1------------------------------------------------------------------------------
2--                                                                          --
3--                         GNAT COMPILER COMPONENTS                         --
4--                                                                          --
5--                              S E M _ C H 8                               --
6--                                                                          --
7--                                 S p e c                                  --
8--                                                                          --
9--          Copyright (C) 1992-2019, Free Software Foundation, Inc.         --
10--                                                                          --
11-- GNAT is free software;  you can  redistribute it  and/or modify it under --
12-- terms of the  GNU General Public License as published  by the Free Soft- --
13-- ware  Foundation;  either version 3,  or (at your option) any later ver- --
14-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
15-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
16-- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
17-- for  more details.  You should have  received  a copy of the GNU General --
18-- Public License  distributed with GNAT; see file COPYING3.  If not, go to --
19-- http://www.gnu.org/licenses for a complete copy of the license.          --
20--                                                                          --
21-- GNAT was originally developed  by the GNAT team at  New York University. --
22-- Extensive contributions were provided by Ada Core Technologies Inc.      --
23--                                                                          --
24------------------------------------------------------------------------------
25
26with Types; use Types;
27package Sem_Ch8 is
28
29   -----------------------------------
30   -- Handling extensions of System --
31   -----------------------------------
32
33   --  For targets that define a much larger System package than given in
34   --  the RM, we use a child package containing additional declarations,
35   --  which is loaded when needed, and whose entities are conceptually
36   --  within System itself. The presence of this auxiliary package is
37   --  controlled with the pragma Extend_System. The following variable
38   --  holds the entity of the auxiliary package, to simplify the special
39   --  visibility rules that apply to it.
40
41   System_Aux_Id : Entity_Id := Empty;
42
43   -----------------
44   -- Subprograms --
45   -----------------
46
47   procedure Analyze_Exception_Renaming         (N : Node_Id);
48   procedure Analyze_Expanded_Name              (N : Node_Id);
49   procedure Analyze_Generic_Function_Renaming  (N : Node_Id);
50   procedure Analyze_Generic_Package_Renaming   (N : Node_Id);
51   procedure Analyze_Generic_Procedure_Renaming (N : Node_Id);
52   procedure Analyze_Object_Renaming            (N : Node_Id);
53   procedure Analyze_Package_Renaming           (N : Node_Id);
54   procedure Analyze_Subprogram_Renaming        (N : Node_Id);
55
56   procedure Analyze_Use_Package (N : Node_Id; Chain : Boolean := True);
57   --  Analyze a use package clause and control (through the Chain parameter)
58   --  whether to add N to the use clause chain for the name denoted within
59   --  use clause N in case we are reanalyzing a use clause because of stack
60   --  manipulation.
61
62   procedure Analyze_Use_Type (N : Node_Id; Chain : Boolean := True);
63   --  Similar to Analyze_Use_Package except the Chain parameter applies to the
64   --  type within N's subtype mark Current_Use_Clause.
65
66   procedure End_Scope;
67   --  Called at end of scope. On exit from blocks and bodies (subprogram,
68   --  package, task, and protected bodies), the name of the current scope
69   --  must be removed from the scope stack, and the local entities must be
70   --  removed from their homonym chains. On exit from record declarations,
71   --  from package specifications, and from tasks and protected type
72   --  specifications, more specialized procedures are invoked.
73
74   procedure End_Use_Clauses (Clause : Node_Id);
75   --  Invoked on scope exit, to undo the effect of local use clauses. Clause
76   --  is the first use-clause of a scope being exited. This can be the current
77   --  scope, or some enclosing scopes when building a clean environment to
78   --  compile an instance body for inlining.
79
80   procedure End_Use_Package (N : Node_Id);
81   procedure End_Use_Type    (N : Node_Id);
82   --  Subsidiaries of End_Use_Clauses. Also called directly for use clauses
83   --  appearing in context clauses.
84
85   procedure Find_Direct_Name
86     (N            : Node_Id;
87      Errors_OK    : Boolean := True;
88      Marker_OK    : Boolean := True;
89      Reference_OK : Boolean := True);
90   --  Given a direct name (Identifier or Operator_Symbol), this routine scans
91   --  the homonym chain for the name, searching for corresponding visible
92   --  entities to find the referenced entity (or in the case of overloading,
93   --  one candidate interpretation). On return, the Entity and Etype fields
94   --  are set. In the non-overloaded case, these are the correct entries.
95   --  In the overloaded case, the flag Is_Overloaded is set, Etype and Entity
96   --  refer to an arbitrary element of the overloads set, and the appropriate
97   --  entries have been added to the overloads table entry for the node. The
98   --  overloading will be disambiguated during type resolution.
99   --
100   --  Note, when this is called during semantic analysis in the overloaded
101   --  case, the entity set will be the most recently declared homonym. In
102   --  particular, the caller may follow the homonym chain checking for all
103   --  entries in the current scope, and that will give all homonyms that are
104   --  declared before the point of call in the current scope. This is useful
105   --  for example in the processing for pragma Inline.
