gcc/ada/contracts.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                            C O N T R A C T S                             --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --          Copyright (C) 2015-2023, 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 that perform analysis and expansion of
  27 --  various contracts.
  28
  29 with Types; use Types;
  30
  31 package Contracts is
  32
  33    procedure Add_Contract_Item (Prag : Node_Id; Id : Entity_Id);
  34    --  Add pragma Prag to the contract of a constant, entry, entry family,
  35    --  [generic] package, package body, protected unit, [generic] subprogram,
  36    --  subprogram body, variable, task unit, or type denoted by Id.
  37    --  The following are valid pragmas:
  38    --
  39    --    Abstract_State
  40    --    Always_Terminates
  41    --    Async_Readers
  42    --    Async_Writers
  43    --    Attach_Handler
  44    --    Constant_After_Elaboration
  45    --    Contract_Cases
  46    --    Depends
  47    --    Effective_Reads
  48    --    Effective_Writes
  49    --    Exceptional_Cases
  50    --    Extensions_Visible
  51    --    Global
  52    --    Initial_Condition
  53    --    Initializes
  54    --    Interrupt_Handler
  55    --    No_Caching
  56    --    Part_Of
  57    --    Postcondition
  58    --    Precondition
  59    --    Refined_Depends
  60    --    Refined_Global
  61    --    Refined_Post
  62    --    Refined_States
  63    --    Side_Effects
  64    --    Subprogram_Variant
  65    --    Test_Case
  66    --    Volatile_Function
  67
  68    procedure Analyze_Contracts (L : List_Id);
  69    --  Analyze the contracts of all eligible constructs found in list L
  70
  71    procedure Analyze_Pragmas_In_Declarations (Body_Id : Entity_Id);
  72    --  Perform early analysis of pragmas at the top of a given subprogram's
  73    --  declarations.
  74    --
  75    --  The purpose of this is to analyze contract-related pragmas for later
  76    --  processing, but also to handle other such pragmas before these
  77    --  declarations get moved to an internal wrapper as part of contract
  78    --  expansion. For example, pragmas Inline, Ghost, Volatile all need to
  79    --  apply directly to the subprogram and not be moved to a wrapper.
  80
  81    procedure Analyze_Entry_Or_Subprogram_Body_Contract (Body_Id : Entity_Id);
  82    --  Analyze all delayed pragmas chained on the contract of entry or
  83    --  subprogram body Body_Id as if they appeared at the end of a declarative
  84    --  region. Pragmas in question are:
  85    --
  86    --    Always_Terminates  (stand alone subprogram body)
  87    --    Contract_Cases     (stand alone subprogram body)
  88    --    Depends            (stand alone subprogram body)
  89    --    Exceptional_Cases  (stand alone subprogram body)
  90    --    Global             (stand alone subprogram body)
  91    --    Postcondition      (stand alone subprogram body)
  92    --    Precondition       (stand alone subprogram body)
  93    --    Refined_Depends
  94    --    Refined_Global
  95    --    Refined_Post
  96    --    Subprogram_Variant (stand alone subprogram body)
  97    --    Test_Case          (stand alone subprogram body)
  98
  99    procedure Analyze_Entry_Or_Subprogram_Contract
 100      (Subp_Id   : Entity_Id;
 101       Freeze_Id : Entity_Id := Empty);
 102    --  Analyze all delayed pragmas chained on the contract of entry or
 103    --  subprogram Subp_Id as if they appeared at the end of a declarative
 104    --  region. The pragmas in question are:
 105    --
 106    --    Always_Terminates
 107    --    Contract_Cases
 108    --    Depends
 109    --    Exceptional_Cases
 110    --    Global
 111    --    Postcondition
 112    --    Precondition
 113    --    Subprogram_Variant
 114    --    Test_Case
 115    --
 116    --  Freeze_Id is the entity of a [generic] package body or a [generic]
 117    --  subprogram body which "freezes" the contract of Subp_Id.
