gcc/ada/sem_elab.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                             S E M _ E L A B                              --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1997-2019, 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
  26 --  This package contains routines which handle access-before-elaboration
  27 --  run-time checks and compile-time diagnostics. See the body for details.
  28
  29 with Types; use Types;
  30
  31 package Sem_Elab is
  32
  33    -----------
  34    -- Types --
  35    -----------
  36
  37    --  The following type classifies the various enclosing levels used in ABE
  38    --  diagnostics.
  39
  40    type Enclosing_Level_Kind is
  41      (Declaration_Level,
  42       --  A construct is at the "declaration level" when it appears within the
  43       --  declarations of a block statement, an entry body, a subprogram body,
  44       --  or a task body, ignoring enclosing packages. Example:
  45
  46       --    package Pack is
  47       --       procedure Proc is                 --  subprogram body
  48       --          package Nested is              --  enclosing package ignored
  49       --             X ...                       --  at declaration level
  50
  51       Generic_Spec_Level,
  52       Generic_Body_Level,
  53       --  A construct is at the "generic level" when it appears in a
  54       --  generic package library unit, ignoring enclosing packages. Example:
  55
  56       --    generic
  57       --    package Pack is                      --  generic package spec
  58       --       package Nested is                 --  enclosing package ignored
  59       --          X ...                          --  at generic library level
  60
  61       Instantiation_Level,
  62       --  A construct is at the "instantiation library level" when it appears
  63       --  in a library unit which is also an instantiation. Example:
  64
  65       --    package Inst is new Gen;             --  at instantiation level
  66
  67       Library_Spec_Level,
  68       Library_Body_Level,
  69       --  A construct is at the "library level" when it appears in a package
  70       --  library unit, ignoring enclosing packages. Example:
  71
  72       --    package body Pack is                 --  package body
  73       --       package Nested is                 --  enclosing package ignored
  74       --          X ...                          --  at library level
  75
  76       No_Level);
  77       --  This value is used to indicate that none of the levels above are in
  78       --  effect.
  79
  80    subtype Generic_Level is Enclosing_Level_Kind range
  81      Generic_Spec_Level ..
  82      Generic_Body_Level;
  83
  84    subtype Library_Level is Enclosing_Level_Kind range
  85      Library_Spec_Level ..
  86      Library_Body_Level;
  87
  88    subtype Library_Or_Instantiation_Level is Enclosing_Level_Kind range
  89      Instantiation_Level ..
  90      Library_Body_Level;
  91
  92    procedure Build_Call_Marker (N : Node_Id);
  93    pragma Inline (Build_Call_Marker);
  94    --  Create a call marker for call or requeue statement N and record it for
  95    --  later processing by the ABE mechanism.
  96
  97    procedure Build_Variable_Reference_Marker
  98      (N     : Node_Id;
  99       Read  : Boolean;
 100       Write : Boolean);
 101    pragma Inline (Build_Variable_Reference_Marker);
 102    --  Create a variable reference marker for arbitrary node N if it mentions a
 103    --  variable, and record it for later processing by the ABE mechanism. Flag
 104    --  Read should be set when the reference denotes a read. Flag Write should
 105    --  be set when the reference denotes a write.
 106
 107    procedure Check_Elaboration_Scenarios;
 108    --  Examine each scenario recorded during analysis/resolution and apply the
 109    --  Ada or SPARK elaboration rules taking into account the model in effect.
 110    --  This processing detects and diagnoses ABE issues, installs conditional
 111    --  ABE checks or guaranteed ABE failures, and ensures the elaboration of
 112    --  units.
 113
 114    function Find_Enclosing_Level (N : Node_Id) return Enclosing_Level_Kind;
 115    pragma Inline (Find_Enclosing_Level);
 116    --  Determine the enclosing level of arbitrary node N
 117
 118    procedure Initialize;
 119    pragma Inline (Initialize);
 120    --  Initialize the internal structures of this unit
 121
 122    procedure Kill_Elaboration_Scenario (N : Node_Id);
 123    --  Determine whether arbitrary node N denotes a scenario which requires
 124    --  ABE diagnostics or runtime checks and eliminate it from a region with
 125    --  dead code.
