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Text File | 1996-09-28 | 50KB | 1,093 lines

------------------------------------------------------------------------------ -- -- -- GNAT COMPILER COMPONENTS -- -- -- -- P A R -- -- -- -- B o d y -- -- -- -- $Revision: 1.88 $ -- -- -- -- Copyright (c) 1992,1993,1994 NYU, All Rights Reserved -- -- -- -- 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, 675 Mass Ave, Cambridge, MA 02139, USA. -- -- -- ------------------------------------------------------------------------------ with Atree; use Atree; with Casing; use Casing; with Csets; use Csets; with Debug; use Debug; with Elists; use Elists; with Errout; use Errout; with Features; use Features; with Fname; use Fname; with Lib; use Lib; with Namet; use Namet; with Nlists; use Nlists; with Nmake; use Nmake; with Opt; use Opt; with Output; use Output; with Scans; use Scans; with Scn; use Scn; with Sinput; use Sinput; with Sinfo; use Sinfo; with Snames; use Snames; with Style; with Table; with Tbuild; use Tbuild; with Types; use Types; procedure Par is Num_Library_Units : Natural := 0; -- Count number of units parsed (relevant only in syntax check only mode, -- since in semantics check mode only a single unit is permitted anyway) Unit_Node : Node_Id; -- Stores compilation unit node for current unit Save_Ada_83_Mode : constant Boolean := Ada_83; -- Saves state of Ada 83 mode switch for restore on exit (since it may -- get reset by occurrence of the Ada_83 or Ada_95 pragmas). Save_Features_On : constant Boolean := Features_On; -- Saves state of Features_On flag for restore on exit (so that a recursive -- call on the compiler does not disturb the proper setting of Features_On) -------------------- -- Error Recovery -- -------------------- -- When an error is encountered, a call is made to one of the Error_Msg -- routines to record the error. If the syntax scan is not derailed by the -- error (e.g. a complaint that logical operators are inconsistent in an -- EXPRESSION), then control returns from the Error_Msg call, and the -- parse continues unimpeded. -- If on the other hand, the Error_Msg represents a situation from which -- the parser cannot recover locally, the exception Error_Resync is raised -- immediately after the call to Error_Msg. Handlers for Error_Resync -- are located at strategic points to resynchronize the parse. For example, -- when an error occurs in a statement, the handler skips to the next -- semicolon and continues the scan from there. -- Each parsing procedure contains a note with the heading "Error recovery" -- which shows if it can propagate the Error_Resync exception. In order -- not to propagate the exception, a procedure must either contain its own -- handler for this exception, or it must not call any other routines which -- propagate the exception. -- Note: the arrangement of Error_Resync handlers is such that it should -- never be possible to transfer control through a procedure which made -- an entry in the scope stack, invalidating the contents of the stack. Error_Resync : exception; -- Exception raised on error that is not handled locally, see above. Last_Resync_Point : Source_Ptr; -- The resynchronization routines in Par.Sync run a risk of getting -- stuck in an infinite loop if they do not skip a token, and the caller -- keeps repeating the same resync call. On the other hand, if they skip -- a token unconditionally, some recovery opportunities are missed. The -- variable Last_Resync_Point records the token location previously set -- by a Resync call, and if a subsequent Resync call occurs at the same -- location, then the Resync routine does guarantee to skip a token. -------------------------------------------- -- Handling Semicolon Used in Place of IS -- -------------------------------------------- -- The following global variables are used in handling the error situation -- of using a semicolon in place of IS in a subprogram declaration as in: -- procedure X (Y : Integer); -- Q : Integer; -- begin -- ... -- end; -- The two contexts in which this can appear are at the outer level, and -- within a declarative region. At the outer level, we know something is -- wrong as soon as we see the Q (or begin, if there are no declarations), -- and we can immediately decide that the semicolon should have been IS. -- The situation in a declarative region is more complex. The declaration -- of Q could belong to the outer region, and we do not know that we have -- an error until we hit the begin. It is still not clear at this point -- from a syntactic point of view that something is wrong, because the -- begin could belong to the enclosing subprogram or package. However, we -- can incorporate a bit of semantic knowledge and note that the body of -- X is missing, so we definitely DO have an error. We diagnose this error -- as semicolon in place of IS on the subprogram line. -- There are two styles for this diagnostic. If the begin immediately -- follows the semicolon, then we can place a flag (IS expected) right -- on the semicolon. Otherwise we do not detect the error until we hit -- the begin which refers back to the line with the semicolon. -- To control the process in the second case, the following global -- variables are set to indicate that we have a subprogram declaration -- whose body is required and has not yet