===================================================================
@@ -5056,6 +5056,7 @@ individually controlled. The warnings t
switch are
@option{-gnatwd} (implicit dereferencing),
@option{-gnatwh} (hiding),
+@option{-gnatw.h} (holes (gaps) in record layouts)
@option{-gnatwl} (elaboration warnings),
@option{-gnatw.o} (warn on values set by out parameters ignored)
and @option{-gnatwt} (tracking of deleted conditional code).
@@ -5258,6 +5259,22 @@ Note that @option{-gnatwa} does not affe
@cindex @option{-gnatwH} (@command{gcc})
This switch suppresses warnings on hiding declarations.
+@item -gnatw.h
+@emph{Activate warnings on holes/gaps in records.}
+@cindex @option{-gnatw.h} (@command{gcc})
+@cindex Record Representation (gaps)
+This switch activates warnings on component clauses in record
+representation clauses that leave holes (gaps) in the record layout.
+If this warning option is active, then record representation clauses
+should specify a contiguous layout, adding unused fill fields if needed.
+Note that @option{-gnatwa} does not affect the setting of this warning option.
+
+@item -gnatw.H
+@emph{Suppress warnings on holes/gaps in records.}
+@cindex @option{-gnatw.H} (@command{gcc})
+This switch suppresses warnings on component clauses in record
+representation clauses that leave holes (haps) in the record layout.
+
@item -gnatwi
@emph{Activate warnings on implementation units.}
@cindex @option{-gnatwi} (@command{gcc})
===================================================================
@@ -1535,9 +1535,11 @@ package body Sem_Ch13 is
elsif Size /= No_Uint then
if VM_Target /= No_VM and then not GNAT_Mode then
+
-- Size clause is not handled properly on VM targets.
-- Display a warning unless we are in GNAT mode, in which
-- case this is useless.
+
Error_Msg_N
("?size clauses are ignored in this configuration", N);
end if;
@@ -3255,6 +3257,9 @@ package body Sem_Ch13 is
Overlap_Check_Required : Boolean;
-- Used to keep track of whether or not an overlap check is required
+ Overlap_Detected : Boolean := False;
+ -- Set True if an overlap is detected
+
Ccount : Natural := 0;
-- Number of component clauses in record rep clause
@@ -3278,6 +3283,7 @@ package body Sem_Ch13 is
procedure Check_Component_Overlap (C1_Ent, C2_Ent : Entity_Id) is
CC1 : constant Node_Id := Component_Clause (C1_Ent);
CC2 : constant Node_Id := Component_Clause (C2_Ent);
+
begin
if Present (CC1) and then Present (CC2) then
@@ -3309,6 +3315,7 @@ package body Sem_Ch13 is
Error_Msg_Node_1 := Component_Name (CC1);
Error_Msg_N
("component& overlaps & #", Component_Name (CC1));
+ Overlap_Detected := True;
end if;
end;
end if;
@@ -3481,12 +3488,14 @@ package body Sem_Ch13 is
if Present (Comp) then
Ccount := Ccount + 1;
+ -- We need a full overlap check if record positions non-monotonic
+
if Fbit <= Max_Bit_So_Far then
Overlap_Check_Required := True;
- else
- Max_Bit_So_Far := Lbit;
end if;
+ Max_Bit_So_Far := Lbit;
+
-- Check bit position out of range of specified size
if Has_Size_Clause (Rectype)
@@ -3505,6 +3514,7 @@ package body Sem_Ch13 is
Error_Msg_NE
("component overlaps tag field of&",
Component_Name (CC), Rectype);
+ Overlap_Detected := True;
end if;
if Hbit < Lbit then
@@ -3654,8 +3664,8 @@ package body Sem_Ch13 is
-- Skip overlap check if entity has no declaration node. This
-- happens with discriminants in constrained derived types.
- -- Probably we are missing some checks as a result, but that
- -- does not seem terribly serious ???
+ -- Possibly we are missing some checks as a result, but that
+ -- does not seem terribly serious.
if No (Declaration_Node (C1_Ent)) then
goto Continue_Main_Component_Loop;
@@ -3699,7 +3709,6 @@ package body Sem_Ch13 is
else
Citem := First (Component_Items (Clist));
-
while Present (Citem) loop
if Nkind (Citem) = N_Component_Declaration then
C2_Ent := Defining_Identifier (Citem);
@@ -3745,6 +3754,183 @@ package body Sem_Ch13 is
end Overlap_Check2;
end if;
+ -- The following circuit deals with warning on record holes (gaps). We
+ -- skip this check if overlap was detected, since it makes sense for the
+ -- programmer to fix this illegality before worrying about warnings.
