| ------------------------------------------------------------------------------ |
| -- -- |
| -- GNAT COMPILER COMPONENTS -- |
| -- -- |
| -- S E M _ E L A B -- |
| -- -- |
| -- S p e c -- |
| -- -- |
| -- Copyright (C) 1997-2001 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- -- |
| -- ware Foundation; either version 2, or (at your option) any later ver- -- |
| -- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- |
| -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- |
| -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License -- |
| -- for more details. You should have received a copy of the GNU General -- |
| -- Public License distributed with GNAT; see file COPYING. If not, write -- |
| -- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, -- |
| -- MA 02111-1307, USA. -- |
| -- -- |
| -- GNAT was originally developed by the GNAT team at New York University. -- |
| -- Extensive contributions were provided by Ada Core Technologies Inc. -- |
| -- -- |
| ------------------------------------------------------------------------------ |
| |
| -- This package contains the routines used to deal with issuing warnings |
| -- for cases of calls that may require warnings about possible access |
| -- before elaboration. |
| |
| with Types; use Types; |
| |
| package Sem_Elab is |
| |
| ----------------------------- |
| -- Description of Approach -- |
| ----------------------------- |
| |
| -- Every non-static call that is encountered by Sem_Res results in |
| -- a call to Check_Elab_Call, with N being the call node, and Outer |
| -- set to its default value of True. |
| |
| -- The goal of Check_Elab_Call is to determine whether or not the |
| -- call in question can generate an access before elaboration |
| -- error (raising Program_Error) either by directly calling a |
| -- subprogram whose body has not yet been elaborated, or indirectly, |
| -- by calling a subprogram whose body has been elaborated, but which |
| -- contains a call to such a subprogram. |
| |
| -- The only calls that we need to look at at the outer level are |
| -- calls that occur in elaboration code. There are two cases. The |
| -- call can be at the outer level of elaboration code, or it can |
| -- be within another unit, e.g. the elaboration code of a subprogram. |
| |
| -- In the case of an elaboration call at the outer level, we must |
| -- trace all calls to outer level routines either within the current |
| -- unit or to other units that are with'ed. For calls within the |
| -- current unit, we can determine if the body has been elaborated |
| -- or not, and if it has not, then a warning is generated. |
| |
| -- Note that there are two subcases. If the original call directly |
| -- calls a subprogram whose body has not been elaborated, then we |
| -- know that an ABE will take place, and we replace the call by |
| -- a raise of Program_Error. If the call is indirect, then we don't |
| -- know that the PE will be raised, since the call might be guarded |
| -- by a conditional. In this case we set Do_Elab_Check on the call |
| -- so that a dynamic check is generated, and output a warning. |
| |
| -- For calls to a subprogram in a with'ed unit, we require that |
| -- a pragma Elaborate_All or pragma Elaborate be present, or that |
| -- the referenced unit have a pragma Preelaborate, pragma Pure, or |
| -- pragma Elaborate_Body. If none of these conditions is met, then |
| -- a warning is generated that a pragma Elaborate_All may be needed. |
| |
| -- For the case of an elaboration call at some inner level, we are |
| -- interested in tracing only calls to subprograms at the same level, |
| -- i.e. those that can be called during elaboration. Any calls to |
| -- outer level routines cannot cause ABE's as a result of the original |
| -- call (there might be an outer level call to the subprogram from |
| -- outside that causes the ABE, but that gets analyzed separately). |
| |
| -- Note that we never trace calls to inner level subprograms, since |
| -- these cannot result in ABE's unless there is an elaboration problem |
| -- at a lower level, which will be separately detected. |
| |
| -- Note on pragma Elaborate. The checking here assumes that a pragma |
| -- Elaborate on a with'ed unit guarantees that subprograms within the |
| -- unit can be called without causing an ABE. This is not in fact the |
| -- case since pragma Elaborate does not guarantee the transititive |
| -- coverage guaranteed by Elaborate_All. However, we leave this issue |
| -- up to the binder, which has generates warnings if there are possible |
| -- problems in the use of pragma Elaborate. |
| |
| -------------------------------------- |
| -- Instantiation Elaboration Errors -- |
| -------------------------------------- |
| |
| -- A special case arises when an instantiation appears in a context |
| -- that is known to be before the body is elaborated, e.g. |
| |
| -- generic package x is ... |
| -- ... |
| -- package xx is new x; |
| -- ... |
| -- package body x is ... |
| |
| -- In this situation it is certain that an elaboration error will |
| -- occur, and an unconditional raise Program_Error statement is |
| -- inserted before the instantiation, and a warning generated. |
| |
| -- The problem is that in this case we have no place to put the |
| -- body of the instantiation. We can't put it in the normal place, |
| -- because it is too early, and will cause errors to occur as a |
| -- result of referencing entities before they are declared. |
| |
| -- Our approach in this case is simply to avoid creating the body |
| -- of the instantiation in such a case. The instantiation spec is |
| -- modified to include dummy bodies for all subprograms, so that |
| -- the resulting code does not contain subprogram specs with no |
| -- corresponding bodies. |
| |
| procedure Check_Elab_Call (N : Node_Id; Outer_Scope : Entity_Id := Empty); |
| -- Check a call for possible elaboration problems. N is either an |
| -- N_Function_Call or N_Procedure_Call_Statement node, and Outer |
| -- indicates whether this is an outer level call from Sem_Res |
| -- (Outer_Scope set to Empty), or an internal recursive call |
| -- (Outer_Scope set to entity of outermost call, see body). |
| |
| procedure Check_Elab_Calls; |
| -- Not all the processing for Check_Elab_Call can be done at the time |
| -- of calls to Check_Elab_Call. This is because for internal calls, we |
| -- need to wait to complete the check until all generic bodies have been |
| -- instantiated. The Check_Elab_Calls procedure cleans up these waiting |
| -- checks. It is called once after the completion of instantiation. |
| |
| procedure Check_Elab_Instantiation |
| (N : Node_Id; |
| Outer_Scope : Entity_Id := Empty); |
| -- Check an instantiation for possible elaboration problems. N is an |
| -- instantiation node (N_Package_Instantiation, N_Function_Instantiation, |
| -- or N_Procedure_Instantiation), and Outer_Scope indicates if this is |
| -- an outer level call from Sem_Ch12 (Outer_Scope set to Empty), or an |
| -- internal recursive call (Outer_Scope set to scope of outermost call, |
| -- see body for further details). The returned value is relevant only |
| -- for an outer level call, and is set to False if an elaboration error |
| -- is bound to occur on the instantiation, and True otherwise. This is |
| -- used by the caller to signal that the body of the instance should |
| -- not be generated (see detailed description in body). |
| |
| procedure Check_Task_Activation (N : Node_Id); |
| -- at the point at which tasks are activated in a package body, check |
| -- that the bodies of the tasks are elaborated. |
| |
| end Sem_Elab; |
