1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1992-2007, 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 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. --
22 -- GNAT was originally developed by the GNAT team at New York University. --
23 -- Extensive contributions were provided by Ada Core Technologies Inc. --
25 ------------------------------------------------------------------------------
27 with Binderr; use Binderr;
28 with Butil; use Butil;
29 with Debug; use Debug;
30 with Fname; use Fname;
32 with Namet; use Namet;
34 with Output; use Output;
35 with Targparm; use Targparm;
39 -- The following data structures are used to represent the graph that is
40 -- used to determine the elaboration order (using a topological sort).
42 -- The following structures are used to record successors. If A is a
43 -- successor of B in this table, it means that A must be elaborated
44 -- before B is elaborated.
46 type Successor_Id is new Nat;
47 -- Identification of single successor entry
49 No_Successor : constant Successor_Id := 0;
50 -- Used to indicate end of list of successors
52 type Elab_All_Id is new Nat;
53 -- Identification of Elab_All entry link
55 No_Elab_All_Link : constant Elab_All_Id := 0;
56 -- Used to indicate end of list
58 -- Succ_Reason indicates the reason for a particular elaboration link
62 -- After directly with's Before, so the spec of Before must be
63 -- elaborated before After is elaborated.
66 -- After directly mentions Before in a pragma Elaborate, so the
67 -- body of Before must be elaborate before After is elaborated.
70 -- After either mentions Before directly in a pragma Elaborate_All,
71 -- or mentions a third unit, X, which itself requires that Before be
72 -- elaborated before unit X is elaborated. The Elab_All_Link list
73 -- traces the dependencies in the latter case.
76 -- This is just like Elab_All, except that the elaborate all was not
77 -- explicitly present in the source, but rather was created by the
78 -- front end, which decided that it was "desirable".
81 -- This is just like Elab, except that the elaborate was not
82 -- explicitly present in the source, but rather was created by the
83 -- front end, which decided that it was "desirable".
86 -- After is a body, and Before is the corresponding spec
88 -- Successor_Link contains the information for one link
90 type Successor_Link is record
98 -- Next successor on this list
100 Reason : Succ_Reason;
101 -- Reason for this link
104 -- Set True if this link is needed for the special Elaborate_Body
105 -- processing described below.
107 Reason_Unit : Unit_Id;
108 -- For Reason = Elab, or Elab_All or Elab_Desirable, records the unit
109 -- containing the pragma leading to the link.
111 Elab_All_Link : Elab_All_Id;
112 -- If Reason = Elab_All or Elab_Desirable, then this points to the
113 -- first elment in a list of Elab_All entries that record the with
114 -- chain leading resulting in this particular dependency.
118 -- Note on handling of Elaborate_Body. Basically, if we have a pragma
119 -- Elaborate_Body in a unit, it means that the spec and body have to
120 -- be handled as a single entity from the point of view of determining
121 -- an elaboration order. What we do is to essentially remove the body
122 -- from consideration completely, and transfer all its links (other
123 -- than the spec link) to the spec. Then when then the spec gets chosen,
124 -- we choose the body right afterwards. We mark the links that get moved
125 -- from the body to the spec by setting their Elab_Body flag True, so
126 -- that we can understand what is going on!
128 Succ_First : constant := 1;
130 package Succ is new Table.Table (
131 Table_Component_Type => Successor_Link,
132 Table_Index_Type => Successor_Id,
133 Table_Low_Bound => Succ_First,
134 Table_Initial => 500,
135 Table_Increment => 200,
136 Table_Name => "Succ");
138 -- For the case of Elaborate_All, the following table is used to record
139 -- chains of with relationships that lead to the Elab_All link. These
140 -- are used solely for diagnostic purposes
142 type Elab_All_Entry is record
143 Needed_By : Unit_Name_Type;
144 -- Name of unit from which referencing unit was with'ed or otherwise
145 -- needed as a result of Elaborate_All or Elaborate_Desirable.
147 Next_Elab : Elab_All_Id;
148 -- Link to next entry on chain (No_Elab_All_Link marks end of list)
151 package Elab_All_Entries is new Table.Table (
152 Table_Component_Type => Elab_All_Entry,
153 Table_Index_Type => Elab_All_Id,
154 Table_Low_Bound => 1,
155 Table_Initial => 2000,
156 Table_Increment => 200,
157 Table_Name => "Elab_All_Entries");
159 -- A Unit_Node record is built for each active unit
161 type Unit_Node_Record is record
163 Successors : Successor_Id;
164 -- Pointer to list of links for successor nodes
167 -- Number of predecessors for this unit. Normally non-negative, but
168 -- can go negative in the case of units chosen by the diagnose error
169 -- procedure (when cycles are being removed from the graph).
172 -- Forward pointer for list of units with no predecessors
175 -- Position in elaboration order (zero = not placed yet)
178 -- Used in computing transitive closure for elaborate all and
179 -- also in locating cycles and paths in the diagnose routines.
181 Elab_Position : Natural;
182 -- Initialized to zero. Set non-zero when a unit is chosen and
183 -- placed in the elaboration order. The value represents the
184 -- ordinal position in the elaboration order.
