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Text File | 1996-09-28 | 23KB | 449 lines

------------------------------------------------------------------------------ -- -- -- GNAT COMPILER COMPONENTS -- -- -- -- L I B -- -- -- -- S p e c -- -- -- -- $Revision: 1.53 $ -- -- -- -- Copyright (c) 1992,1993,1994,1995 NYU, All Rights Reserved -- -- -- -- The GNAT library is free software; you can redistribute it and/or modify -- -- it under terms of the GNU Library General Public License as published by -- -- the Free Software Foundation; either version 2, or (at your option) any -- -- later version. The GNAT library is distributed in the hope that it will -- -- be useful, but WITHOUT ANY WARRANTY; without even the implied warranty -- -- of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU -- -- Library General Public License for more details. You should have -- -- received a copy of the GNU Library General Public License along with -- -- the GNAT library; see the file COPYING.LIB. If not, write to the Free -- -- Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. -- -- -- ------------------------------------------------------------------------------ -- This package contains routines for accessing and outputting the library -- information. It contains the routine to load subsidiary units. with Casing; use Casing; with Table; with Types; use Types; package Lib is -------------------------------------------- -- General Approach to Library Management -- -------------------------------------------- -- As described in GNote #1, when a unit is compiled, all its subsidiary -- units are recompiled, including the following: -- (a) Corresponding spec for a body -- (b) Parent spec of a child library spec -- (d) With'ed specs -- (d) Parent body of a subunit -- (e) Subunits corresponding to any specified stubs -- (f) Bodies of inlined subprograms that are called -- (g) Bodies of generic subprograms or packages that are instantiated -- (h) Bodies of packages containing either of the above two items -- (i) Specs and bodies of runtime units -- (j) Parent specs for with'ed child library units -- If a unit is being compiled only for syntax checking, then no subsidiary -- units are loaded, the the syntax check applies only to the main unit, -- i.e. the one contained in the source submitted to the library. -- If a unit is being compiled for syntax and semantic checking, then only -- cases (a)-(d) loads are performed, since the full semantic checking can -- be carried out without needing (e)-(i) loads. In this case no object -- file, or library information file, is generated, so the missing units -- do not affect the results. -- Specifications of library subprograms, subunits, and generic specs -- and bodies, can only be compiled in syntax/semantic checking mode, -- since no code is ever generated directly for these units. In the case -- of subunits, only the compilation of the ultimate parent unit generates -- actual code. If a subunit is submitted to the compiler in syntax/ -- semantic checking mode, the parent (or parents in the nested case) are -- semantically checked only up to the point of the corresponding stub. -- If code is being generated, then all the above units are required, -- although the need for bodies of inlined procedures can be suppressed -- by the use of a switch that sets the mode to ignore pragma Inline -- statements. -- The two main sections of the front end, Par and Sem, are recursive. -- Compilation proceeds unit by unit making recursive calls as necessary. -- The process is controlled from the GNAT main program, which makes calls -- to Par and Sem sequence for the main unit. -- Par parses the given unit, and then, after the parse is complete, uses -- the Par.Load subprogram to load all its subsidiary units in categories -- (a)-(d) above, installing pointers to the loaded units in the parse -- tree, as described in a later section of this spec. If any of these -- required units is missing, a fatal error is signalled, so that no -- attempt is made to run Sem in such cases, since it is assumed that -- too many cascaded errors would result, and the confusion would not -- be helpful. -- Following the call to Par on the main unit, the entire tree of required -- units is thus loaded, and Sem is called on the main unit. The parameter -- passed to Sem is the unit to be analyzed. The visibility table, which -- is a single global structure, starts out containing only the entries -- for the visible entities in Standard. Every call to Sem establishes a -- new scope stack table, pushing an entry for Standard on entry to provide -- the proper initial scope environment. -- Sem first proceeds to perform semantic analysis on the currently loaded -- units as follows: -- In the case of a body (case (a) above), Sem analyzes the corresponding -- spec, using a recursive call to Sem. As is always expected to be the -- case with calls to Sem, any entities installed in the visibility table -- are removed on exit from Sem, so that these entities have to be -- reinstalled on return to continue the analysis of the body which of -- course needs