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1 ------------------------------------------------------------------------------
2 -- --
3 -- GNAT COMPILER COMPONENTS --
4 -- --
5 -- E X P _ C H 5 --
6 -- --
7 -- B o d y --
8 -- --
9 -- Copyright (C) 1992-2006, 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 2, 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 COPYING. If not, write --
19 -- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
20 -- Boston, MA 02110-1301, USA. --
21 -- --
22 -- GNAT was originally developed by the GNAT team at New York University. --
23 -- Extensive contributions were provided by Ada Core Technologies Inc. --
24 -- --
25 ------------------------------------------------------------------------------
66 -- ??? This flag is temporary. False causes the compiler to use the old
67 -- version of Analyze_Return_Statement; True, the new version, which does
68 -- not yet work. We probably want this to match the corresponding thing
69 -- in sem_ch6.adb.
72 -- Determine if the right hand side of the assignment N is a type
73 -- conversion which requires a change of representation. Called
74 -- only for the array and record cases.
77 -- N is an assignment which assigns an array value. This routine process
78 -- the various special cases and checks required for such assignments,
79 -- including change of representation. Rhs is normally simply the right
80 -- hand side of the assignment, except that if the right hand side is
81 -- a type conversion or a qualified expression, then the Rhs is the
82 -- actual expression inside any such type conversions or qualifications.
84 function Expand_Assign_Array_Loop
92 -- N is an assignment statement which assigns an array value. This routine
93 -- expands the assignment into a loop (or nested loops for the case of a
94 -- multi-dimensional array) to do the assignment component by component.
95 -- Larray and Rarray are the entities of the actual arrays on the left
96 -- hand and right hand sides. L_Type and R_Type are the types of these
97 -- arrays (which may not be the same, due to either sliding, or to a
98 -- change of representation case). Ndim is the number of dimensions and
99 -- the parameter Rev indicates if the loops run normally (Rev = False),
100 -- or reversed (Rev = True). The value returned is the constructed
101 -- loop statement. Auxiliary declarations are inserted before node N
102 -- using the standard Insert_Actions mechanism.
105 -- N is an assignment of a non-tagged record value. This routine handles
106 -- the case where the assignment must be made component by component,
107 -- either because the target is not byte aligned, or there is a change
108 -- of representation.
111 -- Called by Expand_Simple_Return in case we're returning from a procedure
112 -- body, entry body, accept statement, or extended returns statement.
113 -- Note that all non-function returns are simple return statements.
116 -- Expand simple return from function. Called by Expand_Simple_Return in
117 -- case we're returning from a function body.
120 -- Expansion for simple return statements. Calls either
121 -- Expand_Simple_Function_Return or Expand_Non_Function_Return.
124 -- Generate the necessary code for controlled and tagged assignment,
125 -- that is to say, finalization of the target before, adjustement of
126 -- the target after and save and restore of the tag and finalization
127 -- pointers which are not 'part of the value' and must not be changed
128 -- upon assignment. N is the original Assignment node.
131 -- Obsolete code to deal with functions for which
132 -- Function_Returns_With_DSP is True.
135 -- This function is used in processing the assignment of a record or
136 -- indexed component. The argument N is either the left hand or right
137 -- hand side of an assignment, and this function determines if there
138 -- is a record component reference where the record may be bit aligned
139 -- in a manner that causes trouble for the back end (see description
140 -- of Exp_Util.Component_May_Be_Bit_Aligned for further details).
142 ------------------------------
143 -- Change_Of_Representation --
144 ------------------------------
148 begin
149 return
151 and then
155 -------------------------
156 -- Expand_Assign_Array --
157 -------------------------
159 -- There are two issues here. First, do we let Gigi do a block move, or
160 -- do we expand out into a loop? Second, we need to set the two flags
161 -- Forwards_OK and Backwards_OK which show whether the block move (or
162 -- corresponding loops) can be legitimately done in a forwards (low to
163 -- high) or backwards (high to low) manner.
189 -- This switch is set to True if the array move must be done using
190 -- an explicit front end generated loop.
193 -- If the argument is an access to an array, and the assignment is
194 -- converted into a procedure call, apply explicit dereference.
197 -- Test if Exp is a reference to an array whose declaration has
198 -- an address clause, or it is a slice of such an array.
201 -- Test if Exp is a reference to an array which is either a formal
202 -- parameter or a slice of a formal parameter. These are the cases
203 -- where hidden aliasing can occur.
206 -- Determine if Exp is a reference to an array variable which is other
207 -- than an object defined in the current scope, or a slice of such
208 -- an object. Such objects can be aliased to parameters (unlike local
209 -- array references).
211 -----------------------
212 -- Apply_Dereference --
213 -----------------------
217 begin
225 ------------------------
226 -- Has_Address_Clause --
227 ------------------------
230 begin
231 return
234 or else
238 ---------------------
239 -- Is_Formal_Array --
240 ---------------------
243 begin
244 return
246 or else
250 ------------------------
251 -- Is_Non_Local_Array --
252 ------------------------
255 begin
262 -- Determine if Lhs, Rhs are formal arrays or nonlocal arrays
270 -- Start of processing for Expand_Assign_Array
272 begin
273 -- Deal with length check, note that the length check is done with
274 -- respect to the right hand side as given, not a possible underlying
275 -- renamed object, since this would generate incorrect extra checks.
279 -- We start by assuming that the move can be done in either
280 -- direction, i.e. that the two sides are completely disjoint.
285 -- Normally it is only the slice case that can lead to overlap,
286 -- and explicit checks for slices are made below. But there is
287 -- one case where the slice can be implicit and invisible to us
288 -- and that is the case where we have a one dimensional array,
289 -- and either both operands are parameters, or one is a parameter
290 -- and the other is a global variable. In this case the parameter
291 -- could be a slice that overlaps with the other parameter.
293 -- Check for the case of slices requiring an explicit loop. Normally
294 -- it is only the explicit slice cases that bother us, but in the
295 -- case of one dimensional arrays, parameters can be slices that
296 -- are passed by reference, so we can have aliasing for assignments
297 -- from one parameter to another, or assignments between parameters
298 -- and nonlocal variables. However, if the array subtype is a
299 -- constrained first subtype in the parameter case, then we don't
300 -- have to worry about overlap, since slice assignments aren't
301 -- possible (other than for a slice denoting the whole array).
303 -- Note: overlap is never possible if there is a change of
304 -- representation, so we can exclude this case.
307 and then not Crep
308 and then
310 or else
312 or else
314 and then
318 -- In the case of compiling for the Java Virtual Machine,
319 -- slices are always passed by making a copy, so we don't
320 -- have to worry about overlap. We also want to prevent
321 -- generation of "<" comparisons for array addresses,
322 -- since that's a meaningless operation on the JVM.
324 and then not Java_VM
325 then
329 -- Note: the bit-packed case is not worrisome here, since if
330 -- we have a slice passed as a parameter, it is always aligned
331 -- on a byte boundary, and if there are no explicit slices, the
332 -- assignment can be performed directly.
335 -- We certainly must use a loop for change of representation
336 -- and also we use the operand of the conversion on the right
337 -- hand side as the effective right hand side (the component
338 -- types must match in this situation).
345 -- We require a loop if the left side is possibly bit unaligned
348 or else
350 then
353 -- Arrays with controlled components are expanded into a loop
354 -- to force calls to adjust at the component level.
359 -- If object is atomic, we cannot tolerate a loop
362 or else
364 then
367 -- Loop is required if we have atomic components since we have to
368 -- be sure to do any accesses on an element by element basis.
374 then
377 -- Case where no slice is involved
381 -- The following code deals with the case of unconstrained bit
382 -- packed arrays. The problem is that the template for such
383 -- arrays contains the bounds of the actual source level array,
385 -- But the copy of an entire array requires the bounds of the
386 -- underlying array. It would be nice if the back end could take
387 -- care of this, but right now it does not know how, so if we
388 -- have such a type, then we expand out into a loop, which is
389 -- inefficient but works correctly. If we don't do this, we
390 -- get the wrong length computed for the array to be moved.
391 -- The two cases we need to worry about are:
393 -- Explicit deference of an unconstrained packed array type as
394 -- in the following example:
396 -- procedure C52 is
397 -- type BITS is array(INTEGER range <>) of BOOLEAN;
398 -- pragma PACK(BITS);
399 -- type A is access BITS;
400 -- P1,P2 : A;
401 -- begin
402 -- P1 := new BITS (1 .. 65_535);
403 -- P2 := new BITS (1 .. 65_535);
404 -- P2.ALL := P1.ALL;
405 -- end C52;
407 -- A formal parameter reference with an unconstrained bit
408 -- array type is the other case we need to worry about (here
409 -- we assume the same BITS type declared above):
411 -- procedure Write_All (File : out BITS; Contents : BITS);
412 -- begin
413 -- File.Storage := Contents;
414 -- end Write_All;
416 -- We expand to a loop in either of these two cases
418 -- Question for future thought. Another potentially more efficient
419 -- approach would be to create the actual subtype, and then do an
420 -- unchecked conversion to this actual subtype ???
425 -- Function to perform required test for the first case,
426 -- above (dereference of an unconstrained bit packed array)
428 -----------------------
429 -- Is_UBPA_Reference --
430 -----------------------
437 begin
441 then
450 else
452 return
457 else
462 -- Start of processing for Check_Unconstrained_Bit_Packed_Array
464 begin
466 or else
468 then
471 -- Here if we do not have the case of a reference to a bit
472 -- packed unconstrained array case. In this case gigi can
473 -- most certainly handle the assignment if a forwards move
474 -- is allowed.