188 package UNR is new Table.Table (
189 Table_Component_Type => Unit_Node_Record,
190 Table_Index_Type => Unit_Id,
191 Table_Low_Bound => First_Unit_Entry,
192 Table_Initial => 500,
193 Table_Increment => 200,
194 Table_Name => "UNR");
197 -- Head of list of items with no predecessors
200 -- Number of entries not yet dealt with
203 -- Current unit, set by Gather_Dependencies, and picked up in Build_Link
204 -- to set the Reason_Unit field of the created dependency link.
206 Num_Chosen : Natural := 0;
207 -- Number of units chosen in the elaboration order so far
209 -----------------------
210 -- Local Subprograms --
211 -----------------------
213 function Better_Choice (U1, U2 : Unit_Id) return Boolean;
214 -- U1 and U2 are both permitted candidates for selection as the next unit
215 -- to be elaborated. This function determines whether U1 is a better choice
216 -- than U2, i.e. should be elaborated in preference to U2, based on a set
217 -- of heuristics that establish a friendly and predictable order (see body
218 -- for details). The result is True if U1 is a better choice than U2, and
219 -- False if it is a worse choice, or there is no preference between them.
225 Ea_Id : Elab_All_Id := No_Elab_All_Link);
226 -- Establish a successor link, Before must be elaborated before After,
227 -- and the reason for the link is R. Ea_Id is the contents to be placed
228 -- in the Elab_All_Link of the entry.
230 procedure Choose (Chosen : Unit_Id);
231 -- Chosen is the next entry chosen in the elaboration order. This
232 -- procedure updates all data structures appropriately.
234 function Corresponding_Body (U : Unit_Id) return Unit_Id;
235 pragma Inline (Corresponding_Body);
236 -- Given a unit which is a spec for which there is a separate body,
237 -- return the unit id of the body. It is an error to call this routine
238 -- with a unit that is not a spec, or which does not have a separate body.
240 function Corresponding_Spec (U : Unit_Id) return Unit_Id;
241 pragma Inline (Corresponding_Spec);
242 -- Given a unit which is a body for which there is a separate spec,
243 -- return the unit id of the spec. It is an error to call this routine
244 -- with a unit that is not a body, or which does not have a separate spec.
246 procedure Diagnose_Elaboration_Problem;
247 -- Called when no elaboration order can be found. Outputs an appropriate
248 -- diagnosis of the problem, and then abandons the bind.
250 procedure Elab_All_Links
253 Reason : Succ_Reason;
255 -- Used to compute the transitive closure of elaboration links for an
256 -- Elaborate_All pragma (Reason = Elab_All) or for an indication of
257 -- Elaborate_All_Desirable (Reason = Elab_All_Desirable). Unit After has
258 -- a pragma Elaborate_All or the front end has determined that a reference
259 -- probably requires Elaborate_All is required, and unit Before must be
260 -- previously elaborated. First a link is built making sure that unit
261 -- Before is elaborated before After, then a recursive call ensures that
262 -- we also build links for any units needed by Before (i.e. these units
263 -- must/should also be elaborated before After). Link is used to build
264 -- a chain of Elab_All_Entries to explain the reason for a link. The
265 -- value passed is the chain so far.
267 procedure Elab_Error_Msg (S : Successor_Id);
268 -- Given a successor link, outputs an error message of the form
269 -- "$ must be elaborated before $ ..." where ... is the reason.
271 procedure Gather_Dependencies;
272 -- Compute dependencies, building the Succ and UNR tables
274 function Is_Body_Unit (U : Unit_Id) return Boolean;
275 pragma Inline (Is_Body_Unit);
276 -- Determines if given unit is a body
278 function Is_Waiting_Body (U : Unit_Id) return Boolean;
279 pragma Inline (Is_Waiting_Body);
280 -- Determines if U is a waiting body, defined as a body which has
281 -- not been elaborated, but whose spec has been elaborated.
283 function Make_Elab_Entry
284 (Unam : Unit_Name_Type;
285 Link : Elab_All_Id) return Elab_All_Id;
286 -- Make an Elab_All_Entries table entry with the given Unam and Link
288 function Unit_Id_Of (Uname : Unit_Name_Type) return Unit_Id;
289 -- This function uses the Info field set in the names table to obtain
290 -- the unit Id of a unit, given its name id value.
292 function Worse_Choice (U1, U2 : Unit_Id) return Boolean;
293 -- This is like Better_Choice, and has the same interface, but returns
294 -- true if U1 is a worse choice than U2 in the sense of the -h (horrible
295 -- elaboration order) switch. We still have to obey Ada rules, so it is
296 -- not quite the direct inverse of Better_Choice.
298 procedure Write_Dependencies;
299 -- Write out dependencies (called only if appropriate option is set)
301 procedure Write_Elab_All_Chain (S : Successor_Id);
302 -- If the reason for the link S is Elaborate_All or Elaborate_Desirable,
303 -- then this routine will output the "needed by" explanation chain.
