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) 1992-2012, 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_Record_Representation_Clause (N : Node_Id); 37 procedure Analyze_Code_Statement (N : Node_Id); 38 39 procedure Analyze_Aspect_Specifications (N : Node_Id; E : Entity_Id); 40 -- This procedure is called to analyze aspect specifications for node N. E 41 -- is the corresponding entity declared by the declaration node N. Callers 42 -- should check that Has_Aspects (N) is True before calling this routine. 43 44 procedure Adjust_Record_For_Reverse_Bit_Order (R : Entity_Id); 45 -- Called from Freeze where R is a record entity for which reverse bit 46 -- order is specified and there is at least one component clause. Adjusts 47 -- component positions according to either Ada 95 or Ada 2005 (AI-133). 48 49 function Build_Invariant_Procedure_Declaration 50 (Typ : Entity_Id) return Node_Id; 51 -- If a type declaration has a specified invariant aspect, build the 52 -- declaration for the procedure at once, so that calls to it can be 53 -- generated before the body of the invariant procedure is built. This 54 -- is needed in the presence of public expression functions that return 55 -- the type in question. 56 57 procedure Build_Invariant_Procedure (Typ : Entity_Id; N : Node_Id); 58 -- Typ is a private type with invariants (indicated by Has_Invariants being 59 -- set for Typ, indicating the presence of pragma Invariant entries on the 60 -- rep chain, note that Invariant aspects have already been converted to 61 -- pragma Invariant), then this procedure builds the spec and body for the 62 -- corresponding Invariant procedure, inserting them at appropriate points 63 -- in the package specification N. Invariant_Procedure is set for Typ. Note 64 -- that this procedure is called at the end of processing the declarations 65 -- in the visible part (i.e. the right point for visibility analysis of 66 -- the invariant expression). 67 68 procedure Check_Record_Representation_Clause (N : Node_Id); 69 -- This procedure completes the analysis of a record representation clause 70 -- N. It is called at freeze time after adjustment of component clause bit 71 -- positions for possible non-standard bit order. In the case of Ada 2005 72 -- (machine scalar) mode, this adjustment can make substantial changes, so 73 -- some checks, in particular for component overlaps cannot be done at the 74 -- time the record representation clause is first seen, but must be delayed 75 -- till freeze time, and in particular is called after calling the above 76 -- procedure for adjusting record bit positions for reverse bit order. 77 78 procedure Initialize; 79 -- Initialize internal tables for new compilation 80 81 procedure Set_Enum_Esize (T : Entity_Id); 82 -- This routine sets the Esize field for an enumeration type T, based 83 -- on the current representation information available for T. Note that 84 -- the setting of the RM_Size field is not affected. This routine also 85 -- initializes the alignment field to zero. 86 87 function Minimum_Size 88 (T : Entity_Id; 89 Biased : Boolean := False) return Nat; 90 -- Given an elementary type, determines the minimum number of bits required 91 -- to represent all values of the type. This function may not be called 92 -- with any other types. If the flag Biased is set True, then the minimum 93 -- size calculation that biased representation is used in the case of a 94 -- discrete type, e.g. the range 7..8 gives a minimum size of 4 with 95 -- Biased set to False, and 1 with Biased set to True. Note that the 96 -- biased parameter only has an effect if the type is not biased, it 97 -- causes Minimum_Size to indicate the minimum size of an object with 98 -- the given type, of the size the type would have if it were biased. If 99 -- the type is already biased, then Minimum_Size returns the biased size, 100 -- regardless of the setting of Biased. Also, fixed-point types are never 101 -- biased in the current implementation. If the size is not known at 102 -- compile time, this function returns 0. 103 104 procedure Check_Constant_Address_Clause (Expr : Node_Id; U_Ent : Entity_Id); 105 -- Expr is an expression for an address clause. This procedure checks 106 -- that the expression is constant, in the limited sense that it is safe 107 -- to evaluate it at the point the object U_Ent is declared, rather than 108 -- at the point of the address clause. The condition for this to be true 109 -- is that the expression has no variables, no constants declared after 110 -- U_Ent, and no calls to non-pure functions. If this condition is not 111 -- met, then an appropriate error message is posted. This check is applied 112 -- at the point an object with an address clause is frozen, as well as for 113 -- address clauses for tasks and entries. 114 115 procedure Check_Size 116 (N : Node_Id; 117 T : Entity_Id; 118 Siz : Uint; 119 Biased : out Boolean); 120 -- Called when size Siz is specified for subtype T. This subprogram checks 121 -- that the size is appropriate, posting errors on node N as required. 122 -- This check is effective for elementary types and bit-packed arrays. 123 -- For other non-elementary types, a check is only made if an explicit 124 -- size has been given for the type (and the specified size must match). 