visibility of these entities. -- -- In the case of the parent of a child spec (case (b) above), a similar -- call is made to Sem to analyze the parent. Again, on return, the -- entities from the analyzed parent spec have to be installed in the -- visibility table of the caller (the child unit), which must have -- visibility to the entities in its parent spec. -- For with'ed specs (case (c) above), a recursive call to Sem is made -- to analyze each spec in turn. After all the spec's have been analyzed, -- but not till that point, the entities from all the with'ed units are -- reinstalled in the visibility table so that the caller can proceed -- with the analysis of the unit doing the with's with the necessary -- entities made either potentially use visible or visible by selection -- as needed. -- Case (d) arises when Sem is passed a subunit to analyze. This means -- that the main unit is a subunit, and the unit passed to Sem is either -- the main unit, or one of its ancestors that is still a subunit. Since -- analysis must start at the top of the tree, Sem essentially cancels -- the current call by immediately making a call to analyze the parent -- (when this call is finished it immediately returns, so logically this -- call is like a goto). The subunit will then be analyzed at the proper -- time as described for the stub case. Note that we also turn off the -- indication that code should be generated in this case, since the only -- time we generate code for subunits is when compiling the main parent. -- Case (e), subunits corresponding to stubs, are handled as the stubs -- are encountered. There are three sub-cases: -- If the subunit has already been loaded, then this means that the -- main unit was a subunit, and we are back on our way down to it -- after following the initial processing described for case (d). -- In this case we analyze this particular subunit, as described -- for the case where we are generating code, but when we get back -- we are all done, since the rest of the parent is irrelevant. To -- get out of the parent, we raise the exception Subunit_Found, which -- is handled at the outer level of Sem. -- The cases where the subunit has not already been loaded correspond -- to cases where the main unit was a parent. In this case the action -- depends on whether or not we are generating code. If we are not -- generating code, then this is the case where we can simply ignore -- the subunit, since in checking mode we don't even want to insist -- that the subunit exist, much less waste time checking it. -- If we are generating code, then we need to load and analyze -- all subunits. This is achieved with a call to Lib.Load to load -- and parse the unit, followed by processing that installs the -- context clause of the subunit, analyzes the subunit, and then -- removes the context clause (from the visibility chains of the -- parent). Note that we do *not* do a recursive call to Sem in -- this case, precisely because we need to do the analysis of the -- subunit with the current visibility table and scope stack. -- Case (f) applies only to subprograms for which a pragma Inline is -- given, providing that the compiler is operating in the mode where -- pragma Inline's are activated. When the expander encounters a call -- to such a subprogram, it loads the body of the subprogram if it has -- not already been loaded, and calls Sem to process it. -- Case (g) is similar to case (f), except that the body of a generic -- is unconditionally required, regardless of compiler mode settings. -- As in the subprogram case, when the expander encounters a generic -- instantiation, it loads the generic body of the subprogram if it -- has not already been loaded, and calls Sem to process it. -- Case (h) arises when a package contains either an inlined subprogram -- which is called, or a generic which is instantiated. In this case the -- body of the package must be loaded and analyzed with a call to Sem. -- Case (i) is handled by adding implicit with clauses to the context -- clauses of all units that potentially reference the relevant runtime -- entities. Note that since we have the full set of units available, -- the parser can always determine the set of runtime units that is -- needed. These with clauses do not have associated use clauses, so -- all references to the entities must be by selection. Once the with -- clauses have been added, subsequent processing is as for normal -- with clauses. -- Case (j) is also handled by adding appropriate implicit with clauses -- to any unit that withs a child unit. Again there is no use clause, -- and subsequent processing proceeds as for an explicit with clause. -- Sem thus completes the loading of all required units, except those -- required for inline subprogram bodies or inlined generics. If any -- of these load attempts fails, then the expander will not be called, -- even if code was to be generated. If the load attempts all succeed -- then the expander is called, though the attempt to generate code may -- still fail if an error occurs during a load attempt for an inlined -- body or a generic