BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  operator * overide in BDS2006          BorlandTalk.com Forum Index -> C++ Builder (Language C++) View previous topic :: View next topic   Author Message Mark Erickson Guest Posted: Sun Dec 10, 2006 5:00 am    Post subject: operator * overide in BDS2006 Hi, I'm trying to get Turbo Powers ShellShock components to work in BDS2006 C++Builder. The following line - from a header that is generated by BDS when installing the components - causes a compiler error: operator IDropTarget*(void) { return (IDropTarget*)&__IDropTarget; } The error message is: [C++ Error] StShlCtl.hpp(458): E2076 Overloadable operator expected In the help for the error it says that certain operators cannot be overloaded: the field-selection dot (.) dot-star (.*) double colon (: conditional expression (? In the help on Operator Overloading it says that the * (Pointer dereference) is legal overload. I *think* the statement above is an operator * overload? The same statement compiles without error in BCB6. Does anyone have any ideas? Here's a little more code that may help // C++ auto-generated class PASCALIMPLEMENTATION TStCustomShellTreeView : public Comctrls::TCustomTreeView { typedef Comctrls::TCustomTreeView inherited; protected: // Snip lots of that I don't *think* is relevant. private: void *__IDropTarget; /* IDropTarget [DragOver=StDragOver] */ public: operator IDropTarget*(void) { return (IDropTarget*)&__IDropTarget; }; // Delphi original code TStCustomShellTreeView = class(TCustomTreeView, IDropTarget) protected { private } // Snip lots of that I don't *think* is relevant. { IDropTarget declarations } function DragEnter(const dataObj : IDataObject; grfKeyState : Longint; pt : TPoint; var dwEffect : Longint): HResult; stdcall; function IDropTarget.DragOver = StDragOver; function StDragOver(grfKeyState : Longint; pt : TPoint; var dwEffect : Longint): HResult; stdcall; function DragLeave : HResult; stdcall; function Drop(const dataObj : IDataObject; grfKeyState : Longint; pt : TPoint; var dwEffect : Longint): HResult; stdcall; // Snip lots of that I don't *think* is relevant. end; The IDropTarget is an interface I believe which I've never used myself. Thanks Mark -- Back to top Mark Erickson Guest Posted: Sun Dec 10, 2006 9:10 am    Post subject: Re: operator * overide in BDS2006 Hi, Ok, so what's the problem then? Why's the compiler complaining about it? After all BDS generated it . It's the error message that's caused me to think it's an operator * overload. I'm not used to interfaces either so I'm getting nowhere fast with this. The thing that's really getting me is exactly the same code compiles fine in BCB6. Any ideas on how to fix it? I've been trying to get further with it all night but I'm at exactly the same point I was when I posted the original post! Confused! Thanks Mark -- Remy Lebeau (TeamB) wrote: Quote: "Mark Erickson" <mark (AT) merickson (DOT) demon.co.uk> wrote in message news:xn0eusbqtch8in000 (AT) forums (DOT) borland.com... I think the statement above is an operator * overload? It is not overiding the '*' operator at all. It is declaring a new user-defined operator that returns an IDropTarget pointer. That has nothing to do with the '*' operator. Gambit Back to top Remy Lebeau (TeamB) Guest Posted: Sun Dec 10, 2006 9:10 am    Post subject: Re: operator * overide in BDS2006 "Mark Erickson" <mark (AT) merickson (DOT) demon.co.uk> wrote in message news:xn0eusnih1aa00000 (AT) forums (DOT) borland.com... Quote: Hi, Ok, so what's the problem then? Why's the compiler complaining about it? After all BDS generated it Actually, the Pascal compiler generated it. That doesn't mean the C++ compiler has to always like what Pascal produces, which obviously is the case in this situation. What strikes me as odd is that the BCB 6 compiler introduced native support for VCL classes that use multiple inheritance to derive directly from interfaces. So I wonder why Borland hasn't updated the Pascal compiler yet to stop producing such outdated code altogether. In this case, it would make more sense to derive from IDropTarget instead of implmenting it as a data member, ie: class PASCALIMPLEMENTATION TStCustomShellTreeView : public Comctrls::TCustomTreeView, public