+
+ if not Overlap_Detected and Warn_On_Record_Holes then
+ Record_Hole_Check : declare
+ Decl : constant Node_Id := Declaration_Node (Base_Type (Rectype));
+ -- Full declaration of record type
+
+ procedure Check_Component_List
+ (CL : Node_Id;
+ Sbit : Uint;
+ DS : List_Id);
+ -- Check component list CL for holes. The starting bit should be
+ -- Sbit. which is zero for the main record component list and set
+ -- appropriately for recursive calls for variants. DS is set to
+ -- a list of discriminant specifications to be included in the
+ -- consideration of components. It is No_List if none to consider.
+
+ --------------------------
+ -- Check_Component_List --
+ --------------------------
+
+ procedure Check_Component_List
+ (CL : Node_Id;
+ Sbit : Uint;
+ DS : List_Id)
+ is
+ Compl : Integer;
+
+ begin
+ Compl := Integer (List_Length (Component_Items (CL)));
+
+ if DS /= No_List then
+ Compl := Compl + Integer (List_Length (DS));
+ end if;
+
+ declare
+ Comps : array (Natural range 0 .. Compl) of Entity_Id;
+ -- Gather components (zero entry is for sort routine)
+
+ Ncomps : Natural := 0;
+ -- Number of entries stored in Comps (starting at Comps (1))
+
+ Citem : Node_Id;
+ -- One component item or discriminant specification
+
+ Nbit : Uint;
+ -- Starting bit for next component
+
+ CEnt : Entity_Id;
+ -- Component entity
+
+ Variant : Node_Id;
+ -- One variant
+
+ function Lt (Op1, Op2 : Natural) return Boolean;
+ -- Compare routine for Sort
+
+ procedure Move (From : Natural; To : Natural);
+ -- Move routine for Sort
+
+ package Sorting is new GNAT.Heap_Sort_G (Move, Lt);
+
+ --------
+ -- Lt --
+ --------
+
+ function Lt (Op1, Op2 : Natural) return Boolean is
+ begin
+ return Component_Bit_Offset (Comps (Op1))
+ <
+ Component_Bit_Offset (Comps (Op2));
+ end Lt;
+
+ ----------
+ -- Move --
+ ----------
+
+ procedure Move (From : Natural; To : Natural) is
+ begin
+ Comps (To) := Comps (From);
+ end Move;
+
+ begin
+ -- Gather discriminants into Comp
+
+ if DS /= No_List then
+ Citem := First (DS);
+ while Present (Citem) loop
+ if Nkind (Citem) = N_Discriminant_Specification then
+ declare
+ Ent : constant Entity_Id :=
+ Defining_Identifier (Citem);
+ begin
+ if Ekind (Ent) = E_Discriminant then
+ Ncomps := Ncomps + 1;
+ Comps (Ncomps) := Ent;
+ end if;
+ end;
+ end if;
+
+ Next (Citem);
+ end loop;
+ end if;
+
+ -- Gather component entities into Comp
+
+ Citem := First (Component_Items (CL));
+ while Present (Citem) loop
+ if Nkind (Citem) = N_Component_Declaration then
+ Ncomps := Ncomps + 1;
+ Comps (Ncomps) := Defining_Identifier (Citem);
+ end if;
+
+ Next (Citem);
+ end loop;
+
+ -- Now sort the component entities based on the first bit.
+ -- Note we already know there are no overlapping components.
