digitalmars.D - Could new keyword help function hijacking and prevented aliasing
- Matthew Ong (68/68) May 26 2011 Hi All,
- Jacob Carlborg (5/70) May 26 2011 How big is this problem in practice, how often do need overload (NOT
- Matthew Ong (36/38) May 27 2011 On 5/27/2011 2:54 PM, Jacob Carlborg wrote:
- Steven Schveighoffer (23/91) May 27 2011 I don't think it will work that well. Consider how function hijacking
- Matthew Ong (37/150) May 27 2011 Hi Steve,
- Steven Schveighoffer (33/88) May 27 2011 OK, but I don't see the point then. Can't you get the functionality you...
- Matthew Ong (34/67) May 27 2011 Explain please. You lost me. If I am not wrong, final is used to prevent...
- Steven Schveighoffer (78/131) May 27 2011 No, I mean the author of Parent may not know of the existance of child, ...
- Jacob Carlborg (8/88) May 27 2011 DWT is manually ported from Java. A automatic port was tried and it
- Steven Schveighoffer (6/15) May 27 2011 Why is this comment in the file given?
- Jacob Carlborg (9/27) May 27 2011 I have no idea. The major part of DWT is manually ported, as far as I
- Jacob Carlborg (9/17) May 27 2011 DWT is a direct port of the Java library SWT and it tries to stay as
- Matthew Ong (43/56) May 27 2011 feature all the time.
- Jacob Carlborg (20/74) May 27 2011 Of course, from "scratch" can be interpreted in different ways. I use
- Jonathan M Davis (23/42) May 27 2011 Whether reimplementing from scratch or doing a more direct port makes mo...
- Andrei Alexandrescu (5/24) May 27 2011 I can't believe this has fallen off the radar.
- Steven Schveighoffer (22/49) May 27 2011 You have three options:
- Andrei Alexandrescu (14/65) May 27 2011 4. Statically disallow overloaded overridable methods when the
- Steven Schveighoffer (10/20) May 27 2011 I just tried it out. If one implements an overload that is not
- Andrei Alexandrescu (28/50) May 27 2011 Matthew's example fixed is this:
- Dejan Lekic (3/11) May 27 2011 Andrei, there was a discussion about it here on this NG too. I too think...
- Andrei Alexandrescu (10/23) May 27 2011 Just talked to Walter - he did implement something similar that
- Steven Schveighoffer (5/28) May 27 2011 I think maybe this is a good thing for a bug report :)
- Matthew Ong (14/17) May 27 2011 At least not using foo and bar, I am able to understand some of that is
Hi All, Currently within D, to make use of a parent class method you have to do: class Parent{ void methodA(int x){...} } class Child : Parent{ // I understand that it has to do with preventing accidental hijacking alias Parent.methodA methodA; void methodA(long x){...} } void main(string[]){ Child obj=new Child(); obj.methodA(1); // expecting to call Child.methodA but calling Parent.methodA; } and also from this URL. http://www.digitalmars.com/d/2.0/function.html If, through implicit conversions to the base class, those other functions do get called, an std.HiddenFuncError exception is raised. ----------------------------------------------------------------------- That is to prevent silently changing the program's behavior. b.foo(1) could happily be a call to B.foo(long) today. Imagine one of the base classes changed and now there is A.foo(int). Then our b.foo(1) would silently start calling that new function. That would cause a tough bug. Ali // a Better explanation than the document for the current syntax. ------------------------------------------------------------------------ However, there is a foreseeable problem coming when a program grow. How about when the inheritance tree becomes deeper than 4? And more and more overloaded functions are in different classes? That does not meant the calling class/method has a sense if it is calling from Child or Parent. Because, those 2 classes source code might not be available for coder. How does the coder knows about that? Does it mean we have to do more alias at child class at the bottom? Harder to issues solve in the child class at the bottom of the tree. It seem to me that the entire purpose is just to protect auto promotion matching method signature in the base to avoid function hijacking. How about doing this another way? Just a suggestion if you like to avoid parent function from accidental hijack but still needs to be public. New keywords are needed: nooverload and inheritall class Parent{ nooverload void methodA(int x){...} // entirely deny this name to be overloaded. } // this would have avoided the aliasing all over child class and still allow child class to see any >public< method of the parent. class Child: inheritall Parent{ // auto inheriting all parent methods except private ones. As per usual also for package/protected... void methodA(long x){...} // compilation error. because nooverload is used at Parent void methodA(string x){...} // compilation error. because nooverload ... etc void methodB(){ methodA(123); // No error now, and the entire hijacking is avoided. } } void main(string[] args){ Child obj=new Child(); obj.methodB(); // no problem obj.methodA(123); // no accidental hijacking...Always use parent class. } Reverse sequence as Ali has shown can also be avoided because if someone does that by adding 'new' methodA in parent where child already has methodA overloaded already without knowledge. Show up in compilation exception for such cases with -w flag on. How about that? Possible solution? -- Matthew Ong email: ongbp yahoo.com
May 26 2011
On 2011-05-27 08:34, Matthew Ong wrote:Hi All, Currently within D, to make use of a parent class method you have to do: class Parent{ void methodA(int x){...} } class Child : Parent{ // I understand that it has to do with preventing accidental hijacking alias Parent.methodA methodA; void methodA(long x){...} } void main(string[]){ Child obj=new Child(); obj.methodA(1); // expecting to call Child.methodA but calling Parent.methodA; } and also from this URL. http://www.digitalmars.com/d/2.0/function.html If, through implicit conversions to the base class, those other functions do get called, an std.HiddenFuncError exception is raised. ----------------------------------------------------------------------- That is to prevent silently changing the program's behavior. b.foo(1) could happily be a call to B.foo(long) today. Imagine one of the base classes changed and now there is A.foo(int). Then our b.foo(1) would silently start calling that new function. That would cause a tough bug. Ali // a Better explanation than the document for the current syntax. ------------------------------------------------------------------------ However, there is a foreseeable problem coming when a program grow. How about when the inheritance tree becomes deeper than 4? And more and more overloaded functions are in different classes? That does not meant the calling class/method has a sense if it is calling from Child or Parent. Because, those 2 classes source code might not be available for coder. How does the coder knows about that? Does it mean we have to do more alias at child class at the bottom? Harder to issues solve in the child class at the bottom of the tree. It seem to me that the entire purpose is just to protect auto promotion matching method signature in the base to avoid function hijacking. How about doing this another way? Just a suggestion if you like to avoid parent function from accidental hijack but still needs to be public. New keywords are needed: nooverload and inheritall class Parent{ nooverload void methodA(int x){...} // entirely deny this name to be overloaded. } // this would have avoided the aliasing all over child class and still allow child class to see any >public< method of the parent. class Child: inheritall Parent{ // auto inheriting all parent methods except private ones. As per usual also for package/protected... void methodA(long x){...} // compilation error. because nooverload is used at Parent void methodA(string x){...} // compilation error. because nooverload ... etc void methodB(){ methodA(123); // No error now, and the entire hijacking is avoided. } } void main(string[] args){ Child obj=new Child(); obj.methodB(); // no problem obj.methodA(123); // no accidental hijacking...Always use parent class. } Reverse sequence as Ali has shown can also be avoided because if someone does that by adding 'new' methodA in parent where child already has methodA overloaded already without knowledge. Show up in compilation exception for such cases with -w flag on. How about that? Possible solution?How big is this problem in practice, how often do need overload (NOT override) a method in the subclass that exists in the super class? -- /Jacob Carlborg
