ada: Overridden operation field not correctly set for controlling result wrappers

Implicit wrapper overridings generated for functions with
controlling result when deriving with null extension may
have field Overridden_Operation incorrectly set, when making
several such derivations in succession. This happens because
overridings were assumed to come from source, and entities
generated by Derive_Subprograms were also assumed to be
derived from source subprograms. Overridden_Operation could
be set to the entity generated by Derive_Subprograms for the
same type, resulting in a cycle between Overriden_Operation
and Alias fields, causing non-termination in GNATprove.

gcc/ada/

	* sem_ch6.adb (Check_Overriding_Indicator) Remove Comes_From_Source filter.
	(New_Overloaded_Entity) Move up special case of LSP_Subprogram,
	and remove Comes_From_Source filter.

1 files changed, 35 insertions, 47 deletions

diff --git a/gcc/ada/sem_ch6.adb b/gcc/ada/sem_ch6.adb
index e97afda..43aa2e6 100644
--- a/gcc/ada/sem_ch6.adb
+++ b/gcc/ada/sem_ch6.adb
@@ -6916,13 +6916,11 @@ package body Sem_Ch6 is
                --  operation is the inherited primitive (which is available
                --  through the attribute alias)
 
-               if (Is_Dispatching_Operation (Subp)
-                    or else Is_Dispatching_Operation (Overridden_Subp))
+               if Is_Dispatching_Operation (Subp)
                  and then not Comes_From_Source (Overridden_Subp)
                  and then Find_Dispatching_Type (Overridden_Subp) =
                           Find_Dispatching_Type (Subp)
                  and then Present (Alias (Overridden_Subp))
-                 and then Comes_From_Source (Alias (Overridden_Subp))
                then
                   Set_Overridden_Operation    (Subp, Alias (Overridden_Subp));
                   Inherit_Subprogram_Contract (Subp, Alias (Overridden_Subp));
@@ -12565,16 +12563,25 @@ package body Sem_Ch6 is
 
                   Enter_Overloaded_Entity (S);
 
+                  --  LSP wrappers must override the ultimate alias of their
+                  --  wrapped dispatching primitive E; required to traverse the
+                  --  chain of ancestor primitives (see Map_Primitives). They
+                  --  don't inherit contracts.
+
+                  if Is_Wrapper (S)
+                    and then Present (LSP_Subprogram (S))
+                  then
+                     Set_Overridden_Operation (S, Ultimate_Alias (E));
+
                   --  For entities generated by Derive_Subprograms the
                   --  overridden operation is the inherited primitive
                   --  (which is available through the attribute alias).
 
-                  if not (Comes_From_Source (E))
+                  elsif not (Comes_From_Source (E))
                     and then Is_Dispatching_Operation (E)
                     and then Find_Dispatching_Type (E) =
                              Find_Dispatching_Type (S)
                     and then Present (Alias (E))
-                    and then Comes_From_Source (Alias (E))
                   then
                      Set_Overridden_Operation    (S, Alias (E));
                      Inherit_Subprogram_Contract (S, Alias (E));
@@ -12591,20 +12598,8 @@ package body Sem_Ch6 is
                   --  must check whether the target is an init_proc.
 
                   elsif not Is_Init_Proc (S) then
-
-                     --  LSP wrappers must override the ultimate alias of their
-                     --  wrapped dispatching primitive E; required to traverse
-                     --  the chain of ancestor primitives (c.f. Map_Primitives)
-                     --  They don't inherit contracts.
-
-                     if Is_Wrapper (S)
-                       and then Present (LSP_Subprogram (S))
-                     then
-                        Set_Overridden_Operation    (S, Ultimate_Alias (E));
-                     else
-                        Set_Overridden_Operation    (S, E);
-                        Inherit_Subprogram_Contract (S, E);
-                     end if;
+                     Set_Overridden_Operation    (S, E);
+                     Inherit_Subprogram_Contract (S, E);
 
                      Set_Is_Ada_2022_Only (S, Is_Ada_2022_Only (E));
                   end if;
@@ -12619,37 +12614,30 @@ package body Sem_Ch6 is
 
                   --  If S is a user-defined subprogram or a null procedure
                   --  expanded to override an inherited null procedure, or a
-                  --  predefined dispatching primitive then indicate that E
-                  --  overrides the operation from which S is inherited.
+                  --  predefined dispatching primitive, or a function wrapper
+                  --  expanded to override an inherited function with
+                  --  dispatching result, then indicate that S overrides the
+                  --  operation from which E is inherited.
 
-                  if Comes_From_Source (S)
-                    or else
-                      (Present (Parent (S))
-                        and then Nkind (Parent (S)) = N_Procedure_Specification
-                        and then Null_Present (Parent (S)))
-                    or else
-                      (Present (Alias (E))
-                        and then
-                          Is_Predefined_Dispatching_Operation (Alias (E)))
+                  if (not Is_Wrapper (S) or else No (LSP_Subprogram (S)))
+                    and then Present (Alias (E))
+                    and then
+                      (Comes_From_Source (S)
+                       or else
+                         (Nkind (Parent (S)) = N_Procedure_Specification
+                          and then Null_Present (Parent (S)))
+                       or else Is_Predefined_Dispatching_Operation (Alias (E))
+                       or else
+                         (E in E_Function_Id
+                          and then Is_Dispatching_Operation (E)
+                          and then Has_Controlling_Result (E)
+                          and then Is_Wrapper (S)
+                          and then not Is_Dispatch_Table_Wrapper (S)))
                   then
-                     if Present (Alias (E)) then
-
-                        --  LSP wrappers must override the ultimate alias of
-                        --  their wrapped dispatching primitive E; required to
-                        --  traverse the chain of ancestor primitives (see
-                        --  Map_Primitives). They don't inherit contracts.
-
-                        if Is_Wrapper (S)
-                          and then Present (LSP_Subprogram (S))
-                        then
-                           Set_Overridden_Operation    (S, Ultimate_Alias (E));
-                        else
-                           Set_Overridden_Operation    (S, Alias (E));
-                           Inherit_Subprogram_Contract (S, Alias (E));
-                        end if;
+                     Set_Overridden_Operation    (S, Alias (E));
+                     Inherit_Subprogram_Contract (S, Alias (E));
 
-                        Set_Is_Ada_2022_Only (S, Is_Ada_2022_Only (Alias (E)));
-                     end if;
+                     Set_Is_Ada_2022_Only (S, Is_Ada_2022_Only (Alias (E)));
                   end if;
 
                   if Is_Dispatching_Operation (E) then