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diff --git a/BaseTools/Source/C/VfrCompile/Pccts/CHANGES_FROM_133_BEFORE_MR13.txt b/BaseTools/Source/C/VfrCompile/Pccts/CHANGES_FROM_133_BEFORE_MR13.txt deleted file mode 100644 index bba5ecdd64..0000000000 --- a/BaseTools/Source/C/VfrCompile/Pccts/CHANGES_FROM_133_BEFORE_MR13.txt +++ /dev/null @@ -1,3666 +0,0 @@ -
- ------------------------------------------------------------
- This is the second part of a two part file.
- This is a list of changes to pccts 1.33 prior to MR13
- For more recent information see CHANGES_FROM_133.txt
- ------------------------------------------------------------
-
- DISCLAIMER
-
- The software and these notes are provided "as is". They may include
- typographical or technical errors and their authors disclaims all
- liability of any kind or nature for damages due to error, fault,
- defect, or deficiency regardless of cause. All warranties of any
- kind, either express or implied, including, but not limited to, the
- implied warranties of merchantability and fitness for a particular
- purpose are disclaimed.
-
-
-#153. (Changed in MR12b) Bug in computation of -mrhoist suppression set
-
- Consider the following grammar with k=1 and "-mrhoist on":
-
- r1 : (A)? => ((p>>? x /* l1 */
- | r2 /* l2 */
- ;
- r2 : A /* l4 */
- | (B)? => <<q>>? y /* l5 */
- ;
-
- In earlier versions the mrhoist routine would see that both l1 and
- l2 contained predicates and would assume that this prevented either
- from acting to suppress the other predicate. In the example above
- it didn't realize the A at line l4 is capable of suppressing the
- predicate at l1 even though alt l2 contains (indirectly) a predicate.
-
- This is fixed in MR12b.
-
- Reported by Reinier van den Born (reinier@vnet.ibm.com)
-
-#153. (Changed in MR12a) Bug in computation of -mrhoist suppression set
-
- An oversight similar to that described in Item #152 appeared in
- the computation of the set that "covered" a predicate. If a
- predicate expression included a term such as p=AND(q,r) the context
- of p was taken to be context(q) & context(r), when it should have
- been context(q) | context(r). This is fixed in MR12a.
-
-#152. (Changed in MR12) Bug in generation of predicate expressions
-
- The primary purpose for MR12 is to make quite clear that MR11 is
- obsolete and to fix the bug related to predicate expressions.
-
- In MR10 code was added to optimize the code generated for
- predicate expression tests. Unfortunately, there was a
- significant oversight in the code which resulted in a bug in
- the generation of code for predicate expression tests which
- contained predicates combined using AND:
-
- r0 : (r1)* "@" ;
- r1 : (AAA)? => <<p LATEXT(1)>>? r2 ;
- r2 : (BBB)? => <<q LATEXT(1)>>? Q
- | (BBB)? => <<r LATEXT(1)>>? Q
- ;
-
- In MR11 (and MR10 when using "-mrhoist on") the code generated
- for r0 to predict r1 would be equivalent to:
-
- if ( LA(1)==Q &&
- (LA(1)==AAA && LA(1)==BBB) &&
- ( p && ( q || r )) ) {
-
- This is incorrect because it expresses the idea that LA(1)
- *must* be AAA in order to attempt r1, and *must* be BBB to
- attempt r2. The result was that r1 became unreachable since
- both condition can not be simultaneously true.
-
- The general philosophy of code generation for predicates
- can be summarized as follows:
-
- a. If the context is true don't enter an alt
- for which the corresponding predicate is false.
-
- If the context is false then it is okay to enter
- the alt without evaluating the predicate at all.
-
- b. A predicate created by ORing of predicates has
- context which is the OR of their individual contexts.
-
- c. A predicate created by ANDing of predicates has
- (surprise) context which is the OR of their individual
- contexts.
-
- d. Apply these rules recursively.
-
- e. Remember rule (a)
-
- The correct code should express the idea that *if* LA(1) is
- AAA then p must be true to attempt r1, but if LA(1) is *not*
- AAA then it is okay to attempt r1, provided that *if* LA(1) is
- BBB then one of q or r must be true.
-
- if ( LA(1)==Q &&
- ( !(LA(1)==AAA || LA(1)==BBB) ||
- ( ! LA(1) == AAA || p) &&
- ( ! LA(1) == BBB || q || r ) ) ) {
-
- I believe this is fixed in MR12.
-
- Reported by Reinier van den Born (reinier@vnet.ibm.com)
-
-#151a. (Changed in MR12) ANTLRParser::getLexer()
-
- As a result of several requests, I have added public methods to
- get a pointer to the lexer belonging to a parser.
-
- ANTLRTokenStream *ANTLRParser::getLexer() const
-
- Returns a pointer to the lexer being used by the
- parser. ANTLRTokenStream is the base class of
- DLGLexer
-
- ANTLRTokenStream *ANTLRTokenBuffer::getLexer() const
-
- Returns a pointer to the lexer being used by the
- ANTLRTokenBuffer. ANTLRTokenStream is the base
- class of DLGLexer
-
- You must manually cast the ANTLRTokenStream to your program's
- lexer class. Because the name of the lexer's class is not fixed.
- Thus it is impossible to incorporate it into the DLGLexerBase
- class.
-
-#151b.(Changed in MR12) ParserBlackBox member getLexer()
-
- The template class ParserBlackBox now has a member getLexer()
- which returns a pointer to the lexer.
-
-#150. (Changed in MR12) syntaxErrCount and lexErrCount now public
-
- See Item #127 for more information.
-
-#149. (Changed in MR12) antlr option -info o (letter o for orphan)
-
- If there is more than one rule which is not referenced by any
- other rule then all such rules are listed. This is useful for
- alerting one to rules which are not used, but which can still
- contribute to ambiguity. For example:
-
- start : a Z ;
- unused: a A ;
- a : (A)+ ;
-
- will cause an ambiguity report for rule "a" which will be
- difficult to understand if the user forgets about rule "unused"
- simply because it is not used in the grammar.
-
-#148. (Changed in MR11) #token names appearing in zztokens,token_tbl
-
- In a #token statement like the following:
-
- #token Plus "\+"
-
- the string "Plus" appears in the zztokens array (C mode) and
- token_tbl (C++ mode). This string is used in most error
- messages. In MR11 one has the option of using some other string,
- (e.g. "+") in those tables.
-
- In MR11 one can write:
-
- #token Plus ("+") "\+"
- #token RP ("(") "\("
- #token COM ("comment begin") "/\*"
-
- A #token statement is allowed to appear in more than one #lexclass
- with different regular expressions. However, the token name appears
- only once in the zztokens/token_tbl array. This means that only
- one substitute can be specified for a given #token name. The second
- attempt to define a substitute name (different from the first) will
- result in an error message.
-
-#147. (Changed in MR11) Bug in follow set computation
-
- There is a bug in 1.33 vanilla and all maintenance releases
- prior to MR11 in the computation of the follow set. The bug is
- different than that described in Item #82 and probably more
- common. It was discovered in the ansi.g grammar while testing
- the "ambiguity aid" (Item #119). The search for a bug started
- when the ambiguity aid was unable to discover the actual source
- of an ambiguity reported by antlr.
-
- The problem appears when an optimization of the follow set
- computation is used inappropriately. The result is that the
- follow set used is the "worst case". In other words, the error
- can lead to false reports of ambiguity. The good news is that
- if you have a grammar in which you have addressed all reported
- ambiguities you are ok. The bad news is that you may have spent
- time fixing ambiguities that were not real, or used k=2 when
- ck=2 might have been sufficient, and so on.
-
- The following grammar demonstrates the problem:
-
- ------------------------------------------------------------
- expr : ID ;
-
- start : stmt SEMI ;
-
- stmt : CASE expr COLON
- | expr SEMI
- | plain_stmt
- ;
-
- plain_stmt : ID COLON ;
- ------------------------------------------------------------
-
- When compiled with k=1 and ck=2 it will report:
-
- warning: alts 2 and 3 of the rule itself ambiguous upon
- { IDENTIFIER }, { COLON }
-
- When antlr analyzes "stmt" it computes the first[1] set of all
- alternatives. It finds an ambiguity between alts 2 and 3 for ID.
- It then computes the first[2] set for alternatives 2 and 3 to resolve
- the ambiguity. In computing the first[2] set of "expr" (which is
- only one token long) it needs to determine what could follow "expr".
- Under a certain combination of circumstances antlr forgets that it
- is trying to analyze "stmt" which can only be followed by SEMI and
- adds to the first[2] set of "expr" the "global" follow set (including
- "COLON") which could follow "expr" (under other conditions) in the
- phrase "CASE expr COLON".
-
-#146. (Changed in MR11) Option -treport for locating "difficult" alts
-
- It can be difficult to determine which alternatives are causing
- pccts to work hard to resolve an ambiguity. In some cases the
- ambiguity is successfully resolved after much CPU time so there
- is no message at all.
-
- A rough measure of the amount of work being peformed which is
- independent of the CPU speed and system load is the number of
- tnodes created. Using "-info t" gives information about the
- total number of tnodes created and the peak number of tnodes.
-
- Tree Nodes: peak 1300k created 1416k lost 0
-
- It also puts in the generated C or C++ file the number of tnodes
- created for a rule (at the end of the rule). However this
- information is not sufficient to locate the alternatives within
- a rule which are causing the creation of tnodes.
-
- Using:
-
- antlr -treport 100000 ....
-
- causes antlr to list on stdout any alternatives which require the
- creation of more than 100,000 tnodes, along with the lookahead sets
- for those alternatives.
-
- The following is a trivial case from the ansi.g grammar which shows
- the format of the report. This report might be of more interest
- in cases where 1,000,000 tuples were created to resolve the ambiguity.
-
- -------------------------------------------------------------------------
- There were 0 tuples whose ambiguity could not be resolved
- by full lookahead
- There were 157 tnodes created to resolve ambiguity between:
-
- Choice 1: statement/2 line 475 file ansi.g
- Choice 2: statement/3 line 476 file ansi.g
-
- Intersection of lookahead[1] sets:
-
- IDENTIFIER
-
- Intersection of lookahead[2] sets:
-
- LPARENTHESIS COLON AMPERSAND MINUS
- STAR PLUSPLUS MINUSMINUS ONESCOMPLEMENT
- NOT SIZEOF OCTALINT DECIMALINT
- HEXADECIMALINT FLOATONE FLOATTWO IDENTIFIER
- STRING CHARACTER
- -------------------------------------------------------------------------
-
-#145. (Documentation) Generation of Expression Trees
-
- Item #99 was misleading because it implied that the optimization
- for tree expressions was available only for trees created by
- predicate expressions and neglected to mention that it required
- the use of "-mrhoist on". The optimization applies to tree
- expressions created for grammars with k>1 and for predicates with
- lookahead depth >1.