 118
 119    procedure Analyze_Object_Contract
 120      (Obj_Id    : Entity_Id;
 121       Freeze_Id : Entity_Id := Empty);
 122    --  Analyze all delayed pragmas chained on the contract of object Obj_Id as
 123    --  if they appeared at the end of the declarative region. The pragmas to be
 124    --  considered are:
 125    --
 126    --    Async_Readers
 127    --    Async_Writers
 128    --    Depends           (single concurrent object)
 129    --    Effective_Reads
 130    --    Effective_Writes
 131    --    Global            (single concurrent object)
 132    --    Part_Of
 133    --
 134    --  Freeze_Id is the entity of a [generic] package body or a [generic]
 135    --  subprogram body which "freezes" the contract of Obj_Id.
 136
 137    procedure Analyze_Type_Contract (Type_Id : Entity_Id);
 138    --  Analyze all delayed pragmas chained on the contract of object Obj_Id as
 139    --  if they appeared at the end of the declarative region. The pragmas to be
 140    --  considered are:
 141    --
 142    --    Async_Readers
 143    --    Async_Writers
 144    --    Effective_Reads
 145    --    Effective_Writes
 146    --    Postcondition
 147    --    Precondition
 148    --
 149    --  In the case of a protected or task type, there will also be
 150    --  a call to Analyze_Protected_Contract or Analyze_Task_Contract.
 151
 152    procedure Analyze_Package_Body_Contract
 153      (Body_Id   : Entity_Id;
 154       Freeze_Id : Entity_Id := Empty);
 155    --  Analyze all delayed pragmas chained on the contract of package body
 156    --  Body_Id as if they appeared at the end of a declarative region. The
 157    --  pragmas that are considered are:
 158    --
 159    --    Refined_State
 160    --
 161    --  Freeze_Id is the entity of a [generic] package body or a [generic]
 162    --  subprogram body which "freezes" the contract of Body_Id.
 163
 164    procedure Analyze_Package_Contract (Pack_Id : Entity_Id);
 165    --  Analyze all delayed pragmas chained on the contract of package Pack_Id
 166    --  as if they appeared at the end of a declarative region. The pragmas
 167    --  that are considered are:
 168    --
 169    --    Initial_Condition
 170    --    Initializes
 171
 172    procedure Analyze_Protected_Contract (Prot_Id : Entity_Id);
 173    --  Analyze all delayed pragmas chained on the contract of protected unit
 174    --  Prot_Id if they appeared at the end of a declarative region. Currently
 175    --  there are no such pragmas.
 176
 177    procedure Analyze_Subprogram_Body_Stub_Contract (Stub_Id : Entity_Id);
 178    --  Analyze all delayed pragmas chained on the contract of subprogram body
 179    --  stub Stub_Id as if they appeared at the end of a declarative region. The
 180    --  pragmas in question are:
 181    --
 182    --    Always_Terminates
 183    --    Contract_Cases
 184    --    Depends
 185    --    Exceptional_Cases
 186    --    Global
 187    --    Postcondition
 188    --    Precondition
 189    --    Refined_Depends
 190    --    Refined_Global
 191    --    Refined_Post
 192    --    Subprogram_Variant
 193    --    Test_Case
 194
 195    procedure Analyze_Task_Contract (Task_Id : Entity_Id);
 196    --  Analyze all delayed pragmas chained on the contract of task unit Task_Id
 197    --  as if they appeared at the end of a declarative region. The pragmas in
 198    --  question are:
 199    --
 200    --    Depends
 201    --    Global
 202
 203    procedure Build_Entry_Contract_Wrapper (E : Entity_Id; Decl : Node_Id);
 204    --  Build the body of a wrapper procedure for an entry or entry family that
 205    --  has contract cases, preconditions, or postconditions, and add it to the
 206    --  freeze actions of the related synchronized type.
 207    --
 208    --  The body first verifies the preconditions and case guards of the
 209    --  contract cases, then invokes the entry [family], and finally verifies
 210    --  the postconditions and the consequences of the contract cases. E denotes
 211    --  the entry family. Decl denotes the declaration of the enclosing
 212    --  synchronized type.
 213
 214    procedure Create_Generic_Contract (Unit : Node_Id);
 215    --  Create a contract node for a generic package, generic subprogram, or a
 216    --  generic body denoted by Unit by collecting all source contract-related
 217    --  pragmas in the contract of the unit.