476 -- (could it handle the backwards case also???)
483 -- The back end can always handle the assignment if the right side is a
484 -- string literal (note that overlap is definitely impossible in this
485 -- case). If the type is packed, a string literal is always converted
486 -- into aggregate, except in the case of a null slice, for which no
487 -- aggregate can be written. In that case, rewrite the assignment as a
488 -- null statement, a length check has already been emitted to verify
489 -- that the range of the left-hand side is empty.
491 -- Note that this code is not executed if we had an assignment of
492 -- a string literal to a non-bit aligned component of a record, a
493 -- case which cannot be handled by the backend
498 then
505 -- If either operand is bit packed, then we need a loop, since we
506 -- can't be sure that the slice is byte aligned. Similarly, if either
507 -- operand is a possibly unaligned slice, then we need a loop (since
508 -- the back end cannot handle unaligned slices).
514 then
517 -- If we are not bit-packed, and we have only one slice, then no
518 -- overlap is possible except in the parameter case, so we can let
519 -- the back end handle things.
527 -- If the right-hand side is a string literal, introduce a temporary
528 -- for it, for use in the generated loop that will follow.
531 declare
536 begin
537 Decl :=
549 -- Come here to complete the analysis
551 -- Loop_Required: Set to True if we know that a loop is required
552 -- regardless of overlap considerations.
554 -- Forwards_OK: Set to False if we already know that a forwards
555 -- move is not safe, else set to True.
557 -- Backwards_OK: Set to False if we already know that a backwards
558 -- move is not safe, else set to True
560 -- Our task at this stage is to complete the overlap analysis, which
561 -- can result in possibly setting Forwards_OK or Backwards_OK to
562 -- False, and then generating the final code, either by deciding
563 -- that it is OK after all to let Gigi handle it, or by generating
564 -- appropriate code in the front end.
566 declare
584 begin
585 -- Get the expressions for the arrays. If we are dealing with a
586 -- private type, then convert to the underlying type. We can do
587 -- direct assignments to an array that is a private type, but
588 -- we cannot assign to elements of the array without this extra
589 -- unchecked conversion.
593 else
597 Larray :=
598 Unchecked_Convert_To
605 else
609 Rarray :=
610 Unchecked_Convert_To
615 -- If both sides are slices, we must figure out whether
616 -- it is safe to do the move in one direction or the other
617 -- It is always safe if there is a change of representation
618 -- since obviously two arrays with different representations
619 -- cannot possibly overlap.
625 -- If both left and right hand arrays are entity names, and
626 -- refer to different entities, then we know that the move
627 -- is safe (the two storage areas are completely disjoint).
632 then
635 -- Otherwise, we assume the worst, which is that the two
636 -- arrays are the same array. There is no need to check if
637 -- we know that is the case, because if we don't know it,
638 -- we still have to assume it!
640 -- Generally if the same array is involved, then we have
641 -- an overlapping case. We will have to really assume the
642 -- worst (i.e. set neither of the OK flags) unless we can
643 -- determine the lower or upper bounds at compile time and
644 -- compare them.
646 else
662 -- If after that analysis, Forwards_OK is still True, and
663 -- Loop_Required is False, meaning that we have not discovered
664 -- some non-overlap reason for requiring a loop, then we can
665 -- still let gigi handle it.
670 else
672 -- Here is where a memmove would be appropriate ???
676 -- At this stage we have to generate an explicit loop, and
677 -- we have the following cases:
679 -- Forwards_OK = True
681 -- Rnn : right_index := right_index'First;
682 -- for Lnn in left-index loop
683 -- left (Lnn) := right (Rnn);
684 -- Rnn := right_index'Succ (Rnn);
685 -- end loop;
687 -- Note: the above code MUST be analyzed with checks off,
688 -- because otherwise the Succ could overflow. But in any
689 -- case this is more efficient!
691 -- Forwards_OK = False, Backwards_OK = True
693 -- Rnn : right_index := right_index'Last;
694 -- for Lnn in reverse left-index loop
695 -- left (Lnn) := right (Rnn);
696 -- Rnn := right_index'Pred (Rnn);
697 -- end loop;
699 -- Note: the above code MUST be analyzed with checks off,
700 -- because otherwise the Pred could overflow. But in any
701 -- case this is more efficient!
703 -- Forwards_OK = Backwards_OK = False
705 -- This only happens if we have the same array on each side. It is
706 -- possible to create situations using overlays that violate this,
707 -- but we simply do not promise to get this "right" in this case.
709 -- There are two possible subcases. If the No_Implicit_Conditionals
710 -- restriction is set, then we generate the following code:
712 -- declare
713 -- T : constant <operand-type> := rhs;
714 -- begin
715 -- lhs := T;
716 -- end;
718 -- If implicit conditionals are permitted, then we generate:
720 -- if Left_Lo <= Right_Lo then
721 -- <code for Forwards_OK = True above>
722 -- else
723 -- <code for Backwards_OK = True above>
724 -- end if;
726 -- Cases where either Forwards_OK or Backwards_OK is true
733 then
734 declare
739 begin
751 New_Occurrence_Of (
760 else
762 Expand_Assign_Array_Loop
767 -- Case of both are false with No_Implicit_Conditionals
770 declare
774 begin
781 Object_Definition =>
785 Handled_Statement_Sequence =>
793 -- Case of both are false with implicit conditionals allowed
795 else
796 -- Before we generate this code, we must ensure that the
797 -- left and right side array types are defined. They may
798 -- be itypes, and we cannot let them be defined inside the
799 -- if, since the first use in the then may not be executed.
804 -- We normally compare addresses to find out which way round
805 -- to do the loop, since this is realiable, and handles the
806 -- cases of parameters, conversions etc. But we can't do that
807 -- in the bit packed case or the Java VM case, because addresses
808 -- don't work there.
811 Condition :=
813 Left_Opnd =>
816 Prefix =>
818 Prefix =>
822 Prefix =>
823 New_Reference_To
828 Right_Opnd =>
831 Prefix =>
833 Prefix =>
837 Prefix =>
838 New_Reference_To
843 -- For the bit packed and Java VM cases we use the bounds.
844 -- That's OK, because we don't have to worry about parameters,
845 -- since they cannot cause overlap. Perhaps we should worry
846 -- about weird slice conversions ???
848 else
849 -- Copy the bounds and reset the Analyzed flag, because the
850 -- bounds of the index type itself may be universal, and must
851 -- must be reaanalyzed to acquire the proper type for Gigi.
858 Condition :=
868 then
870 -- Call TSS procedure for array assignment, passing the
871 -- the explicit bounds of right and left hand sides.
873 declare
878 begin
899 else
905 Expand_Assign_Array_Loop
910 Expand_Assign_Array_Loop
919 exception
924 ------------------------------
925 -- Expand_Assign_Array_Loop --
926 ------------------------------
928 -- The following is an example of the loop generated for the case of
929 -- a two-dimensional array:
931 -- declare
932 -- R2b : Tm1X1 := 1;
933 -- begin
934 -- for L1b in 1 .. 100 loop
935 -- declare
936 -- R4b : Tm1X2 := 1;
937 -- begin
938 -- for L3b in 1 .. 100 loop
939 -- vm1 (L1b, L3b) := vm2 (R2b, R4b);
940 -- R4b := Tm1X2'succ(R4b);
941 -- end loop;
942 -- end;
943 -- R2b := Tm1X1'succ(R2b);
944 -- end loop;
945 -- end;
947 -- Here Rev is False, and Tm1Xn are the subscript types for the right
948 -- hand side. The declarations of R2b and R4b are inserted before the
949 -- original assignment statement.
951 function Expand_Assign_Array_Loop
959 is
964 -- Entities used as subscripts on left and right sides
968 -- Left and right index types
975 begin
979 else
984 -- Setup index types and subscript entities
986 declare
990 begin
1011 -- Now construct the assignment statement
1013 declare
1017 begin
1023 Assign :=
1025 Name =>
1029 Expression =>
1034 -- We set assignment OK, since there are some cases, e.g. in object
1035 -- declarations, where we are actually assigning into a constant.
1036 -- If there really is an illegality, it was caught long before now,
1037 -- and was flagged when the original assignment was analyzed.
1041 -- Propagate the No_Ctrl_Actions flag to individual assignments
1046 -- Now construct the loop from the inside out, with the last subscript
1047 -- varying most rapidly. Note that Assign is first the raw assignment
1048 -- statement, and then subsequently the loop that wraps it up.
1051 Assign :=
1056 Object_Definition =>
1058 Expression =>
1063 Handled_Statement_Sequence =>
1067 Iteration_Scheme =>
1069 Loop_Parameter_Specification =>
1073 Discrete_Subtype_Definition =>
1077 Assign,
1081 Expression =>
1083 Prefix =>
1093 --------------------------
1094 -- Expand_Assign_Record --
1095 --------------------------
1097 -- The only processing required is in the change of representation
1098 -- case, where we must expand the assignment to a series of field
1099 -- by field assignments.
1105 begin
1106 -- If change of representation, then extract the real right hand
1107 -- side from the type conversion, and proceed with component-wise
1108 -- assignment, since the two types are not the same as far as the
1109 -- back end is concerned.