125 -- The parameter Biased is set False if the size specified did not require 126 -- the use of biased representation, and True if biased representation 127 -- was required to meet the size requirement. Note that Biased is only 128 -- set if the type is not currently biased, but biasing it is the only 129 -- way to meet the requirement. If the type is currently biased, then 130 -- this biased size is used in the initial check, and Biased is False. 131 -- If the size is too small, and an error message is given, then both 132 -- Esize and RM_Size are reset to the allowed minimum value in T. 133 134 function Rep_Item_Too_Early (T : Entity_Id; N : Node_Id) return Boolean; 135 -- Called at the start of processing a representation clause or a 136 -- representation pragma. Used to check that the representation item 137 -- is not being applied to an incomplete type or to a generic formal 138 -- type or a type derived from a generic formal type. Returns False if 139 -- no such error occurs. If this error does occur, appropriate error 140 -- messages are posted on node N, and True is returned. 141 142 function Rep_Item_Too_Late 143 (T : Entity_Id; 144 N : Node_Id; 145 FOnly : Boolean := False) return Boolean; 146 -- Called at the start of processing a representation clause or a 147 -- representation pragma. Used to check that a representation item 148 -- for entity T does not appear too late (according to the rules in 149 -- RM 13.1(9) and RM 13.1(10)). N is the associated node, which in 150 -- the pragma case is the pragma or representation clause itself, used 151 -- for placing error messages if the item is too late. 152 -- 153 -- Fonly is a flag that causes only the freezing rule (para 9) to be 154 -- applied, and the tests of para 10 are skipped. This is appropriate 155 -- for both subtype related attributes (Alignment and Size) and for 156 -- stream attributes, which, although certainly not subtype related 157 -- attributes, clearly should not be subject to the para 10 restrictions 158 -- (see AI95-00137). Similarly, we also skip the para 10 restrictions for 159 -- the Storage_Size case where they also clearly do not apply, and for 160 -- Stream_Convert which is in the same category as the stream attributes. 161 -- 162 -- If the rep item is too late, an appropriate message is output and 163 -- True is returned, which is a signal that the caller should abandon 164 -- processing for the item. If the item is not too late, then False 165 -- is returned, and the caller can continue processing the item. 166 -- 167 -- If no error is detected, this call also as a side effect links the 168 -- representation item onto the head of the representation item chain 169 -- (referenced by the First_Rep_Item field of the entity). 170 -- 171 -- Note: Rep_Item_Too_Late must be called with the underlying type in 172 -- the case of a private or incomplete type. The protocol is to first 173 -- check for Rep_Item_Too_Early using the initial entity, then take the 174 -- underlying type, then call Rep_Item_Too_Late on the result. 175 -- 176 -- Note: Calls to Rep_Item_Too_Late are ignored for the case of attribute 177 -- definition clauses which have From_Aspect_Specification set. This is 178 -- because such clauses are linked on to the Rep_Item chain in procedure 179 -- Sem_Ch13.Analyze_Aspect_Specifications. See that procedure for details. 180 181 function Same_Representation (Typ1, Typ2 : Entity_Id) return Boolean; 182 -- Given two types, where the two types are related by possible derivation, 183 -- determines if the two types have the same representation, or different 184 -- representations, requiring the special processing for representation 185 -- change. A False result is possible only for array, enumeration or 186 -- record types. 187 188 procedure Validate_Unchecked_Conversion 189 (N : Node_Id; 190 Act_Unit : Entity_Id); 191 -- Validate a call to unchecked conversion. N is the node for the actual 192 -- instantiation, which is used only for error messages. Act_Unit is the 193 -- entity for the instantiation, from which the actual types etc. for this 194 -- instantiation can be determined. This procedure makes an entry in a 195 -- table and/or generates an N_Validate_Unchecked_Conversion node. The 196 -- actual checking is done in Validate_Unchecked_Conversions or in the 197 -- back end as required. 198 199 procedure Validate_Unchecked_Conversions; 200 -- This routine is called after calling the backend to validate unchecked 201 -- conversions for size and alignment appropriateness. The reason it is 202 -- called that late is to take advantage of any back-annotation of size 203 -- and alignment performed by the backend. 204 205 procedure Validate_Address_Clauses; 206 -- This is called after the back end has been called (and thus after the 207 -- alignments of objects have been back annotated). It goes through the 208 -- table of saved address clauses checking for suspicious alignments and 209 -- if necessary issuing warnings. 210 211 procedure Validate_Independence; 212 -- This is called after the back end has been called (and thus after the 213 -- layout of components has been back annotated). It goes through the 214 -- table of saved pragma Independent[_Component] entries, checking that 215 -- independence can be achieved, and if necessary issuing error messages. 