309 function Better_Choice (U1, U2 : Unit_Id) return Boolean is
310 UT1 : Unit_Record renames Units.Table (U1);
311 UT2 : Unit_Record renames Units.Table (U2);
315 Write_Str ("Better_Choice (");
316 Write_Unit_Name (UT1.Uname);
318 Write_Unit_Name (UT2.Uname);
322 -- Note: the checks here are applied in sequence, and the ordering is
323 -- significant (i.e. the more important criteria are applied first).
325 -- Prefer a waiting body to any other case
327 if Is_Waiting_Body (U1) and not Is_Waiting_Body (U2) then
329 Write_Line (" True: u1 is waiting body, u2 is not");
334 elsif Is_Waiting_Body (U2) and not Is_Waiting_Body (U1) then
336 Write_Line (" False: u2 is waiting body, u1 is not");
341 -- Prefer a predefined unit to a non-predefined unit
343 elsif UT1.Predefined and not UT2.Predefined then
345 Write_Line (" True: u1 is predefined, u2 is not");
350 elsif UT2.Predefined and not UT1.Predefined then
352 Write_Line (" False: u2 is predefined, u1 is not");
357 -- Prefer an internal unit to a non-internal unit
359 elsif UT1.Internal and not UT2.Internal then
361 Write_Line (" True: u1 is internal, u2 is not");
365 elsif UT2.Internal and not UT1.Internal then
367 Write_Line (" False: u2 is internal, u1 is not");
372 -- Prefer a body to a spec
374 elsif Is_Body_Unit (U1) and not Is_Body_Unit (U2) then
376 Write_Line (" True: u1 is body, u2 is not");
381 elsif Is_Body_Unit (U2) and not Is_Body_Unit (U1) then
383 Write_Line (" False: u2 is body, u1 is not");
388 -- If both are waiting bodies, then prefer the one whose spec is
389 -- more recently elaborated. Consider the following:
395 -- The normal waiting body preference would have placed the body of
396 -- A before the spec of B if it could. Since it could not, there it
397 -- must be the case that A depends on B. It is therefore a good idea
398 -- to put the body of B first.
400 elsif Is_Waiting_Body (U1) and then Is_Waiting_Body (U2) then
402 Result : constant Boolean :=
403 UNR.Table (Corresponding_Spec (U1)).Elab_Position >
404 UNR.Table (Corresponding_Spec (U2)).Elab_Position;
408 Write_Line (" True: based on waiting body elab positions");
410 Write_Line (" False: based on waiting body elab positions");
418 -- Remaining choice rules are disabled by Debug flag -do
420 if not Debug_Flag_O then
422 -- The following deal with the case of specs which have been marked
423 -- as Elaborate_Body_Desirable. We generally want to delay these
424 -- specs as long as possible, so that the bodies have a better chance
425 -- of being elaborated closer to the specs.
427 -- If we have two units, one of which is a spec for which this flag
428 -- is set, and the other is not, we prefer to delay the spec for
429 -- which the flag is set.
431 if not UT1.Elaborate_Body_Desirable
432 and then UT2.Elaborate_Body_Desirable
435 Write_Line (" True: u1 is elab body desirable, u2 is not");
440 elsif not UT2.Elaborate_Body_Desirable
441 and then UT1.Elaborate_Body_Desirable
444 Write_Line (" False: u1 is elab body desirable, u2 is not");
449 -- If we have two specs that are both marked as Elaborate_Body
450 -- desirable, we prefer the one whose body is nearer to being able
451 -- to be elaborated, based on the Num_Pred count. This helps to
452 -- ensure bodies are as close to specs as possible.
454 elsif UT1.Elaborate_Body_Desirable
455 and then UT2.Elaborate_Body_Desirable
458 Result : constant Boolean :=
459 UNR.Table (Corresponding_Body (U1)).Num_Pred <
460 UNR.Table (Corresponding_Body (U2)).Num_Pred;
464 Write_Line (" True based on Num_Pred compare");
466 Write_Line (" False based on Num_Pred compare");
475 -- If we fall through, it means that no preference rule applies, so we
476 -- use alphabetical order to at least give a deterministic result.
479 Write_Line (" choose on alpha order");
482 return Uname_Less (UT1.Uname, UT2.Uname);
493 Ea_Id : Elab_All_Id := No_Elab_All_Link)
499 Succ.Table (Succ.Last).Before := Before;
500 Succ.Table (Succ.Last).Next := UNR.Table (Before).Successors;
501 UNR.Table (Before).Successors := Succ.Last;
502 Succ.Table (Succ.Last).Reason := R;
503 Succ.Table (Succ.Last).Reason_Unit := Cur_Unit;
504 Succ.Table (Succ.Last).Elab_All_Link := Ea_Id;
506 -- Deal with special Elab_Body case. If the After of this link is
507 -- a body whose spec has Elaborate_All set, and this is not the link
508 -- directly from the body to the spec, then we make the After of the
509 -- link reference its spec instead, marking the link appropriately.