 218
 219    procedure Freeze_Previous_Contracts (Body_Decl : Node_Id);
 220    --  Freeze the contracts of all source constructs found in the declarative
 221    --  list which contains entry, package, protected, subprogram, or task body
 222    --  denoted by Body_Decl. In addition, freeze the contract of the nearest
 223    --  enclosing package body.
 224
 225    procedure Inherit_Subprogram_Contract
 226      (Subp      : Entity_Id;
 227       From_Subp : Entity_Id);
 228    --  Inherit relevant contract items from source subprogram From_Subp. Subp
 229    --  denotes the destination subprogram. The inherited items are:
 230    --    Extensions_Visible
 231    --    Side_Effects
 232    --  ??? it would be nice if this routine handles Pre'Class and Post'Class
 233
 234    procedure Instantiate_Subprogram_Contract (Templ : Node_Id; L : List_Id);
 235    --  Instantiate all source pragmas found in the contract of the generic
 236    --  subprogram declaration template denoted by Templ. The instantiated
 237    --  pragmas are added to list L.
 238
 239    procedure Make_Class_Precondition_Subps
 240      (Subp_Id         : Entity_Id;
 241       Late_Overriding : Boolean := False);
 242    --  Build helpers that at run time evaluate statically and dynamically the
 243    --  class-wide preconditions of Subp_Id; build also the indirect-call
 244    --  wrapper (ICW) required to check class-wide preconditions when the
 245    --  subprogram is invoked through an access-to-subprogram, or when it
 246    --  overrides an inherited class-wide precondition (see AI12-0195-1).
 247    --  Late_Overriding enables special handling required for late-overriding
 248    --  subprograms.
 249    --
 250    --  For example, if we have a subprogram with the following profile:
 251    --
 252    --     procedure Prim (Obj : TagTyp; <additional formals>)
 253    --       with Pre'Class => F1 (Obj) and F2(Obj)
 254    --
 255    --  We build the following helper that evaluates statically the class-wide
 256    --  precondition:
 257    --
 258    --    function PrimSP (Obj : TagTyp) return Boolean is
 259    --    begin
 260    --       return F1 (Obj) and F2(Obj);
 261    --    end PrimSP;
 262    --
 263    --   ... and the following helper that evaluates dynamically the class-wide
 264    --   precondition:
 265    --
 266    --    function PrimDP (Obj : TagTyp'Class; ...) return Boolean is
 267    --    begin
 268    --       return F1 (Obj) and F2(Obj);
 269    --    end PrimSP;
 270    --
 271    --   ... and the following indirect-call wrapper (ICW) that is used by the
 272    --   code generated by the compiler for indirect calls:
 273    --
 274    --    procedure PrimICW (Obj : TagTyp; <additional formals> is
 275    --    begin
 276    --       if not PrimSP (Obj) then
 277    --          $raise_assert_failure ("failed precondition in call at ...");
 278    --       end if;
 279    --
 280    --       Prim (Obj, ...);
 281    --    end Prim;
 282
 283    procedure Merge_Class_Conditions (Spec_Id : Entity_Id);
 284    --  Merge and preanalyze all class-wide conditions of Spec_Id (class-wide
 285    --  preconditions merged with operator or-else; class-wide postconditions
 286    --  merged with operator and-then). Ignored pre/postconditions are also
 287    --  merged since, although they are not required to generate code, their
 288    --  preanalysis is required to perform semantic checks. Resulting merged
 289    --  expressions are later installed by the expander in helper subprograms
 290    --  which are invoked from the caller side; they are also used to build
 291    --  the dispatch-table wrapper (DTW), if required.
 292
 293    procedure Preanalyze_Class_Conditions (Spec_Id : Entity_Id);
 294    --  Preanalyze class-wide pre-/postconditions of the given subprogram
 295    --  specification.
 296
 297    procedure Process_Class_Conditions_At_Freeze_Point (Typ : Entity_Id);
 298    --  Merge, preanalyze, and check class-wide pre/postconditions of Typ
 299    --  primitives.
 300
 301    procedure Save_Global_References_In_Contract
 302      (Templ  : Node_Id;
 303       Gen_Id : Entity_Id);
 304    --  Save all global references found within the aspect specifications and
 305    --  the contract-related source pragmas assocated with generic template
 306    --  Templ. Gen_Id denotes the entity of the analyzed generic copy.
 307
 308 end Contracts;