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0 pointsryao7mo ago0 comments

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 allowed in a vtable, but both are fine to do in C.

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17186274407mo ago

As it isn't the compiler that creates the vtable, you can also have the equivalent of this as the last parameter or where you want it to be.

> It could also contain variables that are non-pointers.

The convention of it being a pure vtable is that it just doesn't.

> Neither is allowed in a vtable

Who is the vtable membership authority? :-)

ryaoOP7mo 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, but if the things you get are not the equivalent of member function pointers, it is not a vtable.

17186274407mo ago

> In computer programming, a virtual method table (VMT), virtual function table, virtual call table, dispatch table, vtable, or vftable is a mechanism used in a programming language to support dynamic dispatch (or run-time method binding). (Wikipedia)

When its a table of function pointers used for dynamic dispatch, to me it's a vtable. I don't care about their type signatures as long as they logically belong to the object in question.

You seem to have a different very narrow definition of vtables, so the discussion is kind of useless.

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17186274407mo ago

As it isn't the compiler that creates the vtable, you can also have the equivalent of this as the last parameter or where you want it to be.

> It could also contain variables that are non-pointers.

The convention of it being a pure vtable is that it just doesn't.

> Neither is allowed in a vtable

Who is the vtable membership authority? :-)

ryaoOP7mo ago

17186274407mo ago

When its a table of function pointers used for dynamic dispatch, to me it's a vtable. I don't care about their type signatures as long as they logically belong to the object in question.

You seem to have a different very narrow definition of vtables, so the discussion is kind of useless.

1 more reply

j / k navigate · click thread line to collapse