1------------------------------------------------------------------------------ 2-- -- 3-- GNAT COMPILER COMPONENTS -- 4-- -- 5-- S E M _ C H 1 3 -- 6-- -- 7-- S p e c -- 8-- -- 9-- Copyright (C) 1992-2015, 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 Table; 27with Types; use Types; 28with Uintp; use Uintp; 29 30package Sem_Ch13 is 31 procedure Analyze_At_Clause (N : Node_Id); 32 procedure Analyze_Attribute_Definition_Clause (N : Node_Id); 33 procedure Analyze_Enumeration_Representation_Clause (N : Node_Id); 34 procedure Analyze_Free_Statement (N : Node_Id); 35 procedure Analyze_Freeze_Entity (N : Node_Id); 36 procedure Analyze_Freeze_Generic_Entity (N : Node_Id); 37 procedure Analyze_Record_Representation_Clause (N : Node_Id); 38 procedure Analyze_Code_Statement (N : Node_Id); 39 40 procedure Analyze_Aspect_Specifications (N : Node_Id; E : Entity_Id); 41 -- This procedure is called to analyze aspect specifications for node N. E 42 -- is the corresponding entity declared by the declaration node N. Callers 43 -- should check that Has_Aspects (N) is True before calling this routine. 44 45 procedure Analyze_Aspect_Specifications_On_Body_Or_Stub (N : Node_Id); 46 -- Analyze the aspect specifications of [generic] subprogram body or stub 47 -- N. Callers should check that Has_Aspects (N) is True before calling the 48 -- routine. This routine diagnoses misplaced aspects that should appear on 49 -- the initial declaration of N and offers suggestions for replacements. 50 51 procedure Adjust_Record_For_Reverse_Bit_Order (R : Entity_Id); 52 -- Called from Freeze where R is a record entity for which reverse bit 53 -- order is specified and there is at least one component clause. Adjusts 54 -- component positions according to either Ada 95 or Ada 2005 (AI-133). 55 56 function Build_Invariant_Procedure_Declaration 57 (Typ : Entity_Id) return Node_Id; 58 -- If a type declaration has a specified invariant aspect, build the 59 -- declaration for the procedure at once, so that calls to it can be 60 -- generated before the body of the invariant procedure is built. This 61 -- is needed in the presence of public expression functions that return 62 -- the type in question. 63 64 procedure Build_Invariant_Procedure (Typ : Entity_Id; N : Node_Id); 65 -- Typ is a private type with invariants (indicated by Has_Invariants being 66 -- set for Typ, indicating the presence of pragma Invariant entries on the 67 -- rep chain, note that Invariant aspects have already been converted to 68 -- pragma Invariant), then this procedure builds the spec and body for the 69 -- corresponding Invariant procedure, inserting them at appropriate points 70 -- in the package specification N. Invariant_Procedure is set for Typ. Note 71 -- that this procedure is called at the end of processing the declarations 72 -- in the visible part (i.e. the right point for visibility analysis of 73 -- the invariant expression). 74 75 procedure Check_Record_Representation_Clause (N : Node_Id); 76 -- This procedure completes the analysis of a record representation clause 77 -- N. It is called at freeze time after adjustment of component clause bit 78 -- positions for possible non-standard bit order. In the case of Ada 2005 79 -- (machine scalar) mode, this adjustment can make substantial changes, so 80 -- some checks, in particular for component overlaps cannot be done at the 81 -- time the record representation clause is first seen, but must be delayed 82 -- till freeze time, and in particular is called after calling the above 83 -- procedure for adjusting record bit positions for reverse bit order. 84 85 procedure Initialize; 86 -- Initialize internal tables for new compilation 87 88 procedure Kill_Rep_Clause (N : Node_Id); 89 -- This procedure is called for a rep clause N when we are in -gnatI mode 90 -- (Ignore_Rep_Clauses). It replaces the node N with a null statement. This 91 -- is only called if Ignore_Rep_Clauses is True. 92 93 procedure Set_Enum_Esize (T : Entity_Id); 94 -- This routine sets the Esize field for an enumeration type T, based 95 -- on the current representation information available for T. Note that 96 -- the setting of the RM_Size field is not affected. This routine also 97 -- initializes the alignment field to zero. 98 99 function Minimum_Size 100 (T : Entity_Id; 101 Biased : Boolean := False) return Nat; 102 -- Given an elementary type, determines the minimum number of bits required 103 -- to represent all values of the type. This function may not be called 104 -- with any other types. If the flag Biased is set True, then the minimum 105 -- size calculation that biased representation is used in the case of a 106 -- discrete type, e.g. the range 7..8 gives a minimum size of 4 with 107 -- Biased set to False, and 1 with Biased set to True. Note that the 108 -- biased parameter only has an effect if the type is not biased, it 109 -- causes Minimum_Size to indicate the minimum size of an object with 110 -- the given type, of the size the type would have if it were biased. If 111 -- the type is already biased, then Minimum_Size returns the biased size, 112 -- regardless of the setting of Biased. Also, fixed-point types are never 113 -- biased in the current implementation. If the size is not known at 114 -- compile time, this function returns 0. 