May 26 2011
On 5/27/2011 2:54 PM, Jacob Carlborg wrote: Hi Jacob, See some of the source code shown here. I did not code them, but can sense the pattern is not too productive brain cycle invested. Cycle= trying to locate up the tree of inherited object. BTW, default D documentation is Not too friendly for inheritance tree navigation. Unlike in java. Not to promote deep inheritance tree. I actually like to flatten them using interface template and adaptor pattern. Memory usage and object tree creation clock cycle is smaller. With overloading and also runtime dynamic method invocation, it makes http://hg.dsource.org/projects/dwt2/file/d00e8db0a568/base/src/java/io/ByteArrayInputStream.dHow big is this problem in practice, how often do need overload (NOT override) a method in the subclass that exists in the super class?Actually, the argument of reason of using alias is to prevent hijacking as mentioned by others in the URL. Overloading is actually more frequent than overriding base on data modeling because of polymorphic nature of the OOP concept. I can see no point of doing various naming for a single calculation. Yes, it can be done with various different name, Google Go does NOT have overloading. ie: // Please note, the internal logics of such methods may or may be the same, because of dependent of business logic. Hence, functional template might not be needed. class RiskAccessment{ double calculate(NormalAccount acc, double intrest){...} double calculate(CurrentAccount acc, double intrest){...} double calculate(FixedDeposit acc, double intrest){...} double calculate(FixedIncome acc, double intrest){...} double calculate(Equity acc, double intrest){...} double calculate(FixedAssets acc, double intrest){...} } and many other such patterns. Overriding is for entirely different thing. Hence, I suggested the 2 new keywords solutions. -- Matthew Ong email: ongbp yahoo.com
May 27 2011
On Fri, 27 May 2011 02:34:34 -0400, Matthew Ong <ongbp yahoo.com> wrote:Hi All, Currently within D, to make use of a parent class method you have to do: class Parent{ void methodA(int x){...} } class Child : Parent{ // I understand that it has to do with preventing accidental hijacking alias Parent.methodA methodA; void methodA(long x){...} } void main(string[]){ Child obj=new Child(); obj.methodA(1); // expecting to call Child.methodA but calling Parent.methodA; } and also from this URL. http://www.digitalmars.com/d/2.0/function.html If, through implicit conversions to the base class, those other functions do get called, an std.HiddenFuncError exception is raised. ----------------------------------------------------------------------- That is to prevent silently changing the program's behavior. b.foo(1) could happily be a call to B.foo(long) today. Imagine one of the base classes changed and now there is A.foo(int). Then our b.foo(1) would silently start calling that new function. That would cause a tough bug. Ali // a Better explanation than the document for the current syntax. ------------------------------------------------------------------------ However, there is a foreseeable problem coming when a program grow. How about when the inheritance tree becomes deeper than 4? And more and more overloaded functions are in different classes? That does not meant the calling class/method has a sense if it is calling from Child or Parent. Because, those 2 classes source code might not be available for coder. How does the coder knows about that? Does it mean we have to do more alias at child class at the bottom? Harder to issues solve in the child class at the bottom of the tree. It seem to me that the entire purpose is just to protect auto promotion matching method signature in the base to avoid function hijacking. How about doing this another way? Just a suggestion if you like to avoid parent function from accidental hijack but still needs to be public. New keywords are needed: nooverload and inheritall class Parent{ nooverload void methodA(int x){...} // entirely deny this name to be overloaded. } // this would have avoided the aliasing all over child class and still allow child class to see any >public< method of the parent. class Child: inheritall Parent{ // auto inheriting all parent methods except private ones. As per usual also for package/protected... void methodA(long x){...} // compilation error. because nooverload is used at Parent void methodA(string x){...} // compilation error. because nooverload ... etc void methodB(){ methodA(123); // No error now, and the entire hijacking is avoided. } } void main(string[] args){ Child obj=new Child(); obj.methodB(); // no problem obj.methodA(123); // no accidental hijacking...Always use parent class. } Reverse sequence as Ali has shown can also be avoided because if someone does that by adding 'new' methodA in parent where child already has methodA overloaded already without knowledge. Show up in compilation exception for such cases with -w flag on. How about that? Possible solution?I don't think it will work that well. Consider how function hijacking happens. For instance, the parent class author may not even know his code is being overridden, and he may simply not mark his base function as nooverload. Let's say that the child is inheriting all the parent's methods because he wanted a different method (an already existing one), and the author of the parent class adds methodA (without the nooverload attribute) after the child is already written. That's an unintentional hijack. The problem is the child is relying on the parent to cooperate in preventing hijacking, instead of controlling whether its functions can be hijacked or not. In the current solution, the system warns me or throws an error if a function becomes hijacked. If this happens, I can examine the code and add an alias if needed. It happens rarely for me. Do you have cases where you have to "alias all over the place"? Maybe you are not doing something correctly, you shouldn't need this feature all the time. Note that drastic proposals like this are very unlikely to be accepted. Especially for something that has been in use and not really complained about for years. You need to present a very compelling argument, including real examples is helpful. Also, if there's any way to get rid of adding a keyword, you have a much better shot of success. No keywords have been added to the language for a long time. -Steve
May 27 2011
On 5/27/2011 7:08 PM, Steven Schveighoffer wrote:On Fri, 27 May 2011 02:34:34 -0400, Matthew Ong <ongbp yahoo.com> wrote:Hi Steve, Please note that the proposal is not to remove the existing function hijacking detection but as an alternative to the existing aliasing.Hi All, Currently within D, to make use of a parent class method you have to do: class Parent{ void methodA(int x){...} } class Child : Parent{ // I understand that it has to do with preventing accidental hijacking alias Parent.methodA methodA; void methodA(long x){...} } void main(string[]){ Child obj=new Child(); obj.methodA(1); // expecting to call Child.methodA but calling Parent.methodA; } and also from this URL. http://www.digitalmars.com/d/2.0/function.html If, through implicit conversions to the base class, those other functions do get called, an std.HiddenFuncError exception is raised. ----------------------------------------------------------------------- That is to prevent silently changing the program's behavior. b.foo(1) could happily be a call to B.foo(long) today. Imagine one of the base classes changed and now there is A.foo(int). Then our b.foo(1) would silently start calling that new function. That would cause a tough bug. Ali // a Better explanation than the document for the current syntax. ------------------------------------------------------------------------ However, there is a foreseeable problem coming when a program grow. How about when the inheritance tree becomes deeper than 4? And more and more overloaded functions are in different classes? That does not meant the calling class/method has a sense if it is calling from Child or Parent. Because, those 2 classes source code might not be available for coder. How does the coder knows about that? Does it mean we have to do more alias at child class at the bottom? Harder to issues solve in the child class at the bottom of the tree. It seem to me that the entire purpose is just to protect auto promotion matching method signature in the base to avoid function hijacking. How about doing this another way? Just a suggestion if you like to avoid parent function from accidental hijack but still needs to be public. New keywords are needed: nooverload and inheritall class Parent{ nooverload void methodA(int x){...