This patch adds a check in the analysis of quantified expressions to detect an
unused loop variable and issue a warning.
------------
-- Source --
------------
-- warnings.adb
with Ada.Containers.Doubly_Linked_Lists;
procedure Warnings is
package DLL is new Ada.Containers.Doubly_Linked_Lists (Natural, "=");
type Test_Array is array (Natural range <>, Natural range <>) of Natural;
function Factorial (Val : Natural) return Natural is
begin
if Val > 1 then
return Val * Factorial (Val - 1);
end if;
return 1;
end Factorial;
TA : constant Test_Array (1 .. 3, 1 .. 4) := (others => (others => 0));
Flag : Boolean;
L : DLL.List;
begin
Flag := (for all Element of TA => Element > 1);
Flag := (for some Element of TA => Factorial (3) = 6);
Flag := (for all Element of L => Element > 1);
Flag := (for some Element of L => Factorial (3) = 6);
Flag := (for all Element in 1 .. 4 => Factorial (Element) > 0);
Flag := (for some Element in 1 .. 4 => Factorial (3) = 6);
Flag := (for all Element in DLL.Iterate (L) => DLL.Element (Element) > 1);
Flag := (for some Element in DLL.Iterate (L) => Factorial (3) = 6);
end Warnings;
----------------------------
-- Compilation and output --
----------------------------
$ gcc -c -gnat12 -gnatw.t warnings.adb
warnings.adb:23:22: warning: unused variable "Element"
warnings.adb:25:22: warning: unused variable "Element"
warnings.adb:27:22: warning: unused variable "Element"
warnings.adb:29:22: warning: unused variable "Element"
Tested on x86_64-pc-linux-gnu, committed on trunk
2013-04-25 Hristian Kirtchev <kirtc...@adacore.com>
* sem_ch4.adb (Analyze_Quantified_Expression):
Add local variable Loop_Id. Verify that the loop variable
is used within the condition of the quantified expression.
(Referenced): New routine.
Index: sem_ch4.adb
===================================================================
--- sem_ch4.adb (revision 198287)
+++ sem_ch4.adb (working copy)
@@ -3510,6 +3510,9 @@
-- Determine whether if expression If_Expr lacks an else part or if it
-- has one, it evaluates to True.
+ function Referenced (Id : Entity_Id; Expr : Node_Id) return Boolean;
+ -- Determine whether entity Id is referenced within expression Expr
+
--------------------
-- Is_Empty_Range --
--------------------
@@ -3561,9 +3564,44 @@
and then Is_True (Expr_Value (Else_Expr)));
end No_Else_Or_Trivial_True;
+ ----------------
+ -- Referenced --
+ ----------------
+
+ function Referenced (Id : Entity_Id; Expr : Node_Id) return Boolean is
+ Seen : Boolean := False;
+
+ function Is_Reference (N : Node_Id) return Traverse_Result;
+ -- Determine whether node N denotes a reference to Id. If this is the
+ -- case, set global flag Seen to True and stop the traversal.
+
+ function Is_Reference (N : Node_Id) return Traverse_Result is
+ begin
+ if Is_Entity_Name (N)
+ and then Present (Entity (N))
+ and then Entity (N) = Id
+ then
+ Seen := True;
+ return Abandon;
+ else
+ return OK;
+ end if;
+ end Is_Reference;
+
+ procedure Inspect_Expression is new Traverse_Proc (Is_Reference);
+
+ -- Start of processing for Referenced
+
+ begin
+ Inspect_Expression (Expr);
+
+ return Seen;
+ end Referenced;
+
-- Local variables
Cond : constant Node_Id := Condition (N);
+ Loop_Id : Entity_Id;
QE_Scop : Entity_Id;
-- Start of processing for Analyze_Quantified_Expression
@@ -3590,22 +3628,39 @@
if Present (Iterator_Specification (N)) then
Preanalyze (Iterator_Specification (N));
+ -- Do not proceed with the analysis when the range of iteration is
+ -- empty. The appropriate error is issued by Is_Empty_Range.
+
if Is_Entity_Name (Name (Iterator_Specification (N)))
and then Is_Empty_Range (Etype (Name (Iterator_Specification (N))))
then
return;
end if;
- else
+ else pragma Assert (Present (Loop_Parameter_Specification (N)));
Preanalyze (Loop_Parameter_Specification (N));
end if;
Preanalyze_And_Resolve (Cond, Standard_Boolean);
End_Scope;
-
Set_Etype (N, Standard_Boolean);
+ -- Verify that the loop variable is used within the condition of the
+ -- quantified expression.
+
+ if Present (Iterator_Specification (N)) then
+ Loop_Id := Defining_Identifier (Iterator_Specification (N));
+ else
+ Loop_Id := Defining_Identifier (Loop_Parameter_Specification (N));
+ end if;
+
+ if Warn_On_Suspicious_Contract
+ and then not Referenced (Loop_Id, Cond)
+ then
+ Error_Msg_N ("?T?unused variable &", Loop_Id);
+ end if;
+
-- Diagnose a possible misuse of the "some" existential quantifier. When
-- we have a quantified expression of the form
--