106   --
107   --  Flag Errors_OK should be set when error diagnostics are desired. Flag
108   --  Marker_OK should be set when a N_Variable_Reference_Marker needs to be
109   --  generated for a SPARK object in order to detect elaboration issues. Flag
110   --  Reference_OK should be set when N must generate a cross reference.
111
112   procedure Find_Selected_Component (N : Node_Id);
113   --  Resolve various cases of selected components, recognize expanded names
114
115   procedure Find_Type (N : Node_Id);
116   --  Perform name resolution, and verify that the name found is that of a
117   --  type. On return the Entity and Etype fields of the node N are set
118   --  appropriately. If it is an incomplete type whose full declaration has
119   --  been seen, they are set to the entity in the full declaration. If it
120   --  is an incomplete type associated with an interface visible through a
121   --  limited-with clause, whose full declaration has been seen, they are
122   --  set to the entity in the full declaration. Similarly, if the type is
123   --  private, it has received a full declaration, and we are in the private
124   --  part or body of the package, then the two fields are set to the entity
125   --  of the full declaration as well. This procedure also has special
126   --  processing for 'Class attribute references.
127
128   function Has_Loop_In_Inner_Open_Scopes (S : Entity_Id) return Boolean;
129   --  S is the entity of an open scope. This function determines if there is
130   --  an inner scope of S which is a loop (i.e. it appears somewhere in the
131   --  scope stack after S).
132
133   function In_Open_Scopes (S : Entity_Id) return Boolean;
134   --  S is the entity of a scope. This function determines if this scope is
135   --  currently open (i.e. it appears somewhere in the scope stack).
136
137   procedure Initialize;
138   --  Initializes data structures used for visibility analysis. Must be
139   --  called before analyzing each new main source program.
140
141   procedure Install_Use_Clauses
142     (Clause             : Node_Id;
143      Force_Installation : Boolean := False);
144   --  Applies the use clauses appearing in a given declarative part,
145   --  when the corresponding scope has been placed back on the scope
146   --  stack after unstacking to compile a different context (subunit or
147   --  parent of generic body). Force_Installation is used when called from
148   --  Analyze_Subunit.Re_Install_Use_Clauses to insure that, after the
149   --  analysis of the subunit, the parent's environment is again identical.
150
151   procedure Mark_Use_Clauses (Id : Node_Or_Entity_Id);
152   --  Mark a given entity or node Id's relevant use clauses as effective,
153   --  including redundant ones and ones outside of the current scope.
154
155   procedure Push_Scope (S : Entity_Id);
156   --  Make new scope stack entry, pushing S, the entity for a scope onto the
157   --  top of the scope table. The current setting of the scope suppress flags
158   --  is saved for restoration on exit.
159
160   procedure Pop_Scope;
161   --  Remove top entry from scope stack, restoring the saved setting of the
162   --  scope suppress flags.
163
164   function Present_System_Aux (N : Node_Id := Empty) return Boolean;
165   --  Return True if the auxiliary system file has been successfully loaded.
166   --  Otherwise attempt to load it, using the name supplied by a previous
167   --  Extend_System pragma, and report on the success of the load. If N is
168   --  present, it is a selected component whose prefix is System, or else a
169   --  with-clause on system. N is absent when the function is called to find
170   --  the visibility of implicit operators.
171
172   function Save_Scope_Stack
173     (Handle_Use : Boolean := True) return Elist_Id;
174   procedure Restore_Scope_Stack
175     (List       : Elist_Id;
176      Handle_Use : Boolean := True);
177   --  These two subprograms are called from Semantics, when a unit U1 is to
178   --  be compiled in the course of the compilation of another unit U2. This
179   --  happens whenever Rtsfind is called. U1, the unit retrieved by Rtsfind,
180   --  must be compiled in its own context, and the current scope stack
181   --  containing U2 and local scopes must be made unreachable. This is
182   --  achieved using a call to Save_Scope_Stack. On return, the contents
183   --  of the scope stack must be made accessible again with a call to
184   --  Restore_Scope_Stack.
185   --
186   --  The flag Handle_Use indicates whether local use clauses must be removed
187   --  or installed. In the case of inlining of instance bodies, the visibility
188   --  handling is done fully in Inline_Instance_Body, and use clauses are
189   --  handled there. Save_Scope_Stack returns the list of entities which have
190   --  been temporarily removed from visibility; that list must be passed to
191   --  Restore_Scope_Stack to restore their visibility.
192
193   procedure Set_Use (L : List_Id);
194   --  Find use clauses that are declarative items in a package declaration
195   --  and set the potentially use-visible flags of imported entities before
196   --  analyzing the corresponding package body.
197
198   procedure Update_Use_Clause_Chain;
199   --  Called at the end of a declarative region to detect unused use type
200   --  clauses and maintain the Current_Use_Clause for type entities.
201
202   procedure ws;
203   --  Debugging routine for use in gdb: dump all entities on scope stack
204
205   procedure we (S : Entity_Id);
206   --  Debugging routine for use in gdb: dump all entities in given scope
207
208end Sem_Ch8;
209