IDropTarget { //... }; Quote: It's the error message that's caused me to think it's an operator * overload. Like I said, it has nothing to do with the * operator. Do not be confused by the fact that there is an * in the signature. The * is tied to the IDropTarget portion, declaring it as a pointer. The actual * operator is something completely different. Quote: The thing that's really getting me is exactly the same code compiles fine in BCB6. BDS uses a newer compiler. Obviously, Borland broke something along the way. Quote: Any ideas on how to fix it? Do you have all of the BDS patches installed? Gambit Back to top Remy Lebeau (TeamB) Guest Posted: Sun Dec 10, 2006 9:10 am    Post subject: Re: operator * overide in BDS2006 "Mark Erickson" <mark (AT) merickson (DOT) demon.co.uk> wrote in message news:xn0eusbqtch8in000 (AT) forums (DOT) borland.com... Quote: I *think* the statement above is an operator * overload? It is not overiding the '*' operator at all. It is declaring a new user-defined operator that returns an IDropTarget pointer. That has nothing to do with the '*' operator. Gambit Back to top Mark Erickson Guest Posted: Sun Dec 10, 2006 3:31 pm    Post subject: Re: operator * overide in BDS2006 Yes update 2 and hotfixes 1 and 3 to 6. I skipped 2 as I don't use CaliberRM. (not even sure what it's for to be honest). I suppose editing the header to inherit as you suggest would be daft considering the remark at the top of the file says not to do it. Are these headers re-created every time you build an app or just when you build the components? If the latter then is there any other reason not to edit the header directly? I've started to have a go at TP's Async Pro now and am getting equally weird errors. Why did they sell up! grr! I need some kip! Thanks Mark -- Remy Lebeau (TeamB) wrote: Quote: "Mark Erickson" <mark (AT) merickson (DOT) demon.co.uk> wrote in message news:xn0eusnih1aa00000 (AT) forums (DOT) borland.com... [snip] Do you have all of the BDS patches installed? Gambit Back to top Remy Lebeau (TeamB) Guest Posted: Mon Dec 11, 2006 4:43 am    Post subject: Re: operator * overide in BDS2006 "Mark Erickson" <mark (AT) merickson (DOT) demon.co.uk> wrote in message news:xn0eussb37slah001 (AT) forums (DOT) borland.com... Quote: Are these headers re-created every time you build an app or just when you build the components? Just when compiling the original Pascal code. Gambit Back to top Jean-Marie Babet Guest Posted: Wed Dec 13, 2006 1:05 am    Post subject: Re: operator * overide in BDS2006 Hello, Quote: What strikes me as odd is that the BCB 6 compiler introduced native support for VCL classes that use multiple inheritance to derive directly from interfaces. So I wonder why Borland hasn't updated the Pascal compiler yet to stop producing such outdated code altogether. In this case, it would make more sense to derive from IDropTarget instead of implmenting it as a data member, ie: Well, because there's a subtlety in the way C++ and Delphi work. In Delphi the methods of an interface you inherit from can be implemented by the base class you derive from. Given IBase, IDerived and TBase and TDerived: IBase {}; TBase : IBase {...}; // TBase implements IBase IDerived: IBase {...}; TDerived: TBase, IDerived {...}; In Delphi (and other languages where interfaces are native), TDerived has to implement just the methods unique to IDerived; the methods of IBase are inherited from TBase. However, that's not the case in C++: TDerived has to implement methods of IBase even though all it will probably do is to delegate to TBase::methodName. Interfaces are not any different from any other class in C++ and the rules of multiple inheritance dictate that a class implements all pure virtual methods of its base types, lest it be an abstract type. Anyone who has used TInterfacedObject in C++ finds out that QI/AddRef/Release cannot be left out as in Delphi. Or when the wizard generates SOAP or XMLDataBinding classes, you've noticed these macros (see XMLNodeImp.h) that basically delegate all methods of the base interface. At some point, we did switch DCC32 to emit interfaces as inherited but that made a lot of classes abstract from a C++ point of view. Emitting inline versions of all interface