1114 -- If this may be a case of a large bit aligned component, then
1115 -- proceed with component-wise assignment, to avoid possible
1116 -- clobbering of other components sharing bits in the first or
1117 -- last byte of the component to be assigned.
1120 or
1122 then
1125 -- If neither condition met, then nothing special to do, the back end
1126 -- can handle assignment of the entire component as a single entity.
1128 else
1132 -- At this stage we know that we must do a component wise assignment
1134 declare
1142 function Find_Component
1145 -- Find the component with the given name in the underlying record
1146 -- declaration for Typ. We need to use the actual entity because
1147 -- the type may be private and resolution by identifier alone would
1148 -- fail.
1150 function Make_Component_List_Assign
1153 -- Returns a sequence of statements to assign the components that
1154 -- are referenced in the given component list. The flag U_U is
1155 -- used to force the usage of the inferred value of the variant
1156 -- part expression as the switch for the generated case statement.
1158 function Make_Field_Assign
1161 -- Given C, the entity for a discriminant or component, build an
1162 -- assignment for the corresponding field values. The flag U_U
1163 -- signals the presence of an Unchecked_Union and forces the usage
1164 -- of the inferred discriminant value of C as the right hand side
1165 -- of the assignment.
1168 -- Given CI, a component items list, construct series of statements
1169 -- for fieldwise assignment of the corresponding components.
1171 --------------------
1172 -- Find_Component --
1173 --------------------
1175 function Find_Component
1178 is
1182 begin
1195 --------------------------------
1196 -- Make_Component_List_Assign --
1197 --------------------------------
1199 function Make_Component_List_Assign
1202 is
1213 begin
1232 Statements =>
1237 -- If we have an Unchecked_Union, use the value of the inferred
1238 -- discriminant of the variant part expression as the switch
1239 -- for the case statement. The case statement may later be
1240 -- folded.
1243 Expr :=
1248 else
1249 Expr :=
1252 Selector_Name =>
1265 -----------------------
1266 -- Make_Field_Assign --
1267 -----------------------
1269 function Make_Field_Assign
1272 is
1276 begin
1277 -- In the case of an Unchecked_Union, use the discriminant
1278 -- constraint value as on the right hand side of the assignment.
1281 Expr :=
1285 else
1286 Expr :=
1292 A :=
1294 Name =>
1297 Selector_Name =>
1301 -- Set Assignment_OK, so discriminants can be assigned
1307 ------------------------
1308 -- Make_Field_Assigns --
1309 ------------------------
1315 begin
1320 Append_To
1330 -- Start of processing for Expand_Assign_Record
1332 begin
1333 -- Note that we use the base types for this processing. This results
1334 -- in some extra work in the constrained case, but the change of
1335 -- representation case is so unusual that it is not worth the effort.
1337 -- First copy the discriminants. This is done unconditionally. It
1338 -- is required in the unconstrained left side case, and also in the
1339 -- case where this assignment was constructed during the expansion
1340 -- of a type conversion (since initialization of discriminants is
1341 -- suppressed in this case). It is unnecessary but harmless in
1342 -- other cases.
1350 else
1358 -- We know the underlying type is a record, but its current view
1359 -- may be private. We must retrieve the usable record declaration.
1363 then
1365 else
1371 then
1376 else
1377 Insert_Actions
1387 -----------------------------------
1388 -- Expand_N_Assignment_Statement --
1389 -----------------------------------
1391 -- This procedure implements various cases where an assignment statement
1392 -- cannot just be passed on to the back end in untransformed state.
1401 begin
1402 -- Ada 2005 (AI-327): Handle assignment to priority of protected object
1404 -- Rewrite an assignment to X'Priority into a run-time call.
1406 -- For example: X'Priority := New_Prio_Expr;
1407 -- ...is expanded into Set_Ceiling (X._Object, New_Prio_Expr);
1409 -- Note that although X'Priority is notionally an object, it is quite
1410 -- deliberately not defined as an aliased object in the RM. This means
1411 -- that it works fine to rewrite it as a call, without having to worry
1412 -- about complications that would other arise from X'Priority'Access,
1413 -- which is illegal, because of the lack of aliasing.
1416 declare
1424 begin
1425 -- Handle chains of renamings
1431 loop
1435 -- The attribute Priority applied to protected objects has been
1436 -- previously expanded into calls to the Get_Ceiling run-time
1437 -- subprogram.
1441 or else
1443 then
1444 -- Look for the enclosing concurrent type
1453 -- Generate the first actual of the call
1460 Object_Parm :=
1462 Prefix =>
1464 Prefix => New_Reference_To
1465 (First_Entity
1467 Loc),
1468 Selector_Name =>
1472 -- Select the appropriate run-time call
1475 RT_Subprg_Name :=
1477 else
1478 RT_Subprg_Name :=
1482 Call :=
1485 Parameter_Associations =>
1496 -- First deal with generation of range check if required. For now we do
1497 -- this only for discrete types.
1501 then
1506 -- Check for a special case where a high level transformation is
1507 -- required. If we have either of:
1509 -- P.field := rhs;
1510 -- P (sub) := rhs;
1512 -- where P is a reference to a bit packed array, then we have to unwind
1513 -- the assignment. The exact meaning of being a reference to a bit
1514 -- packed array is as follows:
1516 -- An indexed component whose prefix is a bit packed array is a
1517 -- reference to a bit packed array.
1519 -- An indexed component or selected component whose prefix is a
1520 -- reference to a bit packed array is itself a reference ot a
1521 -- bit packed array.
1523 -- The required transformation is
1525 -- Tnn : prefix_type := P;
1526 -- Tnn.field := rhs;
1527 -- P := Tnn;
1529 -- or
1531 -- Tnn : prefix_type := P;
1532 -- Tnn (subscr) := rhs;
1533 -- P := Tnn;
1535 -- Since P is going to be evaluated more than once, any subscripts
1536 -- in P must have their evaluation forced.
1539 or else
1542 then
1543 declare
1550 begin
1551 -- Insert the post assignment first, because we want to copy
1552 -- the BPAR_Expr tree before it gets analyzed in the context
1553 -- of the pre assignment. Note that we do not analyze the
1554 -- post assignment yet (we cannot till we have completed the
1555 -- analysis of the pre assignment). As usual, the analysis
1556 -- of this post assignment will happen on its own when we
1557 -- "run into" it after finishing the current assignment.
1564 -- At this stage BPAR_Expr is a reference to a bit packed
1565 -- array where the reference was not expanded in the original
1566 -- tree, since it was on the left side of an assignment. But
1567 -- in the pre-assignment statement (the object definition),
1568 -- BPAR_Expr will end up on the right hand side, and must be
1569 -- reexpanded. To achieve this, we reset the analyzed flag
1570 -- of all selected and indexed components down to the actual
1571 -- indexed component for the packed array.
1574 loop
1578 or else
1580 then
1582 else
1587 -- Now we can insert and analyze the pre-assignment
1589 -- If the right-hand side requires a transient scope, it has
1590 -- already been placed on the stack. However, the declaration is
1591 -- inserted in the tree outside of this scope, and must reflect
1592 -- the proper scope for its variable. This awkward bit is forced
1593 -- by the stricter scope discipline imposed by GCC 2.97.
1595 declare
1597 Scope_Is_Transient
1600 begin
1612 Pop_Scope;
1616 -- Now fix up the original assignment and continue processing
1621 -- We do not need to reanalyze that assignment, and we do not need
1622 -- to worry about references to the temporary, but we do need to
1623 -- make sure that the temporary is not marked as a true constant
1624 -- since we now have a generate assignment to it!
1630 -- When we have the appropriate type of aggregate in the
1631 -- expression (it has been determined during analysis of the
1632 -- aggregate by setting the delay flag), let's perform in place
1633 -- assignment and thus avoid creating a temporay.
1642 -- Apply discriminant check if required. If Lhs is an access type
1643 -- to a designated type with discriminants, we must always check.
1647 -- Skip discriminant check if change of representation. Will be
1648 -- done when the change of representation is expanded out.
1654 -- If the type is private without discriminants, and the full type
1655 -- has discriminants (necessarily with defaults) a check may still be
1656 -- necessary if the Lhs is aliased. The private determinants must be
1657 -- visible to build the discriminant constraints.
1659 -- Only an explicit dereference that comes from source indicates
1660 -- aliasing. Access to formals of protected operations and entries
1661 -- create dereferences but are not semantic aliasings.
1667 then
1668 declare
1670 begin
1677 -- If the Lhs has a private type with unknown discriminants, it
1678 -- may have a full view with discriminants, but those are nameable
1679 -- only in the underlying type, so convert the Rhs to it before
1680 -- potential checking.
1684 then
1688 -- In the access type case, we need the same discriminant check,
1689 -- and also range checks if we have an access to constrained array.
1693 then
1696 -- Skip discriminant check if change of representation. Will be
1697 -- done when the change of representation is expanded out.
1711 declare
1715 begin
1716 C_Es :=
1717 Range_Check
1719 Target_Typ,
1722 Insert_Range_Checks
1724 N,
1725 Target_Typ,
1727 Lhs);
1732 -- Apply range check for access type case
1737 then
1739 Apply_Range_Check
1743 -- Ada 2005 (AI-231): Generate the run-time check
1748 then
1752 -- Case of assignment to a bit packed array element
1756 then
1760 -- Build-in-place function call case. Note that we're not yet doing
1761 -- build-in-place for user-written assignment statements; the
1762 -- assignment here came from can aggregate.