511 if Units.Table (After).Utype = Is_Body then
512 Cspec := Corresponding_Spec (After);
514 if Units.Table (Cspec).Elaborate_Body
515 and then Cspec /= Before
517 Succ.Table (Succ.Last).After := Cspec;
518 Succ.Table (Succ.Last).Elab_Body := True;
519 UNR.Table (Cspec).Num_Pred := UNR.Table (Cspec).Num_Pred + 1;
524 -- Fall through on normal case
526 Succ.Table (Succ.Last).After := After;
527 Succ.Table (Succ.Last).Elab_Body := False;
528 UNR.Table (After).Num_Pred := UNR.Table (After).Num_Pred + 1;
535 procedure Choose (Chosen : Unit_Id) is
541 Write_Str ("Choosing Unit ");
542 Write_Unit_Name (Units.Table (Chosen).Uname);
546 -- Add to elaboration order. Note that units having no elaboration
547 -- code are not treated specially yet. The special casing of this
548 -- is in Bindgen, where Gen_Elab_Calls skips over them. Meanwhile
549 -- we need them here, because the object file list is also driven
550 -- by the contents of the Elab_Order table.
552 Elab_Order.Increment_Last;
553 Elab_Order.Table (Elab_Order.Last) := Chosen;
555 -- Remove from No_Pred list. This is a little inefficient and may
556 -- be we should doubly link the list, but it will do for now!
558 if No_Pred = Chosen then
559 No_Pred := UNR.Table (Chosen).Nextnp;
562 -- Note that we just ignore the situation where it does not
563 -- appear in the No_Pred list, this happens in calls from the
564 -- Diagnose_Elaboration_Problem routine, where cycles are being
565 -- removed arbitrarily from the graph.
568 while U /= No_Unit_Id loop
569 if UNR.Table (U).Nextnp = Chosen then
570 UNR.Table (U).Nextnp := UNR.Table (Chosen).Nextnp;
574 U := UNR.Table (U).Nextnp;
578 -- For all successors, decrement the number of predecessors, and
579 -- if it becomes zero, then add to no predecessor list.
581 S := UNR.Table (Chosen).Successors;
582 while S /= No_Successor loop
583 U := Succ.Table (S).After;
584 UNR.Table (U).Num_Pred := UNR.Table (U).Num_Pred - 1;
587 Write_Str (" decrementing Num_Pred for unit ");
588 Write_Unit_Name (Units.Table (U).Uname);
589 Write_Str (" new value = ");
590 Write_Int (Int (UNR.Table (U).Num_Pred));
594 if UNR.Table (U).Num_Pred = 0 then
595 UNR.Table (U).Nextnp := No_Pred;
599 S := Succ.Table (S).Next;
602 -- All done, adjust number of units left count and set elaboration pos
604 Num_Left := Num_Left - 1;
605 Num_Chosen := Num_Chosen + 1;
606 UNR.Table (Chosen).Elab_Position := Num_Chosen;
607 Units.Table (Chosen).Elab_Position := Num_Chosen;
609 -- If we just chose a spec with Elaborate_Body set, then we
610 -- must immediately elaborate the body, before any other units.
612 if Units.Table (Chosen).Elaborate_Body then
614 -- If the unit is a spec only, then there is no body. This is a bit
615 -- odd given that Elaborate_Body is here, but it is valid in an
616 -- RCI unit, where we only have the interface in the stub bind.
618 if Units.Table (Chosen).Utype = Is_Spec_Only
619 and then Units.Table (Chosen).RCI
623 Choose (Corresponding_Body (Chosen));
628 ------------------------
629 -- Corresponding_Body --
630 ------------------------
632 -- Currently if the body and spec are separate, then they appear as
633 -- two separate units in the same ALI file, with the body appearing
634 -- first and the spec appearing second.
636 function Corresponding_Body (U : Unit_Id) return Unit_Id is
638 pragma Assert (Units.Table (U).Utype = Is_Spec);
640 end Corresponding_Body;
642 ------------------------
643 -- Corresponding_Spec --
644 ------------------------
646 -- Currently if the body and spec are separate, then they appear as
647 -- two separate units in the same ALI file, with the body appearing
648 -- first and the spec appearing second.
650 function Corresponding_Spec (U : Unit_Id) return Unit_Id is
652 pragma Assert (Units.Table (U).Utype = Is_Body);
654 end Corresponding_Spec;
656 ----------------------------------
657 -- Diagnose_Elaboration_Problem --
658 ----------------------------------
660 procedure Diagnose_Elaboration_Problem is
662 function Find_Path (Ufrom, Uto : Unit_Id; ML : Nat) return Boolean;
663 -- Recursive routine used to find a path from node Ufrom to node Uto.
664 -- If a path exists, returns True and outputs an appropriate set of
665 -- error messages giving the path. Also calls Choose for each of the
666 -- nodes so that they get removed from the remaining set. There are
667 -- two cases of calls, either Ufrom = Uto for an attempt to find a
668 -- cycle, or Ufrom is a spec and Uto the corresponding body for the
669 -- case of an unsatisfiable Elaborate_Body pragma. ML is the minimum
670 -- acceptable length for a path.
676 function Find_Path (Ufrom, Uto : Unit_Id; ML : Nat) return Boolean is
678 function Find_Link (U : Unit_Id; PL : Nat) return Boolean;
679 -- This is the inner recursive routine, it determines if a path
680 -- exists from U to Uto, and if so returns True and outputs the
681 -- appropriate set of error messages. PL is the path length
687 function Find_Link (U : Unit_Id; PL : Nat) return Boolean is
691 -- Recursion ends if we are at terminating node and the path
692 -- is sufficiently long, generate error message and return True.