115 116 procedure Check_Constant_Address_Clause (Expr : Node_Id; U_Ent : Entity_Id); 117 -- Expr is an expression for an address clause. This procedure checks 118 -- that the expression is constant, in the limited sense that it is safe 119 -- to evaluate it at the point the object U_Ent is declared, rather than 120 -- at the point of the address clause. The condition for this to be true 121 -- is that the expression has no variables, no constants declared after 122 -- U_Ent, and no calls to non-pure functions. If this condition is not 123 -- met, then an appropriate error message is posted. This check is applied 124 -- at the point an object with an address clause is frozen, as well as for 125 -- address clauses for tasks and entries. 126 127 procedure Check_Size 128 (N : Node_Id; 129 T : Entity_Id; 130 Siz : Uint; 131 Biased : out Boolean); 132 -- Called when size Siz is specified for subtype T. This subprogram checks 133 -- that the size is appropriate, posting errors on node N as required. 134 -- This check is effective for elementary types and bit-packed arrays. 135 -- For other non-elementary types, a check is only made if an explicit 136 -- size has been given for the type (and the specified size must match). 137 -- The parameter Biased is set False if the size specified did not require 138 -- the use of biased representation, and True if biased representation 139 -- was required to meet the size requirement. Note that Biased is only 140 -- set if the type is not currently biased, but biasing it is the only 141 -- way to meet the requirement. If the type is currently biased, then 142 -- this biased size is used in the initial check, and Biased is False. 143 -- If the size is too small, and an error message is given, then both 144 -- Esize and RM_Size are reset to the allowed minimum value in T. 145 146 function Rep_Item_Too_Early (T : Entity_Id; N : Node_Id) return Boolean; 147 -- Called at start of processing a representation clause/pragma. Used to 148 -- check that the representation item is not being applied to an incomplete 149 -- type or to a generic formal type or a type derived from a generic formal 150 -- type. Returns False if no such error occurs. If this error does occur, 151 -- appropriate error messages are posted on node N, and True is returned. 152 153 generic 154 with procedure Replace_Type_Reference (N : Node_Id); 155 procedure Replace_Type_References_Generic (N : Node_Id; T : Entity_Id); 156 -- This is used to scan an expression for a predicate or invariant aspect 157 -- replacing occurrences of the name of the subtype to which the aspect 158 -- applies with appropriate references to the parameter of the predicate 159 -- function or invariant procedure. The procedure passed as a generic 160 -- parameter does the actual replacement of node N, which is either a 161 -- simple direct reference to T, or a selected component that represents 162 -- an appropriately qualified occurrence of T. 163 164 function Rep_Item_Too_Late 165 (T : Entity_Id; 166 N : Node_Id; 167 FOnly : Boolean := False) return Boolean; 168 -- Called at the start of processing a representation clause or a 169 -- representation pragma. Used to check that a representation item for 170 -- entity T does not appear too late (according to the rules in RM 13.1(9) 171 -- and RM 13.1(10)). N is the associated node, which in the pragma case 172 -- is the pragma or representation clause itself, used for placing error 173 -- messages if the item is too late. 174 -- 175 -- Fonly is a flag that causes only the freezing rule (para 9) to be 176 -- applied, and the tests of para 10 are skipped. This is appropriate for 177 -- both subtype related attributes (Alignment and Size) and for stream 178 -- attributes, which, although certainly not subtype related attributes, 179 -- clearly should not be subject to the para 10 restrictions (see 180 -- AI95-00137). Similarly, we also skip the para 10 restrictions for 181 -- the Storage_Size case where they also clearly do not apply, and for 182 -- Stream_Convert which is in the same category as the stream attributes. 183 -- 184 -- If the rep item is too late, an appropriate message is output and True 185 -- is returned, which is a signal that the caller should abandon processing 186 -- for the item. If the item is not too late, then False is returned, and 187 -- the caller can continue processing the item. 188 -- 189 -- If no error is detected, this call also as a side effect links the 190 -- representation item onto the head of the representation item chain 191 -- (referenced by the First_Rep_Item field of the entity). 