1766 then
1771 then
1776 begin
1777 -- In the controlled case, we need to make sure that function
1778 -- calls are evaluated before finalizing the target. In all
1779 -- cases, it makes the expansion easier if the side-effects
1780 -- are removed first.
1785 -- Avoid recursion in the mechanism
1789 -- If dispatching assignment, we need to dispatch to _assign
1793 -- If the type is tagged, we may as well use the predefined
1794 -- primitive assignment. This avoids inlining a lot of code
1795 -- and in the class-wide case, the assignment is replaced by
1796 -- dispatch call to _assign. Note that this cannot be done
1797 -- when discriminant checks are locally suppressed (as in
1798 -- extension aggregate expansions) because otherwise the
1799 -- discriminant check will be performed within the _assign
1800 -- call. It is also suppressed for assignmments created by the
1801 -- expander that correspond to initializations, where we do
1802 -- want to copy the tag (No_Ctrl_Actions flag set True).
1803 -- by the expander and we do not need to mess with tags ever
1804 -- (Expand_Ctrl_Actions flag is set True in this case).
1808 and then Expand_Ctrl_Actions
1810 then
1811 -- Fetch the primitive op _assign and proper type to call
1812 -- it. Because of possible conflits between private and
1813 -- full view the proper type is fetched directly from the
1814 -- operation profile.
1816 declare
1821 begin
1822 -- If the assignment is dispatching, make sure to use the
1823 -- proper type.
1831 -- In case of assignment to a class-wide tagged type, before
1832 -- the assignment we generate run-time check to ensure that
1833 -- the tag of the Target is covered by the tag of the source
1838 then
1841 Condition =>
1844 Name => New_Reference_To
1848 Prefix =>
1850 Selector_Name =>
1853 Prefix =>
1855 Selector_Name =>
1869 else
1872 -- We can't afford to have destructive Finalization Actions
1873 -- in the Self assignment case, so if the target and the
1874 -- source are not obviously different, code is generated to
1875 -- avoid the self assignment case
1876 --
1877 -- if lhs'address /= rhs'address then
1878 -- <code for controlled and/or tagged assignment>
1879 -- end if;
1882 and then Expand_Ctrl_Actions
1883 then
1886 Condition =>
1888 Left_Opnd =>
1893 Right_Opnd =>
1901 -- We need to set up an exception handler for implementing
1902 -- 7.6.1 (18). The remaining adjustments are tackled by the
1903 -- implementation of adjust for record_controllers (see
1904 -- s-finimp.adb)
1906 -- This is skipped if we have no finalization
1908 if Expand_Ctrl_Actions
1910 then
1913 Handled_Statement_Sequence =>
1918 Exception_Choices =>
1922 Reason =>
1923 PE_Finalize_Raised_Exception)
1924 ))))));
1930 Handled_Statement_Sequence =>
1933 -- If no restrictions on aborts, protect the whole assignement
1934 -- for controlled objects as per 9.8(11)
1937 and then Expand_Ctrl_Actions
1938 and then Abort_Allowed
1939 then
1940 declare
1942 New_Internal_Entity
1945 begin
1953 Expand_At_End_Handler
1958 -- N has been rewritten to a block statement for which it is
1959 -- known by construction that no checks are necessary: analyze
1960 -- it with all checks suppressed.
1966 -- Array types
1969 declare
1972 begin
1974 or else
1976 loop
1984 -- Record types
1990 -- Scalar types. This is where we perform the processing related
1991 -- to the requirements of (RM 13.9.1(9-11)) concerning the handling
1992 -- of invalid scalar values.
1996 -- Case where right side is known valid
2000 -- Here the right side is valid, so it is fine. The case to
2001 -- deal with is when the left side is a local variable reference
2002 -- whose value is not currently known to be valid. If this is
2003 -- the case, and the assignment appears in an unconditional
2004 -- context, then we can mark the left side as now being valid.
2009 then
2013 -- Case where right side may be invalid in the sense of the RM
2014 -- reference above. The RM does not require that we check for
2015 -- the validity on an assignment, but it does require that the
2016 -- assignment of an invalid value not cause erroneous behavior.
2018 -- The general approach in GNAT is to use the Is_Known_Valid flag
2019 -- to avoid the need for validity checking on assignments. However
2020 -- in some cases, we have to do validity checking in order to make
2021 -- sure that the setting of this flag is correct.
2023 else
2024 -- Validate right side if we are validating copies
2026 if Validity_Checks_On
2027 and then Validity_Check_Copies
2028 then
2029 -- Skip this if left hand side is an array or record component
2030 -- and elementary component validity checks are suppressed.
2033 or else
2035 and then not Validity_Check_Components
2036 then
2038 else
2042 -- We can propagate this to the left side where appropriate
2047 then
2051 -- Otherwise check to see what should be done
2053 -- If left side is a local variable, then we just set its
2054 -- flag to indicate that its value may no longer be valid,
2055 -- since we are copying a potentially invalid value.
2060 -- Check for case of a nonlocal variable on the left side
2061 -- which is currently known to be valid. In this case, we
2062 -- simply ensure that the right side is valid. We only play
2063 -- the game of copying validity status for local variables,
2064 -- since we are doing this statically, not by tracing the
2065 -- full flow graph.
2069 then
2070 -- Note that the Ensure_Valid call is ignored if the
2071 -- Validity_Checking mode is set to none so we do not
2072 -- need to worry about that case here.
2076 -- In all other cases, we can safely copy an invalid value
2077 -- without worrying about the status of the left side. Since
2078 -- it is not a variable reference it will not be considered
2079 -- as being known to be valid in any case.
2081 else
2087 -- Defend against invalid subscripts on left side if we are in
2088 -- standard validity checking mode. No need to do this if we
2089 -- are checking all subscripts.
2091 if Validity_Checks_On
2092 and then Validity_Check_Default
2093 and then not Validity_Check_Subscripts
2094 then
2098 exception
2103 ------------------------------
2104 -- Expand_N_Block_Statement --
2105 ------------------------------
2107 -- Encode entity names defined in block statement
2110 begin
2114 -----------------------------
2115 -- Expand_N_Case_Statement --
2116 -----------------------------
2127 begin
2128 -- Check for the situation where we know at compile time which
2129 -- branch will be taken
2134 -- Move the statements from this alternative after the case
2135 -- statement. They are already analyzed, so will be skipped
2136 -- by the analyzer.
2140 -- That leaves the case statement as a shell. So now we can kill all
2141 -- other alternatives in the case statement.
2145 declare
2148 begin
2149 -- Loop through case alternatives, skipping pragmas, and skipping
2150 -- the one alternative that we select (and therefore retain).
2156 then
2168 -- Here if the choice is not determined at compile time
2170 declare
2179 begin
2183 else
2187 -- First step is to worry about possible invalid argument. The RM
2188 -- requires (RM 5.4(13)) that if the result is invalid (e.g. it is
2189 -- outside the base range), then Constraint_Error must be raised.
2191 -- Case of validity check required (validity checks are on, the
2192 -- expression is not known to be valid, and the case statement
2193 -- comes from source -- no need to validity check internally
2194 -- generated case statements).
2200 -- If there is only a single alternative, just replace it with
2201 -- the sequence of statements since obviously that is what is
2202 -- going to be executed in all cases.
2207 -- We still need to evaluate the expression if it has any
2208 -- side effects.
2214 -- That leaves the case statement as a shell. The alternative
2215 -- that will be executed is reset to a null list. So now we can
2216 -- kill the entire case statement.
2223 -- An optimization. If there are only two alternatives, and only
2224 -- a single choice, then rewrite the whole case statement as an
2225 -- if statement, since this can result in susbequent optimizations.
2226 -- This helps not only with case statements in the source of a
2227 -- simple form, but also with generated code (discriminant check
2228 -- functions in particular)
2239 -- For TRUE, generate "expression", not expression = true
2243 then
2246 -- For FALSE, generate "expression" and switch then/else
2250 then
2255 -- For a range, generate "expression in range"
2263 then
2264 Cond :=
2269 -- For any other subexpression "expression = value"
2271 else
2272 Cond :=
2278 -- Now rewrite the case as an IF
2290 -- If the last alternative is not an Others choice, replace it
2291 -- with an N_Others_Choice. Note that we do not bother to call
2292 -- Analyze on the modified case statement, since it's only effect
2293 -- would be to compute the contents of the Others_Discrete_Choices
2294 -- which is not needed by the back end anyway.
2296 -- The reason we do this is that the back end always needs some
2297 -- default for a switch, so if we have not supplied one in the
2298 -- processing above for validity checking, then we need to
2299 -- supply one here.
2303 Set_Others_Discrete_Choices
2310 -----------------------------
2311 -- Expand_N_Exit_Statement --
2312 -----------------------------
2314 -- The only processing required is to deal with a possible C/Fortran
2315 -- boolean value used as the condition for the exit statement.
2318 begin
2322 ----------------------------------------
2323 -- Expand_N_Extended_Return_Statement --
2324 ----------------------------------------
2326 -- If there is a Handled_Statement_Sequence, we rewrite this:
2328 -- return Result : T := <expression> do
2329 -- <handled_seq_of_stms>
2330 -- end return;
2332 -- to be:
2334 -- declare
2335 -- Result : T := <expression>;
2336 -- begin
2337 -- <handled_seq_of_stms>
2338 -- return Result;
2339 -- end;
2341 -- Otherwise (no Handled_Statement_Sequence), we rewrite this:
2343 -- return Result : T := <expression>;
2345 -- to be:
2347 -- return <expression>;
2349 -- unless it's build-in-place or there's no <expression>, in which case
2350 -- we generate:
2352 -- declare
2353 -- Result : T := <expression>;
2354 -- begin
2355 -- return Result;
2356 -- end;
2358 -- Note that this case could have been written by the user as an extended
2359 -- return statement, or could have been transformed to this from a simple
2360 -- return statement.
