gcc/ada/sem_warn.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                             S E M _ W A R N                              --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1999-2006, 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 ------------------------------------------------------------------------------
  26
  27 --  This package contains the routines used to deal with issuing warnings
  28 --  about uses of uninitialized variables and unused with's. It also has
  29 --  some unrelated routines related to the generation of warnings.
  30
  31 with Types; use Types;
  32
  33 package Sem_Warn is
  34
  35    --------------------
  36    -- Initialization --
  37    --------------------
  38
  39    function Set_Warning_Switch (C : Character) return Boolean;
  40    --  This function sets the warning switch or switches corresponding to
  41    --  the given character. It is used for processing a -gnatw switch on the
  42    --  command line, or a string literal in pragma Warnings.
  43
  44    ------------------------------------------
  45    -- Routines to Handle Unused References --
  46    ------------------------------------------
  47
  48    procedure Check_References (E : Entity_Id; Anod : Node_Id := Empty);
  49    --  Called at the end of processing a declarative region. The entity E
  50    --  is the entity for the scope. All entities declared in the region,
  51    --  as indicated by First_Entity and the entity chain, are checked to
  52    --  see if they are variables for which warnings need to be posted for
  53    --  either no assignments, or a use before an assignment or no references
  54    --  at all. The Anod node is present for the case of an accept statement,
  55    --  and references the accept statement. This is used to place the warning
  56    --  messages in the right place.
  57
  58    procedure Check_Unset_Reference (N : Node_Id);
  59    --  N is the node for an expression which occurs in a reference position,
  60    --  e.g. as the right side of an assignment. This procedure checks to see
  61    --  if the node is a reference to a variable entity where the entity has
  62    --  Not_Assigned set. If so, the Unset_Reference field is set if it is not
  63    --  the first occurrence. No warning is posted, instead warnings will be
  64    --  posted later by Check_References. The reason we do things that
  65    --  way is that if there are no assignments anywhere, we prefer to flag
  66    --  the entity, rather than a reference to it. Note that for the purposes
  67    --  of this routine, a type conversion or qualified expression whose
  68    --  expression is an entity is also processed. The reason that we do not
  69    --  process these at the point of occurrence is that both these constructs
  70    --  can occur in non-reference positions (e.g. as out parameters).
  71
  72    procedure Check_Unused_Withs (Spec_Unit : Unit_Number_Type := No_Unit);
  73    --  This routine performs two kinds of checks. It checks that all with'ed
  74    --  units are referenced, and that at least one entity of each with'ed
  75    --  unit is referenced (the latter check catches units that are only
  76    --  referenced in a use or package renaming statement). Appropriate
  77    --  warning messages are generated if either of these situations is
  78    --  detected.
  79    --
  80    --  A special case arises when a package body or a subprogram body with
  81    --  a separate spec is being compiled. In this case, a with may appear
  82    --  on the spec, but be needed only by the body. This still generates
  83    --  a warning, but the text is different (the with is not redundant,
  84    --  it is misplaced).
  85    --
  86    --  This special case is implemented by making an initial call to this
  87    --  procedure with Spec_Unit set to the unit number of the separate spec.
  88    --  This call does not generate any warning messages, but instead may
  89    --  result in flags being set in the N_With_Clause node that record that
  90    --  there was no use in the spec.
  91    --
  92    --  The main call (made after all units have been analyzed, with Spec_Unit
  93    --  set to the default value of No_Unit) generates the required warnings
  94    --  using the flags set by the initial call where appropriate to specialize
  95    --  the text of the warning messages.
  96
  97    ---------------------
  98    -- Output Routines --
  99    ---------------------
 100
 101    procedure Output_Obsolescent_Entity_Warnings (N : Node_Id; E : Entity_Id);
 102    --  N is a reference to obsolescent entity E, for which appropriate warning
 103    --  messages are to be generated (caller has already checked that warnings
 104    --  are active and appropriate for this entity).
 105
 106    procedure Output_Unreferenced_Messages;
 107    --  Warnings about unreferenced entities are collected till the end of
 108    --  the compilation process (see Check_Unset_Reference for further
 109    --  details). This procedure outputs waiting warnings, if any.
 110
 111    ----------------------------
 112    -- Other Warning Routines --
 113    ----------------------------
 114
 115    procedure Check_Code_Statement (N : Node_Id);
 116    --  Peform warning checks on a code statement node
 117
 118    procedure Warn_On_Known_Condition (C : Node_Id);
 119    --  C is a node for a boolean expression resluting from a relational
 120    --  or membership operation. If the expression has a compile time known
 121    --  value, then a warning is output if all the following conditions hold:
 122    --
 123    --    1. Original expression comes from source. We don't want to generate
 124    --       warnings for internally generated conditionals.
 125    --
 126    --    2. As noted above, the expression is a relational or membership
 127    --       test, we don't want to generate warnings for boolean variables
 128    --       since this is typical of conditional compilation in Ada.
 129    --
 130    --    3. The expression appears in a statement, rather than a declaration.
 131    --       In practice, most occurrences in declarations are legitimate
 132    --       conditionalizations, but occurrences in statements are often
 133    --       errors for which the warning is useful.
 134    --
 135    --    4. The expression does not occur within an instantiation. A non-
 136    --       static expression in a generic may become constant because of
 137    --       the attributes of the actuals, and we do not want to warn on
 138    --       these legitimate constant foldings.
 139    --
 140    --  If all these conditions are met, the warning is issued noting that
 141    --  the result of the test is always false or always true as appropriate.
 142
 143    procedure Warn_On_Suspicious_Index (Name : Entity_Id; X : Node_Id);
 144    --  This is called after resolving an indexed component or a slice. Name
 145    --  is the entity for the name of the indexed array, and X is the subscript
 146    --  for the indexed component case, or one of the bounds in the slice case.
 147    --  If Name is an unconstrained parameter of a standard string type, and
 148    --  the index is of the form of a literal or Name'Length [- literal], then
 149    --  a warning is generated that the subscripting operation is possibly
 150    --  incorrectly assuming a lower bound of 1.
 151
 152    procedure Warn_On_Useless_Assignment
 153      (Ent : Entity_Id;
 154       Loc : Source_Ptr := No_Location);
 155    --  Called to check if we have a case of a useless assignment to the given
 156    --  entity Ent, as indicated by a non-empty Last_Assignment field. This call
 157    --  should only be made if Warn_On_Modified_Unread is True, and if Ent is in
 158    --  the extended main source unit. Loc is No_Location for the end of block
 159    --  call (warning msg says value unreferenced), or the it is the location of
 160    --  an overwriting assignment (warning msg points to this assignment).
 161
 162    procedure Warn_On_Useless_Assignments (E : Entity_Id);
 163    pragma Inline (Warn_On_Useless_Assignments);
 164    --  Called at the end of a block or subprogram. Scans the entities of the
 165    --  block or subprogram to see if there are any variables for which useless
 166    --  assignments were made (assignments whose values were never read).
 167
 168 end Sem_Warn;