------------------------------------------------------------------------------ -- -- -- GNAT COMPILER COMPONENTS -- -- -- -- E X P _ D I S P -- -- -- -- S p e c -- -- -- -- Copyright (C) 1992-2018, Free Software Foundation, Inc. -- -- -- -- GNAT is free software; you can redistribute it and/or modify it under -- -- terms of the GNU General Public License as published by the Free Soft- -- -- ware Foundation; either version 3, or (at your option) any later ver- -- -- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License -- -- for more details. You should have received a copy of the GNU General -- -- Public License distributed with GNAT; see file COPYING3. If not, go to -- -- http://www.gnu.org/licenses for a complete copy of the license. -- -- -- -- GNAT was originally developed by the GNAT team at New York University. -- -- Extensive contributions were provided by Ada Core Technologies Inc. -- -- -- ------------------------------------------------------------------------------ -- This package contains routines involved in tagged types and dynamic -- dispatching expansion. with Types; use Types; with Uintp; use Uintp; package Exp_Disp is ------------------------------------- -- Predefined primitive operations -- ------------------------------------- -- The predefined primitive operations (PPOs) are subprograms generated -- by GNAT for a particular tagged type. Their role is to provide support -- for different Ada language features such as the attribute 'Size or -- handling of dispatching triggers in select statements. PPOs are created -- when a tagged type is expanded or frozen. These subprograms are later -- collected and inserted into the dispatch table of a tagged type at -- fixed positions. Some of the PPOs that manipulate data in tagged objects -- require the generation of thunks. -- List of predefined primitive operations -- Leading underscores designate reserved names. Bracketed numerical -- values represent dispatch table slot numbers. -- _Size (1) - implementation of the attribute 'Size for any tagged -- type. Constructs of the form Prefix'Size are converted into -- Prefix._Size. -- TSS_Stream_Read (2) - implementation of the stream attribute Read -- for any tagged type. -- TSS_Stream_Write (3) - implementation of the stream attribute Write -- for any tagged type. -- TSS_Stream_Input (4) - implementation of the stream attribute Input -- for any tagged type. -- TSS_Stream_Output (5) - implementation of the stream attribute -- Output for any tagged type. -- Op_Eq (6) - implementation of the equality operator for any non- -- limited tagged type. -- _Assign (7) - implementation of the assignment operator for any -- non-limited tagged type. -- TSS_Deep_Adjust (8) - implementation of the finalization operation -- Adjust for any non-limited tagged type. -- TSS_Deep_Finalize (9) - implementation of the finalization -- operation Finalize for any non-limited tagged type. -- _Disp_Asynchronous_Select (10) - used in the expansion of ATC with -- dispatching triggers. Null implementation for limited interfaces, -- full body generation for types that implement limited interfaces, -- not generated for the rest of the cases. See Expand_N_Asynchronous_ -- Select in Exp_Ch9 for more information. -- _Disp_Conditional_Select (11) - used in the expansion of conditional -- selects with dispatching triggers. Null implementation for limited -- interfaces, full body generation for types that implement limited -- interfaces, not generated for the rest of the cases. See Expand_N_ -- Conditional_Entry_Call in Exp_Ch9 for more information. -- _Disp_Get_Prim_Op_Kind (12) - helper routine used in the expansion -- of ATC with dispatching triggers. Null implementation for limited -- interfaces, full body generation for types that implement limited -- interfaces, not generated for the rest of the cases. -- _Disp_Get_Task_Id (13) - helper routine used in the expansion of -- Abort, attributes 'Callable and 'Terminated for task interface -- class-wide types. Full body generation for task types, null -- implementation for limited interfaces, not generated for the rest -- of the cases. See Expand_N_Attribute_Reference in Exp_Attr and -- Expand_N_Abort_Statement in Exp_Ch9 for more information. -- _Disp_Requeue (14) - used in the expansion of dispatching requeue -- statements. Null implementation is