} // entirely deny this name to be overloaded. } // this would have avoided the aliasing all over child class and still allow child class to see any >public< method of the parent. class Child: inheritall Parent{ // auto inheriting all parent methods except private ones. As per usual also for package/protected... void methodA(long x){...} // compilation error. because nooverload is used at Parent void methodA(string x){...} // compilation error. because nooverload ... etc void methodB(){ methodA(123); // No error now, and the entire hijacking is avoided. } } void main(string[] args){ Child obj=new Child(); obj.methodB(); // no problem obj.methodA(123); // no accidental hijacking...Always use parent class. } Reverse sequence as Ali has shown can also be avoided because if someone does that by adding 'new' methodA in parent where child already has methodA overloaded already without knowledge. Show up in compilation exception for such cases with -w flag on. How about that? Possible solution?I don't think it will work that well. Consider how function hijacking happens. For instance, the parent class author may not even know his code is being overridden, and he may simply not mark his base function as nooverload. Let's say that the child is inheriting all the parent's methods because he wanted a different method (an already existing one), and the author of the parent class adds methodA (without the nooverload attribute) after the child is already written. That's an unintentional hijack. The problem is the child is relying on the parent to cooperate in preventing hijacking, instead of controlling whether its functions can be hijacked or not. In the current solution, the system warns me or throws an error if a function becomes hijacked. If this happens, I can examine the code and add an alias if needed. It happens rarely for me. Do you have cases where you have to "alias all over the place"? Maybe you are not doing something correctly, you shouldn't need this feature all the time. Note that drastic proposals like this are very unlikely to be accepted. Especially for something that has been in use and not really complained about for years. You need to present a very compelling argument, including real examples is helpful. Also, if there's any way to get rid of adding a keyword, you have a much better shot of success. No keywords have been added to the language for a long time. -SteveConsider how function hijacking happens. For instance, the parent class author may not even know his code is being overridden, and he may simply not mark his base function as nooverload.From OO stand point, overloading is NOT overriding. Please do not mix up the two. Fundamentally different. http://users.soe.ucsc.edu/~charlie/book/notes/chap7/sld012.htmparent class adds methodA (without the nooverload attribute)If that happens, still flag as function hijacking using existing detection. Please note that I did NOT ask for the removal of using aliasing on existing source code for inherited overloaded function. BTW, default D documentation is Not too friendly for inheritance tree navigation. Unlike in java. However, new keywords can be added to the compiler. So that future code can be written without spending many brain cycle on looking up such alias. Let the compiler do the hard work of AST searching rather than a manual process. We have quad core now a days, even in asia. Have you systemetic go over the proposal I posted and gave your counter arguement? How about the fact that currently there are such aliasing all over the child class. From what I understand D inheritance is Not automatic, if I am wrong do let me know. Do you have cases where you have to "alias all over the place"? news://news.digitalmars.com:119/iri4am$2dl3$1 digitalmars.com http://hg.dsource.org/projects/dwt2/file/d00e8db0a568/base/src/java/io/By eArrayInputStream.dMaybe you are not doing something correctly, you shouldn't need thisfeature all the time. Not me, others that has coded the dwt and I suspect other code ininstead of controlling whether its functions can be hijacked or not.Why NOT? If a problem can be prevented easily as an modifier keyword. Hijacking is not a feature, it is a problem correct???No keywords have been added to the language for a long time.Perhaps there is no-one that seen different from angle? Most source code development process needs to look at at least 7 different dimensions. Inheritance down the tree, up the tree, interfaces and its implementation, changes over time, testing, cpu cycle, memory creation cycle. That is just single threaded model. That is a tasks burdensome enough for most person. -- Matthew Ong email: ongbp yahoo.com
May 27 2011
On Fri, 27 May 2011 07:42:17 -0400, Matthew Ong <ongbp yahoo.com> wrote:On 5/27/2011 7:08 PM, Steven Schveighoffer wrote:OK, but I don't see the point then. Can't you get the functionality you desire already?I don't think it will work that well. Consider how function hijacking happens. For instance, the parent class author may not even know his code is being overridden, and he may simply not mark his base function as nooverload. Let's say that the child is inheriting all the parent's methods because he wanted a different method (an already existing one), and the author of the parent class adds methodA (without the nooverload attribute) after the child is already written. That's an unintentional hijack. The problem is the child is relying on the parent to cooperate in preventing hijacking, instead of controlling whether its functions can be hijacked or not. In the current solution, the system warns me or throws an error if a function becomes hijacked. If this happens, I can examine the code and add an alias if needed. It happens rarely for me. Do you have cases where you have to "alias all over the place"? Maybe you are not doing something correctly, you shouldn't need this feature all the time. Note that drastic proposals like this are very unlikely to be accepted. Especially for something that has been in use and not really complained about for years. You need to present a very compelling argument, including real examples is helpful. Also, if there's any way to get rid of adding a keyword, you have a much better shot of success. No keywords have been added to the language for a long time. -SteveHi Steve, Please note that the proposal is not to remove the existing function hijacking detection but as an alternative to the existing aliasing.>Consider how function hijacking happens. For instance, the parent >class author may not even know his code is being overridden, and he >may simply not mark his base function as nooverload. From OO stand point, overloading is NOT overriding. Please do not mix up the two. Fundamentally different.Sorry, I used the wrong term, I meant derived or extended.