+
+ Sorting.Sort (Ncomps);
+
+ -- Loop through entries checking for holes
+
+ Nbit := Sbit;
+ for J in 1 .. Ncomps loop
+ CEnt := Comps (J);
+ Error_Msg_Uint_1 := Component_Bit_Offset (CEnt) - Nbit;
+
+ if Error_Msg_Uint_1 > 0 then
+ Error_Msg_NE
+ ("?^-bit gap before component&",
+ Component_Name (Component_Clause (CEnt)), CEnt);
+ end if;
+
+ Nbit := Component_Bit_Offset (CEnt) + Esize (CEnt);
+ end loop;
+
+ -- Process variant parts recursively if present
+
+ if Present (Variant_Part (CL)) then
+ Variant := First (Variants (Variant_Part (CL)));
+ while Present (Variant) loop
+ Check_Component_List
+ (Component_List (Variant), Nbit, No_List);
+ Next (Variant);
+ end loop;
+ end if;
+ end;
+ end Check_Component_List;
+
+ -- Start of processing for Record_Hole_Check
+
+ begin
+ declare
+ Sbit : Uint;
+
+ begin
+ if Is_Tagged_Type (Rectype) then
+ Sbit := UI_From_Int (System_Address_Size);
+ else
+ Sbit := Uint_0;
+ end if;
+
+ if Nkind (Decl) = N_Full_Type_Declaration
+ and then Nkind (Type_Definition (Decl)) = N_Record_Definition
+ then
+ Check_Component_List
+ (Component_List (Type_Definition (Decl)),
+ Sbit,
+ Discriminant_Specifications (Decl));
+ end if;
+ end;
+ end Record_Hole_Check;
+ end if;
+
-- For records that have component clauses for all components, and whose
-- size is less than or equal to 32, we need to know the size in the
-- front end to activate possible packed array processing where the
===================================================================
@@ -3087,6 +3087,7 @@ package body Sem_Warn is
Warn_On_Overlap := True;
Warn_On_Parameter_Order := True;
Warn_On_Questionable_Missing_Parens := True;
+ Warn_On_Record_Holes := True;
Warn_On_Redundant_Constructs := True;
Warn_On_Reverse_Bit_Order := True;
Warn_On_Unchecked_Conversion := True;
@@ -3098,6 +3099,12 @@ package body Sem_Warn is
when 'g' =>
Set_GNAT_Mode_Warnings;
+ when 'h' =>
+ Warn_On_Record_Holes := True;
+
+ when 'H' =>
+ Warn_On_Record_Holes := False;
+
when 'i' =>
Warn_On_Overlap := True;
@@ -3262,6 +3269,7 @@ package body Sem_Warn is
Warn_On_Obsolescent_Feature := False;
Warn_On_Overlap := False;
Warn_On_Parameter_Order := False;
+ Warn_On_Record_Holes := False;
Warn_On_Questionable_Missing_Parens := False;
Warn_On_Redundant_Constructs := False;
Warn_On_Reverse_Bit_Order := False;
===================================================================
@@ -6,7 +6,7 @@
-- --
-- S p e c --
-- --
+-- Copyright (C) 1999-2010, Free Software Foundation, Inc. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
@@ -33,6 +33,20 @@ with Types; use Types;
package Sem_Warn is
+ -------------------
+ -- Warning Flags --
+ -------------------
+
+ -- These flags are activated or deactivated by -gnatw switches and control
+ -- whether warnings of a given class will be generated or not.
+
+ -- Note: most of these flags are still in opt, but the plan is to move them
+ -- here as time goes by.
+
+ Warn_On_Record_Holes : Boolean := False;
+ -- Warn when explicit record component clauses leave uncovered holes (gaps)
+ -- in a record layout. Off by default, set by -gnatw.h (but not -gnatwa).