provided for protected, task -- and synchronized interfaces. Protected and task types implementing -- concurrent interfaces receive full bodies. See Expand_N_Requeue_ -- Statement in Exp_Ch9 for more information. -- _Disp_Timed_Select (15) - used in the expansion of timed selects -- with dispatching triggers. Null implementation for limited -- interfaces, full body generation for types that implement limited -- interfaces, not generated for the rest of the cases. See Expand_N_ -- Timed_Entry_Call for more information. -- Life cycle of predefined primitive operations -- The specifications and bodies of the PPOs are created by -- Make_Predefined_Primitive_Specs and Predefined_Primitive_Bodies -- in Exp_Ch3. The generated specifications are immediately analyzed, -- while the bodies are left as freeze actions to the tagged type for -- which they are created. -- PPOs are collected and added to the Primitive_Operations list of -- a type by the regular analysis mechanism. -- PPOs are frozen by Exp_Ch3.Predefined_Primitive_Freeze -- Thunks for PPOs are created by Make_DT -- Dispatch table positions of PPOs are set by Set_All_DT_Position -- Calls to PPOs proceed as regular dispatching calls. If the PPO -- has a thunk, a call proceeds as a regular dispatching call with -- a thunk. -- Guidelines for addition of new predefined primitive operations -- Update the value of constant Max_Predef_Prims in a-tags.ads to -- indicate the new number of PPOs. -- Introduce a new predefined name for the new PPO in Snames.ads and -- Snames.adb. -- Categorize the new PPO name as predefined by adding an entry in -- Is_Predefined_Dispatching_Operation in Exp_Disp. -- Generate the specification of the new PPO in Make_Predefined_ -- Primitive_Spec in Exp_Ch3.adb. The Is_Internal flag of the defining -- identifier of the specification must be set to True. -- Generate the body of the new PPO in Predefined_Primitive_Bodies in -- Exp_Ch3.adb. The Is_Internal flag of the defining identifier of the -- specification must be set to True. -- If the new PPO requires a thunk, add an entry in Freeze_Subprogram -- in Exp_Ch6.adb. -- When generating calls to a PPO, use Find_Prim_Op from Exp_Util.ads -- to retrieve the entity of the operation directly. -- Number of predefined primitive operations added by the Expander -- for a tagged type. If more predefined primitive operations are -- added, the following items must be changed: -- Ada.Tags.Max_Predef_Prims - indirect use -- Exp_Disp.Default_Prim_Op_Position - indirect use -- Exp_Disp.Set_All_DT_Position - direct use procedure Apply_Tag_Checks (Call_Node : Node_Id); -- Generate checks required on dispatching calls function Building_Static_DT (Typ : Entity_Id) return Boolean; pragma Inline (Building_Static_DT); -- Returns true when building statically allocated dispatch tables function Building_Static_Secondary_DT (Typ : Entity_Id) return Boolean; pragma Inline (Building_Static_Secondary_DT); -- Returns true when building statically allocated secondary dispatch -- tables procedure Build_Static_Dispatch_Tables (N : Node_Id); -- N is a library level package declaration or package body. Build the -- static dispatch table of the tagged types defined at library level. In -- case of package declarations with private part the generated nodes are -- added at the end of the list of private declarations. Otherwise they are -- added to the end of the list of public declarations. In case of package -- bodies they are added to the end of the list of declarations of the -- package body. function Convert_Tag_To_Interface (Typ : Entity_Id; Expr : Node_Id) return Node_Id; pragma Inline (Convert_Tag_To_Interface); -- This function is used in class-wide interface conversions; the expanded -- code generated to convert a tagged object to a class-wide interface type -- involves referencing the tag component containing the secondary dispatch -- table associated with the interface. Given the expression Expr that -- references a tag component, we cannot generate an unchecked conversion -- to leave the expression decorated with the class-wide interface type Typ -- because an unchecked conversion cannot be seen as a no-op. An unchecked -- conversion is conceptually a function call and therefore the RM allows -- the backend to obtain a copy of the value of the actual object and store -- it in some other place (like a register); in such case the interface -- conversion is not equivalent to a displacement of the pointer to the -- interface and any further displacement fails. Although the functionality -- of this function is simple and could be done directly, the purpose of -- this routine is to leave well documented in the sources these -- occurrences. -- If Expr is an N_Selected_Component that references a tag generate: -- type ityp is non null access Typ; -- ityp!