>parent class adds methodA (without the nooverload attribute) If that happens, still flag as function hijacking using existing detection. Please note that I did NOT ask for the removal of using aliasing on existing source code for inherited overloaded function.Yes, but you marked the child as inheritall, doesn't this implicitly pull in the parent functions as if an alias were entered? Eseentially, the inheritall keyword disables all inheritance hijacking checks. Or did I misunderstand this?BTW, default D documentation is Not too friendly for inheritance tree navigation. Unlike in java.This is definitely a problem, ddoc is very underdeveloped. There are some alternative doc generators out there, I think Tango uses dil, which is a d-based compiler that does not yet generate code, but will generate docs (and much better docs at that). But let's not add features to cover up another problem that should be fixed in its own right.However, new keywords can be added to the compiler. So that future code can be written without spending many brain cycle on looking up such alias. Let the compiler do the hard work of AST searching rather than a manual process. We have quad core now a days, even in asia.The issue is not whether the compiler can search the AST, the issue is whether it makes functions easier to be hijacked.Have you systemetic go over the proposal I posted and gave your counter arguement? How about the fact that currently there are such aliasing all over the child class. From what I understand D inheritance is Not automatic, if I am wrong do let me know. Do you have cases where you have to "alias all over the place"? news://news.digitalmars.com:119/iri4am$2dl3$1 digitalmars.com http://hg.dsource.org/projects/dwt2/file/d00e8db0a568/base/src/java/io/ByteArrayInputStream.dOnly read is required to be aliased, due to the base function read(byte[] b). All the others are unnecessary. I may see why you see so many cases -- dwt was likely ran through a java to d converter, and such converters often add unnecessary lines, because it is easier to do that than to examine each individual case. This further weakens your proposal in two ways: 1. The compiler does not need to foster to one small specific porting tool which does not generate optimal code. 2. Your argument is based on having to manually search for functions to alias, yet this tool clearly did all the aliasing for you. Essentially, your proposal makes it easier to make D inheritance rules more like Java ones, and I don't think we need such a feature. It's already possible to do this via alias, and D's stance is specifically *against* Java-style inheritance.>instead of controlling whether its functions can be hijacked or not. Why NOT? If a problem can be prevented easily as an modifier keyword. Hijacking is not a feature, it is a problem correct???Anti-hijacking is a feature. Your proposal removes that when you use inheritall. -Steve
May 27 2011
On 5/27/2011 8:08 PM, Steven Schveighoffer wrote:Sorry, I used the wrong term, I meant derived or extended.Explain please. You lost me. If I am not wrong, final is used to prevent overriding. Is that what you are talking about?Yes, but you marked the child as inheritall, doesn't this implicitly pull in the parent functions as if an alias were entered? Eseentially, the inheritall keyword disables all inheritance hijacking checks. Or did I misunderstand this?inheritall only to that single class and not from child to child and so on. Because of the nooverload keyword. There is a better way to further enhance that anti-hijacking proctection. It is a manually controlled approaches by developer of the child class.This is definitely a problem, ddoc is very underdeveloped. There are some alternative doc generators out there, I think Tango uses dil, which is a d-based compiler that does not yet generate code, but will generate docs (and much better docs at that).Do both improvement. Please also support my post on: Example within documentations of D seriously need some improvement. Please place in the issue you see there compare to others languages already has.But let's not add features to cover up another problem that should be fixed in its own right.NO. It is not a feature to cover up that problem. It prevents the same issue with less manual work.The issue is not whether the compiler can search the AST, the issue is whether it makes functions easier to be hijacked.I believe the 2 feature does not make it easier to be hijacked. See above. Compiler can search the AST is key. Most source code development process needs to look at at least 7 different dimensions. Inheritance down the tree, up the tree, interfaces and its implementation, changes over time, testing, cpu cycle, memory creation cycle. That is just single threaded model.Only read is required to be aliased, due to the base function read(byte[] b). All the others are unnecessary. I may see why you see so many cases -- dwt was likely ran through a java to d converter, and such converters often add unnecessary lines, because it is easier to do that than to examine each individual case.It does not seem to be because the dwt library has many different authors. If yes, please give some idea on how to do that via a converter.This further weakens your proposal in two ways: 1. The compiler does not need to foster to one small specific porting tool which does not generate optimal code.I am referring to manually written and naturally grown business library. I do agrees that a language is not design based on how a generated tool create its code.2. Your argument is based on having to manually search for functions to alias, yet this tool clearly did all the aliasing for you.Yes. If and ONLY if you are doing auto java to D conversion. How about when the hand coded library grow?Essentially, your proposal makes it easier to make D inheritance rules more like Java ones, and I don't think we need such a feature. It's already possible to do this via alias, and D's stance is specifically *against* Java-style inheritance.Yes. I can see some of the problem that might have from reading the unintentional function hijacking. That is why I am proposing the new keyword to make thing easier for people to inherit AND ALSO prevent highjacking.-- Matthew Ong email: ongbp yahoo.comAnti-hijacking is a feature. Your proposal removes that when you use inheritall. -Steveinstead of controlling whether its functions can be hijacked or not.Why NOT? If a problem can be prevented easily as an modifier keyword. Hijacking is not a feature, it is a problem correct???
May 27 2011
On Fri, 27 May 2011 08:36:08 -0400, Matthew Ong <ongbp yahoo.com> wrote:On 5/27/2011 8:08 PM, Steven Schveighoffer wrote:No, I mean the author of Parent may not know of the existance of child, and its implementation of methodA. Let me walk you through a scenario. Author 1 implements Parent: class Parent { void methodB(int i) {...} } Author 2 wants to inherit from Parent, but he also wants to overload methodB, so he writes: class Child : Parent { void methodB(string s) {...} void methodA(long l) {...} } To allow one to call the parent's methodB, he uses your new keyword: class Child : inheritall Parent ... Now, sometime in the future, Author 1, without knowing about Author 2's derivation of his work, decides to add methodA which does something completely different from Child's implementation: class Parent { void methodB(int i) {...} void methodA(int i) {...} } Because Child is marked as inheritall, it compiles without complaint, and a call to childinstance.methodA(1) now calls the new Parent's methodA, when previously it called Child's methodA. This is a form of hijacking. Compare this to if you simply aliased methodB: class Child : Parent { alias Parent.methodB methodB; .... } Now, the hijacking introduced with methodA is properly disallowed, and calling methodA on the base throws a hidden function error.Sorry, I used the wrong term, I meant derived or extended.Explain please. You lost me. If I am not wrong, final is used to prevent overriding. Is that what you are talking about?Isn't nooverload supposed to be on the Parent class? How would Author 1 know about Child and know he should put nooverload on methodA when he adds it?Yes, but you marked the child as inheritall, doesn't this implicitly pull in the parent functions as if an alias were entered? Eseentially, the inheritall keyword disables all inheritance hijacking checks. Or did I misunderstand this?inheritall only to that single class and not from child to child and so on. Because of the nooverload keyword. There is a better way to further enhance that anti-hijacking proctection. It is a manually controlled approaches by developer of the child class.The poor navigability of DDoc generated documentation is not a new problem. It's been bad for years. It receives little attention because there are few people working on the compiler, and their time is spent improving the code generating features. I suspect someone else will have to step up in order to get ddoc to generate better docs. IMO the largest problem is that dmd is written in C++, and avoiding C++ is one of the main reasons many people are here ;)This is definitely a