[Ada] Warn about unreachable code after calls with No_Return
Commit Message
GNAT was already warning about unreachable code after raise/goto/exit
statements, but not after calls to procedures with No_Return. Now this
warning is extended.
Also, previously the warning was suppressed for unreachable RETURN after
RAISE statements. Now this suppression is narrowed to functions, because
only in function such a RETURN statement might be indeed needed (where
it is the only RETURN statement of a function).
Tested on x86_64-pc-linux-gnu, committed on trunk
gcc/ada/
* sem_ch5.adb (Check_Unreachable_Code): Extend suppression to
calls with No_Return aspect, but narrow it to functions.
* sem_res.adb (Resolve_Call): Warn about unreachable code after
calls with No_Return.
@@ -4418,12 +4418,20 @@ package body Sem_Ch5 is
elsif Comes_From_Source (Nxt)
and then Is_Statement (Nxt)
then
- -- Special very annoying exception. If we have a return that
- -- follows a raise, then we allow it without a warning, since
- -- the Ada RM annoyingly requires a useless return here.
-
- if Nkind (Original_Node (N)) /= N_Raise_Statement
- or else Nkind (Nxt) /= N_Simple_Return_Statement
+ -- Special very annoying exception. Ada RM 6.5(5) annoyingly
+ -- requires functions to have at least one return statement, so
+ -- don't complain about a simple return that follows a raise or a
+ -- call to procedure with No_Return.
+
+ if not (Present (Current_Subprogram)
+ and then Ekind (Current_Subprogram) = E_Function
+ and then (Nkind (Original_Node (N)) = N_Raise_Statement
+ or else
+ (Nkind (N) = N_Procedure_Call_Statement
+ and then Is_Entity_Name (Name (N))
+ and then Present (Entity (Name (N)))
+ and then No_Return (Entity (Name (N)))))
+ and then Nkind (Nxt) = N_Simple_Return_Statement)
then
-- The rather strange shenanigans with the warning message
-- here reflects the fact that Kill_Dead_Code is very good at
@@ -62,6 +62,7 @@ with Sem_Case; use Sem_Case;
with Sem_Cat; use Sem_Cat;
with Sem_Ch3; use Sem_Ch3;
with Sem_Ch4; use Sem_Ch4;
+with Sem_Ch5; use Sem_Ch5;
with Sem_Ch6; use Sem_Ch6;
with Sem_Ch8; use Sem_Ch8;
with Sem_Ch13; use Sem_Ch13;
@@ -7193,6 +7194,14 @@ package body Sem_Res is
Analyze_Dimension_Call (N, Nam);
+ -- Check unreachable code after calls to procedures with No_Return
+
+ if Ekind (Nam) = E_Procedure
+ and then No_Return (Nam)
+ then
+ Check_Unreachable_Code (N);
+ end if;
+
-- All done, evaluate call and deal with elaboration issues
Eval_Call (N);