[gcc r11-5419] [Ada] Crash on task declaration with Restriction_Warning (No_Tasking)

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

https://gcc.gnu.org/g:52424b13d80af31b6004995c1910fb9ee0ab1939

commit r11-5419-g52424b13d80af31b6004995c1910fb9ee0ab1939
Author: Ed Schonberg <schonberg@adacore.com>
Date:   Tue Oct 27 09:24:51 2020 -0400

    [Ada] Crash on task declaration with Restriction_Warning (No_Tasking)
    
    gcc/ada/
    
            * sem_prag.adb (Process_Restrictions_Or_Restriction_Warnings):
            when the restriction is a configuration pragma and specifies
            No_Tasking, a global flag is set to reject task declarations,
            and to prevent the construction of Master entities. The flag
            must not be set if the pragma is a Restriction_Warning, in which
            case task declarationns are allowed.

Diff:
---
 gcc/ada/sem_prag.adb | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/gcc/ada/sem_prag.adb b/gcc/ada/sem_prag.adb
index 9c57ee31c89..02cf0bc5648 100644
--- a/gcc/ada/sem_prag.adb
+++ b/gcc/ada/sem_prag.adb
@@ -10438,10 +10438,13 @@ package body Sem_Prag is
                      Add_To_Config_Boolean_Restrictions (No_Elaboration_Code);
                   end if;
 
-               --  Special processing for No_Tasking restriction placed in
-               --  a configuration pragmas file.
+               --  Special processing for No_Tasking restriction (not just a
+               --  warning) when it appears as a configuration pragmas.
 
-               elsif R_Id = No_Tasking and then No (Cunit (Main_Unit)) then
+               elsif R_Id = No_Tasking
+                 and then No (Cunit (Main_Unit))
+                 and then not Warn
+               then
                   Set_Global_No_Tasking;
                end if;