body. ----------------- -- Global Data -- ----------------- Current_Sem_Unit : Unit_Number_Type; -- Unit number of unit currently being analyzed/expanded. This is set when -- ever a new unit is entered, saving and restoring the old value, so that -- it always reflects the unit currently being analyzed. ----------------- -- Units Table -- ----------------- -- The units table has an entry for each unit (source file) read in by the -- current compilation. The table is indexed by the unit number value, -- The first entry in the table, subscript Main_Unit, is for the main file. -- Each entry in this units table contains the following data. -- Unit_File_Name -- The name of the source file containing the unit. Set when the entry -- is created by a call to Lib.Load, and then cannot be changed. -- Source_Index -- The index in the source file table of the corresponding source file. -- Set when the entry is created by a call to Lib.Load and then cannot -- be changed. -- Expected_Unit -- This is the expected unit name for a file other than the main unit, -- since these are cases where we load the unit using Lib.Load and we -- know the unit that is expected. It must be the same as Unit_Name -- if it is set (see test in Par.Load). Expected_Unit is set to -- No_Name for the main unit. -- Unit_Name -- The name of the unit. Initialized to No_Name by Lib.Load, and then -- set by the parser when the unit is parsed to the unit name actually -- found in the file (which should, in the absence of errors) be the -- same name as Expected_Unit. -- Cunit -- Pointer to the N_Compilation_Unit node. Initially set to Empty by -- Lib.Load, and then reset to the required node by the parser when -- the unit is parsed. -- Cunit_Entity -- Pointer to the entity node for the compilation unit. Initially set -- to Empty by Lib.Load, and then reset to the required entity by the -- parser when the unit is parsed. -- Fatal_Error -- A flag that is initialized to False, and gets set to True if a fatal -- error occurs during the processing of a unit. A fatal error is one -- defined as serious enough to stop the next phase of the compiler -- from running (i.e. fatal error during parsing stops semantics, -- fatal error during semantics stops code generation). Note that -- currently, errors of any kind cause Fatal_Error to be set, but -- eventually perhaps only errors labeled as Fatal_Errors should be -- this severe if we decide to try Sem on sources with minor errors. -- Generate_Code -- This flag is set True for all units in the current file for which -- code is to be generated. This includes the unit explicitly compiled, -- together with its specification, and any subunits. -- Loading -- A flag that is used to catch circular WITH dependencies. It is set -- True when an entry is initially created in the file table, and set -- False when the load is completed, or ends with an error. -- Main_Priority -- This field is used to indicate the priority of a possible main -- program, as set by a pragma Priority. A value of -1 indicates -- that the default priority is to be used (and is also used for -- entries that do not correspond to possible main programs). -- Serial_Number -- This field holds a serial number used by New_Internal_Name to -- generate unique temporary numbers on a unit by unit basis. The -- only access to this field is via the Increment_Serial_Number -- routine which increments the current value and returns it. -- Version -- This field holds the version of the unit, which is stored -- internally as a 32-bit unsigned number. Access to the version -- information is not direct, but is done through the routines -- described below. When a unit table entry is created, the version -- reflects the version of the corresponding source file. Calls to -- Update_Version are then made to reflect the versions of any units -- on which this unit is semantically dependent. -- The units table is reset to empty at the start of the compilation of -- each main unit by Lib.Initialize. Entries are then added by calls to -- the Lib.Load procedure. The following subprograms are used to access -- and modify entries in the Units table. Individual entries are accessed -- using a unit number value which ranges from Main_Unit (the first entry, -- which is always for the current main unit) to Last_Unit. Default_Main_Priority : constant Int := -1; -- Value used in Main_Priority field to indicate default main priority function Unit_File_Name (U : Unit_Number_Type) return File_Name_Type; function Unit_Name (U : Unit_Number_Type) return Unit_Name_Type; function Expected_Unit (U : Unit_Number_Type) return Unit_Name_Type; function Source_Index (U : Unit_Number_Type) return Source_File_Index; function Cunit (U : Unit_Number_Type) return Node_Id; function Cunit_Entity (U : Unit_Number_Type) return Entity_Id; function Fatal_Error (U : Unit_Number_Type) return Boolean; function Generate_Code (U : Unit_Number_Type) return Boolean; function Loading (U : Unit_Number_Type) return Boolean; function Main_Priority (U : Unit_Number_Type) return Int; -- Get value of named field from given units table entry procedure Set_Unit_Name (U : Unit_Number_Type; N : Unit_Name_Type); procedure Set_Cunit (U : Unit_Number_Type; N : Node_Id); procedure Set_Cunit_Entity (U : Unit_Number_Type; E : Entity_Id); procedure Set_Fatal_Error (U : Unit_Number_Type; B : Boolean := True); procedure Set_Generate_Code (U : Unit_Number_Type; B : Boolean := True); procedure Set_Loading (U : Unit_Number_Type; B : Boolean := True); procedure Set_Main_Priority (U : Unit_Number_Type; P : Int); -- Set value of named field for given units table entry subtype Version_String is String (1 .. 