-
- In MR11 the optimized version is always used so the -mrhoist on
- option need not be specified.
-
-#144. (Changed in MR11) Incorrect test for exception group
-
- In testing for a rule's exception group the label a pointer
- is compared against '\0'. The intention is "*pointer".
-
- Reported by Jeffrey C. Fried (Jeff@Fried.net).
-
-#143. (Changed in MR11) Optional ";" at end of #token statement
-
- Fixes problem of:
-
- #token X "x"
-
- <<
- parser action
- >>
-
- Being confused with:
-
- #token X "x" <<lexical action>>
-
-#142. (Changed in MR11) class BufFileInput subclass of DLGInputStream
-
- Alexey Demakov (demakov@kazbek.ispras.ru) has supplied class
- BufFileInput derived from DLGInputStream which provides a
- function lookahead(char *string) to test characters in the
- input stream more than one character ahead.
-
- The default amount of lookahead is specified by the constructor
- and defaults to 8 characters. This does *not* include the one
- character of lookahead maintained internally by DLG in member "ch"
- and which is not available for testing via BufFileInput::lookahead().
-
- This is a useful class for overcoming the one-character-lookahead
- limitation of DLG without resorting to a lexer capable of
- backtracking (like flex) which is not integrated with antlr as is
- DLG.
-
- There are no restrictions on copying or using BufFileInput.* except
- that the authorship and related information must be retained in the
- source code.
-
- The class is located in pccts/h/BufFileInput.* of the kit.
-
-#141. (Changed in MR11) ZZDEBUG_CONSUME for ANTLRParser::consume()
-
- A debug aid has been added to file ANTLRParser::consume() in
- file AParser.cpp:
-
- #ifdef ZZDEBUG_CONSUME_ACTION
- zzdebug_consume_action();
- #endif
-
- Suggested by Sramji Ramanathan (ps@kumaran.com).
-
-#140. (Changed in MR11) #pred to define predicates
-
- +---------------------------------------------------+
- | Note: Assume "-prc on" for this entire discussion |
- +---------------------------------------------------+
-
- A problem with predicates is that each one is regarded as
- unique and capable of disambiguating cases where two
- alternatives have identical lookahead. For example:
-
- rule : <<pred(LATEXT(1))>>? A
- | <<pred(LATEXT(1))>>? A
- ;
-
- will not cause any error messages or warnings to be issued
- by earlier versions of pccts. To compare the text of the
- predicates is an incomplete solution.
-
- In 1.33MR11 I am introducing the #pred statement in order to
- solve some problems with predicates. The #pred statement allows
- one to give a symbolic name to a "predicate literal" or a
- "predicate expression" in order to refer to it in other predicate
- expressions or in the rules of the grammar.
-
- The predicate literal associated with a predicate symbol is C
- or C++ code which can be used to test the condition. A
- predicate expression defines a predicate symbol in terms of other
- predicate symbols using "!", "&&", and "||". A predicate symbol
- can be defined in terms of a predicate literal, a predicate
- expression, or *both*.
-
- When a predicate symbol is defined with both a predicate literal
- and a predicate expression, the predicate literal is used to generate
- code, but the predicate expression is used to check for two
- alternatives with identical predicates in both alternatives.
-
- Here are some examples of #pred statements:
-
- #pred IsLabel <<isLabel(LATEXT(1))>>?
- #pred IsLocalVar <<isLocalVar(LATEXT(1))>>?
- #pred IsGlobalVar <<isGlobalVar(LATEXT(1)>>?
- #pred IsVar <<isVar(LATEXT(1))>>? IsLocalVar || IsGlobalVar
- #pred IsScoped <<isScoped(LATEXT(1))>>? IsLabel || IsLocalVar
-
- I hope that the use of EBNF notation to describe the syntax of the
- #pred statement will not cause problems for my readers (joke).
-
- predStatement : "#pred"
- CapitalizedName
- (
- "<<predicate_literal>>?"
- | "<<predicate_literal>>?" predOrExpr
- | predOrExpr
- )
- ;
-
- predOrExpr : predAndExpr ( "||" predAndExpr ) * ;
-
- predAndExpr : predPrimary ( "&&" predPrimary ) * ;
-
- predPrimary : CapitalizedName
- | "!" predPrimary
- | "(" predOrExpr ")"
- ;
-
- What is the purpose of this nonsense ?
-
- To understand how predicate symbols help, you need to realize that
- predicate symbols are used in two different ways with two different
- goals.
-
- a. Allow simplification of predicates which have been combined
- during predicate hoisting.
-
- b. Allow recognition of identical predicates which can't disambiguate
- alternatives with common lookahead.
-
- First we will discuss goal (a). Consider the following rule:
-
- rule0: rule1
- | ID
- | ...
- ;
-
- rule1: rule2
- | rule3
- ;
-
- rule2: <<isX(LATEXT(1))>>? ID ;
- rule3: <<!isX(LATEXT(1)>>? ID ;
-
- When the predicates in rule2 and rule3 are combined by hoisting
- to create a prediction expression for rule1 the result is:
-
- if ( LA(1)==ID
- && ( isX(LATEXT(1) || !isX(LATEXT(1) ) ) { rule1(); ...
-
- This is inefficient, but more importantly, can lead to false
- assumptions that the predicate expression distinguishes the rule1
- alternative with some other alternative with lookahead ID. In
- MR11 one can write:
-
- #pred IsX <<isX(LATEXT(1))>>?
-
- ...
-
- rule2: <<IsX>>? ID ;
- rule3: <<!IsX>>? ID ;
-
- During hoisting MR11 recognizes this as a special case and
- eliminates the predicates. The result is a prediction
- expression like the following:
-
- if ( LA(1)==ID ) { rule1(); ...
-
- Please note that the following cases which appear to be equivalent
- *cannot* be simplified by MR11 during hoisting because the hoisting
- logic only checks for a "!" in the predicate action, not in the
- predicate expression for a predicate symbol.
-
- *Not* equivalent and is not simplified during hoisting:
-
- #pred IsX <<isX(LATEXT(1))>>?
- #pred NotX <<!isX(LATEXT(1))>>?
- ...
- rule2: <<IsX>>? ID ;
- rule3: <<NotX>>? ID ;
-
- *Not* equivalent and is not simplified during hoisting:
-
- #pred IsX <<isX(LATEXT(1))>>?
- #pred NotX !IsX
- ...
- rule2: <<IsX>>? ID ;
- rule3: <<NotX>>? ID ;
-
- Now we will discuss goal (b).
-
- When antlr discovers that there is a lookahead ambiguity between
- two alternatives it attempts to resolve the ambiguity by searching
- for predicates in both alternatives. In the past any predicate
- would do, even if the same one appeared in both alternatives:
-
- rule: <<p(LATEXT(1))>>? X
- | <<p(LATEXT(1))>>? X
- ;
-
- The #pred statement is a start towards solving this problem.
- During ambiguity resolution (*not* predicate hoisting) the
- predicates for the two alternatives are expanded and compared.
- Consider the following example:
-
- #pred Upper <<isUpper(LATEXT(1))>>?
- #pred Lower <<isLower(LATEXT(1))>>?
- #pred Alpha <<isAlpha(LATEXT(1))>>? Upper || Lower
-
- rule0: rule1
- | <<Alpha>>? ID
- ;
-
- rule1:
- | rule2
- | rule3
- ...
- ;
-
- rule2: <<Upper>>? ID;
- rule3: <<Lower>>? ID;
-
- The definition of #pred Alpha expresses:
-
- a. to test the predicate use the C code "isAlpha(LATEXT(1))"
-
- b. to analyze the predicate use the information that
- Alpha is equivalent to the union of Upper and Lower,
-
- During ambiguity resolution the definition of Alpha is expanded
- into "Upper || Lower" and compared with the predicate in the other
- alternative, which is also "Upper || Lower". Because they are
- identical MR11 will report a problem.
-
- -------------------------------------------------------------------------
- t10.g, line 5: warning: the predicates used to disambiguate rule rule0
- (file t10.g alt 1 line 5 and alt 2 line 6)
- are identical when compared without context and may have no
- resolving power for some lookahead sequences.
- -------------------------------------------------------------------------
-
- If you use the "-info p" option the output file will contain:
-
- +----------------------------------------------------------------------+
- |#if 0 |
- | |
- |The following predicates are identical when compared without |
- | lookahead context information. For some ambiguous lookahead |
- | sequences they may not have any power to resolve the ambiguity. |
- | |
- |Choice 1: rule0/1 alt 1 line 5 file t10.g |
- | |
- | The original predicate for choice 1 with available context |
- | information: |
- | |
- | OR expr |
- | |
- | pred << Upper>>? |
- | depth=k=1 rule rule2 line 14 t10.g |
- | set context: |
- | ID |
- | |
- | pred << Lower>>? |
- | depth=k=1 rule rule3 line 15 t10.g |
- | set context: |
- | ID |
- | |
- | The predicate for choice 1 after expansion (but without context |
- | information): |
- | |
- | OR expr |
- | |
- | pred << isUpper(LATEXT(1))>>? |
- | depth=k=1 rule line 1 t10.g |
- | |
- | pred << isLower(LATEXT(1))>>? |
- | depth=k=1 rule line 2 t10.g |
- | |
- | |
- |Choice 2: rule0/2 alt 2 line 6 file t10.g |
- | |
- | The original predicate for choice 2 with available context |
- | information: |
- | |
- | pred << Alpha>>? |
- | depth=k=1 rule rule0 line 6 t10.g |
- | set context: |
- | ID |
- | |
- | The predicate for choice 2 after expansion (but without context |
- | information): |
- | |
- | OR expr |
- | |
- | pred << isUpper(LATEXT(1))>>? |
- | depth=k=1 rule line 1 t10.g |
- | |
- | pred << isLower(LATEXT(1))>>? |
- | depth=k=1 rule line 2 t10.g |
- | |
- | |
- |#endif |
- +----------------------------------------------------------------------+
-
- The comparison of the predicates for the two alternatives takes
- place without context information, which means that in some cases
- the predicates will be considered identical even though they operate
- on disjoint lookahead sets. Consider:
-
- #pred Alpha
-
- rule1: <<Alpha>>? ID
- | <<Alpha>>? Label
- ;
-
- Because the comparison of predicates takes place without context
- these will be considered identical. The reason for comparing
- without context is that otherwise it would be necessary to re-evaluate
- the entire predicate expression for each possible lookahead sequence.
- This would require more code to be written and more CPU time during
- grammar analysis, and it is not yet clear whether anyone will even make
- use of the new #pred facility.