methods inherited from some base type in the hierarchy required major rework of .HPP emission. After chatting with the compiler person about this issue, we opted to keep the current model - although, if time allows, I plan to switch the interface conversion operator generated in .hpp files to go through TObject::GetInterface to ensure reference counting is done properly. Cheers, Bruneau. Back to top Remy Lebeau (TeamB) Guest Posted: Wed Dec 13, 2006 2:49 am    Post subject: Re: operator * overide in BDS2006 "Jean-Marie Babet" <bbabet (AT) borland (DOT) com> wrote in message news:457efc75$1 (AT) newsgroups (DOT) borland.com... Quote: In Delphi (and other languages where interfaces are native), TDerived has to implement just the methods unique to IDerived; the methods of IBase are inherited from TBase. However, that's not the case in C++ It is if you use virtual inheritance. Quote: TDerived has to implement methods of IBase even though all it will probably do is to delegate to TBase::methodName. In your example, if I use virtual inheritance for IBase, the following works: #include <stdio.h> class IBase { public: virtual void OutputMsg1() = 0; virtual void OutputMsg2() = 0; }; class TBase : virtual public IBase { public: TBase() { printf("%s\n", __FUNC__); } virtual ~TBase() { printf("%s\n", __FUNC__); } virtual void OutputMsg1() { printf("%s\n", __FUNC__); } }; class IDerived : virtual public IBase { public: virtual void OutputMsg3() = 0; }; class TDerived : public TBase, public IDerived { public: TDerived() : TBase() { printf("%s\n", __FUNC__); } virtual ~TDerived() { printf("%s\n", __FUNC__); } virtual void OutputMsg2() { printf("%s\n", __FUNC__); } virtual void OutputMsg3() { printf("%s\n", __FUNC__); } }; int main(int argc, char* argv[]) { TDerived d; IBase *pb = &d; pb->OutputMsg1(); pb->OutputMsg2(); d.OutputMsg3(); return 0; } I get the following output: TBase::TBase TDerived::TDerived TBase::OutputMsg1 <-- inherited TDerived::OutputMsg2 TDerived::OutputMsg3 Quote: Anyone who has used TInterfacedObject in C++ finds out that QI/AddRef/Release cannot be left out as in Delphi. That is because those specific methods in particular are mapped differently in C++ than in Delphi. But that does not apply to interfaces in general. The only reason to implement all of the interface methods in the derived class is when there are multiple vtable entries for duplicate interfaces (in this case, IBase is coming from both TBase and IDerived when not using virtual inheritance, so both have to be implemented separately). But virtual inheritance merges the duplicates together. Then you can implement the methods in a base class and inherit them in a derived class. Quote: At some point, we did switch DCC32 to emit interfaces as inherited but that made a lot of classes abstract from a C++ point of view. Borland was probably trying to use public inheritance for the interfaces. Try using virtual inheritance instance. Quote: Emitting inline versions of all interface methods inherited from some base type in the hierarchy required major rework of .HPP emission. After chatting with the compiler person about this issue, we opted to keep the .. current model - although, if time allows, I plan to switch the interface conversion Quote: operator generated in .hpp files to go through TObject::GetInterface to ensure reference counting is done properly. That will have subtle effects on existing code that relies on the reference count not being incremented by the operator. Gambit Back to top Jean-Marie Babet Guest Posted: Wed Dec 13, 2006 7:17 am    Post subject: Re: operator * overide in BDS2006 Quote: In Delphi (and other languages where interfaces are native), TDerived has to implement just the methods unique to IDerived; the methods of IBase are inherited from TBase. However, that's not the case in C++ It is if you use virtual inheritance. Yes, virtual inheritance is good C++ solution to the generic interface problem but it cannot be used to expose classes with interfaces that are implemented in Delphi to the C++ side: the binary layout of a class with a virtual base is different from when the base is not virtual. Virtual inheritance implies a 'virtual base class table' pointer within the vtable; virtual inheritance