problem, ddoc is very underdeveloped. There are some alternative doc generators out there, I think Tango uses dil, which is a d-based compiler that does not yet generate code, but will generate docs (and much better docs at that).Do both improvement. Please also support my post on: Example within documentations of D seriously need some improvement. Please place in the issue you see there compare to others languages already has.I'm saying the poor navigability of DDoc documentation is not a justification for your proposal. It might be less manual work, but I would argue the manual work is minuscule to begin with.But let's not add features to cover up another problem that should be fixed in its own right.NO. It is not a feature to cover up that problem. It prevents the same issue with less manual work.It seems too easy to remove hijacking protection using inheritall. I don't think the nooverload keyword is necessary if inheritall doesn't exist, and it seems like something that would be rarely used. I just don't see enough simplification or improvements to justify allowing an easy off-switch for hijack protection. You should know, the very first post I made on this newsgroup (almost 4 years ago) was to complain about not overloading against base functions, and it lead to improved error detection (the hidden func exception), and the hijacking article being written. I think at this point, you have a 0% chance of getting Walter to change it. I don't want to discourage people from coming up with new and interesting ideas, but this one is not new.The issue is not whether the compiler can search the AST, the issue is whether it makes functions easier to be hijacked.I believe the 2 feature does not make it easier to be hijacked. See above. Compiler can search the AST is key. Most source code development process needs to look at at least 7 different dimensions. Inheritance down the tree, up the tree, interfaces and its implementation, changes over time, testing, cpu cycle, memory creation cycle. That is just single threaded model.I'm not saying the entire code based is simply the output of a java converter, I'm saying the *aliases* are the result of the converter. I don't see why any person would waste the time to alias in all the base class' functions they are fully overriding, why wouldn't they just do the ones that are necessary? Looking again at the code, there is more evidence in the first line: /* language convertion www.dsource.org/project/tioport */ Note the url is incorrect, it should be: http://www.dsource.org/projects/tioport "The TioPort Project does Java to D conversion of whole libraries and applications."Only read is required to be aliased, due to the base function read(byte[] b). All the others are unnecessary. I may see why you see so many cases -- dwt was likely ran through a java to d converter, and such converters often add unnecessary lines, because it is easier to do that than to examine each individual case.It does not seem to be because the dwt library has many different authors.A fully manually written code base would not contain so many aliases.This further weakens your proposal in two ways: 1. The compiler does not need to foster to one small specific porting tool which does not generate optimal code.I am referring to manually written and naturally grown business library. I do agrees that a language is not design based on how a generated tool create its code.Then adding the occasional alias is good enough. -Steve2. Your argument is based on having to manually search for functions to alias, yet this tool clearly did all the aliasing for you.Yes. If and ONLY if you are doing auto java to D conversion. How about when the hand coded library grow?
May 27 2011
On 2011-05-27 14:08, Steven Schveighoffer wrote:On Fri, 27 May 2011 07:42:17 -0400, Matthew Ong <ongbp yahoo.com> wrote:DWT is manually ported from Java. A automatic port was tried and it didn't workout that well, too much of the Java standard library needed to be reimplemented in D. The port tries to stay as close to the original code base as possible to ease merging future versions of SWT and to minimize porting bugs. -- /Jacob CarlborgOn 5/27/2011 7:08 PM, Steven Schveighoffer wrote:OK, but I don't see the point then. Can't you get the functionality you desire already?I don't think it will work that well. Consider how function hijacking happens. For instance, the parent class author may not even know his code is being overridden, and he may simply not mark his base function as nooverload. Let's say that the child is inheriting all the parent's methods because he wanted a different method (an already existing one), and the author of the parent class adds methodA (without the nooverload attribute) after the child is already written. That's an unintentional hijack. The problem is the child is relying on the parent to cooperate in preventing hijacking, instead of controlling whether its functions can be hijacked or not. In the current solution, the system warns me or throws an error if a function becomes hijacked. If this happens, I can examine the code and add an alias if needed. It happens rarely for me. Do you have cases where you have to "alias all over the place"? Maybe you are not doing something correctly, you shouldn't need this feature all the time. Note that drastic proposals like this are very unlikely to be accepted. Especially for something that has been in use and not really complained about for years. You need to present a very compelling argument, including real examples is helpful. Also, if there's any way to get rid of adding a keyword, you have a much better shot of success. No keywords have been added to the language for a long time. -SteveHi Steve, Please note that the proposal is not to remove the existing function hijacking detection but as an alternative to the existing aliasing.Sorry, I used the wrong term, I meant derived or extended.Consider how function hijacking happens. For instance, the parent class author may not even know his code is being overridden, and he may simply not mark his base function as nooverload.From OO stand point, overloading is NOT overriding. Please do not mix up the two. Fundamentally different.Yes, but you marked the child as inheritall, doesn't this implicitly pull in the parent functions as if an alias were entered? Eseentially, the inheritall keyword disables all inheritance hijacking checks. Or did I misunderstand this?parent class adds methodA (without the nooverload attribute)If that happens, still flag as function hijacking using existing detection. Please note that I did NOT ask for the removal of using aliasing on existing source code for inherited overloaded function.BTW, default D documentation is Not too friendly for inheritance tree navigation. Unlike in java.This is definitely a problem, ddoc is very underdeveloped. There are some alternative doc generators out there, I think Tango uses dil, which is a d-based compiler that does not yet generate code, but will generate docs (and much better docs at that). But let's not add features to cover up another problem that should be fixed in its own right.However, new keywords can be added to the compiler. So that future code can be written without spending many brain cycle on looking up such alias. Let the compiler do the hard work of AST searching rather than a manual process. We have quad core now a days, even in asia.The issue is not whether the compiler can search the AST, the issue is whether it makes functions easier to be hijacked.Have you systemetic go over the proposal I posted and gave your counter arguement? How about the fact that currently there are such aliasing all over the child class. From what I understand D inheritance is Not automatic, if I am wrong do let me know. Do you have cases where you have to "alias all over the place"? news://news.digitalmars.com:119/iri4am$2dl3$1 digitalmars.com http://hg.dsource.org/projects/dwt2/file/d00e8db0a568/base/src/java/io/ByteArrayInputStream.dOnly read is required to be aliased, due to the base function read(byte[] b). All the others are unnecessary. I may see why you see so many cases -- dwt was likely ran through a java to d converter, and such converters often add unnecessary lines, because it is easier to do that than to examine each individual case.