-
- A temporary workaround might be to use different #pred statements
- for predicates you know have different context. This would avoid
- extraneous warnings.
-
- The above example might be termed a "false positive". Comparison
- without context will also lead to "false negatives". Consider the
- following example:
-
- #pred Alpha
- #pred Beta
-
- rule1: <<Alpha>>? A
- | rule2
- ;
-
- rule2: <<Alpha>>? A
- | <<Beta>>? B
- ;
-
- The predicate used for alt 2 of rule1 is (Alpha || Beta). This
- appears to be different than the predicate Alpha used for alt1.
- However, the context of Beta is B. Thus when the lookahead is A
- Beta will have no resolving power and Alpha will be used for both
- alternatives. Using the same predicate for both alternatives isn't
- very helpful, but this will not be detected with 1.33MR11.
-
- To properly handle this the predicate expression would have to be
- evaluated for each distinct lookahead context.
-
- To determine whether two predicate expressions are identical is
- difficult. The routine may fail to identify identical predicates.
-
- The #pred feature also compares predicates to see if a choice between
- alternatives which is resolved by a predicate which makes the second
- choice unreachable. Consider the following example:
-
- #pred A <<A(LATEXT(1)>>?
- #pred B <<B(LATEXT(1)>>?
- #pred A_or_B A || B
-
- r : s
- | t
- ;
- s : <<A_or_B>>? ID
- ;
- t : <<A>>? ID
- ;
-
- ----------------------------------------------------------------------------
- t11.g, line 5: warning: the predicate used to disambiguate the
- first choice of rule r
- (file t11.g alt 1 line 5 and alt 2 line 6)
- appears to "cover" the second predicate when compared without context.
- The second predicate may have no resolving power for some lookahead
- sequences.
- ----------------------------------------------------------------------------
-
-#139. (Changed in MR11) Problem with -gp in C++ mode
-
- The -gp option to add a prefix to rule names did not work in
- C++ mode. This has been fixed.
-
- Reported by Alexey Demakov (demakov@kazbek.ispras.ru).
-
-#138. (Changed in MR11) Additional makefiles for non-MSVC++ MS systems
-
- Sramji Ramanathan (ps@kumaran.com) has supplied makefiles for
- building antlr and dlg with Win95/NT development tools that
- are not based on MSVC5. They are pccts/antlr/AntlrMS.mak and
- pccts/dlg/DlgMS.mak.
-
- The first line of the makefiles require a definition of PCCTS_HOME.
-
- These are in additiion to the AntlrMSVC50.* and DlgMSVC50.*
- supplied by Jeff Vincent (JVincent@novell.com).
-
-#137. (Changed in MR11) Token getType(), getText(), getLine() const members
-
- --------------------------------------------------------------------
- If you use ANTLRCommonToken this change probably does not affect you.
- --------------------------------------------------------------------
-
- For a long time it has bothered me that these accessor functions
- in ANTLRAbstractToken were not const member functions. I have
- refrained from changing them because it require users to modify
- existing token class definitions which are derived directly
- from ANTLRAbstractToken. I think it is now time.
-
- For those who are not used to C++, a "const member function" is a
- member function which does not modify its own object - the thing
- to which "this" points. This is quite different from a function
- which does not modify its arguments
-
- Most token definitions based on ANTLRAbstractToken have something like
- the following in order to create concrete definitions of the pure
- virtual methods in ANTLRAbstractToken:
-
- class MyToken : public ANTLRAbstractToken {
- ...
- ANTLRTokenType getType() {return _type; }
- int getLine() {return _line; }
- ANTLRChar * getText() {return _text; }
- ...
- }
-
- The required change is simply to put "const" following the function
- prototype in the header (.h file) and the definition file (.cpp if
- it is not inline):
-
- class MyToken : public ANTLRAbstractToken {
- ...
- ANTLRTokenType getType() const {return _type; }
- int getLine() const {return _line; }
- ANTLRChar * getText() const {return _text; }
- ...
- }
-
- This was originally proposed a long time ago by Bruce
- Guenter (bruceg@qcc.sk.ca).
-
-#136. (Changed in MR11) Added getLength() to ANTLRCommonToken
-
- Classes ANTLRCommonToken and ANTLRCommonTokenNoRefCountToken
- now have a member function:
-
- int getLength() const { return strlen(getText()) }
-
- Suggested by Sramji Ramanathan (ps@kumaran.com).
-
-#135. (Changed in MR11) Raised antlr's own default ZZLEXBUFSIZE to 8k
-
-#134a. (ansi_mr10.zip) T.J. Parr's ANSI C grammar made 1.33MR11 compatible
-
- There is a typographical error in the definition of BITWISEOREQ:
-
- #token BITWISEOREQ "!=" should be "\|="
-
- When this change is combined with the bugfix to the follow set cache
- problem (Item #147) and a minor rearrangement of the grammar
- (Item #134b) it becomes a k=1 ck=2 grammar.
-
-#134b. (ansi_mr10.zip) T.J. Parr's ANSI C grammar made 1.33MR11 compatible
-
- The following changes were made in the ansi.g grammar (along with
- using -mrhoist on):
-
- ansi.g
- ======
- void tracein(char *) ====> void tracein(const char *)
- void traceout(char *) ====> void traceout(const char *)
-
- <LT(1)->getType()==IDENTIFIER ? isTypeName(LT(1)->getText()) : 1>>?
- ====> <<isTypeName(LT(1)->getText())>>?
-
- <<(LT(1)->getType()==LPARENTHESIS && LT(2)->getType()==IDENTIFIER) ? \
- isTypeName(LT(2)->getText()) : 1>>?
- ====> (LPARENTHESIS IDENTIFIER)? => <<isTypeName(LT(2)->getText())>>?
-
- <<(LT(1)->getType()==LPARENTHESIS && LT(2)->getType()==IDENTIFIER) ? \
- isTypeName(LT(2)->getText()) : 1>>?
- ====> (LPARENTHESIS IDENTIFIER)? => <<isTypeName(LT(2)->getText())>>?
-
- added to init(): traceOptionValueDefault=0;
- added to init(): traceOption(-1);
-
- change rule "statement":
-
- statement
- : plain_label_statement
- | case_label_statement
- | <<;>> expression SEMICOLON
- | compound_statement
- | selection_statement
- | iteration_statement
- | jump_statement
- | SEMICOLON
- ;
-
- plain_label_statement
- : IDENTIFIER COLON statement
- ;
-
- case_label_statement
- : CASE constant_expression COLON statement
- | DEFAULT COLON statement
- ;
-
- support.cpp
- ===========
- void tracein(char *) ====> void tracein(const char *)
- void traceout(char *) ====> void traceout(const char *)
-
- added to tracein(): ANTLRParser::tracein(r); // call superclass method
- added to traceout(): ANTLRParser::traceout(r); // call superclass method
-
- Makefile
- ========
- added to AFLAGS: -mrhoist on -prc on
-
-#133. (Changed in 1.33MR11) Make trace options public in ANTLRParser
-
- In checking T.J. Parr's ANSI C grammar for compatibility with
- 1.33MR11 discovered that it was inconvenient to have the
- trace facilities with protected access.
-
-#132. (Changed in 1.33MR11) Recognition of identical predicates in alts
-
- Prior to 1.33MR11, there would be no ambiguity warning when the
- very same predicate was used to disambiguate both alternatives:
-
- test: ref B
- | ref C
- ;
-
- ref : <<pred(LATEXT(1)>>? A
-
- In 1.33MR11 this will cause the warning:
-
- warning: the predicates used to disambiguate rule test
- (file v98.g alt 1 line 1 and alt 2 line 2)
- are identical and have no resolving power
-
- ----------------- Note -----------------
-
- This is different than the following case
-
- test: <<pred(LATEXT(1))>>? A B
- | <<pred(LATEXT(1)>>? A C
- ;
-
- In this case there are two distinct predicates
- which have exactly the same text. In the first
- example there are two references to the same
- predicate. The problem represented by this
- grammar will be addressed later.
-
-#131. (Changed in 1.33MR11) Case insensitive command line options
-
- Command line switches like "-CC" and keywords like "on", "off",
- and "stdin" are no longer case sensitive in antlr, dlg, and sorcerer.
-
-#130. (Changed in 1.33MR11) Changed ANTLR_VERSION to int from string
-
- The ANTLR_VERSION was not an integer, making it difficult to
- perform conditional compilation based on the antlr version.
-
- Henceforth, ANTLR_VERSION will be:
-
- (base_version * 10000) + release number
-
- thus 1.33MR11 will be: 133*100+11 = 13311
-
- Suggested by Rainer Janssen (Rainer.Janssen@Informatik.Uni-Oldenburg.DE).
-
-#129. (Changed in 1.33MR11) Addition of ANTLR_VERSION to <parserName>.h
-
- The following code is now inserted into <parserName>.h amd
- stdpccts.h:
-
- #ifndef ANTLR_VERSION
- #define ANTLR_VERSION 13311
- #endif
-
- Suggested by Rainer Janssen (Rainer.Janssen@Informatik.Uni-Oldenburg.DE)
-
-#128. (Changed in 1.33MR11) Redundant predicate code in (<<pred>>? ...)+
-
- Prior to 1.33MR11, the following grammar would generate
- redundant tests for the "while" condition.
-
- rule2 : (<<pred>>? X)+ X
- | B
- ;
-
- The code would resemble:
-
- if (LA(1)==X) {
- if (pred) {
- do {
- if (!pred) {zzfailed_pred(" pred");}
- zzmatch(X); zzCONSUME;
- } while (LA(1)==X && pred && pred);
- } else {...
-
- With 1.33MR11 the redundant predicate test is omitted.
-
-#127. (Changed in 1.33MR11)
-
- Count Syntax Errors Count DLG Errors
- ------------------- ----------------
-
- C++ mode ANTLRParser:: DLGLexerBase::
- syntaxErrCount lexErrCount
- C mode zzSyntaxErrCount zzLexErrCount
-
- The C mode variables are global and initialized to 0.
- They are *not* reset to 0 automatically when antlr is
- restarted.
-
- The C++ mode variables are public. They are initialized
- to 0 by the constructors. They are *not* reset to 0 by the
- ANTLRParser::init() method.
-
- Suggested by Reinier van den Born (reinier@vnet.ibm.com).
-
-#126. (Changed in 1.33MR11) Addition of #first <<...>>
-
- The #first <<...>> inserts the specified text in the output
- files before any other #include statements required by pccts.
- The only things before the #first text are comments and
- a #define ANTLR_VERSION.
-
- Requested by and Esa Pulkkinen (esap@cs.tut.fi) and Alexin
- Zoltan (alexin@inf.u-szeged.hu).
