sem_ch12.ads, [...] (Instantiate_Type): If the formal is a derived type with…

sem_ch12.ads, [...] (Instantiate_Type): If the formal is a derived type with interface progenitors use the analyzed...

2007-08-14  Ed Schonberg  <schonberg@adacore.com>
	    Gary Dismukes  <dismukes@adacore.com>
	    Thomas Quinot  <quinot@adacore.com>

	* sem_ch12.ads, sem_ch12.adb (Instantiate_Type): If the formal is a
	derived type with interface progenitors use the analyzed formal as the
	parent of the actual, to create renamings for all the inherited
	operations in Derive_Subprograms.
	(Collect_Previous_Instances): new procedure within of
	Load_Parent_Of_Generic, to instantiate all bodies in the compilation
	unit being loaded, to ensure that the generation of global symbols is
	consistent in different compilation modes.
	(Is_Tagged_Ancestor): New function testing the ancestor relation that
	takes progenitor types into account.
	(Validate_Derived_Type_Instance): Enforce the rule of 3.9.3(9) by
	traversing over the primitives of the formal and actual types to locate
	any abstract subprograms of the actual type that correspond to a
	nonabstract subprogram of the formal type's ancestor type(s), and issue
	an error if such is found.
	(Analyze_Package_Instantiation, Analyze_Subprogram_Instantiation,
	Instantiate_Package_Body, Instantiate_Subprogram_Body):
	Remove bogus guard around calls to Inherit_Context.
	(Reset_Entity): If the entity is the selector of a selected component
	that denotes a named number, propagate constant-folding to the generic
	template only if the named number is global to the generic unit.
	(Set_Instance_Env): Only reset the compilation switches when compiling
	a predefined or internal unit.

From-SVN: r127443

gcc/ada/sem_ch12.ads

@@ -6,7 +6,7 @@
 --                                                                          --
 --                                 S p e c                                  --
 --                                                                          --
---          Copyright (C) 1992-2006, Free Software Foundation, Inc.         --
+--          Copyright (C) 1992-2007, Free Software Foundation, Inc.         --
 --                                                                          --
 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
 -- terms of the  GNU General Public License as published  by the Free Soft- --
@@ -58,8 +58,7 @@ package Sem_Ch12 is
    function Copy_Generic_Node
      (N             : Node_Id;
       Parent_Id     : Node_Id;
-      Instantiating : Boolean)
-      return          Node_Id;
+      Instantiating : Boolean) return Node_Id;
    --  Copy the tree for a generic unit or its body. The unit is copied
    --  repeatedly: once to produce a copy on which semantic analysis of
    --  the generic is performed, and once for each instantiation. The tree
@@ -76,11 +75,30 @@ package Sem_Ch12 is
    --  of the ancestors of a child generic that is being instantiated.
 
    procedure Instantiate_Package_Body
-     (Body_Info    : Pending_Body_Info;
-      Inlined_Body : Boolean := False);
+     (Body_Info     : Pending_Body_Info;
+      Inlined_Body  : Boolean := False;
+      Body_Optional : Boolean := False);
    --  Called after semantic analysis, to complete the instantiation of
    --  package instances. The flag Inlined_Body is set if the body is
    --  being instantiated on the fly for inlined purposes.
+   --
+   --  The flag Body_Optional indicates that the call is for an instance
+   --  that precedes the current instance in the same declarative part.
+   --  This call is needed when instantiating a nested generic whose body
+   --  is to be found in the body of an instance. Normally we instantiate
+   --  package bodies only when they appear in the main unit, or when their
+   --  contents are needed for a nested generic G. If unit U contains several
+   --  instances I1, I2, etc. and I2 contains a nested generic, then when U
+   --  appears in the context of some other unit P that contains an instance
+   --  of G, we compile the body of I2, but not that of I1. However, when we
+   --  compile U as the main unit, we compile both bodies. This will lead to
+   --  lead to link-time errors if the compilation of I1 generates public
+   --  symbols, because those in I2 will receive different names in both
+   --  cases. This forces us to analyze the body of I1 even when U is not the
+   --  main unit. We don't want this additional mechanism to generate an error
+   --  when the body of the generic for I1 is not present, and this is the
+   --  reason for the presence of the flag Body_Optional, which is exchanged
+   --  between the current procedure and Load_Parent_Of_Generic.
 
    procedure Instantiate_Subprogram_Body
      (Body_Info : Pending_Body_Info);