been found. The prefix SIS -- stands for "Subprogram IS" handling. SIS_Entry_Active : Boolean; -- Set True to indicate that an entry is active (i.e. that a subprogram -- declaration has been encountered, and no body for this subprogram has -- been encountered). The remaining fields are valid only if this is True. SIS_Labl : Node_Id; -- Subprogram designator SIS_Sloc : Source_Ptr; -- Source location of FUNCTION/PROCEDURE keyword SIS_Ecol : Column_Number; -- Column number of FUNCTION/PROCEDURE keyword SIS_Semicolon_Sloc : Source_Ptr; -- Source location of semicolon at end of subprogram declaration SIS_Declaration_Node : Node_Id; -- Pointer to tree node for subprogram declaration SIS_Missing_Semicolon_Message : Error_Msg_Id; -- Used to save message ID of missing semicolon message (which will be -- modified to missing IS if necessary). Set to No_Error_Msg in the -- normal (non-error) case. -- Five things can happen to an active SIS entry -- 1. If a BEGIN is encountered with an SIS entry active, then we have -- exactly the situation in which we know the body of the subprogram is -- missing. After posting an error message, we change the spec to a body, -- rechaining the declarations that intervened between the spec and BEGIN. -- 2. Another subprogram declaration or body is encountered. In this -- case the entry gets overwritten with the information for the new -- subprogram declaration. We don't catch some nested cases this way, -- but it doesn't seem worth the effort. -- 3. A nested declarative region (e.g. package declaration or package -- body) is encountered. The SIS active indication is reset at the start -- of such a nested region. Again, like case 2, this causes us to miss -- some nested cases, but it doesn't seen worth the effort to stack and -- unstack the SIS information. Maybe we will reconsider this if we ever -- get a complaint about a missed case :-) -- 4. We encounter a valid pragma INTERFACE or IMPORT that effectively -- supplies the missing body. In this case we reset the entry. -- 5. We encounter the end of the declarative region without encoutering -- a BEGIN first. In this situation we simply reset the entry. We know -- that there is a missing body, but it seems more reasonable to let the -- later semantic checking discover this. -------------------------------------------- -- Handling IS Used in Place of Semicolon -- -------------------------------------------- -- This is a somewhat trickier situation, and we can't catch it in all -- cases, but we do our best to detect common situations resulting from -- a "cut and paste" operation which forgets to change the IS to semicolon. -- Consider the following example: -- package body X is -- procedure A; -- procedure B is -- procedure C; -- ... -- procedure D is -- begin -- ... -- end; -- begin -- ... -- end; -- The trouble is that the section of text from PROCEDURE B through END; -- consitutes a valid procedure body, and the danger is that we find out -- far too late that something is wrong (indeed most compilers will behave -- uncomfortably on the above example). -- We have two approaches to helping to control this situation. First we -- make every attempt to avoid swallowing the last END; if we can be -- sure that some error will result from doing so. In particular, we won't -- accept the END; unless it is exactly correct (in particular it must not -- have incorrect name tokens), and we won't accept it if it is immediately -- followed by end of file, WITH or SEPARATE (all tokens that unmistakeably -- signal the start of a compilation unit, and which therefore allow us to -- reserve the END; for the outer level.) For more details on this aspect -- of the handling, see package Par.Endh. -- If we can avoid eating up the END; then the result in the absense of -- any additional steps would be to post a missing END referring back to -- the subprogram with the bogus IS. Similarly, if the enclosing package -- has no BEGIN, then the result is a missing BEGIN message, which again -- refers back to the subprogram header. -- Such an error message is not too bad (it's already a big improvement -- over what many parsers do), but it's not ideal, because the declarations -- following the IS have been absorbed into the wrong scope. In the above -- case, this could result for example in a bogus complaint that the body -- of D was missing from the package. -- To catch at least some of these cases, we take the following additional -- steps. First, a subprogram body is marked as having a suspicious IS if -- the declaration line is followed by a line which starts with a symbol -- that can start a declaration in the same column, or to the left of the -- column in which the FUNCTION or PROCEDURE starts (normal style is to -- indent any declarations which really belong a subprogram). If such a -- subprogram encounters a missing BEGIN or missing END, then we decide -- that the IS should have been a semicolon, and the subprogram body node -- is marked (by setting the Bad_Is_Detected flag true. -- The processing for a declarative part checks to see if the last -- declaration scanned is marked in this way, and if it is, the tree -- is modified to reflect the IS being interpreted as a semicolon. --------------------------------------------------- -- Parser Type Definitions and Control Variables -- --------------------------------------------------- -- The following variable and associated type declaration are used by the -- expression parsing routines to return more detailed information about -- the categorization of a parsed expression. type Expr_Form_Type is ( EF_Simple_Name, -- Simple name, i.e. possibly qualified identifier EF_Name, -- Simple expression which could also be a name EF_Simple, -- Simple expression which is not call or name EF_Non_Simple); -- Expression that is not a simple expression Expr_Form : Expr_Form_Type; -- The following type is used for calls to P_Subprogram, P_Package, P_Task, -- P_Protected to indicate which of several possibilities is acceptable. type Pf_Rec is record Spcn : Boolean; -- True if specification OK Decl : Boolean; -- True if declaration OK Gins : Boolean; -- True if generic instantiation OK Pbod : Boolean; -- True if proper body OK Rnam : Boolean; -- True if renaming declaration OK Stub : Boolean; -- True if body stub OK Fil1 : Boolean; -- Filler to fill to 8 bits Fil2 : Boolean; -- Filler to fill to 8 bits end record; pragma Pack (Pf_Rec); function T return Boolean renames True; function F return Boolean renames False; Pf_Decl_Gins_Pbod_Rnam_Stub : constant Pf_Rec := Pf_Rec'(F, T, T, T, T, T, F, F); Pf_Decl : constant Pf_Rec := Pf_Rec'(F, T, F, F, F, F, F, F); Pf_Decl_Gins_Pbod_Rnam : constant Pf_Rec := Pf_Rec'(F, T, T, T, T, F, F, F); Pf_Pbod : constant Pf_Rec := Pf_Rec'(F, F, F, T, F, F, F, F); Pf_Spcn : constant Pf_Rec := Pf_Rec'(T, F, F, F, F, F, F, F); -- The above are the only allowed values of Pf_Rec arguments type SS_Rec is record Eftm : Boolean; -- ELSIF can terminate sequence Eltm : Boolean; -- ELSE can terminate sequence Extm : Boolean; -- EXCEPTION can terminate sequence Ortm : Boolean; -- OR can terminate sequence Sreq : Boolean; -- at least one statement required Tatm : Boolean; -- THEN ABORT can terminate sequence Whtm : Boolean; -- WHEN can terminate sequence Unco : Boolean; -- Unconditional terminate after one statement end record; pragma Pack (SS_Rec); SS_Eftm_Eltm_Sreq : constant SS_Rec := SS_Rec'(T, T, F, F, T, F, F, F); SS_Eltm : constant SS_Rec := SS_Rec'(F, T, F, F, F, F, F, F); SS_Eltm_Ortm : constant SS_Rec := SS_Rec'(F, T, F, T, F, F, F, F); SS_Eltm_Ortm_Tatm : constant SS_Rec := SS_Rec'(F, T, F, T, F, T, F, F); SS_Extm_Sreq : constant SS_Rec := SS_Rec'(F, F, T, F, T, F, F, F); SS_None : constant SS_Rec := SS_Rec'(F, F, F, F, F, F, F, F); SS_Ortm : constant SS_Rec := SS_Rec'(F, F, F, T, F, F, F, F); SS_Ortm_Sreq : constant SS_Rec := SS_Rec'(F, F, F, T, T, F, F, F); SS_Sreq : constant SS_Rec := SS_Rec'(F, F, F, F, T, F, F, F); SS_Sreq_Whtm : constant SS_Rec := SS_Rec'(F, F, F, F, T, F, T, F); SS_Whtm : constant SS_Rec := SS_Rec'(F, F, F, F, F, F, T, F); SS_Unco : constant SS_Rec := SS_Rec'(F, F, F, F, F, F, F, T); type End_Action_Type is ( -- Type used to describe the result of the Pop_End_Context call Accept_As_Scanned, -- Current end sequence is entirely c correct. In this case Token and -- the scan pointer are left pointing past the end sequence (i.e. they -- are unchanged from the values set on entry to Pop_End_Context). Insert_And_Accept, -- Current end sequence is to be left in place to satisfy some outer -- scope. Token and the scan pointer are set to point to the end -- token, and should be left there. A message has been generated -- indicating a missing end sequence. This status is also used for -- the case when no end token is present. Skip_And_Accept, -- The end sequence is incorrect (and an error message has been -- posted), but it will still be accepted. In this case Token and -- the scan pointer point back to the end token, and the caller -- should skip past the end sequence before proceeding. Skip_And_Reject); -- The end sequence is judged to belong to an unrecognized inner -- scope. An appropriate message has been issued and the caller -- should skip past the end sequence and then proceed as though -- no end sequence had been encountered. End_Action : End_Action_Type; -- The variable set by Pop_End_Context call showing which of the four -- decisions described above is judged the best. Label_List : Elist_Id; -- List of label nodes for labels appearing in the current compilation. -- Used by Par.Labl to construct the corresponding implicit declarations. ----------------- -- Scope Table -- ----------------- -- The scope table, also referred to as the scope stack, is used to -- record the current scope context. It is organized as a stack, with -- inner nested entries corresponding to higher entries on the stack. -- An entry is made when the parser encounters the opening of a nested -- construct (such as a record, task, package etc.), and then package -- Par.Endh uses this stack to deal with END lines (including properly -- dealing with END nesting errors). type SS_End_Type is -- Type of end entry required for this scope. The last two entries are -- used only in the subprogram body case to mark the case of a suspicious -- IS, or a bad IS (i.e. suspicions confirmed by missing BEGIN or END). -- See separate section on dealing with IS used in place of semicolon. -- Note that for many purposes E_Name, E_Suspicious_Is and E_Bad_Is are -- treated the same (E_Suspicious_Is and E_Bad_Is are simply special cases -- of E_Name). They are placed at the end of the enumeration so that a -- test