-
-#125. (Changed in 1.33MR11) Lookahead for (guard)? && <<p>>? predicates
-
- When implementing the new style of guard predicate (Item #113)
- in 1.33MR10 I decided to temporarily ignore the problem of
- computing the "narrowest" lookahead context.
-
- Consider the following k=1 grammar:
-
- start : a
- | b
- ;
-
- a : (A)? && <<pred1(LATEXT(1))>>? ab ;
- b : (B)? && <<pred2(LATEXT(1))>>? ab ;
-
- ab : A | B ;
-
- In MR10 the context for both "a" and "b" was {A B} because this is
- the first set of rule "ab". Normally, this is not a problem because
- the predicate which follows the guard inhibits any ambiguity report
- by antlr.
-
- In MR11 the first set for rule "a" is {A} and for rule "b" it is {B}.
-
-#124. A Note on the New "&&" Style Guarded Predicates
-
- I've been asked several times, "What is the difference between
- the old "=>" style guard predicates and the new style "&&" guard
- predicates, and how do you choose one over the other" ?
-
- The main difference is that the "=>" does not apply the
- predicate if the context guard doesn't match, whereas
- the && form always does. What is the significance ?
-
- If you have a predicate which is not on the "leading edge"
- it cannot be hoisted. Suppose you need a predicate that
- looks at LA(2). You must introduce it manually. The
- classic example is:
-
- castExpr :
- LP typeName RP
- | ....
- ;
-
- typeName : <<isTypeName(LATEXT(1))>>? ID
- | STRUCT ID
- ;
-
- The problem is that typeName isn't on the leading edge
- of castExpr, so the predicate isTypeName won't be hoisted into
- castExpr to help make a decision on which production to choose.
-
- The *first* attempt to fix it is this:
-
- castExpr :
- <<isTypeName(LATEXT(2))>>?
- LP typeName RP
- | ....
- ;
-
- Unfortunately, this won't work because it ignores
- the problem of STRUCT. The solution is to apply
- isTypeName() in castExpr if LA(2) is an ID and
- don't apply it when LA(2) is STRUCT:
-
- castExpr :
- (LP ID)? => <<isTypeName(LATEXT(2))>>?
- LP typeName RP
- | ....
- ;
-
- In conclusion, the "=>" style guarded predicate is
- useful when:
-
- a. the tokens required for the predicate
- are not on the leading edge
- b. there are alternatives in the expression
- selected by the predicate for which the
- predicate is inappropriate
-
- If (b) were false, then one could use a simple
- predicate (assuming "-prc on"):
-
- castExpr :
- <<isTypeName(LATEXT(2))>>?
- LP typeName RP
- | ....
- ;
-
- typeName : <<isTypeName(LATEXT(1))>>? ID
- ;
-
- So, when do you use the "&&" style guarded predicate ?
-
- The new-style "&&" predicate should always be used with
- predicate context. The context guard is in ADDITION to
- the automatically computed context. Thus it useful for
- predicates which depend on the token type for reasons
- other than context.
-
- The following example is contributed by Reinier van den Born
- (reinier@vnet.ibm.com).
-
- +-------------------------------------------------------------------------+
- | This grammar has two ways to call functions: |
- | |
- | - a "standard" call syntax with parens and comma separated args |
- | - a shell command like syntax (no parens and spacing separated args) |
- | |
- | The former also allows a variable to hold the name of the function, |
- | the latter can also be used to call external commands. |
- | |
- | The grammar (simplified) looks like this: |
- | |
- | fun_call : ID "(" { expr ("," expr)* } ")" |
- | /* ID is function name */ |
- | | "@" ID "(" { expr ("," expr)* } ")" |
- | /* ID is var containing fun name */ |
- | ; |
- | |
- | command : ID expr* /* ID is function name */ |
- | | path expr* /* path is external command name */ |
- | ; |
- | |
- | path : ID /* left out slashes and such */ |
- | | "@" ID /* ID is environment var */ |
- | ; |
- | |
- | expr : .... |
- | | "(" expr ")"; |
- | |
- | call : fun_call |
- | | command |
- | ; |
- | |
- | Obviously the call is wildly ambiguous. This is more or less how this |
- | is to be resolved: |
- | |
- | A call begins with an ID or an @ followed by an ID. |
- | |
- | If it is an ID and if it is an ext. command name -> command |
- | if followed by a paren -> fun_call |
- | otherwise -> command |
- | |
- | If it is an @ and if the ID is a var name -> fun_call |
- | otherwise -> command |
- | |
- | One can implement these rules quite neatly using && predicates: |
- | |
- | call : ("@" ID)? && <<isVarName(LT(2))>>? fun_call |
- | | (ID)? && <<isExtCmdName>>? command |
- | | (ID "(")? fun_call |
- | | command |
- | ; |
- | |
- | This can be done better, so it is not an ideal example, but it |
- | conveys the principle. |
- +-------------------------------------------------------------------------+
-
-#123. (Changed in 1.33MR11) Correct definition of operators in ATokPtr.h
-
- The return value of operators in ANTLRTokenPtr:
-
- changed: unsigned ... operator !=(...)
- to: int ... operator != (...)
- changed: unsigned ... operator ==(...)
- to: int ... operator == (...)
-
- Suggested by R.A. Nelson (cowboy@VNET.IBM.COM)
-
-#122. (Changed in 1.33MR11) Member functions to reset DLG in C++ mode
-
- void DLGFileReset(FILE *f) { input = f; found_eof = 0; }
- void DLGStringReset(DLGChar *s) { input = s; p = &input[0]; }
-
- Supplied by R.A. Nelson (cowboy@VNET.IBM.COM)
-
-#121. (Changed in 1.33MR11) Another attempt to fix -o (output dir) option
-
- Another attempt is made to improve the -o option of antlr, dlg,
- and sorcerer. This one by JVincent (JVincent@novell.com).
-
- The current rule:
-
- a. If -o is not specified than any explicit directory
- names are retained.
-
- b. If -o is specified than the -o directory name overrides any
- explicit directory names.
-
- c. The directory name of the grammar file is *not* stripped
- to create the main output file. However it is stil subject
- to override by the -o directory name.
-
-#120. (Changed in 1.33MR11) "-info f" output to stdout rather than stderr
-
- Added option 0 (e.g. "-info 0") which is a noop.
-
-#119. (Changed in 1.33MR11) Ambiguity aid for grammars
-
- The user can ask for additional information on ambiguities reported
- by antlr to stdout. At the moment, only one ambiguity report can
- be created in an antlr run.
-
- This feature is enabled using the "-aa" (Ambiguity Aid) option.
-
- The following options control the reporting of ambiguities:
-
- -aa ruleName Selects reporting by name of rule
- -aa lineNumber Selects reporting by line number
- (file name not compared)
-
- -aam Selects "multiple" reporting for a token
- in the intersection set of the
- alternatives.
-
- For instance, the token ID may appear dozens
- of times in various paths as the program
- explores the rules which are reachable from
- the point of an ambiguity. With option -aam
- every possible path the search program
- encounters is reported.
-
- Without -aam only the first encounter is
- reported. This may result in incomplete
- information, but the information may be
- sufficient and much shorter.
-
- -aad depth Selects the depth of the search.
- The default value is 1.
-
- The number of paths to be searched, and the
- size of the report can grow geometrically
- with the -ck value if a full search for all
- contributions to the source of the ambiguity
- is explored.
-
- The depth represents the number of tokens
- in the lookahead set which are matched against
- the set of ambiguous tokens. A depth of 1
- means that the search stops when a lookahead
- sequence of just one token is matched.
-
- A k=1 ck=6 grammar might generate 5,000 items
- in a report if a full depth 6 search is made
- with the Ambiguity Aid. The source of the
- problem may be in the first token and obscured
- by the volume of data - I hesitate to call
- it information.
-
- When the user selects a depth > 1, the search
- is first performed at depth=1 for both
- alternatives, then depth=2 for both alternatives,
- etc.
-
- Sample output for rule grammar in antlr.g itself:
-
- +---------------------------------------------------------------------+
- | Ambiguity Aid |
- | |
- | Choice 1: grammar/70 line 632 file a.g |
- | Choice 2: grammar/82 line 644 file a.g |
- | |
- | Intersection of lookahead[1] sets: |
- | |
- | "\}" "class" "#errclass" "#tokclass" |
- | |
- | Choice:1 Depth:1 Group:1 ("#errclass") |
- | 1 in (...)* block grammar/70 line 632 a.g |
- | 2 to error grammar/73 line 635 a.g |
- | 3 error error/1 line 894 a.g |
- | 4 #token "#errclass" error/2 line 895 a.g |
- | |
- | Choice:1 Depth:1 Group:2 ("#tokclass") |
- | 2 to tclass grammar/74 line 636 a.g |
- | 3 tclass tclass/1 line 937 a.g |
- | 4 #token "#tokclass" tclass/2 line 938 a.g |
- | |
- | Choice:1 Depth:1 Group:3 ("class") |
- | 2 to class_def grammar/75 line 637 a.g |
- | 3 class_def class_def/1 line 669 a.g |
- | 4 #token "class" class_def/3 line 671 a.g |
- | |
- | Choice:1 Depth:1 Group:4 ("\}") |
- | 2 #token "\}" grammar/76 line 638 a.g |
- | |
- | Choice:2 Depth:1 Group:5 ("#errclass") |
- | 1 in (...)* block grammar/83 line 645 a.g |
- | 2 to error grammar/93 line 655 a.g |
- | 3 error error/1 line 894 a.g |
- | 4 #token "#errclass" error/2 line 895 a.g |
- | |
- | Choice:2 Depth:1 Group:6 ("#tokclass") |
- | 2 to tclass grammar/94 line 656 a.g |
- | 3 tclass tclass/1 line 937 a.g |
- | 4 #token "#tokclass" tclass/2 line 938 a.g |
- | |
- | Choice:2 Depth:1 Group:7 ("class") |
- | 2 to class_def grammar/95 line 657 a.g |
- | 3 class_def class_def/1 line 669 a.g |
- | 4 #token "class" class_def/3 line 671 a.g |
- | |
- | Choice:2 Depth:1 Group:8 ("\}") |
- | 2 #token "\}" grammar/96 line 658 a.g |
- +---------------------------------------------------------------------+
-
- For a linear lookahead set ambiguity (where k=1 or for k>1 but
- when all lookahead sets [i] with i<k all have degree one) the
- reports appear in the following order:
-
- for (depth=1 ; depth <= "-aad depth" ; depth++) {
- for (alternative=1; alternative <=2 ; alternative++) {
- while (matches-are-found) {
- group++;
- print-report
- };
- };
- };
-
- For reporting a k-tuple ambiguity, the reports appear in the
- following order:
-
- for (depth=1 ; depth <= "-aad depth" ; depth++) {
- while (matches-are-found) {
- for (alternative=1; alternative <=2 ; alternative++) {
- group++;
- print-report
- };
- };
- };
-
- This is because matches are generated in different ways for
- linear lookahead and k-tuples.