(Expr'Address).all -- if Expr is an N_Function_Call to Ada.Tags.Displace then generate: -- type ityp is non null access Typ; -- ityp!(Expr).all function CPP_Num_Prims (Typ : Entity_Id) return Nat; -- Return the number of primitives of the C++ part of the dispatch table. -- For types that are not derivations of CPP types return 0. function Elab_Flag_Needed (Typ : Entity_Id) return Boolean; -- Return True if the elaboration of the tagged type Typ is completed at -- run time by the execution of code located in the IP routine and the -- expander must generate an extra elaboration flag to avoid performing -- such elaboration twice. procedure Expand_Dispatching_Call (Call_Node : Node_Id); -- Expand the call to the operation through the dispatch table and perform -- the required tag checks when appropriate. For CPP types tag checks are -- not relevant. procedure Expand_Interface_Actuals (Call_Node : Node_Id); -- Ada 2005 (AI-251): Displace all the actuals corresponding to class-wide -- interfaces to reference the interface tag of the actual object procedure Expand_Interface_Conversion (N : Node_Id); -- Ada 2005 (AI-251): N is a type-conversion node. Displace the pointer -- to the object to give access to the interface tag associated with the -- dispatch table of the target type. procedure Expand_Interface_Thunk (Prim : Node_Id; Thunk_Id : out Entity_Id; Thunk_Code : out Node_Id); -- Ada 2005 (AI-251): When a tagged type implements abstract interfaces we -- generate additional subprograms (thunks) associated with each primitive -- Prim to have a layout compatible with the C++ ABI. The thunk displaces -- the pointers to the actuals that depend on the controlling type before -- transferring control to the target subprogram. If there is no need to -- generate the thunk then Thunk_Id and Thunk_Code are set to Empty. -- Otherwise they are set to the defining identifier and the subprogram -- body of the generated thunk. function Has_CPP_Constructors (Typ : Entity_Id) return Boolean; -- Returns true if the type has CPP constructors function Is_Expanded_Dispatching_Call (N : Node_Id) return Boolean; -- Returns true if N is the expanded code of a dispatching call function Make_DT (Typ : Entity_Id; N : Node_Id := Empty) return List_Id; -- Expand the declarations for the Dispatch Table. The node N is the -- declaration that forces the generation of the table. It is used to place -- error messages when the declaration leads to the freezing of a given -- primitive operation that has an incomplete non- tagged formal. function Make_Disp_Asynchronous_Select_Body (Typ : Entity_Id) return Node_Id; -- Ada 2005 (AI-345): Generate the body of the primitive operation of type -- Typ used for dispatching in asynchronous selects. Generate a null body -- if Typ is an interface type. function Make_Disp_Asynchronous_Select_Spec (Typ : Entity_Id) return Node_Id; -- Ada 2005 (AI-345): Generate the specification of the primitive operation -- of type Typ used for dispatching in asynchronous selects. function Make_Disp_Conditional_Select_Body (Typ : Entity_Id) return Node_Id; -- Ada 2005 (AI-345): Generate the body of the primitive operation of type -- Typ used for dispatching in conditional selects. Generate a null body -- if Typ is an interface type. function Make_Disp_Conditional_Select_Spec (Typ : Entity_Id) return Node_Id; -- Ada 2005 (AI-345): Generate the specification of the primitive operation -- of type Typ used for dispatching in conditional selects. function Make_Disp_Get_Prim_Op_Kind_Body (Typ : Entity_Id) return Node_Id; -- Ada 2005 (AI-345): Generate the body of the primitive operation of type -- Typ used for retrieving the callable entity kind during dispatching in -- asynchronous selects. Generate a null body if Typ is an interface type. function Make_Disp_Get_Prim_Op_Kind_Spec (Typ : Entity_Id) return Node_Id; -- Ada 2005 (AI-345): Generate the specification of the primitive operation -- of the type Typ use for retrieving the callable entity kind during -- dispatching in asynchronous selects. function Make_Disp_Get_Task_Id_Body (Typ : Entity_Id) return Node_Id; -- Ada 2005 (AI-345): Generate body of the primitive operation of type Typ -- used for retrieving the _task_id field of a task interface class- wide -- type. Generate a null body if Typ is an interface or a non-task type. function Make_Disp_Get_Task_Id_Spec (Typ : Entity_Id) return Node_Id; -- Ada 2005 (AI-345): Generate the specification of the primitive operation -- of type Typ used for retrieving the _task_id field of a task interface -- class-wide type. function Make_Disp_Requeue_Body (Typ : Entity_Id) return Node_Id; -- Ada 2005 (AI05-0030): Generate the body of the primitive operation of -- type Typ used for dispatching on requeue statements. Generate a body -- containing a single null-statement if Typ is an interface type. function Make_Disp_Requeue_Spec (Typ : Entity_Id) return Node_Id; -- Ada 2005 (AI05-0030): Generate the specification of the primitive -- operation of type Typ used for dispatching requeue statements. function Make_Disp_Timed_Select_Body (Typ : Entity_Id) return Node_Id; -- Ada 2005 (AI-345): Generate the body of the primitive operation of type -- Typ used for dispatching in timed selects. Generate a body containing -- a single null-statement if Typ is an interface type. function Make_Disp_Timed_Select_Spec (Typ : Entity_Id) return Node_Id; -- Ada 2005 (AI-345): Generate the specification of the primitive operation -- of type Typ used for dispatching in timed selects. function Make_Select_Specific_Data_Table (Typ : Entity_Id) return List_Id; -- Ada 2005 (AI-345): Create and populate the auxiliary table in the TSD -- of Typ used for dispatching in asynchronous, conditional and timed -- selects. Generate code to set the primitive operation kinds and entry -- indexes of primitive operations and primitive wrappers. function Make_Tags (Typ : Entity_Id) return List_Id; -- Generate the entities associated with the primary and secondary tags of -- Typ and fill the contents of Access_Disp_Table. In case of library level -- tagged types this routine imports the forward declaration of the tag -- entity, that will be declared and exported by Make_DT. function Register_Primitive (Loc : Source_Ptr; Prim : Entity_Id) return List_Id; -- Build code to register Prim in the primary or secondary dispatch table. -- If Prim is associated with a secondary dispatch table then generate also -- its thunk and register it in the associated secondary dispatch table. -- In general the dispatch tables are always generated by Make_DT and -- Make_Secondary_DT; this routine is only used in two corner cases: -- -- 1) To construct the dispatch table of a tagged type whose parent -- is a CPP_Class (see Build_Init_Procedure). -- 2) To handle late overriding of dispatching operations (see -- Check_Dispatching_Operation and Make_DT). -- -- The caller is responsible for inserting the generated code in the -- proper place. procedure Set_All_DT_Position (Typ : Entity_Id); -- Set the DT_Position field for each primitive operation. In the CPP -- Class case check that no pragma CPP_Virtual is missing and that the -- DT_Position are coherent procedure Set_CPP_Constructors (Typ : Entity_Id); -- Typ is a CPP_Class type. Create the Init procedures of that type -- required to handle its default and non-default constructors. The -- functions to which pragma CPP_Constructor is applied in the sources -- are functions returning this type, and having an implicit access to the -- target object in its first argument; such implicit argument is explicit -- in the IP procedures built here. procedure Set_DT_Position_Value (Prim : Entity_Id; Value : Uint); -- Set the position of a dispatching primitive its dispatch table. For -- subprogram wrappers propagate the value to the wrapped subprogram. procedure Set_DTC_Entity_Value (Tagged_Type : Entity_Id; Prim : Entity_Id); -- Set the definite value of the DTC_Entity value associated with a given -- primitive of a tagged type. For subprogram wrappers, propagate the value -- to the wrapped subprogram. procedure Write_DT (Typ : Entity_Id); pragma Export (Ada, Write_DT); -- Debugging procedure (to be called within gdb) end Exp_Disp;