for >= E_Name catches all three cases efficiently. (E_Dummy, -- dummy entry at outer level E_Case, -- END CASE; E_If, -- END IF; E_Loop, -- END LOOP; E_Record, -- END RECORD; E_Select, -- END SELECT; E_Name, -- END [name]; E_Suspicious_Is, -- END [name]; (case of suspicious IS) E_Bad_Is); -- END [name]; (case of bad IS) type Scope_Table_Entry is record Etyp : SS_End_Type; Lreq : Boolean; Ecol : Column_Number; Labl : Node_Id; Decl : List_Id; Sloc : Source_Ptr; S_Is : Source_Ptr; end record; -- Single entry in the table. The fields are used as follows: -- The Lreq field is a flag indicating whether the label, if present, -- is required to appear on the end line. It is referenced only in the -- case of Etyp = E_Name or E_Suspicious_Is where the name may or may not -- be required (yes for labeled block, no in other cases). Note that for -- all cases except begin, the question of whether a label is required -- can be determined from the other fields (for loop, it is required if -- it is present, and for the other constructs it is never required or -- allowed). -- The Ecol field contains the absolute column number (with tabs expanded) -- of the expected column of the end assuming normal Ada indentation usage. -- If the RM_Column_Check mode is set, this value is used in assessing the -- syntactic correctness of various constructs. Otherwise it is used only -- to control heuristic error recovery actions. -- The Labl field is used only for the LOOP and BEGIN cases, and is the -- Node_Id value of the label name. For all cases except child units, -- this value is an entity whose Chars field contains the name pointer -- that identifies the label uniquely. For the child unit case the Labl -- field references an N_Defining_Program_Unit_Name node for the name. -- For cases other than LOOP or BEGIN, the Label field is set to Error, -- indicating that it is an error to have a label on the end line. -- The Decl field points to the list of declarations (i.e. the declarative -- part) associated with this construct. It is set only in the END [name] -- cases, and is set to No_List for all other cases which do not have a -- declarative unit associated with them. This is used for determining the -- proper location for implicit label declarations. -- Sloc is the source location of the opening token of the construct. This -- is used to refer back to this line in error messages (such as missing -- or incorrect end lines). The Sloc field is not used, and is not set, if -- a label is present (the Labl field provides the text name of the label -- in this case, which is fine for error messages). -- S_Is is relevant only if Etyp is set to E_Suspicious_Is or E_Bad_Is. -- It records the location of the IS that is considered to be suspicious. -- The following declares the scope table itself. The Last field is the -- stack pointer, so that Scope.Table (Scope.Last) is the top entry. The -- oldest entry, at Scope_Stack (0), is a dummy entry with Etyp set to -- E_Dummy, and the other fields undefined. This dummy entry ensures that -- Scope_Stack (Scope_Stack_Ptr).Etyp can always be tested, and that the -- scope stack pointer is always in range. package Scope is new Table ( Table_Component_Type => Scope_Table_Entry, Table_Index_Type => Int, Table_Low_Bound => 0, Table_Initial => 50, Table_Increment => 100, Table_Name => "Scope"); --------------------------------- -- Parsing Routines by Chapter -- --------------------------------- -- Uncommented declarations in this section simply parse the construct -- corresponding to their name, and return an ID value for the Node or -- List that is created. package Ch2 is function P_Identifier return Node_Id; function P_Pragma return Node_Id; procedure P_Pragmas_Misplaced; -- Skips misplaced pragmas with a complaint procedure P_Pragmas_Opt (List : List_Id); -- Parses optional pragmas and appends them to the List end Ch2; package Ch3 is Missing_Begin_Msg : Error_Msg_Id; -- This variable is set by a call to P_Declarative_Part. Normaly it -- is set to No_Error_Msg, indicating that no special processing is -- required by the caller. The special case arises when a statement -- is found in the sequence of declarations. In this case the Id of -- the message issued ("declaration expected") is preserved in this -- variable, then the caller can change it to an appropriate missing -- begin message if indeed the BEGIN is missing. function P_Access_Definition return Node_Id; function P_Access_Type_Definition return Node_Id; function P_Array_Type_Definition return Node_Id; function P_Basic_Declarative_Items return List_Id; function P_Constraint_Opt return Node_Id; function P_Declarative_Part return List_Id; function P_Defining_Identifier return Node_Id; function P_Discrete_Choice_List return List_Id; function P_Discrete_Range return Node_Id; function P_Discrete_Subtype_Definition return Node_Id; function P_Known_Discriminant_Part_Opt return List_Id; function P_Signed_Integer_Type_Definition return Node_Id; function P_Range return Node_Id; function P_Range_Or_Subtype_Mark return Node_Id; function P_Range_Constraint return Node_Id; function P_Record_Definition return Node_Id; function P_Subtype_Indication return Node_Id; function P_Subtype_Mark return Node_Id; function P_Subtype_Mark_Resync return Node_Id; function P_Unknown_Discriminant_Part_Opt return Boolean; procedure