-
-#118. (Changed in 1.33MR11) DEC VMS makefile and VMS related changes
-
- Revised makefiles for DEC/VMS operating system for antlr, dlg,
- and sorcerer.
-
- Reduced names of routines with external linkage to less than 32
- characters to conform to DEC/VMS linker limitations.
-
- Jean-Francois Pieronne discovered problems with dlg and antlr
- due to the VMS linker not being case sensitive for names with
- external linkage. In dlg the problem was with "className" and
- "ClassName". In antlr the problem was with "GenExprSets" and
- "genExprSets".
-
- Added genmms, a version of genmk for the DEC/VMS version of make.
- The source is in directory pccts/support/DECmms.
-
- All VMS contributions by Jean-Francois Pieronne (jfp@iname.com).
-
-#117. (Changed in 1.33MR10) new EXPERIMENTAL predicate hoisting code
-
- The hoisting of predicates into rules to create prediction
- expressions is a problem in antlr. Consider the following
- example (k=1 with -prc on):
-
- start : (a)* "@" ;
- a : b | c ;
- b : <<isUpper(LATEXT(1))>>? A ;
- c : A ;
-
- Prior to 1.33MR10 the code generated for "start" would resemble:
-
- while {
- if (LA(1)==A &&
- (!LA(1)==A || isUpper())) {
- a();
- }
- };
-
- This code is wrong because it makes rule "c" unreachable from
- "start". The essence of the problem is that antlr fails to
- recognize that there can be a valid alternative within "a" even
- when the predicate <<isUpper(LATEXT(1))>>? is false.
-
- In 1.33MR10 with -mrhoist the hoisting of the predicate into
- "start" is suppressed because it recognizes that "c" can
- cover all the cases where the predicate is false:
-
- while {
- if (LA(1)==A) {
- a();
- }
- };
-
- With the antlr "-info p" switch the user will receive information
- about the predicate suppression in the generated file:
-
- --------------------------------------------------------------
- #if 0
-
- Hoisting of predicate suppressed by alternative without predicate.
- The alt without the predicate includes all cases where
- the predicate is false.
-
- WITH predicate: line 7 v1.g
- WITHOUT predicate: line 7 v1.g
-
- The context set for the predicate:
-
- A
-
- The lookahead set for the alt WITHOUT the semantic predicate:
-
- A
-
- The predicate:
-
- pred << isUpper(LATEXT(1))>>?
- depth=k=1 rule b line 9 v1.g
- set context:
- A
- tree context: null
-
- Chain of referenced rules:
-
- #0 in rule start (line 5 v1.g) to rule a
- #1 in rule a (line 7 v1.g)
-
- #endif
- --------------------------------------------------------------
-
- A predicate can be suppressed by a combination of alternatives
- which, taken together, cover a predicate:
-
- start : (a)* "@" ;
-
- a : b | ca | cb | cc ;
-
- b : <<isUpper(LATEXT(1))>>? ( A | B | C ) ;
-
- ca : A ;
- cb : B ;
- cc : C ;
-
- Consider a more complex example in which "c" covers only part of
- a predicate:
-
- start : (a)* "@" ;
-
- a : b
- | c
- ;
-
- b : <<isUpper(LATEXT(1))>>?
- ( A
- | X
- );
-
- c : A
- ;
-
- Prior to 1.33MR10 the code generated for "start" would resemble:
-
- while {
- if ( (LA(1)==A || LA(1)==X) &&
- (! (LA(1)==A || LA(1)==X) || isUpper()) {
- a();
- }
- };
-
- With 1.33MR10 and -mrhoist the predicate context is restricted to
- the non-covered lookahead. The code resembles:
-
- while {
- if ( (LA(1)==A || LA(1)==X) &&
- (! (LA(1)==X) || isUpper()) {
- a();
- }
- };
-
- With the antlr "-info p" switch the user will receive information
- about the predicate restriction in the generated file:
-
- --------------------------------------------------------------
- #if 0
-
- Restricting the context of a predicate because of overlap
- in the lookahead set between the alternative with the
- semantic predicate and one without
- Without this restriction the alternative without the predicate
- could not be reached when input matched the context of the
- predicate and the predicate was false.
-
- WITH predicate: line 11 v4.g
- WITHOUT predicate: line 12 v4.g
-
- The original context set for the predicate:
-
- A X
-
- The lookahead set for the alt WITHOUT the semantic predicate:
-
- A
-
- The intersection of the two sets
-
- A
-
- The original predicate:
-
- pred << isUpper(LATEXT(1))>>?
- depth=k=1 rule b line 15 v4.g
- set context:
- A X
- tree context: null
-
- The new (modified) form of the predicate:
-
- pred << isUpper(LATEXT(1))>>?
- depth=k=1 rule b line 15 v4.g
- set context:
- X
- tree context: null
-
- #endif
- --------------------------------------------------------------
-
- The bad news about -mrhoist:
-
- (a) -mrhoist does not analyze predicates with lookahead
- depth > 1.
-
- (b) -mrhoist does not look past a guarded predicate to
- find context which might cover other predicates.
-
- For these cases you might want to use syntactic predicates.
- When a semantic predicate fails during guess mode the guess
- fails and the next alternative is tried.
-
- Limitation (a) is illustrated by the following example:
-
- start : (stmt)* EOF ;
-
- stmt : cast
- | expr
- ;
- cast : <<isTypename(LATEXT(2))>>? LP ID RP ;
-
- expr : LP ID RP ;
-
- This is not much different from the first example, except that
- it requires two tokens of lookahead context to determine what
- to do. This predicate is NOT suppressed because the current version
- is unable to handle predicates with depth > 1.
-
- A predicate can be combined with other predicates during hoisting.
- In those cases the depth=1 predicates are still handled. Thus,
- in the following example the isUpper() predicate will be suppressed
- by line #4 when hoisted from "bizarre" into "start", but will still
- be present in "bizarre" in order to predict "stmt".
-
- start : (bizarre)* EOF ; // #1
- // #2
- bizarre : stmt // #3
- | A // #4
- ;
-
- stmt : cast
- | expr
- ;
-
- cast : <<isTypename(LATEXT(2))>>? LP ID RP ;
-
- expr : LP ID RP ;
- | <<isUpper(LATEXT(1))>>? A
-
- Limitation (b) is illustrated by the following example of a
- context guarded predicate:
-
- rule : (A)? <<p>>? // #1
- (A // #2
- |B // #3
- ) // #4
- | <<q>> B // #5
- ;
-
- Recall that this means that when the lookahead is NOT A then
- the predicate "p" is ignored and it attempts to match "A|B".
- Ideally, the "B" at line #3 should suppress predicate "q".
- However, the current version does not attempt to look past
- the guard predicate to find context which might suppress other
- predicates.
-
- In some cases -mrhoist will lead to the reporting of ambiguities
- which were not visible before:
-
- start : (a)* "@";
- a : bc | d;
- bc : b | c ;
-
- b : <<isUpper(LATEXT(1))>>? A;
- c : A ;
-
- d : A ;
-
- In this case there is a true ambiguity in "a" between "bc" and "d"
- which can both match "A". Without -mrhoist the predicate in "b"
- is hoisted into "a" and there is no ambiguity reported. However,
- with -mrhoist, the predicate in "b" is suppressed by "c" (as it
- should be) making the ambiguity in "a" apparent.
-
- The motivations for these changes were hoisting problems reported
- by Reinier van den Born (reinier@vnet.ibm.com) and several others.
-
-#116. (Changed in 1.33MR10) C++ mode: tracein/traceout rule name is (const char *)
-
- The prototype for C++ mode routine tracein (and traceout) has changed from
- "char *" to "const char *".
-
-#115. (Changed in 1.33MR10) Using guess mode with exception handlers in C mode
-
- The definition of the C mode macros zzmatch_wsig and zzsetmatch_wsig
- neglected to consider guess mode. When control passed to the rule's
- parse exception handler the routine would exit without ever closing the
- guess block. This would lead to unpredictable behavior.
-
- In 1.33MR10 the behavior of exceptions in C mode and C++ mode should be
- identical.
-
-#114. (Changed in 1.33MR10) difference in [zz]resynch() between C and C++ modes
-
- There was a slight difference in the way C and C++ mode resynchronized
- following a parsing error. The C routine would sometimes skip an extra
- token before attempting to resynchronize.
-
- The C routine was changed to match the C++ routine.
-
-#113. (Changed in 1.33MR10) new context guarded pred: (g)? && <<p>>? expr
-
- The existing context guarded predicate:
-
- rule : (guard)? => <<p>>? expr
- | next_alternative
- ;
-
- generates code which resembles:
-
- if (lookahead(expr) && (!guard || pred)) {
- expr()
- } else ....
-
- This is not suitable for some applications because it allows
- expr() to be invoked when the predicate is false. This is
- intentional because it is meant to mimic automatically computed
- predicate context.
-
- The new context guarded predicate uses the guard information
- differently because it has a different goal. Consider:
-
- rule : (guard)? && <<p>>? expr
- | next_alternative
- ;
-
- The new style of context guarded predicate is equivalent to:
-
- rule : <<guard==true && pred>>? expr
- | next_alternative
- ;
-
- It generates code which resembles:
-
- if (lookahead(expr) && guard && pred) {
- expr();
- } else ...
-
- Both forms of guarded predicates severely restrict the form of
- the context guard: it can contain no rule references, no
- (...)*, no (...)+, and no {...}. It may contain token and
- token class references, and alternation ("|").
-
- Addition for 1.33MR11: in the token expression all tokens must
- be at the same height of the token tree:
-
- (A ( B | C))? && ... is ok (all height 2)
- (A ( B | ))? && ... is not ok (some 1, some 2)
- (A B C D | E F G H)? && ... is ok (all height 4)
- (A B C D | E )? && ... is not ok (some 4, some 1)
-
- This restriction is required in order to properly compute the lookahead
- set for expressions like:
-
- rule1 : (A B C)? && <<pred>>? rule2 ;
- rule2 : (A|X) (B|Y) (C|Z);
-
- This addition was suggested by Rienier van den Born (reinier@vnet.ibm.com)
-
-#112. (Changed in 1.33MR10) failed validation predicate in C guess mode
-
- John Lilley (jlilley@empathy.com) suggested that failed validation
- predicates abort a guess rather than reporting a failed error.
- This was installed in C++ mode (Item #4). Only now was it noticed
- that the fix was never installed for C mode.
