This patch implements additional warnings for suspicious mod values
as shown by the following test program. These warnings are under
control of the warning flag -gnatw.m (on by default).
1. package susmod is
2. type r is mod 2 * 32;
|
>>> warning: suspicious "mod" value, was ** intended?
3. H : Integer := 2458;
4. J : Integer := H mod 2 * 32;
|
>>> warning: suspicious "mod" value, was ** intended?
5. end susmod;
Tested on x86_64-pc-linux-gnu, committed on trunk
2012-01-30 Robert Dewar <de...@adacore.com>
* sem.adb (Analyze): Call Analyze_Mod for N_Op_Mod mode.
* sem_ch3.adb (Modular_Type_Declaration): Warn on mod value of
form 2 * small-literal.
* sem_ch4.adb (Analyze_Mod): New procedure (warn on suspicious
mod value).
* sem_ch4.ads (Analyze_Mod): New procedure.
Index: sem_ch3.adb
===================================================================
--- sem_ch3.adb (revision 183704)
+++ sem_ch3.adb (working copy)
@@ -16808,6 +16808,21 @@
-- Start of processing for Modular_Type_Declaration
begin
+ -- If the mod expression is (exactly) 2 * literal, where literal is
+ -- 64 or less,then almost certainly the * was meant to be **. Warn!
+
+ if Warn_On_Suspicious_Modulus_Value
+ and then Nkind (Mod_Expr) = N_Op_Multiply
+ and then Nkind (Left_Opnd (Mod_Expr)) = N_Integer_Literal
+ and then Intval (Left_Opnd (Mod_Expr)) = Uint_2
+ and then Nkind (Right_Opnd (Mod_Expr)) = N_Integer_Literal
+ and then Intval (Right_Opnd (Mod_Expr)) <= Uint_64
+ then
+ Error_Msg_N ("suspicious MOD value, was '*'* intended'??", Mod_Expr);
+ end if;
+
+ -- Proceed with analysis of mod expression
+
Analyze_And_Resolve (Mod_Expr, Any_Integer);
Set_Etype (T, T);
Set_Ekind (T, E_Modular_Integer_Type);
Index: sem.adb
===================================================================
--- sem.adb (revision 183694)
+++ sem.adb (working copy)
@@ -6,7 +6,7 @@
-- --
-- B o d y --
-- --
--- Copyright (C) 1992-2011, Free Software Foundation, Inc. --
+-- Copyright (C) 1992-2012, 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- --
@@ -376,7 +376,7 @@
Analyze_Unary_Op (N);
when N_Op_Mod =>
- Analyze_Arithmetic_Op (N);
+ Analyze_Mod (N);
when N_Op_Multiply =>
Analyze_Arithmetic_Op (N);
Index: sem_ch4.adb
===================================================================
--- sem_ch4.adb (revision 183694)
+++ sem_ch4.adb (working copy)
@@ -6,7 +6,7 @@
-- --
-- B o d y --
-- --
--- Copyright (C) 1992-2011, Free Software Foundation, Inc. --
+-- Copyright (C) 1992-2012, 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- --
@@ -62,6 +62,7 @@
with Sinfo; use Sinfo;
with Snames; use Snames;
with Tbuild; use Tbuild;
+with Uintp; use Uintp;
package body Sem_Ch4 is
@@ -2637,6 +2638,34 @@
end if;
end Analyze_Membership_Op;
+ -----------------
+ -- Analyze_Mod --
+ -----------------
+
+ procedure Analyze_Mod (N : Node_Id) is
+ begin
+ -- A special warning check, if we have an expression of the form:
+ -- expr mod 2 * literal
+ -- where literal is 64 or less, then probably what was meant was
+ -- expr mod 2 ** literal
+ -- so issue an appropriate warning.
+
+ if Warn_On_Suspicious_Modulus_Value
+ and then Nkind (Right_Opnd (N)) = N_Integer_Literal
+ and then Intval (Right_Opnd (N)) = Uint_2
+ and then Nkind (Parent (N)) = N_Op_Multiply
+ and then Nkind (Right_Opnd (Parent (N))) = N_Integer_Literal
+ and then Intval (Right_Opnd (Parent (N))) <= Uint_64
+ then
+ Error_Msg_N
+ ("suspicious MOD value, was '*'* intended'??", Parent (N));
+ end if;
+
+ -- Remaining processing is same as for other arithmetic operators
+
+ Analyze_Arithmetic_Op (N);
+ end Analyze_Mod;
+
----------------------
-- Analyze_Negation --
----------------------
Index: sem_ch4.ads
===================================================================
--- sem_ch4.ads (revision 183694)
+++ sem_ch4.ads (working copy)
@@ -6,7 +6,7 @@
-- --
-- S p e c --
-- --
--- Copyright (C) 1992-2011, Free Software Foundation, Inc. --
+-- Copyright (C) 1992-2012, 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- --
@@ -39,6 +39,7 @@
procedure Analyze_Expression_With_Actions (N : Node_Id);
procedure Analyze_Logical_Op (N : Node_Id);
procedure Analyze_Membership_Op (N : Node_Id);
+ procedure Analyze_Mod (N : Node_Id);
procedure Analyze_Negation (N : Node_Id);
procedure Analyze_Null (N : Node_Id);
procedure Analyze_Qualified_Expression (N : Node_Id);