P_Component_Items (Decls : List_Id); -- Scan out one or more component items and append them to the -- given list. Only scans out more than one declaration in the -- case where the source has a single declaration with multiple -- defining identifiers. function Init_Expr_Opt (P : Boolean := False) return Node_Id; -- If an initialization expression is present (:= expression), then -- it is scanned out and returned, otherwise Empty is returned if no -- initialization expression is present. This procedure also handles -- certain common error cases cleanly. The parameter P indicates if -- a right paren can follow the expression (default = no right paren -- allowed). function P_Subtype_Indication (Subtype_Mark : Node_Id) return Node_Id; -- This version of P_Subtype_Indication is called when the caller has -- already scanned out the subtype mark which is passed as a parameter. function P_Subtype_Mark_Attribute (Type_Node : Node_Id) return Node_Id; -- Parse a subtype mark attribute. The caller has already parsed the -- subtype mark, which is passed in as the argument, and has checked -- that the current token is apostrophe. end Ch3; package Ch4 is function P_Aggregate return Node_Id; function P_Expression return Node_Id; function P_Expression_No_Right_Paren return Node_Id; function P_Function_Name return Node_Id; function P_Name return Node_Id; function P_Qualified_Simple_Name return Node_Id; function P_Qualified_Simple_Name_Resync return Node_Id; function P_Simple_Expression return Node_Id; function P_Qualified_Expression (Subtype_Mark : Node_Id) return Node_Id; -- This routine scans out a qualified expression when the caller has -- already scanned out the name and apostrophe of the construct. function P_Range_Attribute_Reference (Prefix_Node : Node_Id) return Node_Id; -- Scan a range attribute reference. The caller has scanned out the -- prefix. The current token is known to be an apostrophe and the -- following token is known to be RANGE. end Ch4; package Ch5 is function P_Statement_Name (Name_Node : Node_Id) return Node_Id; -- Given a node representing a name (which is a call), converts it -- to the syntactically corresponding procedure call statement. function P_Sequence_Of_Statements (SS_Flags : SS_Rec) return List_Id; -- The argument indicates the acceptable termination tokens. -- See body in Par.Ch5 for details of the use of this parameter. procedure Parse_Decls_Begin_End (Parent : Node_Id); -- Parses declarations and handled statement sequence, setting -- fields of Parent node appropriately. end Ch5; package Ch6 is function P_Designator return Node_Id; function P_Defining_Program_Unit_Name return Node_Id; function P_Formal_Part return List_Id; function P_Parameter_Profile return List_Id; function P_Return_Statement return Node_Id; function P_Subprogram_Specification return Node_Id; procedure P_Mode (Node : Node_Id); -- Sets In_Present and/or Out_Present flags in Node scanning past -- IN, OUT or IN OUT tokens in the source. function P_Subprogram (Pf_Flags : Pf_Rec) return Node_Id; -- Scans out any construct starting with either of the keywords -- PROCEDURE or FUNCTION. The parameter indicates which possible -- possible kinds of construct (body, spec, instantiation etc.) -- are permissible in the current context. end Ch6; package Ch7 is function P_Package (Pf_Flags : Pf_Rec) return Node_Id; -- Scans out any construct starting with the keyword PACKAGE. The -- parameter indicates which possible kinds of construct (body, spec, -- instantiation etc.) are permissible in the current context. end Ch7; package Ch8 is function P_Use_Clause return Node_Id; end Ch8; package Ch9 is function P_Abort_Statement return Node_Id; function P_Abortable_Part return Node_Id; function P_Accept_Statement return Node_Id; function P_Delay_Statement return Node_Id; function P_Entry_Body return Node_Id; function P_Protected return Node_Id; function P_Requeue_Statement return Node_Id; function P_Select_Statement return Node_Id; function P_Task return Node_Id; function P_Terminate_Alternative return Node_Id; end Ch9; package Ch10 is function P_Compilation_Unit return Node_Id; end Ch10; package Ch11 is function P_Handled_Sequence_Of_Statements return Node_Id; function P_Raise_Statement return Node_Id; function Parse_Exception_Handlers return List_Id; -- Parses the partial construct EXCEPTION followed by a list of -- exception handlers which appears in a number of productions, -- and returns the list of exception handlers. end Ch11; package Ch12 is function P_Generic return Node_Id; function P_Generic_Actual_Part_Opt return List_Id; end Ch12; package Ch13 is function P_Representation_Clause return Node_Id; function P_Code_Statement (Subtype_Mark : Node_Id) return Node_Id; -- Function to parse a code statement. The caller has scanned out -- the name to be used as the subtype mark (but has not checked that -- it is suitable for use as a subtype mark, i.e. is either an -- identifier or a selected component). The current token is an -- apostrophe and the following token is either a left paren or -- RANGE (the latter being an error to be caught by P_Code_Statement. end Ch13; -- Note: the parsing for annexe I features (i.e. obsolescent features) -- is found in the logical section where these features would be if -- they were not obsolescent. In particular: -- Delta constraint is