1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1992-2010, Free Software Foundation, Inc. --
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. --
21 -- GNAT was originally developed by the GNAT team at New York University. --
22 -- Extensive contributions were provided by Ada Core Technologies Inc. --
24 ------------------------------------------------------------------------------
27 with Types; use Types;
28 with Uintp; use Uintp;
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);
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.
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).
49 procedure Build_Invariant_Procedure (Typ : Entity_Id; N : Node_Id);
50 -- Typ is a private type with invariants (indicated by Has_Invariants being
51 -- set for Typ, indicating the presence of pragma Invariant entries on the
52 -- rep chain, note that Invariant aspects have already been converted to
53 -- pragma Invariant), then this procedure builds the spec and body for the
54 -- corresponding Invariant procedure, inserting them at appropriate points
55 -- in the package specification N. Invariant_Procedure is set for Typ. Note
56 -- that this procedure is called at the end of processing the declarations
57 -- in the visible part (i.e. the right point for visibility analysis of
58 -- the invariant expression).
60 procedure Check_Record_Representation_Clause (N : Node_Id);
61 -- This procedure completes the analysis of a record representation clause
62 -- N. It is called at freeze time after adjustment of component clause bit
63 -- positions for possible non-standard bit order. In the case of Ada 2005
64 -- (machine scalar) mode, this adjustment can make substantial changes, so
65 -- some checks, in particular for component overlaps cannot be done at the
66 -- time the record representation clause is first seen, but must be delayed
67 -- till freeze time, and in particular is called after calling the above
68 -- procedure for adjusting record bit positions for reverse bit order.
71 -- Initialize internal tables for new compilation
73 procedure Set_Enum_Esize (T : Entity_Id);
74 -- This routine sets the Esize field for an enumeration type T, based
75 -- on the current representation information available for T. Note that
76 -- the setting of the RM_Size field is not affected. This routine also
77 -- initializes the alignment field to zero.
81 Biased : Boolean := False) return Nat;
82 -- Given an elementary type, determines the minimum number of bits required
83 -- to represent all values of the type. This function may not be called
84 -- with any other types. If the flag Biased is set True, then the minimum
85 -- size calculation that biased representation is used in the case of a
86 -- discrete type, e.g. the range 7..8 gives a minimum size of 4 with
87 -- Biased set to False, and 1 with Biased set to True. Note that the
88 -- biased parameter only has an effect if the type is not biased, it
89 -- causes Minimum_Size to indicate the minimum size of an object with
90 -- the given type, of the size the type would have if it were biased. If
91 -- the type is already biased, then Minimum_Size returns the biased size,
92 -- regardless of the setting of Biased. Also, fixed-point types are never
93 -- biased in the current implementation. If the size is not known at
94 -- compile time, this function returns 0.
96 procedure Check_Constant_Address_Clause (Expr : Node_Id; U_Ent : Entity_Id);
97 -- Expr is an expression for an address clause. This procedure checks
98 -- that the expression is constant, in the limited sense that it is safe
99 -- to evaluate it at the point the object U_Ent is declared, rather than
100 -- at the point of the address clause. The condition for this to be true
101 -- is that the expression has no variables, no constants declared after
102 -- U_Ent, and no calls to non-pure functions. If this condition is not
103 -- met, then an appropriate error message is posted. This check is applied
104 -- at the point an object with an address clause is frozen, as well as for
105 -- address clauses for tasks and entries.
111 Biased : out Boolean);
112 -- Called when size Siz is specified for subtype T. This subprogram checks
113 -- that the size is appropriate, posting errors on node N as required.
114 -- This check is effective for elementary types and bit-packed arrays.
115 -- For other non-elementary types, a check is only made if an explicit
116 -- size has been given for the type (and the specified size must match).
117 -- The parameter Biased is set False if the size specified did not require
118 -- the use of biased representation, and True if biased representation
119 -- was required to meet the size requirement. Note that Biased is only
120 -- set if the type is not currently biased, but biasing it is the only
121 -- way to meet the requirement. If the type is currently biased, then
122 -- this biased size is used in the initial check, and Biased is False.
