ryao

9 ms·

61.
by ryao 1y ago
The vtable pointer corresponds to the actual type in languages that use vtables to implement inheritance, so you do know the type. Read my previous comment for the bug that would happen if what us being used in Linux were actually used for
62.
by ryao 1y ago
Read the definition again. The programming language here is not the one using this. It is the programmer using it.
63.
by ryao 1y ago
You are correct. I am only highly proficient in a few of them. The others are ones that I have used for varying sized projects for varying reasons, but I only learned the subsets I needed for my purposes. I would say my ability in the other
64.
by ryao 1y ago
My proficiency in them varies. I have used them for projects, such that I can write code in them (provided I have references to read), but when I do, I only learn/use the subset of the language that I need. If I want to read code other
65.
by ryao 1y ago
The point of the vtable is to allow dynamic dispatch based on the actual type of an object. When you have a function that does not need a this pointer, it no longer depends on the type of the object and putting it in there anyway could caus
66.
by ryao 1y ago
Static member functions are tied to the class while virtual member functions are tied to the object. If you throw the static member functions into a vtable, you will at best have a bug where the static member function from a different class
67.
by ryao 1y ago
You can take the API for a linked list and implement a balanced binary search tree behind it, but continuing to call it a linked list after doing that is wrong. Similarly, you can do pointer indirections the same way a vtable would do them,
68.
by ryao 1y ago
The curiosity of learning is infeasible given that there are >15,000 programming languages. You might say to only learn the major/influential languages, but I have found my curiosity to wane with every additional language that I lea
69.
by ryao 1y ago
I was referring to POSIX functions when talking about stubs versus unimplemented functions. Messaging in a programming language is a different animal; one that I have yet to fully understand. Objective C for example resolves messages to fun
70.
by ryao 1y ago
You were not discussing the article in your previous reply. That said, I have repeated explained why both you and the author article are wrong to describe that structure of function pointers as a vtable by giving examples of it containing t
71.
by ryao 1y ago
What guarantee do you have that ->ops is a vtable? It could contain function pointers that don’t take an implicit this argument like struct file_operations in Linux does. It could also contain variables that are non-pointers. Neither is
72.
by ryao 1y ago
It would be an improvement on C++ since you would avoid the horrendous error messages from ridiculously long types, slow compile times, exception handling nightmares, bloat from RTTI and constant worry that operators might not mean what you
73.
by ryao 1y ago
Supporting an explicit this is required to be able to access the member variable when a local variable hides it under scoping rules. As another person replied, C++ does indeed have an implicit this.
74.
by ryao 1y ago
The guy was referring to the explicit case where bar is a member variable. The cases where it is in the local scope under scoping rules or the global scope are not really an issue, since you can check the function definition to find if it i
75.
by ryao 1y ago
vtables contain function pointers to functions that take “this” pointers. The author mentions struct file_operations as an example of a vtable. struct file_operations contains a pointer to a function that does not take “this” pointer. It is
76.
by ryao 1y ago
You caused me to do some digging. That publication is dated November 1962. The Lisp 1.5 manual’s preface is dated August 17, 1962, which is even older. It describes lambdas and property lists, which seem like they can be used to implement A
77.
by ryao 1y ago
> Sorry, but where did you got this definition from? It is from experience with object oriented languages (mainly C++ and Java). Technically, you can do everything manually, but that involves shoehorning things into the OO paradigm that
78.
by ryao 1y ago
The article mentions file_operations, but ignores that it has what would be a static member function in C++ in the form of ->check_flags(), which is never in a vtable. The article author is describing overlap between object oriented prog
79.
by ryao 1y ago
In hindsight, I had your remark confused with another remark insisting that struct inode_operations is a vtable, despite it having what would be static member functions in C++, which are never in vtables, and there being no inheritance hier
80.
by ryao 1y ago
Unlike OOLs, C does not enforce contracts around structures (objects). You are free to do literally anything you want to them.
81.
by ryao 1y ago
I would call returning something being implemented as a stub rather than being unimplemented. When something is unimplemented and you try to call it, you crash due to a NULL/invalid pointer dereference, not get an error back. Of course
82.
by ryao 1y ago
It is not a vtable. It is a structure of function pointers called struct inode_operations. It is reused for all inodes in that filesystem. If you get it from one callback, you can safely use it on another struct inode on the same filesystem
83.
by ryao 1y ago
The entire point of OOP in every OOP language that I have ever used has been to have the language try to constrain what you can do by pushing restrictions on syntactic sugar involving objects, inheritance and encapsulation, so I would say y
84.
by ryao 1y ago
By this logic, C is an objective oriented language. It is widely held to not be. That is why there were two separate approaches to extend it to make it object oriented, C++ and Objective-C.
85.
by ryao 1y ago
Object oriented programming implies certain contracts that the compiler enforces that are not enforced with data abstraction. Given that object oriented programming and data abstraction two live side by side in C++, we can spot the differen
86.
by ryao 1y ago
Member function pointers and member functions in C++ are two different things. Member function pointers are not OOP. They are data abstraction. The entire point of OOP is to make contracts with the compiler that forcibly tie certain things
87.
by ryao 1y ago
OOP cannot be a formalization of what predated it because the predating patterns support things that OOP explicitly disallows, like instantiation with unimplemented functions. That is extremely useful when you want to implement an optional
88.
by ryao 1y ago
Not allowing a variable to implicitly refer to a member variable makes it much easier to find. If it is not declared in the function and there is no implicit dereferencing of a this pointer, the variable is global. If the variable name is
89.
by ryao 1y ago
Good point. I had misunderstood the previous comment as suggesting that this be passed to the member function as an explicit argument, rather than requiring dereferences of this be explicit. The latter makes far more sense and I agree it ma
90.
by ryao 1y ago
You are wrong about those invocations being invalid. Such patterns happen in filesystem code fairly often. The best example off the top of my head is: error = old_dir->i_op->rename(rd->new_mnt_idmap, old_dir, old_dentry, new_dir, n

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