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) 1992-2019, 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 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_Aspects_On_Subprogram_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. Note: 54 -- component positions are normally adjusted as per AI95-0133, unless 55 -- -gnatd.p is used to restore original Ada 95 mode. 56 57 procedure Check_Record_Representation_Clause (N : Node_Id); 58 -- This procedure completes the analysis of a record representation clause 59 -- N. It is called at freeze time after adjustment of component clause bit 60 -- positions for possible non-standard bit order. In the case of Ada 2005 61 -- (machine scalar) mode, this adjustment can make substantial changes, so 62 -- some checks, in particular for component overlaps cannot be done at the 63 -- time the record representation clause is first seen, but must be delayed 64 -- till freeze time, and in particular is called after calling the above 65 -- procedure for adjusting record bit positions for reverse bit order. 66 67 procedure Initialize; 68 -- Initialize internal tables for new compilation 69 70 procedure Kill_Rep_Clause (N : Node_Id); 71 -- This procedure is called for a rep clause N when we are in -gnatI mode 72 -- (Ignore_Rep_Clauses). It replaces the node N with a null statement. This 73 -- is only called if Ignore_Rep_Clauses is True. 74 75 procedure Set_Enum_Esize (T : Entity_Id); 76 -- This routine sets the Esize field for an enumeration type T, based 77 -- on the current representation information available for T. Note that 78 -- the setting of the RM_Size field is not affected. This routine also 79 -- initializes the alignment field to zero. 80 81 function Minimum_Size 82 (T : Entity_Id; 83 Biased : Boolean := False) return Nat; 84 -- Given an elementary type, determines the minimum number of bits required 85 -- to represent all values of the type. This function may not be called 86 -- with any other types. If the flag Biased is set True, then the minimum 87 -- size calculation that biased representation is used in the case of a 88 -- discrete type, e.g. the range 7..8 gives a minimum size of 4 with 89 -- Biased set to False, and 1 with Biased set to True. Note that the 90 -- biased parameter only has an effect if the type is not biased, it 91 -- causes Minimum_Size to indicate the minimum size of an object with 92 -- the given type, of the size the type would have if it were biased. If 93 -- the type is already biased, then Minimum_Size returns the biased size, 94 -- regardless of the setting of Biased. Also, fixed-point types are never 95 -- biased in the current implementation. If the size is not known at 96 -- compile time, this function returns 0. 97 98 procedure Check_Constant_Address_Clause (Expr : Node_Id; U_Ent : Entity_Id); 99 -- Expr is an expression for an address clause. This procedure checks 100 -- that the expression is constant, in the limited sense that it is safe 101 -- to evaluate it at the point the object U_Ent is declared, rather than 102 -- at the point of the address clause. The condition for this to be true 103 -- is that the expression has no variables, no constants declared after 104 -- U_Ent, and no calls to non-pure functions. If this condition is not 105 -- met, then an appropriate error message is posted. This check is applied 106 -- at the point an object with an address clause is frozen, as well as for 107 -- address clauses for tasks and entries. 108 109 procedure Check_Size 110 (N : Node_Id; 111 T : Entity_Id; 112 Siz : Uint; 113 Biased : out Boolean); 114 -- Called when size Siz is specified for subtype T. This subprogram checks 115 -- that the size is appropriate, posting errors on node N as required. 116 -- This check is effective for elementary types and bit-packed arrays. 117 -- For other non-elementary types, a check is only made if an explicit 118 -- size has been given for the type (and the specified size must match). 119 -- The parameter Biased is set False if the size specified did not require 120 -- the use of biased representation, and True if biased representation 121 -- was required to meet the size requirement. Note that Biased is only 122 -- set if the type is not currently biased, but biasing it is the only 123 -- way to meet the requirement. If the type is currently biased, then 124 -- this biased size is used in the initial check, and Biased is False. 