8); function Version_Get (U : Unit_Number_Type) return Version_String; -- Returns the version as a string with 8 hex digits (upper case letters) function Last_Unit return Unit_Number_Type; -- Unit number of last allocated unit function Num_Units return Nat; -- Number of units currently in unit table function Get_Sloc_Unit_Number (S : Source_Ptr) return Unit_Number_Type; -- Return unit number of file identified by given source pointer value. -- This call must always succeed, since any valid source pointer value -- belongs to some previously loaded module. function Get_Cunit_Unit_Number (N : Node_Id) return Unit_Number_Type; -- Return unit number of the unit whose N_Compilation_Unit node is the -- one passed as an argument. This must always succeed since the node -- could not have been built without making a unit table entry. function Get_Cunit_Entity_Unit_Number (E : Entity_Id) return Unit_Number_Type; -- Return unit number of the unit whose compilation unit spec entity is -- the one passed as an argument. This must always succeed since the -- entity could not have been built without making a unit table entry. procedure Tree_Write; -- Writes out internal tables to current tree file using Tree_Write procedure Tree_Read; -- Initializes internal tables from current tree file using Tree_Read function Is_Loaded (Uname : Unit_Name_Type) return Boolean; -- Determines if unit with given name is already loaded, i.e. there is -- already an entry in the file table with this unit name for which the -- corresponding file was found and parsed. Note that the Fatal_Error flag -- of this entry must be checked before proceeding with further processing. procedure List; -- Lists units in active library (i.e. generates output consisting of a -- sorted listing of the units represented in File table, with the -- exception of the main unit). private pragma Inline (Unit_File_Name); pragma Inline (Unit_Name); pragma Inline (Source_Index); pragma Inline (Cunit); pragma Inline (Cunit_Entity); pragma Inline (Fatal_Error); pragma Inline (Generate_Code); pragma Inline (Loading); pragma Inline (Main_Priority); pragma Inline (Set_Unit_Name); pragma Inline (Set_Cunit); pragma Inline (Set_Cunit_Entity); pragma Inline (Set_Fatal_Error); pragma Inline (Set_Generate_Code); pragma Inline (Set_Loading); pragma Inline (Set_Main_Priority); type Version_Id is mod 2 ** 32; type Unit_Record is record Unit_File_Name : File_Name_Type; Unit_Name : Unit_Name_Type; Expected_Unit : Unit_Name_Type; Source_Index : Source_File_Index; Cunit : Node_Id; Cunit_Entity : Node_Id; Fatal_Error : Boolean; Generate_Code : Boolean; Loading : Boolean; Main_Priority : Int; Serial_Number : Int; Version : Version_Id; end record; package Units is new Table ( Table_Component_Type => Unit_Record, Table_Index_Type => Unit_Number_Type, Table_Low_Bound => Main_Unit, Table_Initial => 50, Table_Increment => 100, Table_Name => "Units"); -- The following table stores strings from pragma Linker_Option lines package Linker_Option_Lines is new Table ( Table_Component_Type => String_Id, Table_Index_Type => Integer, Table_Low_Bound => 1, Table_Initial => 10, Table_Increment => 100, Table_Name => "Linker_Option_Lines"); Load_Msg_Sloc : Source_Ptr; -- Location for placing error messages (a token in the main source text) -- This is set from Sloc (Enode) by Load only in the case where this Sloc -- is in the main source file. This ensures that not found messages and -- circular dependency messages reference the original with in this source. type Unit_Ref_Table is array (Pos range <>) of Unit_Number_Type; -- Type to hold list of indirect references to unit number table -- The Load_Stack table contains a list of unit numbers (indexes into the -- unit table) of units being loaded on a single dependency chain. The -- First entry is the main unit. The second entry, if present is a unit -- on which the first unit depends, etc. This stack is used to generate -- error messages showing the dependency chain if a file is not found. -- The Load function makes an entry in this table when it is called, and -- removes the entry just before it returns. package Load_Stack is new Table ( Table_Component_Type => Unit_Number_Type, Table_Index_Type => Nat, Table_Low_Bound => 0, Table_Initial => 10, Table_Increment => 100, Table_Name => "Lib.Load_Stack"); procedure Sort (Tbl : in out Unit_Ref_Table); -- This procedure sorts the given unit reference table in order of -- ascending unit names, where the ordering relation is as described -- by the comparison routines provided by package Uname. end Lib;