694 if U = Uto and then PL >= ML then
698 -- All done if already visited, otherwise mark as visited
700 elsif UNR.Table (U).Visited then
703 -- Otherwise mark as visited and look at all successors
706 UNR.Table (U).Visited := True;
708 S := UNR.Table (U).Successors;
709 while S /= No_Successor loop
710 if Find_Link (Succ.Table (S).After, PL + 1) then
716 S := Succ.Table (S).Next;
719 -- Falling through means this does not lead to a path
725 -- Start of processing for Find_Path
728 -- Initialize all non-chosen nodes to not visisted yet
730 for U in Units.First .. Units.Last loop
731 UNR.Table (U).Visited := UNR.Table (U).Elab_Position /= 0;
734 -- Now try to find the path
736 return Find_Link (Ufrom, 0);
739 -- Start of processing for Diagnose_Elaboration_Error
744 -- Output state of things if debug flag N set
753 Write_Str ("Diagnose_Elaboration_Problem called");
755 Write_Str ("List of remaining unchosen units and predecessors");
758 for U in Units.First .. Units.Last loop
759 if UNR.Table (U).Elab_Position = 0 then
760 NP := UNR.Table (U).Num_Pred;
762 Write_Str (" Unchosen unit: #");
765 Write_Unit_Name (Units.Table (U).Uname);
766 Write_Str (" (Num_Pred = ");
772 if Units.Table (U).Elaborate_Body then
774 (" (not chosen because of Elaborate_Body)");
777 Write_Str (" ****************** why not chosen?");
782 -- Search links list to find unchosen predecessors
784 for S in Succ.First .. Succ.Last loop
786 SL : Successor_Link renames Succ.Table (S);
790 and then UNR.Table (SL.Before).Elab_Position = 0
792 Write_Str (" unchosen predecessor: #");
793 Write_Int (Int (SL.Before));
795 Write_Unit_Name (Units.Table (SL.Before).Uname);
803 Write_Str (" **************** Num_Pred value wrong!");
811 -- Output the header for the error, and manually increment the
812 -- error count. We are using Error_Msg_Output rather than Error_Msg
813 -- here for two reasons:
815 -- This is really only one error, not one for each line
816 -- We want this output on standard output since it is voluminous
818 -- But we do need to deal with the error count manually in this case
820 Errors_Detected := Errors_Detected + 1;
821 Error_Msg_Output ("elaboration circularity detected", Info => False);
823 -- Try to find cycles starting with any of the remaining nodes that have
824 -- not yet been chosen. There must be at least one (there is some reason
825 -- we are being called!)
827 for U in Units.First .. Units.Last loop
828 if UNR.Table (U).Elab_Position = 0 then
829 if Find_Path (U, U, 1) then
830 raise Unrecoverable_Error;
835 -- We should never get here, since we were called for some reason,
836 -- and we should have found and eliminated at least one bad path.
839 end Diagnose_Elaboration_Problem;
845 procedure Elab_All_Links
848 Reason : Succ_Reason;
852 if UNR.Table (Before).Visited then
856 -- Build the direct link for Before
858 UNR.Table (Before).Visited := True;
859 Build_Link (Before, After, Reason, Link);
861 -- Process all units with'ed by Before recursively
864 Units.Table (Before).First_With .. Units.Table (Before).Last_With
866 -- Skip if this with is an interface to a stand-alone library.
867 -- Skip also if no ALI file for this with, happens with certain
868 -- specialized generic files that do not get compiled.