123 -- If the size is too small, and an error message is given, then both
124 -- Esize and RM_Size are reset to the allowed minimum value in T.
126 function Rep_Item_Too_Early (T : Entity_Id; N : Node_Id) return Boolean;
127 -- Called at the start of processing a representation clause or a
128 -- representation pragma. Used to check that the representation item
129 -- is not being applied to an incomplete type or to a generic formal
130 -- type or a type derived from a generic formal type. Returns False if
131 -- no such error occurs. If this error does occur, appropriate error
132 -- messages are posted on node N, and True is returned.
134 function Rep_Item_Too_Late
137 FOnly : Boolean := False) return Boolean;
138 -- Called at the start of processing a representation clause or a
139 -- representation pragma. Used to check that a representation item
140 -- for entity T does not appear too late (according to the rules in
141 -- RM 13.1(9) and RM 13.1(10)). N is the associated node, which in
142 -- the pragma case is the pragma or representation clause itself, used
143 -- for placing error messages if the item is too late.
145 -- Fonly is a flag that causes only the freezing rule (para 9) to be
146 -- applied, and the tests of para 10 are skipped. This is appropriate
147 -- for both subtype related attributes (Alignment and Size) and for
148 -- stream attributes, which, although certainly not subtype related
149 -- attributes, clearly should not be subject to the para 10 restrictions
150 -- (see AI95-00137). Similarly, we also skip the para 10 restrictions for
151 -- the Storage_Size case where they also clearly do not apply, and for
152 -- Stream_Convert which is in the same category as the stream attributes.
154 -- If the rep item is too late, an appropriate message is output and
155 -- True is returned, which is a signal that the caller should abandon
156 -- processing for the item. If the item is not too late, then False
157 -- is returned, and the caller can continue processing the item.
159 -- If no error is detected, this call also as a side effect links the
160 -- representation item onto the head of the representation item chain
161 -- (referenced by the First_Rep_Item field of the entity).
163 -- Note: Rep_Item_Too_Late must be called with the underlying type in
164 -- the case of a private or incomplete type. The protocol is to first
165 -- check for Rep_Item_Too_Early using the initial entity, then take the
166 -- underlying type, then call Rep_Item_Too_Late on the result.
168 -- Note: Calls to Rep_Item_Too_Late are ignored for the case of attribute
169 -- definition clauses which have From_Aspect_Specification set. This is
170 -- because such clauses are linked on to the Rep_Item chain in procedure
171 -- Sem_Ch13.Analyze_Aspect_Specifications. See that procedure for details.
173 function Same_Representation (Typ1, Typ2 : Entity_Id) return Boolean;
174 -- Given two types, where the two types are related by possible derivation,
175 -- determines if the two types have the same representation, or different
176 -- representations, requiring the special processing for representation
177 -- change. A False result is possible only for array, enumeration or
180 procedure Validate_Unchecked_Conversion
182 Act_Unit : Entity_Id);
183 -- Validate a call to unchecked conversion. N is the node for the actual
184 -- instantiation, which is used only for error messages. Act_Unit is the
185 -- entity for the instantiation, from which the actual types etc. for this
186 -- instantiation can be determined. This procedure makes an entry in a
187 -- table and/or generates an N_Validate_Unchecked_Conversion node. The
188 -- actual checking is done in Validate_Unchecked_Conversions or in the
189 -- back end as required.
191 procedure Validate_Unchecked_Conversions;
192 -- This routine is called after calling the backend to validate unchecked
193 -- conversions for size and alignment appropriateness. The reason it is
194 -- called that late is to take advantage of any back-annotation of size
195 -- and alignment performed by the backend.
197 procedure Validate_Address_Clauses;
198 -- This is called after the back end has been called (and thus after the
199 -- alignments of objects have been back annotated). It goes through the
200 -- table of saved address clauses checking for suspicious alignments and
201 -- if necessary issuing warnings.
203 procedure Validate_Independence;
204 -- This is called after the back end has been called (and thus after the
205 -- layout of components has been back annotated). It goes through the
206 -- table of saved pragma Independent[_Component] entries, checking that
207 -- independence can be achieved, and if necessary issuing error messages.
