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License: MIT License
Ideas, thoughts, and notes on a typeclass/interface based polymorphism pattern for standard C
License: MIT License
Interface function implementations accept T *
as a first parameter, whereas a corresponding function in a virtual table accepts void *
, thereby making these two function types incompatible (godbolt).
Moreover (6.2.7 Compatible type and composite type
):
All declarations that refer to the same object or function shall have compatible type; otherwise, the behavior is undefined.
And I am curious about this code:
TypeclassName T_to_TypeclassName(T* x)
{
static TypeclassName_vtable const tc = {.func_name = (ReturnType (*const)(void*, ...))(T_func_name) };
return (TypeclassName){.tc = &tc, .self = x};
}
Here, .func_name
and T_func_name
are two declarations to the same function having incompatible types. Then we cast T_func_name
to the type accepting void *
as a first parameter; we cast incompatible types. Does it even follow the standard, or it is UB?
The C99 draft standard: http://www.open-std.org/JTC1/SC22/WG14/www/docs/n1256.pdf
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