@
 static Standard_GUID XmlStorageDriver  ("f78ff4a0-a779-11d5-aab4-0050044b1af1");
 static Standard_GUID XmlRetrievalDriver("f78ff4a1-a779-11d5-aab4-0050044b1af1");
 
-Handle(Standard_Transient) XmlTObjDrivers::Factory(const Standard_GUID& aGUID)
+const Handle(Standard_Transient)& XmlTObjDrivers::Factory(const Standard_GUID& aGUID)
 {
   if(aGUID == XmlStorageDriver)
   {
@@ -71,8 +71,4 @@ void XmlTObjDrivers::AddDrivers (const Handle(XmlMDF_ADriverTable)& aDriverTable
   aDriverTable -> AddDriver (new XmlTObjDrivers_IntSparseArrayDriver(anMsgDrv));
 }
 
-#ifdef _MSC_VER
-#pragma warning(disable:4190) /* disable warning on C++ type returned by C function; should be OK for C++ usage */
-#endif
-
 PLUGIN(XmlTObjDrivers)

src/XmlTObjDrivers/XmlTObjDrivers.hxx

@@ -30,7 +30,7 @@ class XmlTObjDrivers
  public:
   // ---------- PUBLIC METHODS ----------
 
-  Standard_EXPORT static Handle(Standard_Transient) Factory
+  Standard_EXPORT static const Handle(Standard_Transient)& Factory
                         (const Standard_GUID& aGUID);
   // Returns a driver corresponding to <aGUID>. Used for plugin.
 

src/XmlXCAFDrivers/XmlXCAFDrivers.cdl

@@ -33,6 +33,7 @@ is
 
     Factory (aGUID: GUID from Standard)
     returns Transient from Standard;
+    ---C++: return const &
         ---Purpose: Depending from the  ID, returns a list of  storage
         --          or retrieval attribute drivers. Used for plugin.
         --          

src/XmlXCAFDrivers/XmlXCAFDrivers.cxx

@@ -25,7 +25,7 @@
 static Standard_GUID XSStorageDriver  ("f78ff496-a779-11d5-aab4-0050044b1af1");
 static Standard_GUID XSRetrievalDriver("f78ff497-a779-11d5-aab4-0050044b1af1");
 
-Handle(Standard_Transient) XmlXCAFDrivers::Factory(const Standard_GUID& aGUID)
+const Handle(Standard_Transient)& XmlXCAFDrivers::Factory(const Standard_GUID& aGUID)
 {
   if(aGUID == XSStorageDriver)  
   {
@@ -50,7 +50,4 @@ Handle(Standard_Transient) XmlXCAFDrivers::Factory(const Standard_GUID& aGUID)
   return XmlDrivers::Factory (aGUID);
 }
 
-#ifdef _MSC_VER
-#pragma warning(disable:4190) /* disable warning on C++ type returned by C function; should be OK for C++ usage */
-#endif
 PLUGIN(XmlXCAFDrivers)