209 -------------------------------------
210 -- Table for Validate_Independence --
211 -------------------------------------
213 -- If a legal pragma Independent or Independent_Components is given for
214 -- an entity, then an entry is made in this table, to be checked by a
215 -- call to Validate_Independence after back annotation of layout is done.
217 type Independence_Check_Record is record
219 -- The pragma Independent or Independent_Components
222 -- The entity to which it applies
225 package Independence_Checks is new Table.Table (
226 Table_Component_Type => Independence_Check_Record,
227 Table_Index_Type => Int,
228 Table_Low_Bound => 1,
230 Table_Increment => 200,
231 Table_Name => "Independence_Checks");
233 -----------------------------------
234 -- Handling of Aspect Visibility --
235 -----------------------------------
237 -- The visibility of aspects is tricky. First, the visibility is delayed
238 -- to the freeze point. This is not too complicated, what we do is simply
239 -- to leave the aspect "laying in wait" for the freeze point, and at that
240 -- point materialize and analye the corresponding attribute definition
241 -- clause or pragma. There is some special processing for preconditions
242 -- and postonditions, where the pragmas themselves deal with the required
243 -- delay, but basically the approach is the same, delay analysis of the
244 -- expression to the freeze point.
246 -- Much harder is the requirement for diagnosing cases in which an early
247 -- freeze causes a change in visibility. Consider:
249 -- package AspectVis is
250 -- R_Size : constant Integer := 32;
253 -- type R is new Integer with
256 -- R_Size : constant Integer := 64;
257 -- S : constant Integer := R'Size; -- 32 not 64
261 -- Here the 32 not 64 shows what would be expected if this program were
262 -- legal, since the evaluation of R_Size has to be done at the freeze
263 -- point and gets the outer definition not the inner one.
265 -- But the language rule requires this program to be diagnosed as illegal
266 -- because the visibility changes between the freeze point and the end of
267 -- the declarative region.
269 -- To meet this requirement, we first note that the Expression field of the
270 -- N_Aspect_Specification node holds the raw unanalyzed expression, which
271 -- will get used in processing the aspect. At the time of analyzing the
272 -- N_Aspect_Specification node, we create a complete copy of the expression
273 -- and store it in the entity field of the Identifier (an odd usage, but
274 -- the identifier is not used except to identify the aspect, so its Entity
275 -- field is otherwise unused, and we are short of room in the node).
277 -- This copy stays unanalyzed up to the freeze point, where we analyze the
278 -- resulting pragma or attribute definition clause, except that in the
279 -- case of invariants and predicates, we mark occurrences of the subtype
280 -- name as having the entity of the subprogram parameter, so that they
281 -- will not cause trouble in the following steps.
283 -- Then at the freeze point, we create another copy of this unanalyzed
284 -- expression. By this time we no longer need the Expression field for
285 -- other purposes, so we can store it there. Now we have two copies of
286 -- the original unanalyzed expression. One of them gets preanalyzed at
287 -- the freeze point to capture the visibility at the freeze point.
289 -- Now when we hit the freeze all at the end of the declarative part, if
290 -- we come across a frozen entity with delayed aspects, we still have one
291 -- copy of the unanalyzed expression available in the node, and we again
292 -- do a preanalysis using that copy and the visibility at the end of the
293 -- declarative part. Now we have two preanalyzed expression (preanalysis
294 -- is good enough, since we are only interested in referenced entities).
295 -- One captures the visibility at the freeze point, the other captures the
296 -- visibility at the end of the declarative part. We see if the entities
297 -- in these two expressions are the same, by seeing if the two expressions
298 -- are fully conformant, and if not, issue appropriate error messages.
300 -- Quite an awkward procedure, but this is an awkard requirement!
302 procedure Check_Aspect_At_Freeze_Point (ASN : Node_Id);
303 -- Performs the processing described above at the freeze point, ASN is the
304 -- N_Aspect_Specification node for the aspect.
306 procedure Check_Aspect_At_End_Of_Declarations (ASN : Node_Id);
307 -- Performs the processing described above at the freeze all point, and
308 -- issues appropriate error messages if the visibility has indeed changed.
309 -- Again, ASN is the N_Aspect_Specification node for the aspect.
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