 126
 127    procedure Record_Elaboration_Scenario (N : Node_Id);
 128    pragma Inline (Record_Elaboration_Scenario);
 129    --  Determine whether atribtray node N denotes a scenario which requires
 130    --  ABE diagnostics or runtime checks. If this is the case, store N for
 131    --  later processing.
 132
 133    ---------------------------------------------------------------------------
 134    --                                                                       --
 135    --  L E G A C Y    A C C E S S    B E F O R E    E L A B O R A T I O N   --
 136    --                                                                       --
 137    --                          M E C H A N I S M                            --
 138    --                                                                       --
 139    ---------------------------------------------------------------------------
 140
 141    --  This section contains the implementation of the pre-18.x Legacy ABE
 142    --  Mechanism. The mechanism can be activated using switch -gnatH (legacy
 143    --  elaboration checking mode enabled).
 144
 145    procedure Check_Elab_Assign (N : Node_Id);
 146    --  N is either the left side of an assignment, or a procedure argument for
 147    --  a mode OUT or IN OUT formal. This procedure checks for a possible case
 148    --  of access to an entity from elaboration code before the entity has been
 149    --  initialized, and issues appropriate warnings.
 150
 151    procedure Check_Elab_Call
 152      (N            : Node_Id;
 153       Outer_Scope  : Entity_Id := Empty;
 154       In_Init_Proc : Boolean   := False);
 155    --  Check a call for possible elaboration problems. The node N is either an
 156    --  N_Function_Call or N_Procedure_Call_Statement node or an access
 157    --  attribute reference whose prefix is a subprogram.
 158    --
 159    --  If SPARK_Mode is On, then N can also be a variable reference, since
 160    --  SPARK requires the use of Elaborate_All for references to variables
 161    --  in other packages.
 162
 163    --  The Outer_Scope argument indicates whether this is an outer level
 164    --  call from Sem_Res (Outer_Scope set to Empty), or an internal recursive
 165    --  call (Outer_Scope set to entity of outermost call, see body). The flag
 166    --  In_Init_Proc should be set whenever the current context is a type
 167    --  init proc.
 168
 169    --  Note: this might better be called Check_Elab_Reference (to recognize
 170    --  the SPARK case), but we prefer to keep the original name, since this
 171    --  is primarily used for checking for calls that could generate an ABE).
 172
 173    procedure Check_Elab_Calls;
 174    --  Not all the processing for Check_Elab_Call can be done at the time
 175    --  of calls to Check_Elab_Call. This is because for internal calls, we
 176    --  need to wait to complete the check until all generic bodies have been
 177    --  instantiated. The Check_Elab_Calls procedure cleans up these waiting
 178    --  checks. It is called once after the completion of instantiation.
 179
 180    procedure Check_Elab_Instantiation
 181      (N           : Node_Id;
 182       Outer_Scope : Entity_Id := Empty);
 183    --  Check an instantiation for possible elaboration problems. N is an
 184    --  instantiation node (N_Package_Instantiation, N_Function_Instantiation,
 185    --  or N_Procedure_Instantiation), and Outer_Scope indicates if this is
 186    --  an outer level call from Sem_Ch12 (Outer_Scope set to Empty), or an
 187    --  internal recursive call (Outer_Scope set to scope of outermost call,
 188    --  see body for further details). The returned value is relevant only
 189    --  for an outer level call, and is set to False if an elaboration error
 190    --  is bound to occur on the instantiation, and True otherwise. This is
 191    --  used by the caller to signal that the body of the instance should
 192    --  not be generated (see detailed description in body).
 193
 194    procedure Check_Task_Activation (N : Node_Id);
 195    --  At the point at which tasks are activated in a package body, check
 196    --  that the bodies of the tasks are elaborated.
 197
 198 end Sem_Elab;