125 -- If the size is too small, and an error message is given, then both 126 -- Esize and RM_Size are reset to the allowed minimum value in T. 127 128 function Rep_Item_Too_Early (T : Entity_Id; N : Node_Id) return Boolean; 129 -- Called at start of processing a representation clause/pragma. Used to 130 -- check that the representation item is not being applied to an incomplete 131 -- type or to a generic formal type or a type derived from a generic formal 132 -- type. Returns False if no such error occurs. If this error does occur, 133 -- appropriate error messages are posted on node N, and True is returned. 134 135 generic 136 with procedure Replace_Type_Reference (N : Node_Id); 137 procedure Replace_Type_References_Generic (N : Node_Id; T : Entity_Id); 138 -- This is used to scan an expression for a predicate or invariant aspect 139 -- replacing occurrences of the name of the subtype to which the aspect 140 -- applies with appropriate references to the parameter of the predicate 141 -- function or invariant procedure. The procedure passed as a generic 142 -- parameter does the actual replacement of node N, which is either a 143 -- simple direct reference to T, or a selected component that represents 144 -- an appropriately qualified occurrence of T. 145 146 function Rep_Item_Too_Late 147 (T : Entity_Id; 148 N : Node_Id; 149 FOnly : Boolean := False) return Boolean; 150 -- Called at the start of processing a representation clause or a 151 -- representation pragma. Used to check that a representation item for 152 -- entity T does not appear too late (according to the rules in RM 13.1(9) 153 -- and RM 13.1(10)). N is the associated node, which in the pragma case 154 -- is the pragma or representation clause itself, used for placing error 155 -- messages if the item is too late. 156 -- 157 -- Fonly is a flag that causes only the freezing rule (para 9) to be 158 -- applied, and the tests of para 10 are skipped. This is appropriate for 159 -- both subtype related attributes (Alignment and Size) and for stream 160 -- attributes, which, although certainly not subtype related attributes, 161 -- clearly should not be subject to the para 10 restrictions (see 162 -- AI95-00137). Similarly, we also skip the para 10 restrictions for 163 -- the Storage_Size case where they also clearly do not apply, and for 164 -- Stream_Convert which is in the same category as the stream attributes. 165 -- 166 -- If the rep item is too late, an appropriate message is output and True 167 -- is returned, which is a signal that the caller should abandon processing 168 -- for the item. If the item is not too late, then False is returned, and 169 -- the caller can continue processing the item. 170 -- 171 -- If no error is detected, this call also as a side effect links the 172 -- representation item onto the head of the representation item chain 173 -- (referenced by the First_Rep_Item field of the entity). 174 -- 175 -- Note: Rep_Item_Too_Late must be called with the underlying type in the 176 -- case of a private or incomplete type. The protocol is to first check for 177 -- Rep_Item_Too_Early using the initial entity, then take the underlying 178 -- type, then call Rep_Item_Too_Late on the result. 179 -- 180 -- Note: Calls to Rep_Item_Too_Late are ignored for the case of attribute 181 -- definition clauses which have From_Aspect_Specification set. This is 182 -- because such clauses are linked on to the Rep_Item chain in procedure 183 -- Sem_Ch13.Analyze_Aspect_Specifications. See that procedure for details. 184 185 function Same_Representation (Typ1, Typ2 : Entity_Id) return Boolean; 186 -- Given two types, where the two types are related by possible derivation, 187 -- determines if the two types have the same representation, or different 188 -- representations, requiring the special processing for representation 189 -- change. A False result is possible only for array, enumeration or 190 -- record types. 