also triggers C++ to pass a hidden parameter at construction (to suppress base class construction). By using 'virtual' inheritance you'll come closer to the semantics of Delphi interface but it will crash at runtime because of the layout and protocol of C++ virtual inheritance is incompatible with what the Delphi side implements and expects when called. Quote: That will have subtle effects on existing code that relies on the reference count not being incremented by the operator. Well, there are bugs filed currently against these operators because they don't properly handle ref. counting. I'll see if I can emit both the old and new style operators conditionalized via a macro. Cheers, Bruneau. Back to top Guest Posted: Fri Jan 12, 2007 5:33 pm    Post subject: Re: operator * overide in BDS2006 Mark Erickson schrieb: Quote: Hi, I'm trying to get Turbo Powers ShellShock components to work in BDS2006 C++Builder. The following line - from a header that is generated by BDS when installing the components - causes a compiler error: operator IDropTarget*(void) { return (IDropTarget*)&__IDropTarget; } The error message is: [C++ Error] StShlCtl.hpp(458): E2076 Overloadable operator expected In the help for the error it says that certain operators cannot be overloaded: the field-selection dot (.) dot-star (.*) double colon (: conditional expression (?:) In the help on Operator Overloading it says that the * (Pointer dereference) is legal overload. I *think* the statement above is an operator * overload? The same statement compiles without error in BCB6. Does anyone have any ideas? Here's a little more code that may help // C++ auto-generated class PASCALIMPLEMENTATION TStCustomShellTreeView : public Comctrls::TCustomTreeView { typedef Comctrls::TCustomTreeView inherited; protected: // Snip lots of that I don't *think* is relevant. private: void *__IDropTarget; /* IDropTarget [DragOver=StDragOver] */ public: operator IDropTarget*(void) { return (IDropTarget*)&__IDropTarget; }; // Delphi original code TStCustomShellTreeView = class(TCustomTreeView, IDropTarget) protected { private } // Snip lots of that I don't *think* is relevant. { IDropTarget declarations } function DragEnter(const dataObj : IDataObject; grfKeyState : Longint; pt : TPoint; var dwEffect : Longint): HResult; stdcall; function IDropTarget.DragOver = StDragOver; function StDragOver(grfKeyState : Longint; pt : TPoint; var dwEffect : Longint): HResult; stdcall; function DragLeave : HResult; stdcall; function Drop(const dataObj : IDataObject; grfKeyState : Longint; pt : TPoint; var dwEffect : Longint): HResult; stdcall; // Snip lots of that I don't *think* is relevant. end; The IDropTarget is an interface I believe which I've never used myself. Thanks Mark --Hello Mark, I have the same problem. ShellShock runs under C++Builder4, but not in C++Builder 5. Did You get any information about the problem? Thanks Norbert Back to top Thomas Maeder [TeamB] Guest Posted: Fri Jan 12, 2007 10:31 pm    Post subject: Re: operator * overide in BDS2006 Please direct your browser at http://info.borland.com/newsgroups/ and read the newsgroup guidelines. One of them asks us not to quote entire posts we are following up to; instead, please trim the quotes to the parts relevant for your reply. Thanks! Back to top Vaclav Cechura Guest Posted: Fri Jan 19, 2007 7:27 pm    Post subject: Re: operator * overide in BDS2006 Alan Bellingham <alan (AT) lspace (DOT) org> wrote: Quote: You've gone off down the wrong path, due to a confusion over C++ syntax. The syntax is wrong. The word "operator" should immediately precede the name of the operator. It does. This is a standard user-defined conversion function (see 12.3, especially 12.3.2), and as such, the name of the method is 'operator IDropTarget*()', and the type of the return value is therefore 'IDropTarget*' (*not* included in the declaration because it would be redundant). What to say now. You're right, I must have been temporarily blind. Quote: expression "return (IDropTarget*)&__IDropTarget;" is wrong as it tries to return the addres of a class member... This return is correct for the code written. Suddenly, I got it: it converts TStCustomShellTreeView to IDropTarget pointer... I will think twice before