parsed by P_Delta_Constraint (3.5.9) -- At clause is parsed by P_At_Clause (13.1) -- Mod clause is parsed by P_Mod_Clause (13.5.1) ------------------ -- End Handling -- ------------------ -- Routines for handling end lines, including scope recovery package Endh is function Check_End return Boolean; -- Called when an end sequence is required. In the absence of an error -- situation, Token contains Tok_End on entry, but in a missing end -- case, this may not be the case. Pop_End_Context is used to determine -- the appropriate action to be taken. The returned result is True if -- an End sequence was encountered and False if no End sequence was -- present. This occurs if the END keyword encountered was determined -- to be improper and deleted (i.e. Pop_End_Context set End_Action to -- Skip_And_Reject). Note that the END sequence includes a semicolon, -- except in the case of END RECORD, where a semicolon follows the END -- RECORD, but is not part of the record type definition itself. procedure End_Skip; -- Skip past an end sequence. On entry Token contains Tok_End, and we -- we know that the end sequence is syntactically incorrect, and that -- an appropriate error message has already been posted. The mission is -- simply to position the scan pointer to be the best guess of the -- position after the end sequence. We do not issue any additional -- error messages while carrying this out. procedure End_Statements; -- Called when an end is required or expected to terminate a sequence -- of statements. The caller has already made an appropriate entry in -- the Scope.Table to describe the expected form of the end. This can -- only be used in cases where the only appropriate terminator is end. procedure Pop_End_Context; -- Pop_End_Context is called after processing a construct, to pop -- the top entry off the end stack. It decides on the appropriate action -- to take, signalling the result by setting End_Action as described in -- the global variable section. end Endh; ------------------------------------ -- Resynchronization After Errors -- ------------------------------------ -- These procedures are used to resynchronize after errors. Following an -- error which is not immediately locally recoverable, the exception -- Error_Resync is raised. The handler for Error_Resync typically calls -- one of these recovery procedures to resynchronize the source position -- to a point from which parsing can be restarted. -- Note: these procedures output an information message that tokens are -- being skipped, but this message is output only if the option for -- Multiple_Errors_Per_Line is set in Options. package Sync is procedure Resync_Choice; -- Used if an error occurs scanning a choice. The scan pointer is -- advanced to the next vertical bar, arrow, or semicolon, whichever -- comes first. We also quit if we encounter an end of file. procedure Resync_Expression; -- Used if an error is detected during the parsing of an expression. -- It skips past tokens until either a token which cannot be part of -- an expression is encountered (an expression terminator), or if a -- comma or right parenthesis or vertical bar is encountered at the -- current parenthesis level (a parenthesis level counter is maintained -- to carry out this test). procedure Resync_Past_Right_Paren_Or_EOL; -- Used to skip a junk list of items enclosed in parentheses which are -- expected to lie on the current line. Tokens are skipped until a -- right paren is skipped, or until end of line, whichever is first. procedure Resync_Past_Semicolon; -- Used if an error occurs while scanning a sequence of declarations. -- The scan pointer is positioned past the next semicolon and the scan -- resumes. The scan is also resumed on encountering a token which -- starts a declaration (but we make sure to skip at least one token -- in this case, to avoid getting stuck in a loop). procedure Resync_Past_Semicolon_Or_To_Loop_Or_Then; -- Used if an error occurs while scanning a sequence of statements. -- The scan pointer is positioned past the next semicolon, or to the -- next occurrence of either then or loop, and the scan resumes. procedure Resync_To_When; -- Used when an error occurs scanning an entry index specification. -- The scan pointer is positioned to the next WHEN (or to IS or -- semicolon if either of these appear before WHEN, indicating -- another error has occurred). procedure Resync_Semicolon_List; -- Used if an error occurs while scanning a parenthesized list of items -- separated by semicolons. The scan pointer is advanced to the next -- semicolon or right parenthesis at the outer parenthesis level, or -- to the next is or RETURN keyword occurence, whichever comes first. procedure Resync_Cunit; -- Synchronize to next token which could be the start of a compilation -- unit, or to the end of file token. end Sync; ------------------------- -- Token Scan Routines -- ------------------------- -- Routines to check for expected tokens package Tchk is -- Procedures with names of the form T_xxx, where Tok_xxx is a token -- name, check that the current token matches the required token, and -- if so, scan past it. If not, an error is issued indicating that -- the required token is not present (xxx expected). In most cases, the -- scan pointer is not moved in the not-found case, but there are some -- exceptions to