191 192 procedure Validate_Compile_Time_Warning_Error (N : Node_Id); 193 -- N is a pragma Compile_Time_Error or Compile_Warning_Error whose boolean 194 -- expression is not known at compile time. This procedure makes an entry 195 -- in a table. The actual checking is performed by Validate_Compile_Time_ 196 -- Warning_Errors, which is invoked after calling the back end. 197 198 procedure Validate_Compile_Time_Warning_Errors; 199 -- This routine is called after calling the back end to validate pragmas 200 -- Compile_Time_Error and Compile_Time_Warning for size and alignment 201 -- appropriateness. The reason it is called that late is to take advantage 202 -- of any back-annotation of size and alignment performed by the back end. 203 204 procedure Validate_Unchecked_Conversion 205 (N : Node_Id; 206 Act_Unit : Entity_Id); 207 -- Validate a call to unchecked conversion. N is the node for the actual 208 -- instantiation, which is used only for error messages. Act_Unit is the 209 -- entity for the instantiation, from which the actual types etc. for this 210 -- instantiation can be determined. This procedure makes an entry in a 211 -- table and/or generates an N_Validate_Unchecked_Conversion node. The 212 -- actual checking is done in Validate_Unchecked_Conversions or in the 213 -- back end as required. 214 215 procedure Validate_Unchecked_Conversions; 216 -- This routine is called after calling the back end to validate unchecked 217 -- conversions for size and alignment appropriateness. The reason it is 218 -- called that late is to take advantage of any back-annotation of size 219 -- and alignment performed by the back end. 220 221 procedure Validate_Address_Clauses; 222 -- This is called after the back end has been called (and thus after the 223 -- alignments of objects have been back annotated). It goes through the 224 -- table of saved address clauses checking for suspicious alignments and 225 -- if necessary issuing warnings. 226 227 procedure Validate_Independence; 228 -- This is called after the back end has been called (and thus after the 229 -- layout of components has been back annotated). It goes through the 230 -- table of saved pragma Independent[_Component] entries, checking that 231 -- independence can be achieved, and if necessary issuing error messages. 232 233 ------------------------------------- 234 -- Table for Validate_Independence -- 235 ------------------------------------- 236 237 -- If a legal pragma Independent or Independent_Components is given for 238 -- an entity, then an entry is made in this table, to be checked by a 239 -- call to Validate_Independence after back annotation of layout is done. 240 241 type Independence_Check_Record is record 242 N : Node_Id; 243 -- The pragma Independent or Independent_Components 244 245 E : Entity_Id; 246 -- The entity to which it applies 247 end record; 248 249 package Independence_Checks is new Table.Table ( 250 Table_Component_Type => Independence_Check_Record, 251 Table_Index_Type => Int, 252 Table_Low_Bound => 1, 253 Table_Initial => 20, 254 Table_Increment => 200, 255 Table_Name => "Independence_Checks"); 256 257 ----------------------------------- 258 -- Handling of Aspect Visibility -- 259 ----------------------------------- 260 261 -- The visibility of aspects is tricky. First, the visibility is delayed 262 -- to the freeze point. This is not too complicated, what we do is simply 263 -- to leave the aspect "laying in wait" for the freeze point, and at that 264 -- point materialize and analyze the corresponding attribute definition 265 -- clause or pragma. There is some special processing for preconditions 266 -- and postonditions, where the pragmas themselves deal with the required 267 -- delay, but basically the approach is the same, delay analysis of the 268 -- expression to the freeze point. 269 270 -- Much harder is the requirement for diagnosing cases in which an early 271 -- freeze causes a change in visibility. Consider: 272 273 -- package AspectVis is 274 -- R_Size : constant Integer := 32; 275 -- 276 -- package Inner is 277 -- type R is new Integer with 278 -- Size => R_Size; 279 -- F : R; -- freezes 280 -- R_Size : constant Integer := 64; 281 -- S : constant Integer := R'Size; -- 32 not 64 282 -- end Inner; 283 -- end AspectVis; 284 285 -- Here the 32 not 64 shows what would be expected if this program were 286 -- legal, since the evaluation of R_Size has to be done at the freeze 287 -- point and gets the outer definition not the inner one. 288 289 -- But the language rule requires this program to be diagnosed as illegal 290 -- because the visibility changes between the freeze point and the end of 291 -- the declarative region. 