2362 -- That is, we need to have a reified return object if there are statements
2363 -- (which might refer to it) or if we're doing build-in-place (so we can
2364 -- set its address to the final resting place -- but that key part is not
2365 -- yet implemented) or if there is no expression (in which case default
2366 -- initial values might need to be set).
2371 -- F must be of type E_Function or E_Generic_Function. Return True if it
2372 -- uses build-in-place for the result object. In Ada 95, this must be
2373 -- False for inherently limited result type. In Ada 2005, this must be
2374 -- True for inherently limited result type. For other types, we have a
2375 -- choice -- build-in-place is usually more efficient for large things,
2376 -- and less efficient for small things. However, we had better not use
2377 -- build-in-place if the Convention is other than Ada, because that
2378 -- would disturb mixed-language programs.
2379 --
2380 -- Note that for the non-inherently-limited cases, we must make the same
2381 -- decision for Ada 95 and 2005, so that mixed-dialect programs work.
2382 --
2383 -- ???This function will be needed when compiling the call sites;
2384 -- we will have to move it to a more global place.
2386 --------------------------------
2387 -- Is_Build_In_Place_Function --
2388 --------------------------------
2393 begin
2394 -- First, the cases that matter for correctness
2399 -- Note: If you have Convention (C) on an inherently limited
2400 -- type, you're on your own. That is, the C code will have to be
2401 -- carefully written to know about the Ada conventions.
2403 elsif
2405 or else
2407 then
2410 -- Second, the efficiency-related decisions. It would be obnoxiously
2411 -- inefficient to use build-in-place for elementary types. For
2412 -- composites, we could return False if the subtype is known to be
2413 -- small (<= one or two words?) but we don't bother with that yet.
2415 else
2420 ------------------------
2421 -- Local Declarations --
2422 ------------------------
2440 -- Start of processing for Expand_N_Extended_Return_Statement
2442 begin
2445 else
2452 or else Is_Build_In_Place
2454 then
2455 -- Build simple_return_statement that returns the return object
2457 Return_Stm :=
2462 Handled_Stm_Seq :=
2465 else
2466 Handled_Stm_Seq :=
2474 -- Case where we build a block
2477 Result :=
2484 -- Locate the implicit access parameter associated with the
2485 -- the caller-supplied return object and convert the return
2486 -- statement's return object declaration to a renaming of a
2487 -- dereference of the access parameter. If the return object's
2488 -- declaration includes an expression that has not already been
2489 -- expanded as separate assignments, then add an assignment
2490 -- statement to ensure the return object gets initialized.
2492 -- declare
2493 -- Result : T [:= <expression>];
2494 -- begin
2495 -- ...
2497 -- is converted to
2499 -- declare
2500 -- Result : T renames FuncRA.all;
2501 -- [Result := <expression;]
2502 -- begin
2503 -- ...
2505 declare
2515 begin
2516 -- Build-in-place results must be returned by reference
2520 -- Locate the implicit access parameter passed by the caller.
2521 -- It might be better to search for that with a symbol table
2522 -- lookup, but for now we traverse the extra actuals to find
2523 -- the access parameter (currently there can only be one).
2526 exit when
2531 -- ??? pragma Assert (Present (Obj_Acc_Formal));
2533 -- For now we only rewrite the object if we can locate the
2534 -- implicit access parameter. Normally there should be one
2535 -- if Build_In_Place is true, but at the moment it's only
2536 -- created in the more restrictive case of constrained
2537 -- inherently limited result subtypes. ???
2541 -- If the return object's declaration includes an expression
2542 -- and the declaration isn't marked as No_Initialization,
2543 -- then we need to generate an assignment to the object and
2544 -- insert it after the declaration before rewriting it as
2545 -- a renaming (otherwise we'll lose the initialization).
2549 then
2550 Init_Assignment :=
2557 -- ??? Should we be setting the parent of the expression
2558 -- here?
2559 -- Set_Parent
2560 -- (Expression (Init_Assignment), Init_Assignment);
2567 -- Replace the return object declaration with a renaming
2568 -- of a dereference of the implicit access formal.
2570 Obj_Acc_Deref :=
2578 Subtype_Mark => New_Occurrence_Of
2587 -- Case where we do not build a block
2589 else
2590 -- We're about to drop Return_Object_Declarations on the floor, so
2591 -- we need to insert it, in case it got expanded into useful code.
2595 -- Build simple_return_statement that returns the expression directly
2602 -- Set the flag to prevent infinite recursion
2610 -----------------------------
2611 -- Expand_N_Goto_Statement --
2612 -----------------------------
2614 -- Add poll before goto if polling active
2617 begin
2621 ---------------------------
2622 -- Expand_N_If_Statement --
2623 ---------------------------
2625 -- First we deal with the case of C and Fortran convention boolean
2626 -- values, with zero/non-zero semantics.
2628 -- Second, we deal with the obvious rewriting for the cases where the
2629 -- condition of the IF is known at compile time to be True or False.
2631 -- Third, we remove elsif parts which have non-empty Condition_Actions
2632 -- and rewrite as independent if statements. For example:
2634 -- if x then xs
2635 -- elsif y then ys
2636 -- ...
2637 -- end if;
2639 -- becomes
2640 --
2641 -- if x then xs
2642 -- else
2643 -- <<condition actions of y>>
2644 -- if y then ys
2645 -- ...
2646 -- end if;
2647 -- end if;
2649 -- This rewriting is needed if at least one elsif part has a non-empty
2650 -- Condition_Actions list. We also do the same processing if there is
2651 -- a constant condition in an elsif part (in conjunction with the first
2652 -- processing step mentioned above, for the recursive call made to deal
2653 -- with the created inner if, this deals with properly optimizing the
2654 -- cases of constant elsif conditions).
2662 begin
2665 -- The following loop deals with constant conditions for the IF. We
2666 -- need a loop because as we eliminate False conditions, we grab the
2667 -- first elsif condition and use it as the primary condition.
2671 -- If condition is True, we can simply rewrite the if statement
2672 -- now by replacing it by the series of then statements.
2676 -- All the else parts can be killed
2686 -- If condition is False, then we can delete the condition and
2687 -- the Then statements
2689 else
2690 -- We do not delete the condition if constant condition
2691 -- warnings are enabled, since otherwise we end up deleting
2692 -- the desired warning. Of course the backend will get rid
2693 -- of this True/False test anyway, so nothing is lost here.
2701 -- If there are no elsif statements, then we simply replace
2702 -- the entire if statement by the sequence of else statements.
2707 then
2710 else
2718 -- If there are elsif statements, the first of them becomes
2719 -- the if/then section of the rebuilt if statement This is
2720 -- the case where we loop to reprocess this copied condition.
2722 else
2728 -- Hed might have been captured as the condition determining
2729 -- the current value for an entity. Now it is detached from
2730 -- the tree, so a Current_Value pointer in the condition might
2731 -- need to be updated.
2742 -- Loop through elsif parts, dealing with constant conditions and
2743 -- possible expression actions that are present.
2750 -- If there are condition actions, then we rewrite the if
2751 -- statement as indicated above. We also do the same rewrite
2752 -- if the condition is True or False. The further processing
2753 -- of this constant condition is then done by the recursive
2754 -- call to expand the newly created if statement
2758 then
2759 -- Note this is not an implicit if statement, since it is
2760 -- part of an explicit if statement in the source (or of an
2761 -- implicit if statement that has already been tested).
2763 New_If :=
2770 -- Elsif parts for new if come from remaining elsif's of parent
2795 -- No special processing for that elsif part, move to next
2797 else
2803 -- Some more optimizations applicable if we still have an IF statement
2809 -- Another optimization, special cases that can be simplified
2811 -- if expression then
2812 -- return true;
2813 -- else
2814 -- return false;
2815 -- end if;
2817 -- can be changed to:
2819 -- return expression;
2821 -- and
2823 -- if expression then
2824 -- return false;
2825 -- else
2826 -- return true;
2827 -- end if;
2829 -- can be changed to:
2831 -- return not (expression);
2838 then
2839 declare
2843 begin
2845 and then
2847 then
2848 declare
2852 begin
2854 and then
2856 then
2859 then
2868 then
2871 Expression =>
2884 -----------------------------
2885 -- Expand_N_Loop_Statement --
2886 -----------------------------
2888 -- 1. Deal with while condition for C/Fortran boolean
2889 -- 2. Deal with loops with a non-standard enumeration type range
2890 -- 3. Deal with while loops where Condition_Actions is set
2891 -- 4. Insert polling call if required
2897 begin
2906 -- Nothing more to do for plain loop with no iteration scheme
2912 -- Note: we do not have to worry about validity chekcing of the for loop
2913 -- range bounds here, since they were frozen with constant declarations
2914 -- and it is during that process that the validity checking is done.
2916 -- Handle the case where we have a for loop with the range type being
2917 -- an enumeration type with non-standard representation. In this case
2918 -- we expand:
2920 -- for x in [reverse] a .. b loop
2921 -- ...
