[gcc r13-306] [Ada] Detect infinite loops with operators in exit conditions

[Pierre-Marie de Rodat <pmderodat@gcc.gnu.org>]

https://gcc.gnu.org/g:dc9ecb41c8572c53bdcd86e73526e2a27bd3dff9

commit r13-306-gdc9ecb41c8572c53bdcd86e73526e2a27bd3dff9
Author: Piotr Trojanek <trojanek@adacore.com>
Date:   Wed Feb 2 17:19:59 2022 +0100

    [Ada] Detect infinite loops with operators in exit conditions
    
    To warn about infinite loops we detect variables referenced in loop exit
    conditions. We handle references within boolean operators, i.e.
    comparison and negation, which are likely to appear at the top level of
    the condition (e.g. "X > 0"). However, we can easily handle all
    operators, because they are likely to appear inside the condition (e.g.
    "abs (X) > 0.0").
    
    Cleanup related to a new restriction No_Uninitialized_Local_Scalars.
    
    gcc/ada/
    
            * sem_warn.adb (Find_Var): Detect all operators; replace
            "condition" to "expression" in comments, because when this
            routine is called recursively it no longer examines the
            condition.
            (Is_Suspicious_Function_Name): Reduce scope of a local variable
            to avoid shadowing with a parameter of a nested
            Substring_Present function.

Diff:
---
 gcc/ada/sem_warn.adb | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/gcc/ada/sem_warn.adb b/gcc/ada/sem_warn.adb
index f86c2c71736..4d3452242bf 100644
--- a/gcc/ada/sem_warn.adb
+++ b/gcc/ada/sem_warn.adb
@@ -284,15 +284,15 @@ package body Sem_Warn is
 
       procedure Find_Var (N : Node_Id) is
       begin
-         --  Condition is a direct variable reference
+         --  Expression is a direct variable reference
 
          if Is_Entity_Name (N) then
             Ref := N;
             Var := Entity (Ref);
 
-         --  Case of condition is a comparison with compile time known value
+         --  If expression is an operator, check its operands
 
-         elsif Nkind (N) in N_Op_Compare then
+         elsif Nkind (N) in N_Binary_Op then
             if Compile_Time_Known_Value (Right_Opnd (N)) then
                Find_Var (Left_Opnd (N));
 
@@ -305,9 +305,9 @@ package body Sem_Warn is
                return;
             end if;
 
-         --  If condition is a negation, check its operand
+         --  If expression is a unary operator, check its operand
 
-         elsif Nkind (N) = N_Op_Not then
+         elsif Nkind (N) in N_Unary_Op then
             Find_Var (Right_Opnd (N));
 
          --  Case of condition is function call
@@ -445,8 +445,6 @@ package body Sem_Warn is
       ---------------------------------
 
       function Is_Suspicious_Function_Name (E : Entity_Id) return Boolean is
-         S : Entity_Id;
-
          function Substring_Present (S : String) return Boolean;
          --  Returns True if name buffer has given string delimited by non-
          --  alphabetic characters or by end of string. S is lower case.
@@ -473,6 +471,10 @@ package body Sem_Warn is
             return False;
          end Substring_Present;
 
+         --  Local variables
+
+         S : Entity_Id;
+
       --  Start of processing for Is_Suspicious_Function_Name
 
       begin