216 217 ------------------------------------- 218 -- Table for Validate_Independence -- 219 ------------------------------------- 220 221 -- If a legal pragma Independent or Independent_Components is given for 222 -- an entity, then an entry is made in this table, to be checked by a 223 -- call to Validate_Independence after back annotation of layout is done. 224 225 type Independence_Check_Record is record 226 N : Node_Id; 227 -- The pragma Independent or Independent_Components 228 229 E : Entity_Id; 230 -- The entity to which it applies 231 end record; 232 233 package Independence_Checks is new Table.Table ( 234 Table_Component_Type => Independence_Check_Record, 235 Table_Index_Type => Int, 236 Table_Low_Bound => 1, 237 Table_Initial => 20, 238 Table_Increment => 200, 239 Table_Name => "Independence_Checks"); 240 241 ----------------------------------- 242 -- Handling of Aspect Visibility -- 243 ----------------------------------- 244 245 -- The visibility of aspects is tricky. First, the visibility is delayed 246 -- to the freeze point. This is not too complicated, what we do is simply 247 -- to leave the aspect "laying in wait" for the freeze point, and at that 248 -- point materialize and analyze the corresponding attribute definition 249 -- clause or pragma. There is some special processing for preconditions 250 -- and postonditions, where the pragmas themselves deal with the required 251 -- delay, but basically the approach is the same, delay analysis of the 252 -- expression to the freeze point. 253 254 -- Much harder is the requirement for diagnosing cases in which an early 255 -- freeze causes a change in visibility. Consider: 256 257 -- package AspectVis is 258 -- R_Size : constant Integer := 32; 259 -- 260 -- package Inner is 261 -- type R is new Integer with 262 -- Size => R_Size; 263 -- F : R; -- freezes 264 -- R_Size : constant Integer := 64; 265 -- S : constant Integer := R'Size; -- 32 not 64 266 -- end Inner; 267 -- end AspectVis; 268 269 -- Here the 32 not 64 shows what would be expected if this program were 270 -- legal, since the evaluation of R_Size has to be done at the freeze 271 -- point and gets the outer definition not the inner one. 272 273 -- But the language rule requires this program to be diagnosed as illegal 274 -- because the visibility changes between the freeze point and the end of 275 -- the declarative region. 276 277 -- To meet this requirement, we first note that the Expression field of the 278 -- N_Aspect_Specification node holds the raw unanalyzed expression, which 279 -- will get used in processing the aspect. At the time of analyzing the 280 -- N_Aspect_Specification node, we create a complete copy of the expression 281 -- and store it in the entity field of the Identifier (an odd usage, but 282 -- the identifier is not used except to identify the aspect, so its Entity 283 -- field is otherwise unused, and we are short of room in the node). 284 285 -- This copy stays unanalyzed up to the freeze point, where we analyze the 286 -- resulting pragma or attribute definition clause, except that in the 287 -- case of invariants and predicates, we mark occurrences of the subtype 288 -- name as having the entity of the subprogram parameter, so that they 289 -- will not cause trouble in the following steps. 290 291 -- Then at the freeze point, we create another copy of this unanalyzed 292 -- expression. By this time we no longer need the Expression field for 293 -- other purposes, so we can store it there. Now we have two copies of 294 -- the original unanalyzed expression. One of them gets preanalyzed at 295 -- the freeze point to capture the visibility at the freeze point. 296 297 -- Now when we hit the freeze all at the end of the declarative part, if 298 -- we come across a frozen entity with delayed aspects, we still have one 299 -- copy of the unanalyzed expression available in the node, and we again 300 -- do a preanalysis using that copy and the visibility at the end of the 301 -- declarative part. Now we have two preanalyzed expression (preanalysis 302 -- is good enough, since we are only interested in referenced entities). 303 -- One captures the visibility at the freeze point, the other captures the 304 -- visibility at the end of the declarative part. We see if the entities 305 -- in these two expressions are the same, by seeing if the two expressions 306 -- are fully conformant, and if not, issue appropriate error messages. 307 308 -- Quite an awkward procedure, but this is an awkard requirement! 309 310 procedure Analyze_Aspects_At_Freeze_Point (E : Entity_Id); 311 -- Analyze all the delayed aspects for entity E at freezing point 312 313 procedure Check_Aspect_At_Freeze_Point (ASN : Node_Id); 314 -- Performs the processing described above at the freeze point, ASN is the 315 -- N_Aspect_Specification node for the aspect. 316 317 procedure Check_Aspect_At_End_Of_Declarations (ASN : Node_Id); 318 -- Performs the processing described above at the freeze all point, and 319 -- issues appropriate error messages if the visibility has indeed changed. 320 -- Again, ASN is the N_Aspect_Specification node for the aspect. 321 322 procedure Inherit_Aspects_At_Freeze_Point (Typ : Entity_Id); 323 -- Given an entity Typ that denotes a derived type or a subtype, this 324 -- routine performs the inheritance of aspects at the freeze point. 325end Sem_Ch13; 326