2922 -- end loop;
2924 -- to
2926 -- for xP in [reverse] integer
2927 -- range etype'Pos (a) .. etype'Pos (b) loop
2928 -- declare
2929 -- x : constant etype := Pos_To_Rep (xP);
2930 -- begin
2931 -- ...
2932 -- end;
2933 -- end loop;
2936 declare
2944 begin
2947 then
2951 New_Id :=
2955 -- If the type has a contiguous representation, successive
2956 -- values can be generated as offsets from the first literal.
2959 Expr :=
2962 Left_Opnd =>
2966 else
2967 -- Use the constructed array Enum_Pos_To_Rep
2969 Expr :=
2979 Iteration_Scheme =>
2981 Loop_Parameter_Specification =>
2986 Discrete_Subtype_Definition =>
2989 Subtype_Mark =>
2992 Constraint =>
2994 Range_Expression =>
2997 Low_Bound =>
2999 Prefix =>
3005 Relocate_Node
3008 High_Bound =>
3010 Prefix =>
3016 Relocate_Node
3028 Handled_Statement_Sequence =>
3036 -- Second case, if we have a while loop with Condition_Actions set,
3037 -- then we change it into a plain loop:
3039 -- while C loop
3040 -- ...
3041 -- end loop;
3043 -- changed to:
3045 -- loop
3046 -- <<condition actions>>
3047 -- exit when not C;
3048 -- ...
3049 -- end loop
3053 then
3054 declare
3057 begin
3058 ES :=
3060 Condition =>
3067 -- This is not an implicit loop, since it is generated in
3068 -- response to the loop statement being processed. If this
3069 -- is itself implicit, the restriction has already been
3070 -- checked. If not, it is an explicit loop.
3083 -------------------------------
3084 -- Expand_N_Return_Statement --
3085 -------------------------------
3105 begin
3111 -- Case where returned expression is present
3115 -- Always normalize C/Fortran boolean result. This is not always
3116 -- necessary, but it seems a good idea to minimize the passing
3117 -- around of non-normalized values, and in any case this handles
3118 -- the processing of barrier functions for protected types, which
3119 -- turn the condition into a return statement.
3125 then
3130 -- Do validity check if enabled for returns
3132 if Validity_Checks_On
3133 and then Validity_Check_Returns
3134 then
3139 -- Find relevant enclosing scope from which return is returning
3142 loop
3147 then
3150 else
3155 -- ???I believe the above code is no longer necessary
3162 -- If it is a return from procedures do no extra steps
3170 -- Look at the enclosing block to see whether the return is from
3171 -- an accept statement or an entry body.
3178 -- If it is a return from accept statement it should be expanded
3179 -- as a call to RTS Complete_Rendezvous and a goto to the end of
3180 -- the accept body.
3182 -- (cf : Expand_N_Accept_Statement, Expand_N_Selective_Accept,
3183 -- Expand_N_Accept_Alternative in exp_ch9.adb)
3188 Name => New_Reference_To
3191 -- why not insert actions here???
3203 Name => New_Occurrence_Of
3211 -- If it is a return from an entry body, put a Complete_Entry_Body
3212 -- call in front of the return.
3216 Call :=
3218 Name => New_Reference_To
3220 Parameter_Associations => New_List
3222 Prefix =>
3223 New_Reference_To
3224 (Object_Ref
3226 Loc),
3240 -- Check the result expression of a scalar function against the subtype
3241 -- of the function by inserting a conversion. This conversion must
3242 -- eventually be performed for other classes of types, but for now it's
3243 -- only done for scalars. ???
3250 -- Deal with returning variable length objects and controlled types
3252 -- Nothing to do if we are returning by reference, or this is not a
3253 -- type that requires special processing (indicated by the fact that
3254 -- it requires a cleanup scope for the secondary stack case).
3261 -- Mutable records with no variable length components are not
3262 -- returned on the sec-stack, so we need to make sure that the
3263 -- backend will only copy back the size of the actual value, and not
3264 -- the maximum size. We create an actual subtype for this purpose.
3266 declare
3271 begin
3275 then
3285 -- Case of secondary stack not used
3289 -- The DSP method is no longer in use. We would like to ignore DSP
3290 -- while implementing AI-318; hence the raise below.
3296 -- Here what we need to do is to always return by reference, since
3297 -- we will return with the stack pointer depressed. We may need to
3298 -- do a copy to a local temporary before doing this return.
3302 -- Set to True if a local copy is required
3305 -- Used for the target entity if a copy is required
3308 -- Declaration used to create copy if needed
3311 -- Determines if Expr represents a return value for which a
3312 -- copy is required. More specifically, a copy is not required
3313 -- if Expr represents an object or component of an object that
3314 -- is either in the local subprogram frame, or is constant.
3315 -- If a copy is required, then Local_Copy_Required is set True.
3317 ------------------------
3318 -- Test_Copy_Required --
3319 ------------------------
3324 begin
3325 -- If component, test prefix (object containing component)
3328 or else
3330 then
3334 -- See if we have an entity name
3339 -- Constant entity is always OK, no copy required
3344 -- No copy required for local variable
3348 then
3353 -- All other cases require a copy
3358 -- Start of processing for No_Secondary_Stack_Case
3360 begin
3361 -- No copy needed if result is from a function call.
3362 -- In this case the result is already being returned by
3363 -- reference with the stack pointer depressed.
3365 -- To make up for a gcc 2.8.1 deficiency (???), we perform
3366 -- the copy for array types if the constrained status of the
3367 -- target type is different from that of the expression.
3370 and then
3375 then
3378 -- We always need a local copy for a controlled type, since
3379 -- we are required to finalize the local value before return.
3380 -- The copy will automatically include the required finalize.
3381 -- Moreover, gigi cannot make this copy, since we need special
3382 -- processing to ensure proper behavior for finalization.
3384 -- Note: the reason we are returning with a depressed stack
3385 -- pointer in the controlled case (even if the type involved
3386 -- is constrained) is that we must make a local copy to deal
3387 -- properly with the requirement that the local result be
3388 -- finalized.
3391 Copy_Ent :=
3395 -- Build declaration to do the copy, and insert it, setting
3396 -- Assignment_OK, because we may be copying a limited type.
3397 -- In addition we set the special flag to inhibit finalize
3398 -- attachment if this is a controlled type (since this attach
3399 -- must be done by the caller, otherwise if we attach it here
3400 -- we will finalize the returned result prematurely).
3402 Decl :=
3412 -- Now the actual return uses the copied value
3417 -- Since we have made the copy, gigi does not have to, so
3418 -- we set the By_Ref flag to prevent another copy being made.
3422 -- Non-controlled cases
3424 else
3427 -- If a local copy is required, then gigi will make the
3428 -- copy, otherwise, we can return the result directly,
3429 -- so set By_Ref to suppress the gigi copy.
3437 -- Here if secondary stack is used
3439 else
3440 -- Make sure that no surrounding block will reclaim the secondary
3441 -- stack on which we are going to put the result. Not only may this
3442 -- introduce secondary stack leaks but worse, if the reclamation is
3443 -- done too early, then the result we are returning may get
3444 -- clobbered. See example in 7417-003.
3446 declare
3449 begin
3456 -- Optimize the case where the result is a function call. In this
3457 -- case either the result is already on the secondary stack, or is
3458 -- already being returned with the stack pointer depressed and no
3459 -- further processing is required except to set the By_Ref flag to
3460 -- ensure that gigi does not attempt an extra unnecessary copy.
3461 -- (actually not just unnecessary but harmfully wrong in the case
3462 -- of a controlled type, where gigi does not know how to do a copy).
3463 -- To make up for a gcc 2.8.1 deficiency (???), we perform
3464 -- the copy for array types if the constrained status of the
3465 -- target type is different from that of the expression.
3468 and then
3474 then
3477 -- Remove side effects from the expression now so that
3478 -- other part of the expander do not have to reanalyze
3479 -- this node without this optimization
3483 -- For controlled types, do the allocation on the secondary stack
3484 -- manually in order to call adjust at the right time:
3485 -- type Anon1 is access Return_Type;
3486 -- for Anon1'Storage_pool use ss_pool;
3487 -- Anon2 : anon1 := new Return_Type'(expr);
3488 -- return Anon2.all;
3489 -- We do the same for classwide types that are not potentially
3490 -- controlled (by the virtue of restriction No_Finalization) because
3491 -- gigi is not able to properly allocate class-wide types.
3495 then
3496 declare
3506 begin
3511 Alloc_Node :=
3513 Expression =>
3521 Type_Definition =>
3523 Subtype_Indication =>
3538 -- Otherwise use the gigi mechanism to allocate result on the
3539 -- secondary stack.
3541 else
3544 -- If we are generating code for the Java VM do not use
3545 -- SS_Allocate since everything is heap-allocated anyway.
3553 -- Implement the rules of 6.5(8-10), which require a tag check in
3554 -- the case of a limited tagged return type, and tag reassignment
3555 -- for nonlimited tagged results. These actions are needed when
3556 -- the return type is a specific tagged type and the result
3557 -- expression is a conversion or a formal parameter, because in
3558 -- that case the tag of the expression might differ from the tag
3559 -- of the specific result type.
3567 then
3568 -- When the return type is limited, perform a check that the
3569 -- tag of the result is the same as the tag of the return type.