870 if not Withs.Table (W).SAL_Interface
871 and then Withs.Table (W).Afile /= No_File
872 and then Generic_Separately_Compiled (Withs.Table (W).Sfile)
875 (Unit_Id_Of (Withs.Table (W).Uname),
878 Make_Elab_Entry (Withs.Table (W).Uname, Link));
882 -- Process corresponding body, if there is one
884 if Units.Table (Before).Utype = Is_Spec then
886 (Corresponding_Body (Before),
889 (Units.Table (Corresponding_Body (Before)).Uname, Link));
897 procedure Elab_Error_Msg (S : Successor_Id) is
898 SL : Successor_Link renames Succ.Table (S);
901 -- Nothing to do if internal unit involved and no -da flag
905 (Is_Internal_File_Name (Units.Table (SL.Before).Sfile)
907 Is_Internal_File_Name (Units.Table (SL.After).Sfile))
912 -- Here we want to generate output
914 Error_Msg_Unit_1 := Units.Table (SL.Before).Uname;
917 Error_Msg_Unit_2 := Units.Table (Corresponding_Body (SL.After)).Uname;
919 Error_Msg_Unit_2 := Units.Table (SL.After).Uname;
922 Error_Msg_Output (" $ must be elaborated before $", Info => True);
924 Error_Msg_Unit_1 := Units.Table (SL.Reason_Unit).Uname;
929 (" reason: with clause",
934 (" reason: pragma Elaborate in unit $",
939 (" reason: pragma Elaborate_All in unit $",
942 when Elab_All_Desirable =>
944 (" reason: implicit Elaborate_All in unit $",
948 (" recompile $ with -gnatwl for full details",
951 when Elab_Desirable =>
953 (" reason: implicit Elaborate in unit $",
957 (" recompile $ with -gnatwl for full details",
962 (" reason: spec always elaborated before body",
966 Write_Elab_All_Chain (S);
969 Error_Msg_Unit_1 := Units.Table (SL.Before).Uname;
970 Error_Msg_Unit_2 := Units.Table (SL.After).Uname;
972 (" $ must therefore be elaborated before $",
975 Error_Msg_Unit_1 := Units.Table (SL.After).Uname;
977 (" (because $ has a pragma Elaborate_Body)",
981 if not Zero_Formatting then
986 ---------------------
987 -- Find_Elab_Order --
988 ---------------------
990 procedure Find_Elab_Order is
992 Best_So_Far : Unit_Id;
996 Num_Left := Int (Units.Last - Units.First + 1);
998 -- Initialize unit table for elaboration control
1000 for U in Units.First .. Units.Last loop
1002 UNR.Table (UNR.Last).Successors := No_Successor;
1003 UNR.Table (UNR.Last).Num_Pred := 0;
1004 UNR.Table (UNR.Last).Nextnp := No_Unit_Id;
1005 UNR.Table (UNR.Last).Elab_Order := 0;
1006 UNR.Table (UNR.Last).Elab_Position := 0;
1009 -- Output warning if -p used with no -gnatE units
1011 if Pessimistic_Elab_Order
1012 and not Dynamic_Elaboration_Checks_Specified
1014 if OpenVMS_On_Target then
1015 Error_Msg ("?use of /PESSIMISTIC_ELABORATION questionable");
1017 Error_Msg ("?use of -p switch questionable");
1020 Error_Msg ("?since all units compiled with static elaboration model");
1023 -- Gather dependencies and output them if option set
1025 Gather_Dependencies;
1027 -- Output elaboration dependencies if option is set
1029 if Elab_Dependency_Output or Debug_Flag_E then
1033 -- Initialize the no predecessor list
1035 No_Pred := No_Unit_Id;
1037 for U in UNR.First .. UNR.Last loop
1038 if UNR.Table (U).Num_Pred = 0 then
1039 UNR.Table (U).Nextnp := No_Pred;
1044 -- OK, now we determine the elaboration order proper. All we do is to
1045 -- select the best choice from the no predecessor list until all the
1046 -- nodes have been chosen.
1050 -- If there are no nodes with predecessors, then either we are
1051 -- done, as indicated by Num_Left being set to zero, or we have
1052 -- a circularity. In the latter case, diagnose the circularity,
1053 -- removing it from the graph and continue
1055 Get_No_Pred : while No_Pred = No_Unit_Id loop
1056 exit Outer when Num_Left < 1;
1057 Diagnose_Elaboration_Problem;
1058 end loop Get_No_Pred;
1061 Best_So_Far := No_Unit_Id;
1063 -- Loop to choose best entry in No_Pred list
1065 No_Pred_Search : loop
1066 if Debug_Flag_N then
1067 Write_Str (" considering choice of ");
1068 Write_Unit_Name (Units.Table (U).Uname);
1071 if Units.Table (U).Elaborate_Body then
1073 (" Elaborate_Body = True, Num_Pred for body = ");
1075 (Int (UNR.Table (Corresponding_Body (U)).Num_Pred));
1078 (" Elaborate_Body = False");
1084 -- This is a candididate to be considered for choice
1086 if Best_So_Far = No_Unit_Id
1087 or else ((not Pessimistic_Elab_Order)
1088 and then Better_Choice (U, Best_So_Far))
1089 or else (Pessimistic_Elab_Order
1090 and then Worse_Choice (U, Best_So_Far))
1092 if Debug_Flag_N then
1093 Write_Str (" tentatively chosen (best so far)");
1100 U := UNR.Table (U).Nextnp;
1101 exit No_Pred_Search when U = No_Unit_Id;
1102 end loop No_Pred_Search;
1104 -- If no candididate chosen, it means that no unit has No_Pred = 0,
1105 -- but there are units left, hence we have a circular dependency,
1106 -- which we will get Diagnose_Elaboration_Problem to diagnose it.
1108 if Best_So_Far = No_Unit_Id then
1109 Diagnose_Elaboration_Problem;
1111 -- Otherwise choose the best candidate found
1114 Choose (Best_So_Far);
1117 end Find_Elab_Order;
1119 -------------------------
1120 -- Gather_Dependencies --
1121 -------------------------
1123 procedure Gather_Dependencies is
1124 Withed_Unit : Unit_Id;
1127 -- Loop through all units
1129 for U in Units.First .. Units.Last loop
1132 -- If this is not an interface to a stand-alone library and
1133 -- there is a body and a spec, then spec must be elaborated first
1134 -- Note that the corresponding spec immediately follows the body
1136 if not Units.Table (U).SAL_Interface
1137 and then Units.Table (U).Utype = Is_Body
1139 Build_Link (Corresponding_Spec (U), U, Spec_First);
1142 -- If this unit is not an interface to a stand-alone library,
1143 -- process WITH references for this unit ignoring generic units and
1144 -- interfaces to stand-alone libraries.