-
-#111. (Changed in 1.33MR10) moved zzTRACEIN to before init action
-
- When the antlr -gd switch is present antlr generates calls to
- zzTRACEIN at the start of a rule and zzTRACEOUT at the exit
- from a rule. Prior to 1.33MR10 Tthe call to zzTRACEIN was
- after the init-action, which could cause confusion because the
- init-actions were reported with the name of the enclosing rule,
- rather than the active rule.
-
-#110. (Changed in 1.33MR10) antlr command line copied to generated file
-
- The antlr command line is now copied to the generated file near
- the start.
-
-#109. (Changed in 1.33MR10) improved trace information
-
- The quality of the trace information provided by the "-gd"
- switch has been improved significantly. Here is an example
- of the output from a test program. It shows the rule name,
- the first token of lookahead, the call depth, and the guess
- status:
-
- exit rule gusxx {"?"} depth 2
- enter rule gusxx {"?"} depth 2
- enter rule gus1 {"o"} depth 3 guessing
- guess done - returning to rule gus1 {"o"} at depth 3
- (guess mode continues - an enclosing guess is still active)
- guess done - returning to rule gus1 {"Z"} at depth 3
- (guess mode continues - an enclosing guess is still active)
- exit rule gus1 {"Z"} depth 3 guessing
- guess done - returning to rule gusxx {"o"} at depth 2 (guess mode ends)
- enter rule gus1 {"o"} depth 3
- guess done - returning to rule gus1 {"o"} at depth 3 (guess mode ends)
- guess done - returning to rule gus1 {"Z"} at depth 3 (guess mode ends)
- exit rule gus1 {"Z"} depth 3
- line 1: syntax error at "Z" missing SC
- ...
-
- Rule trace reporting is controlled by the value of the integer
- [zz]traceOptionValue: when it is positive tracing is enabled,
- otherwise it is disabled. Tracing during guess mode is controlled
- by the value of the integer [zz]traceGuessOptionValue. When
- it is positive AND [zz]traceOptionValue is positive rule trace
- is reported in guess mode.
-
- The values of [zz]traceOptionValue and [zz]traceGuessOptionValue
- can be adjusted by subroutine calls listed below.
-
- Depending on the presence or absence of the antlr -gd switch
- the variable [zz]traceOptionValueDefault is set to 0 or 1. When
- the parser is initialized or [zz]traceReset() is called the
- value of [zz]traceOptionValueDefault is copied to [zz]traceOptionValue.
- The value of [zz]traceGuessOptionValue is always initialzed to 1,
- but, as noted earlier, nothing will be reported unless
- [zz]traceOptionValue is also positive.
-
- When the parser state is saved/restored the value of the trace
- variables are also saved/restored. If a restore causes a change in
- reporting behavior from on to off or vice versa this will be reported.
-
- When the -gd option is selected, the macro "#define zzTRACE_RULES"
- is added to appropriate output files.
-
- C++ mode
- --------
- int traceOption(int delta)
- int traceGuessOption(int delta)
- void traceReset()
- int traceOptionValueDefault
-
- C mode
- --------
- int zzTraceOption(int delta)
- int zzTraceGuessOption(int delta)
- void zzTraceReset()
- int zzTraceOptionValueDefault
-
- The argument "delta" is added to the traceOptionValue. To
- turn on trace when inside a particular rule one:
-
- rule : <<traceOption(+1);>>
- (
- rest-of-rule
- )
- <<traceOption(-1);>>
- ; /* fail clause */ <<traceOption(-1);>>
-
- One can use the same idea to turn *off* tracing within a
- rule by using a delta of (-1).
-
- An improvement in the rule trace was suggested by Sramji
- Ramanathan (ps@kumaran.com).
-
-#108. A Note on Deallocation of Variables Allocated in Guess Mode
-
- NOTE
- ------------------------------------------------------
- This mechanism only works for heap allocated variables
- ------------------------------------------------------
-
- The rewrite of the trace provides the machinery necessary
- to properly free variables or undo actions following a
- failed guess.
-
- The macro zzUSER_GUESS_HOOK(guessSeq,zzrv) is expanded
- as part of the zzGUESS macro. When a guess is opened
- the value of zzrv is 0. When a longjmp() is executed to
- undo the guess, the value of zzrv will be 1.
-
- The macro zzUSER_GUESS_DONE_HOOK(guessSeq) is expanded
- as part of the zzGUESS_DONE macro. This is executed
- whether the guess succeeds or fails as part of closing
- the guess.
-
- The guessSeq is a sequence number which is assigned to each
- guess and is incremented by 1 for each guess which becomes
- active. It is needed by the user to associate the start of
- a guess with the failure and/or completion (closing) of a
- guess.
-
- Guesses are nested. They must be closed in the reverse
- of the order that they are opened.
-
- In order to free memory used by a variable during a guess
- a user must write a routine which can be called to
- register the variable along with the current guess sequence
- number provided by the zzUSER_GUESS_HOOK macro. If the guess
- fails, all variables tagged with the corresponding guess
- sequence number should be released. This is ugly, but
- it would require a major rewrite of antlr 1.33 to use
- some mechanism other than setjmp()/longjmp().
-
- The order of calls for a *successful* guess would be:
-
- zzUSER_GUESS_HOOK(guessSeq,0);
- zzUSER_GUESS_DONE_HOOK(guessSeq);
-
- The order of calls for a *failed* guess would be:
-
- zzUSER_GUESS_HOOK(guessSeq,0);
- zzUSER_GUESS_HOOK(guessSeq,1);
- zzUSER_GUESS_DONE_HOOK(guessSeq);
-
- The default definitions of these macros are empty strings.
-
- Here is an example in C++ mode. The zzUSER_GUESS_HOOK and
- zzUSER_GUESS_DONE_HOOK macros and myGuessHook() routine
- can be used without change in both C and C++ versions.
-
- ----------------------------------------------------------------------
- <<
-
- #include "AToken.h"
-
- typedef ANTLRCommonToken ANTLRToken;
-
- #include "DLGLexer.h"
-
- int main() {
-
- {
- DLGFileInput in(stdin);
- DLGLexer lexer(&in,2000);
- ANTLRTokenBuffer pipe(&lexer,1);
- ANTLRCommonToken aToken;
- P parser(&pipe);
-
- lexer.setToken(&aToken);
- parser.init();
- parser.start();
- };
-
- fclose(stdin);
- fclose(stdout);
- return 0;
- }
-
- >>
-
- <<
- char *s=NULL;
-
- #undef zzUSER_GUESS_HOOK
- #define zzUSER_GUESS_HOOK(guessSeq,zzrv) myGuessHook(guessSeq,zzrv);
- #undef zzUSER_GUESS_DONE_HOOK
- #define zzUSER_GUESS_DONE_HOOK(guessSeq) myGuessHook(guessSeq,2);
-
- void myGuessHook(int guessSeq,int zzrv) {
- if (zzrv == 0) {
- fprintf(stderr,"User hook: starting guess #%d\n",guessSeq);
- } else if (zzrv == 1) {
- free (s);
- s=NULL;
- fprintf(stderr,"User hook: failed guess #%d\n",guessSeq);
- } else if (zzrv == 2) {
- free (s);
- s=NULL;
- fprintf(stderr,"User hook: ending guess #%d\n",guessSeq);
- };
- }
-
- >>
-
- #token A "a"
- #token "[\t \ \n]" <<skip();>>
-
- class P {
-
- start : (top)+
- ;
-
- top : (which) ? <<fprintf(stderr,"%s is a which\n",s); free(s); s=NULL; >>
- | other <<fprintf(stderr,"%s is an other\n",s); free(s); s=NULL; >>
- ; <<if (s != NULL) free(s); s=NULL; >>
-
- which : which2
- ;
-
- which2 : which3
- ;
- which3
- : (label)? <<fprintf(stderr,"%s is a label\n",s);>>
- | (global)? <<fprintf(stderr,"%s is a global\n",s);>>
- | (exclamation)? <<fprintf(stderr,"%s is an exclamation\n",s);>>
- ;
-
- label : <<s=strdup(LT(1)->getText());>> A ":" ;
-
- global : <<s=strdup(LT(1)->getText());>> A "::" ;
-
- exclamation : <<s=strdup(LT(1)->getText());>> A "!" ;
-
- other : <<s=strdup(LT(1)->getText());>> "other" ;
-
- }
- ----------------------------------------------------------------------
-
- This is a silly example, but illustrates the idea. For the input
- "a ::" with tracing enabled the output begins:
-
- ----------------------------------------------------------------------
- enter rule "start" depth 1
- enter rule "top" depth 2
- User hook: starting guess #1
- enter rule "which" depth 3 guessing
- enter rule "which2" depth 4 guessing
- enter rule "which3" depth 5 guessing
- User hook: starting guess #2
- enter rule "label" depth 6 guessing
- guess failed
- User hook: failed guess #2
- guess done - returning to rule "which3" at depth 5 (guess mode continues
- - an enclosing guess is still active)
- User hook: ending guess #2
- User hook: starting guess #3
- enter rule "global" depth 6 guessing
- exit rule "global" depth 6 guessing
- guess done - returning to rule "which3" at depth 5 (guess mode continues
- - an enclosing guess is still active)
- User hook: ending guess #3
- enter rule "global" depth 6 guessing
- exit rule "global" depth 6 guessing
- exit rule "which3" depth 5 guessing
- exit rule "which2" depth 4 guessing
- exit rule "which" depth 3 guessing
- guess done - returning to rule "top" at depth 2 (guess mode ends)
- User hook: ending guess #1
- enter rule "which" depth 3
- .....
- ----------------------------------------------------------------------
-
- Remember:
-
- (a) Only init-actions are executed during guess mode.
- (b) A rule can be invoked multiple times during guess mode.
- (c) If the guess succeeds the rule will be called once more
- without guess mode so that normal actions will be executed.
- This means that the init-action might need to distinguish
- between guess mode and non-guess mode using the variable
- [zz]guessing.
-
-#107. (Changed in 1.33MR10) construction of ASTs in guess mode
-
- Prior to 1.33MR10, when using automatic AST construction in C++
- mode for a rule, an AST would be constructed for elements of the
- rule even while in guess mode. In MR10 this no longer occurs.
-
-#106. (Changed in 1.33MR10) guess variable confusion
-
- In C++ mode a guess which failed always restored the parser state
- using zzGUESS_DONE as part of zzGUESS_FAIL. Prior to 1.33MR10,
- C mode required an explicit call to zzGUESS_DONE after the
- call to zzGUESS_FAIL.
-
- Consider:
-
- rule : (alpha)? beta
- | ...
- ;
-
- The generated code resembles:
-
- zzGUESS
- if (!zzrv && LA(1)==ID) { <==== line #1
- alpha
- zzGUESS_DONE
- beta
- } else {
- if (! zzrv) zzGUESS_DONE <==== line #2a
- ....