this, see for example T_Id, where the scan pointer is -- moved across a literal appearing where an identifier is expected. procedure T_Abort; procedure T_Arrow; procedure T_At; procedure T_Begin; procedure T_Body; procedure T_Box; procedure T_Colon; procedure T_Colon_Equal; procedure T_Comma; procedure T_Dot_Dot; procedure T_For; procedure T_Greater_Greater; procedure T_Identifier; procedure T_In; procedure T_Is; procedure T_Left_Paren; procedure T_Loop; procedure T_Mod; procedure T_New; procedure T_Of; procedure T_Or; procedure T_Private; procedure T_Range; procedure T_Record; procedure T_Right_Paren; procedure T_Semicolon; procedure T_Then; procedure T_Type; procedure T_Use; procedure T_When; procedure T_With; -- Procedures have names of the form TF_xxx, where Tok_xxx is a token -- name check that the current token matches the required token, and -- if so, scan past it. If not, an error message is issued indicating -- that the required token is not present (xxx expected). -- If the missing token is at the end of the line, then control returns -- immediately after posting the message. If there are remaining tokens -- on the current line, a search is conducted to see if the token -- appears later on the current line, as follows: -- A call to Scan_Save is issued and a forward search for the token -- is carried out. If the token is found on the current line before a -- semicolon, then it is scanned out and the scan continues from that -- point. If not the scan is restored to the point where it was missing. procedure TF_Arrow; procedure TF_Is; procedure TF_Loop; procedure TF_Return; procedure TF_Semicolon; procedure TF_Then; procedure TF_Use; end Tchk; ---------------------- -- Utility Routines -- ---------------------- package Util is function Bad_Spelling_Of (T : Token_Type) return Boolean; -- This function is called in an error situation. It checks if the -- current token is an identifier whose name is a plausible bad -- spelling of the given keyword token, and if so, issues an error -- message, sets Token from T, and returns True. Otherwise Token is -- unchanged, and False is returned. procedure Check_95_Keyword (Token_95, Next : Token_Type); -- This routine checks if the token after the current one matches the -- Next argument. If so, the scan is backed up to the current token -- and Token_Type is changed to Token_95 after issuing an appropriate -- error message ("(Ada 83) keyword xx cannot be used"). If not, -- the scan is backed up with Token_Type unchanged. This routine -- is used to deal with an attempt to use a 95 keyword in Ada 83 -- mode. The caller has typically checked that the current token, -- an identifier, matches one of the 95 keywords. procedure Check_Simple_Expression (E : Node_Id); -- Given an expression E, that has just been scanned, so that Expr_Form -- is still set, outputs an error if E is a non-simple expression. E is -- not modified by this call. procedure Check_Simple_Expression_In_Ada_83 (E : Node_Id); -- Like Check_Simple_Expression, except that the error message is only -- given when operating in Ada 83 mode, and includes "in Ada 83". function Check_Subtype_Mark (Mark : Node_Id) return Node_Id; -- Called to check that a node representing a name (or call) is -- suitable for a subtype mark, i.e, that it is an identifier or -- a selected component. If so, or if it is already Error, then -- it is returned unchanged. Otherwise an error message is issued -- and Error is returned. function Comma_Present return Boolean; -- Used in comma delimited lists to determine if a comma is present, or -- can reasonably be assumed to have been present (an error message is -- generated in the latter case). If True is returned, the scan has been -- positioned past the comma. If False is returned, the scan position -- is unchanged. Note that all comma-delimited lists are terminated by -- a right paren, so the only legitimate tokens when Comma_Present is -- called are right paren and comma. If some other token is found, then -- Comma_Present has the job of deciding whether it is better to pretend -- a comma was present, post a message for a missing comma and return -- True, or return False and let the caller diagnose the missing right -- parenthesis. procedure Discard_Junk_Node (N : Node_Id); procedure Discard_Junk_List (L : List_Id); pragma Inline (Discard_Junk_Node); pragma Inline (Discard_Junk_List); -- These procedures do nothing at all, their effect is simply to discard -- the argument. A typical use is to skip by some junk that is not -- expected in the current context. procedure Ignore (T : Token_Type); -- If current token matches T, then give an error message and skip -- past it, otherwise the call has no effect at all. function Is_Reserved_Identifier return Boolean; -- Test if current token is a reserved identifier. This test is based -- on the token being a keyword and being spelled in typical identifier -- style (i.e. starting with an upper case letter). procedure No_Constraint; -- Called in a place where no constraint is allowed, but one might -- appear due to a common error (e.g. after the type mark in a procedure -- parameter. If a constraint is present, an error message is posted, -- and the constraint is scanned and discarded. procedure Push_Scope_Stack; pragma Inline (Push_Scope_Stack); -- Push a new entry onto the scope