292 293 -- To meet this requirement, we first note that the Expression field of the 294 -- N_Aspect_Specification node holds the raw unanalyzed expression, which 295 -- will get used in processing the aspect. At the time of analyzing the 296 -- N_Aspect_Specification node, we create a complete copy of the expression 297 -- and store it in the entity field of the Identifier (an odd usage, but 298 -- the identifier is not used except to identify the aspect, so its Entity 299 -- field is otherwise unused, and we are short of room in the node). 300 301 -- This copy stays unanalyzed up to the freeze point, where we analyze the 302 -- resulting pragma or attribute definition clause, except that in the 303 -- case of invariants and predicates, we mark occurrences of the subtype 304 -- name as having the entity of the subprogram parameter, so that they 305 -- will not cause trouble in the following steps. 306 307 -- Then at the freeze point, we create another copy of this unanalyzed 308 -- expression. By this time we no longer need the Expression field for 309 -- other purposes, so we can store it there. Now we have two copies of 310 -- the original unanalyzed expression. One of them gets preanalyzed at 311 -- the freeze point to capture the visibility at the freeze point. 312 313 -- Now when we hit the freeze all at the end of the declarative part, if 314 -- we come across a frozen entity with delayed aspects, we still have one 315 -- copy of the unanalyzed expression available in the node, and we again 316 -- do a preanalysis using that copy and the visibility at the end of the 317 -- declarative part. Now we have two preanalyzed expression (preanalysis 318 -- is good enough, since we are only interested in referenced entities). 319 -- One captures the visibility at the freeze point, the other captures the 320 -- visibility at the end of the declarative part. We see if the entities 321 -- in these two expressions are the same, by seeing if the two expressions 322 -- are fully conformant, and if not, issue appropriate error messages. 323 324 -- Quite an awkward approach, but this is an awkard requirement 325 326 procedure Analyze_Aspects_At_Freeze_Point (E : Entity_Id); 327 -- Analyze all the delayed aspects for entity E at freezing point. This 328 -- includes dealing with inheriting delayed aspects from the parent type 329 -- in the case where a derived type is frozen. 330 331 procedure Check_Aspect_At_Freeze_Point (ASN : Node_Id); 332 -- Performs the processing described above at the freeze point, ASN is the 333 -- N_Aspect_Specification node for the aspect. 334 335 procedure Check_Aspect_At_End_Of_Declarations (ASN : Node_Id); 336 -- Performs the processing described above at the freeze all point, and 337 -- issues appropriate error messages if the visibility has indeed changed. 338 -- Again, ASN is the N_Aspect_Specification node for the aspect. 339 340 procedure Inherit_Aspects_At_Freeze_Point (Typ : Entity_Id); 341 -- Given an entity Typ that denotes a derived type or a subtype, this 342 -- routine performs the inheritance of aspects at the freeze point. 343 344 procedure Resolve_Aspect_Expressions (E : Entity_Id); 345 -- Name resolution of an aspect expression happens at the end of the 346 -- current declarative part or at the freeze point for the entity, 347 -- whichever comes first. For declarations in the visible part of a 348 -- package, name resolution takes place before analysis of the private 349 -- part even though the freeze point of the entity may appear later. 350 351 procedure Validate_Iterable_Aspect (Typ : Entity_Id; ASN : Node_Id); 352 -- For SPARK 2014 formal containers. The expression has the form of an 353 -- aggregate, and each entry must denote a function with the proper syntax 354 -- for First, Next, and Has_Element. Optionally an Element primitive may 355 -- also be defined. 356 357 procedure Install_Discriminants (E : Entity_Id); 358 -- Make visible the discriminants of type entity E 359 360 procedure Uninstall_Discriminants (E : Entity_Id); 361 -- Remove visibility to the discriminants of type entity E 362 363end Sem_Ch13; 364