+
------------------------
-- Warnings Off Table --
------------------------
===================================================================
@@ -138,6 +138,8 @@ gcc -c ^ GNAT COMPILE
-gnatwG ^ /WARNINGS=NOUNRECOGNIZED_PRAGMAS
-gnatwh ^ /WARNINGS=HIDING
-gnatwH ^ /WARNINGS=NOHIDING
+-gnatw.h ^ /WARNINGS=AVOIDGAPS
+-gnatw.H ^ /WARNINGS=NOAVOIDGAPS
-gnatwi ^ /WARNINGS=IMPLEMENTATION
-gnatwI ^ /WARNINGS=NOIMPLEMENTATION
-gnatwj ^ /WARNINGS=OBSOLESCENT
===================================================================
@@ -422,6 +422,8 @@ begin
Write_Line (" G turn off warnings for unrecognized pragma");
Write_Line (" h turn on warnings for hiding variable");
Write_Line (" H* turn off warnings for hiding variable");
+ Write_Line (" .h turn on warnings for holes in records");
+ Write_Line (" .H* turn off warnings for holes in records");
Write_Line (" i*+ turn on warnings for implementation unit");
Write_Line (" I turn off warnings for implementation unit");
Write_Line (" .i turn on warnings for overlapping actuals");
===================================================================
@@ -2951,6 +2951,10 @@ package VMS_Data is
"-gnatwh " &
"NOHIDING " &
"-gnatwH " &
+ "AVOIDGAPS " &
+ "-gnatw.h " &
+ "NOAVOIDGAPS " &
+ "-gnatw.H " &
"IMPLEMENTATION " &
"-gnatwi " &
"NOIMPLEMENTATION " &
This patch implements a new warning -gnatw.h that checks for holes (gaps) in records when explicit component clauses do not cover a contiguous sequence of bits starting with the first bit in the record. 1. with System.Storage_Elements; 2. package rechole is 3. type r1 is record -- OK no gaps 4. a, b, c : Integer; 5. end record; 6. for r1 use record 7. a at 0 range 0 .. 31; 8. b at 4 range 0 .. 31; 9. c at 8 range 0 .. 31; 10. end record; 11. 12. type r2 is record -- OK no gaps 13. a, b, c : Boolean; 14. end record; 15. for r2 use record 16. a at 0 range 2 .. 2; 17. b at 0 range 1 .. 1; 18. c at 0 range 0 .. 0; 19. end record; 20. 21. type r3 is record 22. a, b, c : Integer; 23. end record; 24. for r3 use record 25. a at 0 range 0 .. 31; 26. b at 4 range 0 .. 31; 27. c at 12 range 0 .. 31; -- 32-bit gap | >>> warning: 32-bit gap before component "c" 28. end record; 29. 30. type r4 is record 31. a, b, c : Boolean; 32. end record; 33. for r4 use record 34. a at 0 range 4 .. 4; -- 2-bit gap | >>> warning: 2-bit gap before component "a" 35. b at 0 range 1 .. 1; 36. c at 0 range 0 .. 0; 37. end record; 38. 39. type R5 (x : boolean) -- OK, no gaps 40. is record 41. a, b : integer; 42. case x is 43. when false => 44. c : integer; 45. when true => 46. d : integer; 47. end case; 48. end record; 49. for R5 use record 50. x at 0 range 0 .. 31; 51. a at 4 range 0 .. 31; 52. b at 8 range 0 .. 31; 53. c at 12 range 0 .. 31; 54. d at 12 range 0 .. 31; 55. end record; 56. 57. type R6 (x : boolean) is record 58. a, b : integer; 59. case x is 60. when false => 61. c : integer; 62. d : integer; 63. when true => 64. e : integer; 65. end case; 66. end record; 67. for R6 use record 68. x at 0 range 0 .. 31; 69. a at 4 range 0 .. 31; 70. b at 8 range 0 .. 31; 71. c at 12 range 0 .. 31; 72. d at 20 range 0 .. 31; -- 32-bit gap | >>> warning: 32-bit gap before component "d" 73. e at 20 range 0 .. 31; -- 64-bit gap | >>> warning: 64-bit gap before component "e" 74. end record; 75. 76. T : constant := 77. System.Storage_Elements.Integer_Address'Size; 78. 79. type R7 is tagged record -- OK, no gaps 80. a : integer; 81. end record; 82. for R7 use record 83. a at 0 range T .. T + 31; 84. end record; 85. 86. type R8 is tagged record 87. a : integer; 88. end record; 89. for R8 use record 90. a at 0 range -- 1-bit gap | >>> warning: 1-bit gap before component "a" 91. T + 1 .. T + 32; 92. end record; 93. 94. end rechole; Tested on x86_64-pc-linux-gnu, committed on trunk 2010-09-10 Robert Dewar <dewar@adacore.com> * sem_ch13.adb (Check_Record_Representation_Clause): Implement record gap warnings. * sem_warn.ads, sem_warn.adb (Warn_On_Record_Holes): New warning flag. * usage.adb: Add lines for -gnatw.h/H * gnat_ugn.texi: Add documentation for J519-010 Warn on record holes/gaps * ug_words: Add entries for -gnatw.h/-gnatw.H * vms_data.ads: Add entries for [NO]AVOIDGAPS