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[Ada] Hang on loop in generic with subtype indication specifying a range


The compiler may hang when a for loop expanded in a generic
instantiation has a range specified by a subtype indication with an
explicit range that has a bound that is an attribute applied to a
discriminant-dependent array component. The Parent field of the bound
may not be set, which can lead to endless looping when an actual subtype
created for the array component is passed to Insert_Actions. This is
fixed by setting the Parent fields of the copied bounds before
Preanalyze is called on them.

Tested on x86_64-pc-linux-gnu, committed on trunk

2019-08-12  Gary Dismukes  <dismukes@adacore.com>

gcc/ada/

	* sem_ch5.adb (Prepare_Param_Spec_Loop): Set the parents of the
	copied low and high bounds in the case where the loop range is
	given by a discrete_subtype_indication, to prevent hanging (or
	Assert_Failure) in Insert_Actions.

gcc/testsuite/

	* gnat.dg/generic_inst7.adb, gnat.dg/generic_inst7_pkg.adb,
	gnat.dg/generic_inst7_pkg.ads, gnat.dg/generic_inst7_types.ads:
	New testcase.
--- gcc/ada/sem_ch5.adb
+++ gcc/ada/sem_ch5.adb
@@ -3636,11 +3636,16 @@ package body Sem_Ch5 is
             then
                Rng := Range_Expression (Constraint (Rng));
 
-               --  Preanalyze the bounds of the range constraint
+               --  Preanalyze the bounds of the range constraint, setting
+               --  parent fields to associate the copied bounds with the range,
+               --  allowing proper tree climbing during preanalysis.
 
                Low  := New_Copy_Tree (Low_Bound  (Rng));
                High := New_Copy_Tree (High_Bound (Rng));
 
+               Set_Parent (Low, Rng);
+               Set_Parent (High, Rng);
+
                Preanalyze (Low);
                Preanalyze (High);
 

--- /dev/null
new file mode 100644
+++ gcc/testsuite/gnat.dg/generic_inst7.adb
@@ -0,0 +1,11 @@
+--  { dg-do compile }
+
+with Generic_Inst7_Pkg;
+
+procedure Generic_Inst7 is
+
+  package Inst is new Generic_Inst7_Pkg;
+
+begin
+   null;
+end Generic_Inst7;

--- /dev/null
new file mode 100644
+++ gcc/testsuite/gnat.dg/generic_inst7_pkg.adb
@@ -0,0 +1,12 @@
+package body Generic_Inst7_Pkg is
+
+   use type Generic_Inst7_Types.Index;
+
+   procedure Process (List : in out Generic_Inst7_Types.List) is
+   begin
+      for I in Generic_Inst7_Types.Index range 1 .. List.Arr'length loop
+         null;
+      end loop;
+   end Process;
+
+end Generic_Inst7_Pkg;

--- /dev/null
new file mode 100644
+++ gcc/testsuite/gnat.dg/generic_inst7_pkg.ads
@@ -0,0 +1,8 @@
+with Generic_Inst7_Types;
+
+generic
+package Generic_Inst7_Pkg is
+
+   procedure Process (List : in out Generic_Inst7_Types.List);
+
+end Generic_Inst7_Pkg;

--- /dev/null
new file mode 100644
+++ gcc/testsuite/gnat.dg/generic_inst7_types.ads
@@ -0,0 +1,15 @@
+package Generic_Inst7_Types is
+
+   type Index is new Integer range 0 .. 10;
+
+   type Element is record
+      I : Integer;
+   end record;
+
+   type Element_Array is array (Index range <>) of Element;
+
+   type List (Size : Index := 1) is record
+      Arr : Element_Array (1 .. Size);
+   end record;
+
+end Generic_Inst7_Types;


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