May 27 2011
On Fri, 27 May 2011 09:43:39 -0400, Jacob Carlborg <doob me.com> wrote:On 2011-05-27 14:08, Steven Schveighoffer wrote:Why is this comment in the file given? /* language convertion www.dsource.org/project/tioport */ Regardless of whether this was a manual port or not, the profuse aliasing is unnecessary, and does not provide a valid use case for the proposal. -SteveI may see why you see so many cases -- dwt was likely ran through a java to d converter, and such converters often add unnecessary lines, because it is easier to do that than to examine each individual case.DWT is manually ported from Java. A automatic port was tried and it didn't workout that well, too much of the Java standard library needed to be reimplemented in D. The port tries to stay as close to the original code base as possible to ease merging future versions of SWT and to minimize porting bugs.
May 27 2011
On 2011-05-27 16:09, Steven Schveighoffer wrote:On Fri, 27 May 2011 09:43:39 -0400, Jacob Carlborg <doob me.com> wrote:I have no idea. The major part of DWT is manually ported, as far as I know. In this case it seems that not all of the aliases are necessary. But in general, in DWT, we want D to behave as Java, to ease porting. Just for the record, I'm not trying to argument for either anyone's side here, I'm just trying to correct facts about DWT that was incorrect. And apparently I was incorrect as well :) -- /Jacob CarlborgOn 2011-05-27 14:08, Steven Schveighoffer wrote:Why is this comment in the file given? /* language convertion www.dsource.org/project/tioport */ Regardless of whether this was a manual port or not, the profuse aliasing is unnecessary, and does not provide a valid use case for the proposal. -SteveI may see why you see so many cases -- dwt was likely ran through a java to d converter, and such converters often add unnecessary lines, because it is easier to do that than to examine each individual case.DWT is manually ported from Java. A automatic port was tried and it didn't workout that well, too much of the Java standard library needed to be reimplemented in D. The port tries to stay as close to the original code base as possible to ease merging future versions of SWT and to minimize porting bugs.
May 27 2011
On 2011-05-27 13:42, Matthew Ong wrote:On 5/27/2011 7:08 PM, Steven Schveighoffer wrote: Do you have cases where you have to "alias all over the place"? news://news.digitalmars.com:119/iri4am$2dl3$1 digitalmars.com http://hg.dsource.org/projects/dwt2/file/d00e8db0a568/base/src/java/io/ByteArrayInputStream.d >Maybe you are not doing something correctly, you shouldn't need this feature all the time. Not me, others that has coded the dwt and I suspect other code inDWT is a direct port of the Java library SWT and it tries to stay as close to the original code base as possible to easy merges of future release of SWT. When coding my own projects (projects I've written from scratch and not ported from other languages) it's a feature I rarely use, don't know if I ever have used it. -- /Jacob Carlborg
May 27 2011
On 5/27/2011 9:37 PM, Jacob Carlborg wrote:On 2011-05-27 13:42, Matthew Ong wrote:feature all the time. Not me, others that has coded the dwt and I suspect other code inOn 5/27/2011 7:08 PM, Steven Schveighoffer wrote:Maybe you are not doing something correctly, you shouldn't need thisDWT is a direct port of the Java library SWT and it tries to stay as close to the original code base as possible to easy merges of future release of SWT.No problem.I have not worked too much with SWT but people from development world told me they really do not like Swing. Yes. I agree because of the heavy/deep tree inheritance/too much manual copy/paste/undo sort handling. Different topic.DWT is manually ported from Java. A automatic port was tried and it didn't workout that well, too much of the Java standard library needed to be reimplemented in D.Yes. I notice that and notice that the language converter does not work that well because of the semantics of differences in the languages. Not impossible, but too heavy. Unless something like JRuby(JVM) and also IronRuby(.NET) is done and made use of the existing script engine extensions with existing API libray.When coding my own projects (projects I've written from scratch and not ported from other languages) it's a feature I rarely use, don't know if I ever have used it.Actually from scratch is NOT a good approach and migration approach. How do you justify this to business management people or to your client? There are also your learning cycle time. Using Java well know Model-View-Controller as a simple model as a discussion. See: http://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93controller Model= Business Data/IO/Persistance storage Controller= Business Logic and where transaction code are done. View= GUI/Web/Webservices(I am aware webservice is not a view)/Console. Interconnection = how all the MVC are interacting with each other. Those arrow in the diagram top right. Model and Controller typically are similar if not identical across different languages and platform. Most people would just do as much POJO(Plain Old Java Object) as possible here. However when it comes to the View and Interconnection...Those typically changed when moving into different platform. Unless there is someone that port them. Nothing much can be done here.it's a feature I rarely use, don't know if I ever have used it.Because of many years of object-relational database management system (ORDBMS). Most Database table even the flat one like Mysql are design with this concept in mind. Hence, the Model and Controller will have plenty of inheritance tree and mutually dependent code. That would mean alias would be used. If porting SWT has already such syntax and scatted aliases, that would be the burden that coder would have to take on, may I stress, could have been taken over my compiler with new sets of keyword. -- Matthew Ong email: ongbp yahoo.com
May 27 2011
On 2011-05-27 16:38, Matthew Ong wrote:On 5/27/2011 9:37 PM, Jacob Carlborg wrote:Of course, from "scratch" can be interpreted in different ways. I use the standard library and other libraries I need. But often when developing tools for D one can't use already existing tools because they don't support D or, in my opinion, aren't good enough. BWT, I don't have to justify my own private projects to anyone. One last thing: what's wrong with developing something from scratch just for the fun of it or for learning something from it :)On 2011-05-27 13:42, Matthew Ong wrote:feature all the time. Not me, others that has coded the dwt and I suspect other code inOn 5/27/2011 7:08 PM, Steven Schveighoffer wrote:Maybe you are not doing something correctly, you shouldn't need thisDWT is a direct port of the Java library SWT and it tries to stay as close to the original code base as possible to easy merges of future release of SWT.No problem.I have not worked too much with SWT but people from development world told me they really do not like Swing. Yes. I agree because of the heavy/deep tree inheritance/too much manual copy/paste/undo sort handling. Different topic. >DWT is manually ported from Java. A automatic port was tried and it >didn't workout that well, too much of the Java standard library needed >to be reimplemented in D. Yes. I notice that and notice that the language converter does not work that well because of the semantics of differences in the languages. Not impossible, but too heavy. Unless something like JRuby(JVM) and also IronRuby(.NET) is done and made use of