192 -- 193 -- Note: Rep_Item_Too_Late must be called with the underlying type in the 194 -- case of a private or incomplete type. The protocol is to first check for 195 -- Rep_Item_Too_Early using the initial entity, then take the underlying 196 -- type, then call Rep_Item_Too_Late on the result. 197 -- 198 -- Note: Calls to Rep_Item_Too_Late are ignored for the case of attribute 199 -- definition clauses which have From_Aspect_Specification set. This is 200 -- because such clauses are linked on to the Rep_Item chain in procedure 201 -- Sem_Ch13.Analyze_Aspect_Specifications. See that procedure for details. 202 203 function Same_Representation (Typ1, Typ2 : Entity_Id) return Boolean; 204 -- Given two types, where the two types are related by possible derivation, 205 -- determines if the two types have the same representation, or different 206 -- representations, requiring the special processing for representation 207 -- change. A False result is possible only for array, enumeration or 208 -- record types. 209 210 procedure Validate_Unchecked_Conversion 211 (N : Node_Id; 212 Act_Unit : Entity_Id); 213 -- Validate a call to unchecked conversion. N is the node for the actual 214 -- instantiation, which is used only for error messages. Act_Unit is the 215 -- entity for the instantiation, from which the actual types etc. for this 216 -- instantiation can be determined. This procedure makes an entry in a 217 -- table and/or generates an N_Validate_Unchecked_Conversion node. The 218 -- actual checking is done in Validate_Unchecked_Conversions or in the 219 -- back end as required. 220 221 procedure Validate_Unchecked_Conversions; 222 -- This routine is called after calling the backend to validate unchecked 223 -- conversions for size and alignment appropriateness. The reason it is 224 -- called that late is to take advantage of any back-annotation of size 225 -- and alignment performed by the backend. 226 227 procedure Validate_Address_Clauses; 228 -- This is called after the back end has been called (and thus after the 229 -- alignments of objects have been back annotated). It goes through the 230 -- table of saved address clauses checking for suspicious alignments and 231 -- if necessary issuing warnings. 232 233 procedure Validate_Independence; 234 -- This is called after the back end has been called (and thus after the 235 -- layout of components has been back annotated). It goes through the 236 -- table of saved pragma Independent[_Component] entries, checking that 237 -- independence can be achieved, and if necessary issuing error messages. 238 239 ------------------------------------- 240 -- Table for Validate_Independence -- 241 ------------------------------------- 242 243 -- If a legal pragma Independent or Independent_Components is given for 244 -- an entity, then an entry is made in this table, to be checked by a 245 -- call to Validate_Independence after back annotation of layout is done. 246 247 type Independence_Check_Record is record 248 N : Node_Id; 249 -- The pragma Independent or Independent_Components 250 251 E : Entity_Id; 252 -- The entity to which it applies 253 end record; 254 255 package Independence_Checks is new Table.Table ( 256 Table_Component_Type => Independence_Check_Record, 257 Table_Index_Type => Int, 258 Table_Low_Bound => 1, 259 Table_Initial => 20, 260 Table_Increment => 200, 261 Table_Name => "Independence_Checks"); 262 263 ----------------------------------- 264 -- Handling of Aspect Visibility -- 265 ----------------------------------- 266 267 -- The visibility of aspects is tricky. First, the visibility is delayed 268 -- to the freeze point. This is not too complicated, what we do is simply 269 -- to leave the aspect "laying in wait" for the freeze point, and at that 270 -- point materialize and analyze the corresponding attribute definition 271 -- clause or pragma. There is some special processing for preconditions 272 -- and postonditions, where the pragmas themselves deal with the required 273 -- delay, but basically the approach is the same, delay analysis of the 274 -- expression to the freeze point. 275 276 -- Much harder is the requirement for diagnosing cases in which an early 277 -- freeze causes a change in visibility. Consider: 278 279 -- package AspectVis is 280 -- R_Size : constant Integer := 32; 281 -- 282 -- package Inner is 283 -- type R is new Integer with 284 -- Size => R_Size; 285 -- F : R; -- freezes 286 -- R_Size : constant Integer := 64; 287 -- S : constant Integer := R'Size; -- 32 not 64 288 -- end Inner; 289 -- end AspectVis; 290 291 -- Here the 32 not 64 shows what would be expected if this program were 292 -- legal, since the evaluation of R_Size has to be done at the freeze 293 -- point and gets the outer definition not the inner one. 294 295 -- But the language rule requires this program to be diagnosed as illegal 296 -- because the visibility changes between the freeze point and the end of 297 -- the declarative region. 