-
- However, in some cases line #2 was rendered:
-
- if (guessing) zzGUESS_DONE <==== line #2b
-
- This would work for simple test cases, but would fail in
- some cases where there was a guess while another guess was active.
- One kind of failure would be to match up the zzGUESS_DONE at line
- #2b with the "outer" guess which was still active. The outer
- guess would "succeed" when only the inner guess should have
- succeeded.
-
- In 1.33MR10 the behavior of zzGUESS and zzGUESS_FAIL in C and
- and C++ mode should be identical.
-
- The same problem appears in 1.33 vanilla in some places. For
- example:
-
- start : { (sub)? } ;
-
- or:
-
- start : (
- B
- | ( sub )?
- | C
- )+
- ;
-
- generates incorrect code.
-
- The general principle is:
-
- (a) use [zz]guessing only when deciding between a call to zzFAIL
- or zzGUESS_FAIL
-
- (b) use zzrv in all other cases
-
- This problem was discovered while testing changes to item #105.
- I believe this is now fixed. My apologies.
-
-#105. (Changed in 1.33MR10) guess block as single alt of (...)+
-
- Prior to 1.33MR10 the following constructs:
-
- rule_plus : (
- (sub)?
- )+
- ;
-
- rule_star : (
- (sub)?
- )*
- ;
-
- generated incorrect code for the guess block (which could result
- in runtime errors) because of an incorrect optimization of a
- block with only a single alternative.
-
- The fix caused some changes to the fix described in Item #49
- because there are now three code generation sequences for (...)+
- blocks containing a guess block:
-
- a. single alternative which is a guess block
- b. multiple alternatives in which the last is a guess block
- c. all other cases
-
- Forms like "rule_star" can have unexpected behavior when there
- is a syntax error: if the subrule "sub" is not matched *exactly*
- then "rule_star" will consume no tokens.
-
- Reported by Esa Pulkkinen (esap@cs.tut.fi).
-
-#104. (Changed in 1.33MR10) -o option for dlg
-
- There was problem with the code added by item #74 to handle the
- -o option of dlg. This should fix it.
-
-#103. (Changed in 1.33MR10) ANDed semantic predicates
-
- Rescinded.
-
- The optimization was a mistake.
- The resulting problem is described in Item #150.
-
-#102. (Changed in 1.33MR10) allow "class parser : .... {"
-
- The syntax of the class statement ("class parser-name {")
- has been extended to allow for the specification of base
- classes. An arbirtrary number of tokens may now appear
- between the class name and the "{". They are output
- again when the class declaration is generated. For
- example:
-
- class Parser : public MyBaseClassANTLRparser {
-
- This was suggested by a user, but I don't have a record
- of who it was.
-
-#101. (Changed in 1.33MR10) antlr -info command line switch
-
- -info
-
- p - extra predicate information in generated file
-
- t - information about tnode use:
- at the end of each rule in generated file
- summary on stderr at end of program
-
- m - monitor progress
- prints name of each rule as it is started
- flushes output at start of each rule
-
- f - first/follow set information to stdout
-
- 0 - no operation (added in 1.33MR11)
-
- The options may be combined and may appear in any order.
- For example:
-
- antlr -info ptm -CC -gt -mrhoist on mygrammar.g
-
-#100a. (Changed in 1.33MR10) Predicate tree simplification
-
- When the same predicates can be referenced in more than one
- alternative of a block large predicate trees can be formed.
-
- The difference that these optimizations make is so dramatic
- that I have decided to use it even when -mrhoist is not selected.
-
- Consider the following grammar:
-
- start : ( all )* ;
-
- all : a
- | d
- | e
- | f
- ;
-
- a : c A B
- | c A C
- ;
-
- c : <<AAA(LATEXT(2))>>?
- ;
-
- d : <<BBB(LATEXT(2))>>? B C
- ;
-
- e : <<CCC(LATEXT(2))>>? B C
- ;
-
- f : e X Y
- ;
-
- In rule "a" there is a reference to rule "c" in both alternatives.
- The length of the predicate AAA is k=2 and it can be followed in
- alternative 1 only by (A B) while in alternative 2 it can be
- followed only by (A C). Thus they do not have identical context.
-
- In rule "all" the alternatives which refer to rules "e" and "f" allow
- elimination of the duplicate reference to predicate CCC.
-
- The table below summarized the kind of simplification performed by
- 1.33MR10. In the table, X and Y stand for single predicates
- (not trees).
-
- (OR X (OR Y (OR Z))) => (OR X Y Z)
- (AND X (AND Y (AND Z))) => (AND X Y Z)
-
- (OR X (... (OR X Y) ... )) => (OR X (... Y ... ))
- (AND X (... (AND X Y) ... )) => (AND X (... Y ... ))
- (OR X (... (AND X Y) ... )) => (OR X (... ... ))
- (AND X (... (OR X Y) ... )) => (AND X (... ... ))
-
- (AND X) => X
- (OR X) => X
-
- In a test with a complex grammar for a real application, a predicate
- tree with six OR nodes and 12 leaves was reduced to "(OR X Y Z)".
-
- In 1.33MR10 there is a greater effort to release memory used
- by predicates once they are no longer in use.
-
-#100b. (Changed in 1.33MR10) Suppression of extra predicate tests
-
- The following optimizations require that -mrhoist be selected.
-
- It is relatively easy to optimize the code generated for predicate
- gates when they are of the form:
-
- (AND X Y Z ...)
- or (OR X Y Z ...)
-
- where X, Y, Z, and "..." represent individual predicates (leaves) not
- predicate trees.
-
- If the predicate is an AND the contexts of the X, Y, Z, etc. are
- ANDed together to create a single Tree context for the group and
- context tests for the individual predicates are suppressed:
-
- --------------------------------------------------
- Note: This was incorrect. The contexts should be
- ORed together. This has been fixed. A more
- complete description is available in item #152.
- ---------------------------------------------------
-
- Optimization 1: (AND X Y Z ...)
-
- Suppose the context for Xtest is LA(1)==LP and the context for
- Ytest is LA(1)==LP && LA(2)==ID.
-
- Without the optimization the code would resemble:
-
- if (lookaheadContext &&
- !(LA(1)==LP && LA(1)==LP && LA(2)==ID) ||
- ( (! LA(1)==LP || Xtest) &&
- (! (LA(1)==LP || LA(2)==ID) || Xtest)
- )) {...
-
- With the -mrhoist optimization the code would resemble:
-
- if (lookaheadContext &&
- ! (LA(1)==LP && LA(2)==ID) || (Xtest && Ytest) {...
-
- Optimization 2: (OR X Y Z ...) with identical contexts
-
- Suppose the context for Xtest is LA(1)==ID and for Ytest
- the context is also LA(1)==ID.
-
- Without the optimization the code would resemble:
-
- if (lookaheadContext &&
- ! (LA(1)==ID || LA(1)==ID) ||
- (LA(1)==ID && Xtest) ||
- (LA(1)==ID && Ytest) {...
-
- With the -mrhoist optimization the code would resemble:
-
- if (lookaheadContext &&
- (! LA(1)==ID) || (Xtest || Ytest) {...
-
- Optimization 3: (OR X Y Z ...) with distinct contexts
-
- Suppose the context for Xtest is LA(1)==ID and for Ytest
- the context is LA(1)==LP.
-
- Without the optimization the code would resemble:
-
- if (lookaheadContext &&
- ! (LA(1)==ID || LA(1)==LP) ||
- (LA(1)==ID && Xtest) ||
- (LA(1)==LP && Ytest) {...
-
- With the -mrhoist optimization the code would resemble:
-
- if (lookaheadContext &&
- (zzpf=0,
- (LA(1)==ID && (zzpf=1) && Xtest) ||
- (LA(1)==LP && (zzpf=1) && Ytest) ||
- !zzpf) {
-
- These may appear to be of similar complexity at first,
- but the non-optimized version contains two tests of each
- context while the optimized version contains only one
- such test, as well as eliminating some of the inverted
- logic (" !(...) || ").
-
- Optimization 4: Computation of predicate gate trees
-
- When generating code for the gates of predicate expressions
- antlr 1.33 vanilla uses a recursive procedure to generate
- "&&" and "||" expressions for testing the lookahead. As each
- layer of the predicate tree is exposed a new set of "&&" and
- "||" expressions on the lookahead are generated. In many
- cases the lookahead being tested has already been tested.
-
- With -mrhoist a lookahead tree is computed for the entire
- lookahead expression. This means that predicates with identical
- context or context which is a subset of another predicate's
- context disappear.
-
- This is especially important for predicates formed by rules
- like the following:
-
- uppperCaseVowel : <<isUpperCase(LATEXT(1))>>? vowel;
- vowel: : <<isVowel(LATEXT(1))>>? LETTERS;
-
- These predicates are combined using AND since both must be
- satisfied for rule upperCaseVowel. They have identical
- context which makes this optimization very effective.
-
- The affect of Items #100a and #100b together can be dramatic. In
- a very large (but real world) grammar one particular predicate
- expression was reduced from an (unreadable) 50 predicate leaves,
- 195 LA(1) terms, and 5500 characters to an (easily comprehensible)
- 3 predicate leaves (all different) and a *single* LA(1) term.
-
-#99. (Changed in 1.33MR10) Code generation for expression trees
-
- Expression trees are used for k>1 grammars and predicates with
- lookahead depth >1. This optimization must be enabled using
- "-mrhoist on". (Clarification added for 1.33MR11).
-
- In the processing of expression trees, antlr can generate long chains
- of token comparisons. Prior to 1.33MR10 there were many redundant
- parenthesis which caused problems for compilers which could handle
- expressions of only limited complexity. For example, to test an
- expression tree (root R A B C D), antlr would generate something
- resembling:
-
- (LA(1)==R && (LA(2)==A || (LA(2)==B || (LA(2)==C || LA(2)==D)))))
-
- If there were twenty tokens to test then there would be twenty
- parenthesis at the end of the expression.
-
- In 1.33MR10 the generated code for tree expressions resembles:
-
- (LA(1)==R && (LA(2)==A || LA(2)==B || LA(2)==C || LA(2)==D))
-
- For "complex" expressions the output is indented to reflect the LA
- number being tested:
-
- (LA(1)==R
- && (LA(2)==A || LA(2)==B || LA(2)==C || LA(2)==D
- || LA(2)==E || LA(2)==F)
- || LA(1)==S
- && (LA(2)==G || LA(2)==H))
-
-
- Suggested by S. Bochnak (S.Bochnak@@microTool.com.pl),
-
-#98. (Changed in 1.33MR10) Option "-info p"
-
- When the user selects option "-info p" the program will generate
- detailed information about predicates. If the user selects
- "-mrhoist on" additional detail will be provided explaining
- the promotion and suppression of predicates. The output is part
- of the generated file and sandwiched between #if 0/#endif statements.