the existing script engine extensions with existing API libray.When coding my own projects (projects I've written from scratch and not ported from other languages) it's a feature I rarely use, don't know if I ever have used it.Actually from scratch is NOT a good approach and migration approach. How do you justify this to business management people or to your client? There are also your learning cycle time.Using Java well know Model-View-Controller as a simple model as a discussion. See: http://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93controller Model= Business Data/IO/Persistance storage Controller= Business Logic and where transaction code are done. View= GUI/Web/Webservices(I am aware webservice is not a view)/Console. Interconnection = how all the MVC are interacting with each other. Those arrow in the diagram top right. Model and Controller typically are similar if not identical across different languages and platform. Most people would just do as much POJO(Plain Old Java Object) as possible here. However when it comes to the View and Interconnection...Those typically changed when moving into different platform. Unless there is someone that port them. Nothing much can be done here.I'm working with the MVC design pattern every day at work (Ruby on Rails).>it's a feature I rarely use, don't know if I ever have used it. Because of many years of object-relational database management system (ORDBMS). Most Database table even the flat one like Mysql are design with this concept in mind. Hence, the Model and Controller will have plenty of inheritance tree and mutually dependent code. That would mean alias would be used.As I said above: I'm using the MVC design pattern every day at work with Ruby on Rails which has, in my opinion, a great ORM library. It's not very often I create a class hierarchy of the models. Bacially the only hierarchy that exists is inheriting form the framework classes but when separating the framework from the user code there's basically no hierarchy in the user code.If porting SWT has already such syntax and scatted aliases, that would be the burden that coder would have to take on, may I stress, could have been taken over my compiler with new sets of keyword.I can tell you this: after porting (almost) the whole SWT Mac OS X version to D I haven't seen this as a problem. Just inserting a few aliases and the problem is solved. -- /Jacob Carlborg
May 27 2011
On 2011-05-27 12:27, Jacob Carlborg wrote:On 2011-05-27 16:38, Matthew Ong wrote:Whether reimplementing from scratch or doing a more direct port makes more sense depends entirely on what you're doing. And when it's a personal project that you're doing for fun, it's that much more subjective than it would be when working on a project for work. It's definitely best to use as much knowledge as can be gained from the original code as best as possible when porting it to another language, but whether the actual code should be directly ported or just the basic ideas is very much dependent on the code and the situation. Sometimes it would be just plain stupid to rewrite the code, and in others, directly porting it would be a bad move. I recently started on a port of Haskell's Parsec library to D, since I think that it's an absolutely fantastic parsing library. And being as how the original library is in Haskell (which you're _definitely_ not going to port directly to D) and how I wouldn't necessarily want to use whatever the original license is, it just plain makes more sense to take the basic ideas (and to some extent API) of the original and create a D version that applies those. Porting the code directly would make no sense. With something like DWT on the other hand, doing a direct port and thus minimizing the effort of porting changes to it later would make a lot more sense (particularly since Java is a lot closer to D than Haskell). But whether "writing it from scratch" or not is the best choice depends very much on the code, your situation, and your goals for the project. It's not a black and white choice. - Jonathan M DavisOn 5/27/2011 9:37 PM, Jacob Carlborg wrote:Of course, from "scratch" can be interpreted in different ways. I use the standard library and other libraries I need. But often when developing tools for D one can't use already existing tools because they don't support D or, in my opinion, aren't good enough. BWT, I don't have to justify my own private projects to anyone. One last thing: what's wrong with developing something from scratch just for the fun of it or for learning something from it :)When coding my own projects (projects I've written from scratch and not ported from other languages) it's a feature I rarely use, don't know if I ever have used it.Actually from scratch is NOT a good approach and migration approach. How do you justify this to business management people or to your client? There are also your learning cycle time.
May 27 2011
On 5/27/11 1:34 AM, Matthew Ong wrote:Hi All, Currently within D, to make use of a parent class method you have to do: class Parent{ void methodA(int x){...} } class Child : Parent{ // I understand that it has to do with preventing accidental hijacking alias Parent.methodA methodA; void methodA(long x){...} } void main(string[]){ Child obj=new Child(); obj.methodA(1); // expecting to call Child.methodA but calling Parent.methodA; } and also from this URL. http://www.digitalmars.com/d/2.0/function.html If, through implicit conversions to the base class, those other functions do get called, an std.HiddenFuncError exception is raised.I can't believe this has fallen off the radar. There should be no std.HiddenFuncError. Such errors must ALL be detected during compilation. Andrei
May 27 2011
On Fri, 27 May 2011 10:10:25 -0400, Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> wrote:On 5/27/11 1:34 AM, Matthew Ong wrote:You have three options: 1. keep the base implementation in place. If someone casts to the base class, and calls the hidden function, it just works. 2. force the user to override *all* overloads of the base, or alias them in. 3. Throw the hidden function error. 1 is how D used to be. I think Walter has some good case for why it is undesirable. 2 is just annoying. Either you will just alias the base functions (resulting in possible hijacking) or you will implement stub functions that throw an exception. If you want to go this route, I'd rather just have default aliasing of base functions. 2 is the only way to have a "compile" error. It is impossible to statically check if a function using a base class is actually using a derived class that hides the function being called. That is, you can only statically disallow the compilation of the derived class, not the hidden function call. Personally, I think the current implementation (item 3) is the least annoying. -SteveHi All, Currently within D, to make use of a parent class method you have to do: class Parent{ void methodA(int x){...} } class Child : Parent{ // I understand that it has to do with preventing accidental hijacking alias Parent.methodA methodA; void methodA(long x){...} } void main(string[]){ Child obj=new Child(); obj.methodA(1); // expecting to call Child.methodA but calling Parent.methodA; } and also from this URL. http://www.digitalmars.com/d/2.0/function.html If, through implicit conversions to the base class, those other functions do get called, an std.HiddenFuncError exception is raised.I can't believe this has fallen off the radar. There should be no std.HiddenFuncError. Such errors must ALL be detected during compilation.
