FrameAddress¶

The address of the host frame that a frame entry is passed with.

Declaration¶

Syntax¶

FrameAddress(symbol procedure, ttype type, expr? value)

Arguments¶

Argument	Description
`procedure`	a frame entry: an internal procedure, visible here, whose last dummy argument is a `type(c_ptr)` value dummy.
`type`	`type(c_ptr)`, a CPtr.
`value`	always `nil`.

Return values¶

The address of the frame of the instance of the host of procedure that evaluates the expression, or a null pointer when procedure needs no frame.

Description¶

With --fast, the specialize_frame_arguments pass copies a procedure whose dummy procedures are only called or passed on. In the copy, each such dummy procedure is a pair of dummies: a code pointer whose interface has an extra last type(c_ptr) value dummy, and the address of a frame. An actual procedure is passed to the pair as a frame entry, an internal procedure that calls it, and a FrameAddress of the entry.

The nested_vars pass gives a frame entry the frame of its host through that last dummy instead of a frame dummy, so a procedure value of the entry is its plain code address and needs no thunk, and it replaces every FrameAddress: by a PointerToCPtr of the frame object or the frame dummy that a call of the entry from the same place would pass, or by a PointerNullConstant when the entry needs no frame. It is not Fortran: --show-fortran prints it as frame_address(procedure). No FrameAddress remains after nested_vars (asr.verify.nested_vars.frame_address). A procedure that is not a frame entry is reported as asr.verify.frame_address.procedure.

Examples¶

The copy of the recursive a in Knuth’s man or boy test passes its internal procedure b with the frame of the instance:

(FrameAddress
  :procedure (SymbolRef 4 "b__lcompilers_frame_entry")
  :type (CPtr
    :kind CPointer
  )
  :value nil
)