3574 Condition =>
3576 Left_Opnd =>
3579 Selector_Name =>
3581 Right_Opnd =>
3583 New_Reference_To
3586 Loc))),
3589 -- If the result type is a specific nonlimited tagged type,
3590 -- then we have to ensure that the tag of the result is that
3591 -- of the result type. This is handled by making a copy of the
3592 -- expression in the case where it might have a different tag,
3593 -- namely when the expression is a conversion or a formal
3594 -- parameter. We create a new object of the result type and
3595 -- initialize it from the expression, which will implicitly
3596 -- force the tag to be set appropriately.
3598 else
3599 Result_Id :=
3603 Result_Obj :=
3617 -- Ada 2005 (AI-344): If the result type is class-wide, then insert
3618 -- a check that the level of the return expression's underlying type
3619 -- is not deeper than the level of the master enclosing the function.
3620 -- Always generate the check when the type of the return expression
3621 -- is class-wide, when it's a type conversion, or when it's a formal
3622 -- parameter. Otherwise, suppress the check in the case where the
3623 -- return expression has a specific type whose level is known not to
3624 -- be statically deeper than the function's result type.
3629 and then
3637 then
3640 Condition =>
3642 Left_Opnd =>
3644 Name =>
3645 New_Reference_To
3647 Parameter_Associations =>
3649 Prefix =>
3651 Attribute_Name =>
3652 Name_Tag))),
3653 Right_Opnd =>
3659 exception
3664 --------------------------------
3665 -- Expand_Non_Function_Return --
3666 --------------------------------
3680 begin
3681 -- If it is a return from procedures do no extra steps
3686 -- If it is a nested return within an extended one, replace it
3687 -- with a return of the previously declared return object.
3692 Expression =>
3702 -- Look at the enclosing block to see whether the return is from
3703 -- an accept statement or an entry body.
3710 -- If it is a return from accept statement it is expanded as call to
3711 -- RTS Complete_Rendezvous and a goto to the end of the accept body.
3713 -- (cf : Expand_N_Accept_Statement, Expand_N_Selective_Accept,
3714 -- Expand_N_Accept_Alternative in exp_ch9.adb)
3718 Call :=
3720 Name => New_Reference_To
3723 -- why not insert actions here???
3735 Name => New_Occurrence_Of
3743 -- If it is a return from an entry body, put a Complete_Entry_Body
3744 -- call in front of the return.
3747 Call :=
3749 Name => New_Reference_To
3751 Parameter_Associations => New_List
3753 Prefix =>
3754 New_Reference_To
3755 (Object_Ref
3757 Loc),
3765 --------------------------
3766 -- Expand_Simple_Return --
3767 --------------------------
3770 begin
3771 -- Distinguish the function and non-function cases:
3775 when E_Function |
3776 E_Generic_Function =>
3779 when E_Procedure |
3780 E_Generic_Procedure |
3781 E_Entry |
3782 E_Entry_Family |
3783 E_Return_Statement =>
3790 exception
3795 -----------------------------------
3796 -- Expand_Simple_Function_Return --
3797 -----------------------------------
3799 -- The "simple" comes from the syntax rule simple_return_statement.
3800 -- The semantics are not at all simple!
3807 -- The function we are returning from
3810 -- The result type of the function
3818 -- The type of the expression (not necessarily the same as R_Type)
3820 begin
3821 -- The DSP method is no longer in use
3825 -- We rewrite "return <expression>;" to be:
3827 -- return _anon_ : <return_subtype> := <expression>
3829 -- The expansion produced by Expand_N_Extended_Return_Statement will
3830 -- contain simple return statements (for example, a block containing a
3831 -- simple return of the return object), which brings us back here with
3832 -- Comes_From_Extended_Return_Statement set. To avoid infinite
3833 -- recursion, we do not transform into an extended return if
3834 -- Comes_From_Extended_Return_Statement is True.
3836 -- The reason for this design is that for Ada 2005 limited returns, we
3837 -- need to reify the return object, so we can build it "in place",
3838 -- and we need a block statement to hang finalization and tasking stuff
3839 -- off of.
3841 -- ??? In order to avoid disruption, we avoid translating to extended
3842 -- return except in the cases where we really need to (Ada 2005
3843 -- inherently limited). We would prefer eventually to do this
3844 -- translation in all cases except perhaps for the case of Ada 95
3845 -- inherently limited, in order to fully exercise the code in
3846 -- Expand_N_Extended_Return_Statement, and in order to do
3847 -- build-in-place for efficiency when it is not required.
3852 and then not Debug_Flag_Dot_L
3853 then
3854 declare
3870 begin
3877 -- Here we have a simple return statement that is part of the expansion
3878 -- of an extended return statement (either written by the user, or
3879 -- generated by the above code).
3881 -- Always normalize C/Fortran boolean result. This is not always
3882 -- necessary, but it seems a good idea to minimize the passing
3883 -- around of non-normalized values, and in any case this handles
3884 -- the processing of barrier functions for protected types, which
3885 -- turn the condition into a return statement.
3889 then
3894 -- Do validity check if enabled for returns
3896 if Validity_Checks_On
3897 and then Validity_Check_Returns
3898 then
3902 -- Check the result expression of a scalar function against the subtype
3903 -- of the function by inserting a conversion. This conversion must
3904 -- eventually be performed for other classes of types, but for now it's
3905 -- only done for scalars.
3906 -- ???
3913 -- Deal with returning variable length objects and controlled types
3915 -- Nothing to do if we are returning by reference, or this is not a
3916 -- type that requires special processing (indicated by the fact that
3917 -- it requires a cleanup scope for the secondary stack case).
3924 -- Mutable records with no variable length components are not
3925 -- returned on the sec-stack, so we need to make sure that the
3926 -- backend will only copy back the size of the actual value, and not
3927 -- the maximum size. We create an actual subtype for this purpose.
3929 declare
3933 begin
3937 then
3946 -- Case of secondary stack not used
3950 -- The DSP method is no longer in use. We would like to ignore DSP
3951 -- while implementing AI-318; hence the following assertion. Keep the
3952 -- old code around in case DSP is revived someday.
3958 -- Here if secondary stack is used
3960 else
3961 -- Make sure that no surrounding block will reclaim the secondary
3962 -- stack on which we are going to put the result. Not only may this
3963 -- introduce secondary stack leaks but worse, if the reclamation is
3964 -- done too early, then the result we are returning may get
3965 -- clobbered. See example in 7417-003.
3967 declare
3969 begin
3977 -- Optimize the case where the result is a function call. In this
3978 -- case either the result is already on the secondary stack, or is
3979 -- already being returned with the stack pointer depressed and no
3980 -- further processing is required except to set the By_Ref flag to
3981 -- ensure that gigi does not attempt an extra unnecessary copy.
3982 -- (actually not just unnecessary but harmfully wrong in the case
3983 -- of a controlled type, where gigi does not know how to do a copy).
3984 -- To make up for a gcc 2.8.1 deficiency (???), we perform
3985 -- the copy for array types if the constrained status of the
3986 -- target type is different from that of the expression.
3989 and then
3995 then
3998 -- Remove side effects from the expression now so that
3999 -- other part of the expander do not have to reanalyze
4000 -- this node without this optimization
4004 -- For controlled types, do the allocation on the secondary stack
4005 -- manually in order to call adjust at the right time:
4007 -- type Anon1 is access R_Type;
4008 -- for Anon1'Storage_pool use ss_pool;
4009 -- Anon2 : anon1 := new R_Type'(expr);
4010 -- return Anon2.all;
4012 -- We do the same for classwide types that are not potentially
4013 -- controlled (by the virtue of restriction No_Finalization) because
4014 -- gigi is not able to properly allocate class-wide types.
4018 then
4019 declare
4029 begin
4034 Alloc_Node :=
4036 Expression =>
4044 Type_Definition =>
4046 Subtype_Indication =>
4061 -- Otherwise use the gigi mechanism to allocate result on the
4062 -- secondary stack.
4064 else
4067 -- If we are generating code for the Java VM do not use
4068 -- SS_Allocate since everything is heap-allocated anyway.
4076 -- Implement the rules of 6.5(8-10), which require a tag check in
4077 -- the case of a limited tagged return type, and tag reassignment
4078 -- for nonlimited tagged results. These actions are needed when
4079 -- the return type is a specific tagged type and the result
4080 -- expression is a conversion or a formal parameter, because in
4081 -- that case the tag of the expression might differ from the tag
4082 -- of the specific result type.
4090 then
4091 -- When the return type is limited, perform a check that the
4092 -- tag of the result is the same as the tag of the return type.
4097 Condition =>
4099 Left_Opnd =>
4102 Selector_Name =>
4104 Right_Opnd =>
4106 New_Reference_To
4109 Loc))),
4112 -- If the result type is a specific nonlimited tagged type,
4113 -- then we have to ensure that the tag of the result is that
4114 -- of the result type. This is handled by making a copy of the
4115 -- expression in the case where it might have a different tag,
4116 -- namely when the expression is a conversion or a formal
4117 -- parameter. We create a new object of the result type and
4118 -- initialize it from the expression, which will implicitly
4119 -- force the tag to be set appropriately.
4121 else
4122 declare
4131 Object_Definition =>
4136 begin
4145 -- Ada 2005 (AI-344): If the result type is class-wide, then insert
4146 -- a check that the level of the return expression's underlying type
4147 -- is not deeper than the level of the master enclosing the function.