1146 if not Units.Table (U).SAL_Interface then
1148 W in Units.Table (U).First_With .. Units.Table (U).Last_With
1150 if Withs.Table (W).Sfile /= No_File
1151 and then (not Withs.Table (W).SAL_Interface)
1153 -- Check for special case of withing a unit that does not
1154 -- exist any more. If the unit was completely missing we
1155 -- would already have detected this, but a nasty case arises
1156 -- when we have a subprogram body with no spec, and some
1157 -- obsolete unit with's a previous (now disappeared) spec.
1159 if Get_Name_Table_Info (Withs.Table (W).Uname) = 0 then
1160 Error_Msg_File_1 := Units.Table (U).Sfile;
1161 Error_Msg_Unit_1 := Withs.Table (W).Uname;
1162 Error_Msg ("{ depends on $ which no longer exists");
1167 Unit_Id (Unit_Id_Of (Withs.Table (W).Uname));
1169 -- Pragma Elaborate_All case, for this we use the recursive
1170 -- Elab_All_Links procedure to establish the links.
1172 if Withs.Table (W).Elaborate_All then
1174 -- Reset flags used to stop multiple visits to a given
1177 for Uref in UNR.First .. UNR.Last loop
1178 UNR.Table (Uref).Visited := False;
1181 -- Now establish all the links we need
1184 (Withed_Unit, U, Elab_All,
1186 (Withs.Table (W).Uname, No_Elab_All_Link));
1188 -- Elaborate_All_Desirable case, for this we establish
1189 -- the same links as above, but with a different reason.
1191 elsif Withs.Table (W).Elab_All_Desirable then
1193 -- Reset flags used to stop multiple visits to a given
1196 for Uref in UNR.First .. UNR.Last loop
1197 UNR.Table (Uref).Visited := False;
1200 -- Now establish all the links we need
1203 (Withed_Unit, U, Elab_All_Desirable,
1205 (Withs.Table (W).Uname, No_Elab_All_Link));
1207 -- Pragma Elaborate case. We must build a link for the
1208 -- withed unit itself, and also the corresponding body
1211 -- However, skip this processing if there is no ALI file
1212 -- for the WITH entry, because this means it is a
1213 -- generic (even when we fix the generics so that an ALI
1214 -- file is present, we probably still will have no ALI
1215 -- file for unchecked and other special cases).
1217 elsif Withs.Table (W).Elaborate
1218 and then Withs.Table (W).Afile /= No_File
1220 Build_Link (Withed_Unit, U, Withed);
1222 if Units.Table (Withed_Unit).Utype = Is_Spec then
1224 (Corresponding_Body (Withed_Unit), U, Elab);
1227 -- Elaborate_Desirable case, for this we establish
1228 -- the same links as above, but with a different reason.
1230 elsif Withs.Table (W).Elab_Desirable then
1231 Build_Link (Withed_Unit, U, Withed);
1233 if Units.Table (Withed_Unit).Utype = Is_Spec then
1235 (Corresponding_Body (Withed_Unit),
1239 -- Case of normal WITH with no elaboration pragmas, just
1240 -- build the single link to the directly referenced unit
1243 Build_Link (Withed_Unit, U, Withed);
1252 end Gather_Dependencies;
1258 function Is_Body_Unit (U : Unit_Id) return Boolean is
1260 return Units.Table (U).Utype = Is_Body
1261 or else Units.Table (U).Utype = Is_Body_Only;
1264 ---------------------
1265 -- Is_Waiting_Body --
1266 ---------------------
1268 function Is_Waiting_Body (U : Unit_Id) return Boolean is
1270 return Units.Table (U).Utype = Is_Body
1271 and then UNR.Table (Corresponding_Spec (U)).Elab_Position /= 0;
1272 end Is_Waiting_Body;
1274 ---------------------
1275 -- Make_Elab_Entry --
1276 ---------------------
1278 function Make_Elab_Entry
1279 (Unam : Unit_Name_Type;
1280 Link : Elab_All_Id) return Elab_All_Id
1283 Elab_All_Entries.Increment_Last;
1284 Elab_All_Entries.Table (Elab_All_Entries.Last).Needed_By := Unam;
1285 Elab_All_Entries.Table (Elab_All_Entries.Last).Next_Elab := Link;
1286 return Elab_All_Entries.Last;
1287 end Make_Elab_Entry;
1293 function Unit_Id_Of (Uname : Unit_Name_Type) return Unit_Id is
1294 Info : constant Int := Get_Name_Table_Info (Uname);
1296 pragma Assert (Info /= 0 and then Unit_Id (Info) /= No_Unit_Id);
1297 return Unit_Id (Info);
1304 function Worse_Choice (U1, U2 : Unit_Id) return Boolean is
1305 UT1 : Unit_Record renames Units.Table (U1);
1306 UT2 : Unit_Record renames Units.Table (U2);
1309 -- Note: the checks here are applied in sequence, and the ordering is
1310 -- significant (i.e. the more important criteria are applied first).
