From: Gary Dismukes <[email protected]>
The compiler can crash with a Storage_Error for a failed precondition
when compiling a call to a dispatching subprogram where an actual for a
controlling formal is given by an if_expression whose dependent expressions
are tag-indeterminate calls. This problem showed up on a build of Alire
(on the compilation of alire-roots.adb) done during a build_gnat_world
mailserver (as well as having been noticed and reported separately by
another engineering team).
The code in Sem_Disp.Check_Dispatching_Call for checking nondispatching
procedure calls for actuals that are calls to abstract tag-indeterminate
functions did not account for conditional expressions, and attempted to
retrieve the (nonexistent) Expression field from an N_If_Expression node,
failing the precondition for Expression. It was discovered that none of
the code checking for illegal calls to abstract tag-indeterminate functions
in procedure calls is needed, and the whole related "elsif" part is removed
by this change. (Note that there is separate checking done separately
within Check_Dispatching_Call that will catch nondispatching calls to
abstract functions.)
gcc/ada/ChangeLog:
* sem_disp.adb (Check_Dispatching_Call): Remove "elsif" that does error
checking for abstract tag-indeterminate calls (seems to be no longer
needed).
Tested on x86_64-pc-linux-gnu, committed on master.
---
gcc/ada/sem_disp.adb | 50 --------------------------------------------
1 file changed, 50 deletions(-)
diff --git a/gcc/ada/sem_disp.adb b/gcc/ada/sem_disp.adb
index 5a8bd58b8b8..4a940e7f30b 100644
--- a/gcc/ada/sem_disp.adb
+++ b/gcc/ada/sem_disp.adb
@@ -586,7 +586,6 @@ package body Sem_Disp is
Actual : Node_Id;
Formal : Entity_Id;
Control : Node_Id := Empty;
- Func : Entity_Id;
Subp_Entity : constant Entity_Id := Entity (Name (N));
Indeterm_Ctrl_Type : Entity_Id := Empty;
@@ -1099,55 +1098,6 @@ package body Sem_Disp is
Check_Dispatching_Context (N);
- elsif Nkind (N) /= N_Function_Call then
-
- -- The call is not dispatching, so check that there aren't any
- -- tag-indeterminate abstract calls left among its actuals.
-
- Actual := First_Actual (N);
- while Present (Actual) loop
- if Is_Tag_Indeterminate (Actual) then
-
- -- Function call case
-
- if Nkind (Original_Node (Actual)) = N_Function_Call then
- Func := Entity (Name (Original_Node (Actual)));
-
- -- If the actual is an attribute then it can't be abstract
- -- (the only current case of a tag-indeterminate attribute
- -- is the stream Input attribute).
-
- elsif Nkind (Original_Node (Actual)) = N_Attribute_Reference
- then
- Func := Empty;
-
- -- Ditto if it is an explicit dereference
-
- elsif Nkind (Original_Node (Actual)) = N_Explicit_Dereference
- then
- Func := Empty;
-
- -- Only other possibility is a qualified expression whose
- -- constituent expression is itself a call.
-
- else
- Func :=
- Entity (Name (Original_Node
- (Expression (Original_Node (Actual)))));
- end if;
-
- if Present (Func) and then Is_Abstract_Subprogram (Func) then
- Error_Msg_N
- ("call to abstract function must be dispatching",
- Actual);
- end if;
- end if;
-
- Next_Actual (Actual);
- end loop;
-
- Check_Dispatching_Context (N);
-
elsif Nkind (Parent (N)) in N_Subexpr then
Check_Dispatching_Context (N);
--
2.51.0