stack. Scope.Last (the stack pointer) -- is incremented. The caller can then fill in the new top stack entry -- at Scope.Table (Scope.Last). procedure Pop_Scope_Stack; -- Pop an entry off the top of the scope stack. Scope_Last (the scope -- table stack pointer) is decremented by one. It is a fatal error to -- try to pop off the dummy entry at the bottom of the stack (i.e. -- Scope.Last must be non-zero at the time of call). function Separate_Present return Boolean; -- Determines if the current token is either Tok_Separate, or an -- identifier that is a possible misspelling of "separate" followed -- by a semicolon. True is returned if so, otherwise False. function Token_Is_At_Start_Of_Line return Boolean; pragma Inline (Token_Is_At_Start_Of_Line); -- Determines if the current token is the first token on the line end Util; --------------------------------------- -- Specialized Syntax Check Routines -- --------------------------------------- function Prag (Pragma_Node : Node_Id; Semi : Source_Ptr) return Node_Id; -- This function is passed a tree for a pragma that has been scanned out. -- The pragma is syntactically well formed according to the general syntax -- for pragmas and the pragma identifier is for one of the recognized -- pragmas. It performs specific syntactic checks for specific pragmas. -- The result is the input node if it is OK, or Error otherwise. The -- reason that this is separated out is to facilitate the addition -- of implementation defined pragmas. The second parameter records the -- location of the semicolon following the pragma (this is needed for -- correct processing of the List and Page pragmas). The returned value -- is a copy of Pragma_Node, or Error if an error is found. ------------------------- -- Subsidiary Routines -- ------------------------- procedure Labl; -- This procedure creates implicit label declarations for all label that -- are declared in the current unit. Note that this could conceptually -- be done at the point where the labels are declared, but it is tricky -- to do it then, since the tree is not hooked up at the point where the -- label is declared (e.g. a sequence of statements is not yet attached -- to its containing scope at the point a label in the sequence is found) procedure Load; -- This procedure loads all subsidiary units that are required by this -- unit, including with'ed units, specs for bodies, and parents for child -- units. It does not load bodies for inlined procedures and generics, -- since we don't know till semantic analysis is complete what is needed. ----------- -- Stubs -- ----------- -- The package bodies can see all routines defined in all other subpackages use Ch2; use Ch3; use Ch4; use Ch5; use Ch6; use Ch7; use Ch8; use Ch9; use Ch10; use Ch11; use Ch12; use Ch13; use Endh; use Tchk; use Sync; use Util; package body Ch2 is separate; package body Ch3 is separate; package body Ch4 is separate; package body Ch5 is separate; package body Ch6 is separate; package body Ch7 is separate; package body Ch8 is separate; package body Ch9 is separate; package body Ch10 is separate; package body Ch11 is separate; package body Ch12 is separate; package body Ch13 is separate; package body Endh is separate; package body Tchk is separate; package body Sync is separate; package body Util is separate; function Prag (Pragma_Node : Node_Id; Semi : Source_Ptr) return Node_Id is separate; procedure Labl is separate; procedure Load is separate; --------- -- Par -- --------- -- This function is the parse routine called at the outer level. It parses -- the current compilation unit and adds implicit label declarations. begin -- Special processing for language defined units if Fname.Is_Language_Defined_Unit (File_Name (Current_Source_File)) then -- ??? the Fname. prefix here is because of some visibility bug! -- Always force Ada_95 mode for predefined units Ada_83 := False; Ada_95 := True; -- If this is the main unit, disallow compilation unless the -gnatg -- (GNAT mode) switch is set (from a user point of view, the rule is -- that language defined units cannot be recompiled). if Current_Source_Unit = Main_Unit and then not GNAT_Mode and then Operating_Mode = Generate_Code then Error_Msg_SC ("language defined units may not be recompiled"); end if; -- If not predefined unit, set Ada_83 mode from switches else Ada_83 := Ada_83_Switch; Ada_95 := not Ada_83; end if; -- Set features collection from switches (for main unit only) Features_On := Xref_Flag_9 and (Current_Source_Unit = Main_Unit); -- Initialize scope table and other parser control variables Compiler_State := Parsing; Scope.Init; Scope.Increment_Last; Scope.Table (0).Etyp := E_Dummy; SIS_Entry_Active := False; Last_Resync_Point := No_Location; -- Parse compilation unit Label_List := New_Elmt_List; Unit_Node := P_Compilation_Unit; -- An internal error check, the scope stack should now be empty pragma Assert (Scope.Last = 0); -- Remaining steps are to create implicit label declarations and to -- load required subsidiary sources. These steps are required only -- if we are doing semantic checking. if Operating_Mode /= Check_Syntax or else Debug_Flag_F then Par.Labl; Par.Load; end if; -- Restore settings of switches saved on entry Ada_83 := Save_Ada_83_Mode; Ada_95 := not Ada_83; Features_On := Save_Features_On; Set_Comes_From_Source_Default (False); end Par;