298 299 -- To meet this requirement, we first note that the Expression field of the 300 -- N_Aspect_Specification node holds the raw unanalyzed expression, which 301 -- will get used in processing the aspect. At the time of analyzing the 302 -- N_Aspect_Specification node, we create a complete copy of the expression 303 -- and store it in the entity field of the Identifier (an odd usage, but 304 -- the identifier is not used except to identify the aspect, so its Entity 305 -- field is otherwise unused, and we are short of room in the node). 306 307 -- This copy stays unanalyzed up to the freeze point, where we analyze the 308 -- resulting pragma or attribute definition clause, except that in the 309 -- case of invariants and predicates, we mark occurrences of the subtype 310 -- name as having the entity of the subprogram parameter, so that they 311 -- will not cause trouble in the following steps. 312 313 -- Then at the freeze point, we create another copy of this unanalyzed 314 -- expression. By this time we no longer need the Expression field for 315 -- other purposes, so we can store it there. Now we have two copies of 316 -- the original unanalyzed expression. One of them gets preanalyzed at 317 -- the freeze point to capture the visibility at the freeze point. 318 319 -- Now when we hit the freeze all at the end of the declarative part, if 320 -- we come across a frozen entity with delayed aspects, we still have one 321 -- copy of the unanalyzed expression available in the node, and we again 322 -- do a preanalysis using that copy and the visibility at the end of the 323 -- declarative part. Now we have two preanalyzed expression (preanalysis 324 -- is good enough, since we are only interested in referenced entities). 325 -- One captures the visibility at the freeze point, the other captures the 326 -- visibility at the end of the declarative part. We see if the entities 327 -- in these two expressions are the same, by seeing if the two expressions 328 -- are fully conformant, and if not, issue appropriate error messages. 329 330 -- Quite an awkward approach, but this is an awkard requirement 331 332 procedure Analyze_Aspects_At_Freeze_Point (E : Entity_Id); 333 -- Analyze all the delayed aspects for entity E at freezing point. This 334 -- includes dealing with inheriting delayed aspects from the parent type 335 -- in the case where a derived type is frozen. 336 337 procedure Check_Aspect_At_Freeze_Point (ASN : Node_Id); 338 -- Performs the processing described above at the freeze point, ASN is the 339 -- N_Aspect_Specification node for the aspect. 340 341 procedure Check_Aspect_At_End_Of_Declarations (ASN : Node_Id); 342 -- Performs the processing described above at the freeze all point, and 343 -- issues appropriate error messages if the visibility has indeed changed. 344 -- Again, ASN is the N_Aspect_Specification node for the aspect. 345 346 procedure Inherit_Aspects_At_Freeze_Point (Typ : Entity_Id); 347 -- Given an entity Typ that denotes a derived type or a subtype, this 348 -- routine performs the inheritance of aspects at the freeze point. 349 350 procedure Resolve_Aspect_Expressions (E : Entity_Id); 351 -- Name resolution of an aspect expression happens at the end of the 352 -- current declarative part or at the freeze point for the entity, 353 -- whichever comes first. For declarations in the visible part of a 354 -- package, name resolution takes place before analysis of the private 355 -- part even though the freeze point of the entity may appear later. 356 357 procedure Validate_Iterable_Aspect (Typ : Entity_Id; ASN : Node_Id); 358 -- For SPARK 2014 formal containers. The expression has the form of an 359 -- aggregate, and each entry must denote a function with the proper syntax 360 -- for First, Next, and Has_Element. Optionally an Element primitive may 361 -- also be defined. 362 363 ----------------------------------------------------------- 364 -- Visibility of Discriminants in Aspect Specifications -- 365 ----------------------------------------------------------- 366 367 -- The discriminants of a type are visible when analyzing the aspect 368 -- specifications of a type declaration or protected type declaration, 369 -- but not when analyzing those of a subtype declaration. The following 370 -- routines enforce this distinction. 371 372 procedure Install_Discriminants (E : Entity_Id); 373 -- Make visible the discriminants of type entity E 374 375 procedure Push_Scope_And_Install_Discriminants (E : Entity_Id); 376 -- Push scope E and makes visible the discriminants of type entity E if E 377 -- has discriminants and is not a subtype. 378 379 procedure Uninstall_Discriminants (E : Entity_Id); 380 -- Remove visibility to the discriminants of type entity E 381 382 procedure Uninstall_Discriminants_And_Pop_Scope (E : Entity_Id); 383 -- Remove visibility to the discriminants of type entity E and pop the 384 -- scope stack if E has discriminants and is not a subtype. 385 386end Sem_Ch13; 387