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------------------------------------------------------------------------------ -- -- -- GNAT COMPILER COMPONENTS -- -- -- -- S E M _ E L A B -- -- -- -- S p e c -- -- -- -- Copyright (C) 1997-2008, 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 3, 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 COPYING3. If not, go to -- -- http://www.gnu.org/licenses for a complete copy of the license. -- -- -- -- 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 transitive -- 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. The node N is either -- an N_Function_Call or N_Procedure_Call_Statement node. The Outer_Scope -- argument 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_Assign (N : Node_Id); -- N is either the left side of an assignment, or a procedure argument for -- a mode OUT or IN OUT formal. This procedure checks for a possible case -- of access to an entity from elaboration code before the entity has been -- initialized, and issues appropriate warnings. 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;
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