May 27 2011
On 5/27/11 9:26 AM, Steven Schveighoffer wrote:On Fri, 27 May 2011 10:10:25 -0400, Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> wrote:4. Statically disallow overloaded overridable methods when the parameters of one automatically convert to the parameters of another.On 5/27/11 1:34 AM, Matthew Ong wrote:You have three options: 1. keep the base implementation in place. If someone casts to the base class, and calls the hidden function, it just works. 2. force the user to override *all* overloads of the base, or alias them in. 3. Throw the hidden function error.Hi All, Currently within D, to make use of a parent class method you have to do: class Parent{ void methodA(int x){...} } class Child : Parent{ // I understand that it has to do with preventing accidental hijacking alias Parent.methodA methodA; void methodA(long x){...} } void main(string[]){ Child obj=new Child(); obj.methodA(1); // expecting to call Child.methodA but calling Parent.methodA; } and also from this URL. http://www.digitalmars.com/d/2.0/function.html If, through implicit conversions to the base class, those other functions do get called, an std.HiddenFuncError exception is raised.I can't believe this has fallen off the radar. There should be no std.HiddenFuncError. Such errors must ALL be detected during compilation.1 is how D used to be. I think Walter has some good case for why it is undesirable. 2 is just annoying. Either you will just alias the base functions (resulting in possible hijacking) or you will implement stub functions that throw an exception. If you want to go this route, I'd rather just have default aliasing of base functions. 2 is the only way to have a "compile" error. It is impossible to statically check if a function using a base class is actually using a derived class that hides the function being called. That is, you can only statically disallow the compilation of the derived class, not the hidden function call. Personally, I think the current implementation (item 3) is the least annoying. -SteveIt is completely against the spirit of the language to decide that a call is resolved to an invalid method during runtime. There is no other feature remotely related to hiddenfunc. A couple of years ago, Walter gave a talk on hijacking to NWCPP. It all went well until HiddenFunc, at which point Walter's assertion that the way out was by throwing an exception was hotly debated. Several people suggested alternative, of whom one proposed (4) above. Everybody agreed it's a good solution, and Walter had the presence of mind and humility to acknowledge that solution and to promise to look into implementing it. Unfortunately, that event was forgotten... until now. Andrei
May 27 2011
On Fri, 27 May 2011 10:54:14 -0400, Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> wrote:It is completely against the spirit of the language to decide that a call is resolved to an invalid method during runtime. There is no other feature remotely related to hiddenfunc. A couple of years ago, Walter gave a talk on hijacking to NWCPP. It all went well until HiddenFunc, at which point Walter's assertion that the way out was by throwing an exception was hotly debated. Several people suggested alternative, of whom one proposed (4) above. Everybody agreed it's a good solution, and Walter had the presence of mind and humility to acknowledge that solution and to promise to look into implementing it. Unfortunately, that event was forgotten... until now.I just tried it out. If one implements an overload that is not contentious (for example, between int and string), no hidden func error is thrown. So indeed the compiler has a notion of when a function would be hijacked. I thought HiddenFuncError was thrown whenever you called any overloaded base method. So I agree with you, this needs to be fixed. Is there a bugzilla on it, or should we file one? Let's not lose it again. -Steve
May 27 2011
On 5/27/11 10:04 AM, Steven Schveighoffer wrote:On Fri, 27 May 2011 10:54:14 -0400, Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> wrote:Matthew's example fixed is this: class Parent{ void methodA(int x){} } class Child : Parent{ //alias Parent.methodA methodA; void methodA(long x){} } void main(string[]){ Parent obj = new Child(); obj.methodA(1); } The program throws with the alias commented out, doesn't throw with the alias. The desired behavior is to enforce three things: (a) "override" must be required everywhere overriding takes place (no warning, no debug mode etc); (b) if a class introduces a method with parameter types covariant with those of a homonym base method, it must introduce all overloads of that name (via alias or overriding); (c) if a class introduces two overloaded AND overridable methods, those must NOT have covariant parameters. (a) makes sure no undue overriding is ever present, (b) takes care of this example, and (c) takes care of the HiddenFunc examples given online at http://www.digitalmars.com/d/2.0/function.html. If you find the time, please make a bug report out of it and insert a link to this discussion in the report. Thanks much, AndreiIt is completely against the spirit of the language to decide that a call is resolved to an invalid method during runtime. There is no other feature remotely related to hiddenfunc. A couple of years ago, Walter gave a talk on hijacking to NWCPP. It all went well until HiddenFunc, at which point Walter's assertion that the way out was by throwing an exception was hotly debated. Several people suggested alternative, of whom one proposed (4) above. Everybody agreed it's a good solution, and Walter had the presence of mind and humility to acknowledge that solution and to promise to look into implementing it. Unfortunately, that event was forgotten... until now.I just tried it out. If one implements an overload that is not contentious (for example, between int and string), no hidden func error is thrown. So indeed the compiler has a notion of when a function would be hijacked. I thought HiddenFuncError was thrown whenever you called any overloaded base method. So I agree with you, this needs to be fixed. Is there a bugzilla on it, or should we file one? Let's not lose it again. -Steve
May 27 2011
A couple of years ago, Walter gave a talk on hijacking to NWCPP. It all went well until HiddenFunc, at which point Walter's assertion that the way out was by throwing an exception was hotly debated. Several people suggested alternative, of whom one proposed (4) above. Everybody agreed it's a good solution, and Walter had the presence of mind and humility to acknowledge that solution and to promise to look into implementing it. Unfortunately, that event was forgotten... until now. AndreiAndrei, there was a discussion about it here on this NG too. I too think that (4) is definitely the best solution. At least that is what I would like D2 to do...
May 27 2011
On 5/27/11 1:06 PM, Dejan Lekic wrote:Just talked to Walter - he did implement something similar that eliminates HiddenFunc, just only with -w. I ran a couple of tests and I find the behavior reasonable. (He does require introducing all overloads in derived classes, which is more permissive than what I had in mind but still eliminates HiddenFunc.) This is perhaps a good time to move these two -w features into the flag-free compiler: requiring override and detecting hidden functions during compilation. AndreiA couple of years ago, Walter gave a talk on hijacking to NWCPP. It all went well until HiddenFunc, at which point Walter's assertion that the way out was by throwing an exception was hotly debated. Several people suggested alternative, of whom one proposed (4) above. Everybody agreed it's a good solution, and Walter had the presence of mind and humility to acknowledge that solution and to promise to look into implementing it. Unfortunately, that event was forgotten... until now. AndreiAndrei, there was a discussion about it here on this NG too. I too think that (4) is definitely the best solution. At least that is what I would like D2 to do...
May 27 2011
On Fri, 27 May 2011 13:25:51 -0400, Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> wrote:On 5/27/11 1:06 PM, Dejan Lekic wrote:I think maybe this is a good thing for a bug report :) I'll make one. -SteveJust talked to Walter - he did implement something similar that eliminates HiddenFunc, just only with -w. I ran a couple of tests and I find the behavior reasonable. (He does require introducing all overloads in derived classes, which is more permissive than what I had in mind but still eliminates HiddenFunc.) This is perhaps a good time to move these two -w features into the flag-free compiler: requiring override and detecting hidden functions during compilation.A couple of years ago, Walter gave a talk on hijacking to NWCPP. It all went well until HiddenFunc, at which point Walter's assertion that the way out was by throwing an exception was hotly debated. Several people suggested alternative, of whom one proposed (4) above. Everybody agreed it's a good solution, and Walter had the presence of mind and humility to acknowledge that solution and to promise to look into implementing it. Unfortunately, that event was forgotten... until now. AndreiAndrei, there was a discussion about it here on this NG too. I too think that (4) is definitely the best solution. At least that is what I would like D2 to do...
May 27 2011
On 5/27/2011 10:10 PM, Andrei Alexandrescu wrote:On 5/27/11 1:34 AM, Matthew Ong wrote:At least not using foo and bar, I am able to understand some of that is being discussed here. Thank you all.Hi All,2 is just annoying.For the sake of backward compatibility, keep that machination. How about the inheritall and nooverload pair? Or something like that, but different keyword or keyword pair. Could that be a way out of that state of annoyance and counter the spirit of inheritance. I am trying to show something like include-all/exclude-some filter like within a automatic list selections. But *please* make it easy to use and readable. Suggestions? -- Matthew Ong email: ongbp yahoo.com
May 27 2011