[Solved] Decoding declaration(a combination of array and function pointers) in C [closed]

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That code is not a declaration, but it can be interpreted as an expression.

(*I_dont_know())[(int) ((*ptr))]
  1. Call the function I_dont_know with no arguments. This function returns a pointer to something.
  2. Dereference the returned pointer to get some object.
  3. Meanwhile, dereference the value of ptr and cast it to an int value.
  4. Then pass that int value as the argument for the [] (indexing) operator on that object returned in step 2. In C this could be another pointer or an array (arrays decay to pointers too). In C++ this could also be an object with the [] operator overloaded.
  5. As this expression is not on the left-hand-side of an assignment then the value returned from the [] operator sub-expression (i.e. the element at the *ptr-index in the array) will be returned.

Assuming this is C, then the argument to the indexing operator should be cast as size_t and not int. If it’s C++ then it should only be cast to int if the [] operator overload specifically accepts an int parameter operand.

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solved Decoding declaration(a combination of array and function pointers) in C [closed]