1312 -- If either unit is internal, then use Better_Choice, since the
1313 -- language requires that predefined units not mess up in the choice
1314 -- of elaboration order, and for internal units, any problems are
1315 -- ours and not the programmers.
1317 if UT1.Internal or else UT2.Internal then
1318 return Better_Choice (U1, U2);
1320 -- Prefer anything else to a waiting body (!)
1322 elsif Is_Waiting_Body (U1) and not Is_Waiting_Body (U2) then
1325 elsif Is_Waiting_Body (U2) and not Is_Waiting_Body (U1) then
1328 -- Prefer a spec to a body (!)
1330 elsif Is_Body_Unit (U1) and not Is_Body_Unit (U2) then
1333 elsif Is_Body_Unit (U2) and not Is_Body_Unit (U1) then
1336 -- If both are waiting bodies, then prefer the one whose spec is
1337 -- less recently elaborated. Consider the following:
1343 -- The normal waiting body preference would have placed the body of
1344 -- A before the spec of B if it could. Since it could not, there it
1345 -- must be the case that A depends on B. It is therefore a good idea
1346 -- to put the body of B last so that if there is an elaboration order
1347 -- problem, we will find it (that's what horrible order is about)
1349 elsif Is_Waiting_Body (U1) and then Is_Waiting_Body (U2) then
1351 UNR.Table (Corresponding_Spec (U1)).Elab_Position <
1352 UNR.Table (Corresponding_Spec (U2)).Elab_Position;
1355 -- Remaining choice rules are disabled by Debug flag -do
1357 if not Debug_Flag_O then
1359 -- The following deal with the case of specs which have been marked
1360 -- as Elaborate_Body_Desirable. In the normal case, we generally want
1361 -- to delay the elaboration of these specs as long as possible, so
1362 -- that bodies have better chance of being elaborated closer to the
1363 -- specs. Worse_Choice as usual wants to do the opposite and
1364 -- elaborate such specs as early as possible.
1366 -- If we have two units, one of which is a spec for which this flag
1367 -- is set, and the other is not, we normally prefer to delay the spec
1368 -- for which the flag is set, and so Worse_Choice does the opposite.
1370 if not UT1.Elaborate_Body_Desirable
1371 and then UT2.Elaborate_Body_Desirable
1375 elsif not UT2.Elaborate_Body_Desirable
1376 and then UT1.Elaborate_Body_Desirable
1380 -- If we have two specs that are both marked as Elaborate_Body
1381 -- desirable, we normally prefer the one whose body is nearer to
1382 -- being able to be elaborated, based on the Num_Pred count. This
1383 -- helps to ensure bodies are as close to specs as possible. As
1384 -- usual, Worse_Choice does the opposite.
1386 elsif UT1.Elaborate_Body_Desirable
1387 and then UT2.Elaborate_Body_Desirable
1389 return UNR.Table (Corresponding_Body (U1)).Num_Pred >=
1390 UNR.Table (Corresponding_Body (U2)).Num_Pred;
1394 -- If we fall through, it means that no preference rule applies, so we
1395 -- use alphabetical order to at least give a deterministic result. Since
1396 -- Worse_Choice is in the business of stirring up the order, we will
1397 -- use reverse alphabetical ordering.
1399 return Uname_Less (UT2.Uname, UT1.Uname);
1402 ------------------------
1403 -- Write_Dependencies --
1404 ------------------------
1406 procedure Write_Dependencies is
1408 if not Zero_Formatting then
1410 Write_Str (" ELABORATION ORDER DEPENDENCIES");
1415 Info_Prefix_Suppress := True;
1417 for S in Succ_First .. Succ.Last loop
1421 Info_Prefix_Suppress := False;
1423 if not Zero_Formatting then
1426 end Write_Dependencies;
1428 --------------------------
1429 -- Write_Elab_All_Chain --
1430 --------------------------
1432 procedure Write_Elab_All_Chain (S : Successor_Id) is
1433 ST : constant Successor_Link := Succ.Table (S);
1434 After : constant Unit_Name_Type := Units.Table (ST.After).Uname;
1437 Nam : Unit_Name_Type;
1439 First_Name : Boolean := True;
1442 if ST.Reason in Elab_All .. Elab_All_Desirable then
1443 L := ST.Elab_All_Link;
1444 while L /= No_Elab_All_Link loop
1445 Nam := Elab_All_Entries.Table (L).Needed_By;
1446 Error_Msg_Unit_1 := Nam;
1447 Error_Msg_Output (" $", Info => True);
1449 Get_Name_String (Nam);
1451 if Name_Buffer (Name_Len) = 'b' then
1454 (" must be elaborated along with its spec:",
1459 (" which must be elaborated " &
1460 "along with its spec:",
1472 (" which is withed by:",
1477 First_Name := False;
1479 L := Elab_All_Entries.Table (L).Next_Elab;
1482 Error_Msg_Unit_1 := After;
1483 Error_Msg_Output (" $", Info => True);
1485 end Write_Elab_All_Chain;