posting in the future. I promise. Back to top Vaclav Cechura Guest Posted: Fri Jan 19, 2007 7:29 pm    Post subject: Re: operator * overide in BDS2006 "Vaclav Cechura" <no (AT) spam (DOT) please> wrote: Quote: Suddenly, I got it: it converts TStCustomShellTreeView to IDropTarget pointer... I will think twice before posting in the future. I promise. May the subject of the post: "operator * overide in BDS2006" be my excuse. Back to top Alan Bellingham Guest Posted: Fri Jan 19, 2007 7:56 pm    Post subject: Re: operator * overide in BDS2006 "Vaclav Cechura" <n (AT) s (DOT) p> wrote: Quote: May the subject of the post: "operator * overide in BDS2006" be my excuse. Ah, I will have to admit that I rarely notice subjects this far down a thread. Alan Bellingham -- 10th Anniversary ACCU Conference: 11-14 April 2007 - Oxford, UK (Booking now open: see http://accu.org/index.php/conferences for details) Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         BorlandTalk.com Forum Index -> C++ Builder (Language C++) All times are GMT Page 1 of 1   Jump to: Select a forum C++ Builder Newsgroups----------------C++ BuilderC++ Builder (ActiveX)C++ Builder (Announcements)C++ Builder (Command Line Tools)C++ Builder DatabasesC++ Builder Databases (ADO)C++ Builder Databases (Desktop)C++ Builder Databases (InterBase Express)C++ Builder Databases (Multi-Tier)C++ Builder Databases (SQL Servers)C++ Builder (Graphics)C++ Builder (IDE)C++ Builder (Internet)C++ Builder (Internet Socket)C++ Builder (Internet Web)C++ Builder (Jobs)C++ Builder (Language)C++ Builder (Language C++)C++ Builder (Compatibility with MFC)C++ Builder (Native API)C++ Builder (Non-Technical)C++ Builder (Students)C++ Builder (Third Party Tools)C++ Builder (Upgrade)C++ Builder (VCL)C++ Builder (VCL Components Usage)C++ Builder (VCL Components Development)C++ Builder (VCL Usage)C++ Builder (WinAPI)C++ Builder Installation Delphi Newsgroups----------------Delphi (General)Delphi ActiveX Controls UsageDelphi ActiveX Controls DevelopmentDelphi As400Delphi DatabasesDelphi Databases (ADO)Delphi Databases (dbExpress)Delphi Databases (Desktop)Delphi Databases (InterBase Express)Delphi Databases (Multi-Tier)Delphi Databases (SQL Servers)Delphi DeploymentDelphi GraphicsDelphi IDEDelphi InternationalizationDelphi InternetDelphi Internet Isapi-WebBrokerDelphi Internet WebSnapDelphi Internet WinsockDelphi JobsDelphi Language BASMDelphi Language ObjectPascalDelphi Model Driven Architecture (General)Delphi Model Driven Architecture (Third Party)Delphi MultimediaDelphi Native APIDelphi Non-TechnicalDelphi ObjectPascalDelphi OLE AutomationDelphi OO designDelphi OpenToolsAPIDelphi Reporting-ChartingDelphi RTLDelphi StudentsDelphi TeamSourceDelphi Thirdparty ToolsDelphi Thirdparty Tools (General)Delphi Thirdparty Tools (IntraWeb)Delphi Thirdparty Tools (RaveReports)Delphi UpgradeDelphi VCLDelphi VCL ComponentsDelphi VCL Components UsingDelphi VCL Components WritingDelphi WebServices SOAPDelphi WinAPIDelphi XMLDelphi Installationcomp.lang.pascal.delphi.components.misccomp.lang.pascal.delphi.components.usagecomp.lang.pascal.delphi.components.writingcomp.lang.pascal.delphi.databasescomp.lang.pascal.delphi.misccomp.sources.delphi JBuilder Newsgroups----------------JBuilderJBuilder AnnouncementsJBuilder Applet IssuesJBuilder As400JBuilder CompilerJBuilder CORBA/RMIJBuilder DatabasesJBuilder DB SwingJBuilder DebuggerJBuilder DeploymentJBuilder DocumentationJBuilder EnterpriseJBuilder HandheldJBuilder IDEJBuilder JavaJBuilder JavaAPIJBuilder Java LanguageJBuilder Java SwingJBuilder Java BeansJBuilder Java Beans UsageJBuilder Java Beans DevelopmentJBuilder JBCLJBuilder JDataStoreJBuilder JobsJBuilder LinuxJBuilder MacintoshJBuilder & MobileSetJBuilder MultiLingual AppsJBuilder Non-TechnicalJBuilder OpenToolsJBuilder Servlets (JSP)JBuilder StudentsJBuilder Team DevelopmentJBuilder Thirdparty ToolsJBuilder UpgradeJBuilder Installation InterBase Newsgroups----------------InterBaseInterBase Bug DiscussionInterBase GeneralInterBase IBConsoleInterBase OpenSourceInterBase ReplicationInterBase SQLInterBase ThirdpartyInterBase Installation Miscellaneous Borland Newsgroups----------------AppCenterAppServerEnteraVisiBroker  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.