4148 -- Always generate the check when the type of the return expression
4149 -- is class-wide, when it's a type conversion, or when it's a formal
4150 -- parameter. Otherwise, suppress the check in the case where the
4151 -- return expression has a specific type whose level is known not to
4152 -- be statically deeper than the function's result type.
4157 and then
4165 then
4168 Condition =>
4170 Left_Opnd =>
4172 Name =>
4173 New_Reference_To
4175 Parameter_Associations =>
4177 Prefix =>
4179 Attribute_Name =>
4180 Name_Tag))),
4181 Right_Opnd =>
4188 ------------------------------
4189 -- Make_Tag_Ctrl_Assignment --
4190 ------------------------------
4203 -- Tags are not saved and restored when Java_VM because JVM tags
4204 -- are represented implicitly in objects.
4209 begin
4212 -- Finalize the target of the assignment when controlled.
4213 -- We have two exceptions here:
4215 -- 1. If we are in an init proc since it is an initialization
4216 -- more than an assignment
4218 -- 2. If the left-hand side is a temporary that was not initialized
4219 -- (or the parent part of a temporary since it is the case in
4220 -- extension aggregates). Such a temporary does not come from
4221 -- source. We must examine the original node for the prefix, because
4222 -- it may be a component of an entry formal, in which case it has
4223 -- been rewritten and does not appear to come from source either.
4225 -- Case of init proc
4230 -- The left hand side is an uninitialized temporary
4235 then
4237 else
4239 Make_Final_Call (
4245 -- Save the Tag in a local variable Tag_Tmp
4248 Tag_Tmp :=
4255 Expression =>
4259 Loc))));
4261 -- Otherwise Tag_Tmp not used
4263 else
4267 -- Processing for controlled types and types with controlled components
4269 -- Variables of such types contain pointers used to chain them in
4270 -- finalization lists, in addition to user data. These pointers are
4271 -- specific to each object of the type, not to the value being assigned.
4272 -- Thus they need to be left intact during the assignment. We achieve
4273 -- this by constructing a Storage_Array subtype, and by overlaying
4274 -- objects of this type on the source and target of the assignment.
4275 -- The assignment is then rewritten to assignments of slices of these
4276 -- arrays, copying the user data, and leaving the pointers untouched.
4281 -- A reference to the Prev component of the record controller
4284 -- Index of first byte to be copied (used to skip
4285 -- Root_Controlled in controlled objects).
4288 -- Index of last byte to be copied before outermost record
4289 -- controller data.
4292 -- Length of record controller data (Prev and Next pointers)
4295 -- Index of first byte to be copied after outermost record
4296 -- controller data.
4300 -- Used for computation of the size of the data to be copied
4305 function Build_Slice
4309 -- Build and return a slice of an array of type S overlaid
4310 -- on object Rec, with bounds specified by Lo and Hi. If either
4311 -- bound is empty, a default of S'First (respectively S'Last)
4312 -- is used.
4314 -----------------
4315 -- Build_Slice --
4316 -----------------
4318 function Build_Slice
4322 is
4331 -- Access value designating an opaque storage array of
4332 -- type S overlaid on record Rec.
4334 begin
4335 -- Compute slice bounds using S'First (1) and S'Last
4336 -- as default values when not specified by the caller.
4340 else
4348 else
4353 Prefix =>
4354 Opaque,
4359 -- Start of processing for Controlled_Actions
4361 begin
4362 -- Create a constrained subtype of Storage_Array whose size
4363 -- corresponds to the value being assigned.
4365 -- subtype G is Storage_Offset range
4366 -- 1 .. (Expr'Size + Storage_Unit - 1) / Storage_Unit
4378 then
4384 Source_Size :=
4386 Left_Opnd =>
4388 Prefix =>
4390 Attribute_Name =>
4391 Name_Size),
4392 Right_Opnd =>
4395 Source_Size :=
4398 Right_Opnd =>
4402 Range_Type :=
4409 Subtype_Indication =>
4411 Subtype_Mark =>
4414 Range_Expression =>
4419 -- subtype S is Storage_Array (G)
4423 Defining_Identifier =>
4426 Subtype_Indication =>
4428 Subtype_Mark =>
4430 Constraint =>
4432 Constraints =>
4435 -- type A is access S
4437 Opaque_Type :=
4444 Type_Definition =>
4446 Subtype_Indication =>
4447 New_Occurrence_Of (
4450 -- Generate appropriate slice assignments
4454 -- For the case of a controlled object, skip the
4455 -- Root_Controlled part.
4458 First_After_Root :=
4460 First_After_Root,
4463 Prefix =>
4469 -- For the case of a record with controlled components, skip
4470 -- the Prev and Next components of the record controller.
4471 -- These components constitute a 'hole' in the middle of the
4472 -- data to be copied.
4475 Prev_Ref :=
4477 Prefix =>
4480 Selector_Name =>
4484 -- Last index before hole: determined by position of
4485 -- the _Controller.Prev component.
4487 Last_Before_Hole :=
4505 -- Hole length: size of the Prev and Next components
4507 Hole_Length :=
4510 Right_Opnd =>
4512 Left_Opnd =>
4516 Right_Opnd =>
4520 -- First index after hole
4522 First_After_Hole :=
4532 Expression =>
4534 Left_Opnd =>
4536 Left_Opnd =>
4545 -- Assign the first slice (possibly skipping Root_Controlled,
4546 -- up to the beginning of the record controller if present,
4547 -- up to the end of the object if not).
4562 -- If a record controller is present, copy the second slice,
4563 -- from right after the _Controller.Next component up to the
4564 -- end of the object.
4578 else
4582 -- Restore the tag
4587 Name =>
4591 Loc)),
4595 -- Adjust the target after the assignment when controlled (not in the
4596 -- init proc since it is an initialization more than an assignment).
4600 Make_Adjust_Call (
4609 exception
4610 -- Could use comment here ???
4616 -----------------------------
4617 -- No_Secondary_Stack_Case --
4618 -----------------------------
4631 -- Here what we need to do is to always return by reference, since
4632 -- we will return with the stack pointer depressed. We may need to
4633 -- do a copy to a local temporary before doing this return.
4636 -- Set to True if a local copy is required
4639 -- Used for the target entity if a copy is required
4642 -- Declaration used to create copy if needed
4645 -- Determines if Expr represents a return value for which a
4646 -- copy is required. More specifically, a copy is not required
4647 -- if Expr represents an object or component of an object that
4648 -- is either in the local subprogram frame, or is constant.
4649 -- If a copy is required, then Local_Copy_Required is set True.
4651 ------------------------
4652 -- Test_Copy_Required --
4653 ------------------------
4658 begin
4659 -- If component, test prefix (object containing component)
4662 or else
4664 then
4668 -- See if we have an entity name
4673 -- Constant entity is always OK, no copy required
4678 -- No copy required for local variable
4682 then
4687 -- All other cases require a copy
4692 -- Start of processing for No_Secondary_Stack_Case
4694 begin
4695 -- No copy needed if result is from a function call.
4696 -- In this case the result is already being returned by
4697 -- reference with the stack pointer depressed.
4699 -- To make up for a gcc 2.8.1 deficiency (???), we perform
4700 -- the copy for array types if the constrained status of the
4701 -- target type is different from that of the expression.
4704 and then
4709 then
4712 -- We always need a local copy for a controlled type, since
4713 -- we are required to finalize the local value before return.
4714 -- The copy will automatically include the required finalize.
4715 -- Moreover, gigi cannot make this copy, since we need special
4716 -- processing to ensure proper behavior for finalization.
4718 -- Note: the reason we are returning with a depressed stack
4719 -- pointer in the controlled case (even if the type involved
4720 -- is constrained) is that we must make a local copy to deal
4721 -- properly with the requirement that the local result be
4722 -- finalized.
4725 Copy_Ent :=
4729 -- Build declaration to do the copy, and insert it, setting
4730 -- Assignment_OK, because we may be copying a limited type.
4731 -- In addition we set the special flag to inhibit finalize
4732 -- attachment if this is a controlled type (since this attach
4733 -- must be done by the caller, otherwise if we attach it here
4734 -- we will finalize the returned result prematurely).
4736 Decl :=
4746 -- Now the actual return uses the copied value
4751 -- Since we have made the copy, gigi does not have to, so
4752 -- we set the By_Ref flag to prevent another copy being made.
4756 -- Non-controlled cases
4758 else
4761 -- If a local copy is required, then gigi will make the
4762 -- copy, otherwise, we can return the result directly,
4763 -- so set By_Ref to suppress the gigi copy.
4771 ------------------------------------
4772 -- Possible_Bit_Aligned_Component --
4773 ------------------------------------
4776 begin
4779 -- Case of indexed component
4782 declare
4786 begin
4787 -- If we know the component size and it is less than 64, then
4788 -- we are definitely OK. The back end always does assignment
4789 -- of misaligned small objects correctly.
4793 then
4796 -- Otherwise, we need to test the prefix, to see if we are
4797 -- indexing from a possibly unaligned component.
4799 else
4804 -- Case of selected component
4807 declare
4811 begin
4812 -- If there is no component clause, then we are in the clear
4813 -- since the back end will never misalign a large component
4814 -- unless it is forced to do so. In the clear means we need
4815 -- only the recursive test on the prefix.
4819 else
4824 -- If we have neither a record nor array component, it means that
4825 -- we have fallen off the top testing prefixes recursively, and
4826 -- we now have a stand alone object, where we don't have a problem