-
- Consider the following k=1 grammar:
-
- start : ( all ) * ;
-
- all : ( a
- | b
- )
- ;
-
- a : c B
- ;
-
- c : <<LATEXT(1)>>?
- | B
- ;
-
- b : <<LATEXT(1)>>? X
- ;
-
- Below is an excerpt of the output for rule "start" for the three
- predicate options (off, on, and maintenance release style hoisting).
-
- For those who do not wish to use the "-mrhoist on" option for code
- generation the option can be used in a "diagnostic" mode to provide
- valuable information:
-
- a. where one should insert null actions to inhibit hoisting
- b. a chain of rule references which shows where predicates are
- being hoisted
-
- ======================================================================
- Example of "-info p" with "-mrhoist on"
- ======================================================================
- #if 0
-
- Hoisting of predicate suppressed by alternative without predicate.
- The alt without the predicate includes all cases where the
- predicate is false.
-
- WITH predicate: line 11 v36.g
- WITHOUT predicate: line 12 v36.g
-
- The context set for the predicate:
-
- B
-
- The lookahead set for alt WITHOUT the semantic predicate:
-
- B
-
- The predicate:
-
- pred << LATEXT(1)>>? depth=k=1 rule c line 11 v36.g
-
- set context:
- B
- tree context: null
-
- Chain of referenced rules:
-
- #0 in rule start (line 1 v36.g) to rule all
- #1 in rule all (line 3 v36.g) to rule a
- #2 in rule a (line 8 v36.g) to rule c
- #3 in rule c (line 11 v36.g)
-
- #endif
- &&
- #if 0
-
- pred << LATEXT(1)>>? depth=k=1 rule b line 15 v36.g
-
- set context:
- X
- tree context: null
-
- #endif
- ======================================================================
- Example of "-info p" with the default -prc setting ( "-prc off")
- ======================================================================
- #if 0
-
- OR
- pred << LATEXT(1)>>? depth=k=1 rule c line 11 v36.g
-
- set context:
- nil
- tree context: null
-
- pred << LATEXT(1)>>? depth=k=1 rule b line 15 v36.g
-
- set context:
- nil
- tree context: null
-
- #endif
- ======================================================================
- Example of "-info p" with "-prc on" and "-mrhoist off"
- ======================================================================
- #if 0
-
- OR
- pred << LATEXT(1)>>? depth=k=1 rule c line 11 v36.g
-
- set context:
- B
- tree context: null
-
- pred << LATEXT(1)>>? depth=k=1 rule b line 15 v36.g
-
- set context:
- X
- tree context: null
-
- #endif
- ======================================================================
-
-#97. (Fixed in 1.33MR10) "Predicate applied for more than one ... "
-
- In 1.33 vanilla, the grammar listed below produced this message for
- the first alternative (only) of rule "b":
-
- warning: predicate applied for >1 lookahead 1-sequences
- [you may only want one lookahead 1-sequence to apply.
- Try using a context guard '(...)? =>'
-
- In 1.33MR10 the message is issued for both alternatives.
-
- top : (a)*;
- a : b | c ;
-
- b : <<PPP(LATEXT(1))>>? ( AAA | BBB )
- | <<QQQ(LATEXT(1))>>? ( XXX | YYY )
- ;
-
- c : AAA | XXX;
-
-#96. (Fixed in 1.33MR10) Guard predicates ignored when -prc off
-
- Prior to 1.33MR10, guard predicate code was not generated unless
- "-prc on" was selected.
-
- This was incorrect, since "-prc off" (the default) is supposed to
- disable only AUTOMATIC computation of predicate context, not the
- programmer specified context supplied by guard predicates.
-
-#95. (Fixed in 1.33MR10) Predicate guard context length was k, not max(k,ck)
-
- Prior to 1.33MR10, predicate guards were computed to k tokens rather
- than max(k,ck). Consider the following grammar:
-
- a : ( A B C)? => <<AAA(LATEXT(1))>>? (A|X) (B|Y) (C|Z) ;
-
- The code generated by 1.33 vanilla with "-k 1 -ck 3 -prc on"
- for the predicate in "a" resembles:
-
- if ( (! LA(1)==A) || AAA(LATEXT(1))) {...
-
- With 1.33MR10 and the same options the code resembles:
-
- if ( (! (LA(1)==A && LA(2)==B && LA(3)==C) || AAA(LATEXT(1))) {...
-
-#94. (Fixed in 1.33MR10) Predicates followed by rule references
-
- Prior to 1.33MR10, a semantic predicate which referenced a token
- which was off the end of the rule caused an incomplete context
- to be computed (with "-prc on") for the predicate under some circum-
- stances. In some cases this manifested itself as illegal C code
- (e.g. "LA(2)==[Ep](1)" in the k=2 examples below:
-
- all : ( a ) *;
-
- a : <<AAA(LATEXT(2))>>? ID X
- | <<BBB(LATEXT(2))>>? Y
- | Z
- ;
-
- This might also occur when the semantic predicate was followed
- by a rule reference which was shorter than the length of the
- semantic predicate:
-
- all : ( a ) *;
-
- a : <<AAA(LATEXT(2))>>? ID X
- | <<BBB(LATEXT(2))>>? y
- | Z
- ;
-
- y : Y ;
-
- Depending on circumstance, the resulting context might be too
- generous because it was too short, or too restrictive because
- of missing alternatives.
-
-#93. (Changed in 1.33MR10) Definition of Purify macro
-
- Ofer Ben-Ami (gremlin@cs.huji.ac.il) has supplied a definition
- for the Purify macro:
-
- #define PURIFY(r, s) memset((char *) &(r), '\0', (s));
-
- Note: This may not be the right thing to do for C++ objects that
- have constructors. Reported by Bonny Rais (bonny@werple.net.au).
-
- For those cases one should #define PURIFY to an empty macro in the
- #header or #first actions.
-
-#92. (Fixed in 1.33MR10) Guarded predicates and hoisting
-
- When a guarded predicate participates in hoisting it is linked into
- a predicate expression tree. Prior to 1.33MR10 this link was never
- cleared and the next time the guard was used to construct a new
- tree the link could contain a spurious reference to another element
- which had previosly been joined to it in the semantic predicate tree.
-
- For example:
-
- start : ( all ) *;
- all : ( a | b ) ;
-
- start2 : ( all2 ) *;
- all2 : ( a ) ;
-
- a : (A)? => <<AAA(LATEXT(1))>>? A ;
- b : (B)? => <<BBB(LATEXT(1))>>? B ;
-
- Prior to 1.33MR10 the code for "start2" would include a spurious
- reference to the BBB predicate which was left from constructing
- the predicate tree for rule "start" (i.e. or(AAA,BBB) ).
-
- In 1.33MR10 this problem is avoided by cloning the original guard
- each time it is linked into a predicate tree.
-
-#91. (Changed in 1.33MR10) Extensive changes to semantic pred hoisting
-
- ============================================
- This has been rendered obsolete by Item #117
- ============================================
-
-#90. (Fixed in 1.33MR10) Semantic pred with LT(i) and i>max(k,ck)
-
- There is a bug in antlr 1.33 vanilla and all maintenance releases
- prior to 1.33MR10 which allows semantic predicates to reference
- an LT(i) or LATEXT(i) where i is larger than max(k,ck). When
- this occurs antlr will attempt to mark the ith element of an array
- in which there are only max(k,ck) elements. The result cannot
- be predicted.
-
- Using LT(i) or LATEXT(i) for i>max(k,ck) is reported as an error
- in 1.33MR10.
-
-#89. Rescinded
-
-#88. (Fixed in 1.33MR10) Tokens used in semantic predicates in guess mode
-
- Consider the behavior of a semantic predicate during guess mode:
-
- rule : a:A (
- <<test($a)>>? b:B
- | c:C
- );
-
- Prior to MR10 the assignment of the token or attribute to
- $a did not occur during guess mode, which would cause the
- semantic predicate to misbehave because $a would be null.
-
- In 1.33MR10 a semantic predicate with a reference to an
- element label (such as $a) forces the assignment to take
- place even in guess mode.
-
- In order to work, this fix REQUIRES use of the $label format
- for token pointers and attributes referenced in semantic
- predicates.
-
- The fix does not apply to semantic predicates using the
- numeric form to refer to attributes (e.g. <<test($1)>>?).
- The user will receive a warning for this case.
-
- Reported by Rob Trout (trout@mcs.cs.kent.edu).
-
-#87. (Fixed in 1.33MR10) Malformed guard predicates
-
- Context guard predicates may contain only references to
- tokens. They may not contain references to (...)+ and
- (...)* blocks. This is now checked. This replaces the
- fatal error message in item #78 with an appropriate
- (non-fatal) error messge.
-
- In theory, context guards should be allowed to reference
- rules. However, I have not had time to fix this.
- Evaluation of the guard takes place before all rules have
- been read, making it difficult to resolve a forward reference
- to rule "zzz" - it hasn't been read yet ! To postpone evaluation
- of the guard until all rules have been read is too much
- for the moment.
-
-#86. (Fixed in 1.33MR10) Unequal set size in set_sub
-
- Routine set_sub() in pccts/support/set/set.h did not work
- correctly when the sets were of unequal sizes. Rewrote
- set_equ to make it simpler and remove unnecessary and
- expensive calls to set_deg(). This routine was not used
- in 1.33 vanila.
-
-#85. (Changed in 1.33MR10) Allow redefinition of MaxNumFiles
-
- Raised the maximum number of input files to 99 from 20.
- Put a #ifndef/#endif around the "#define MaxNumFiles 99".
-
-#84. (Fixed in 1.33MR10) Initialize zzBadTok in macro zzRULE
-
- Initialize zzBadTok to NULL in zzRULE macro of AParser.h.
- in order to get rid of warning messages.
-
-#83. (Fixed in 1.33MR10) False warnings with -w2 for #tokclass
-
- When -w2 is selected antlr gives inappropriate warnings about
- #tokclass names not having any associated regular expressions.
- Since a #tokclass is not a "real" token it will never have an
- associated regular expression and there should be no warning.
-
- Reported by Derek Pappas (derek.pappas@eng.sun.com)
-
-#82. (Fixed in 1.33MR10) Computation of follow sets with multiple cycles
-
- Reinier van den Born (reinier@vnet.ibm.com) reported a problem
- in the computation of follow sets by antlr. The problem (bug)
- exists in 1.33 vanilla and all maintenance releases prior to 1.33MR10.
-
- The problem involves the computation of follow sets when there are
- cycles - rules which have mutual references. I believe the problem
- is restricted to cases where there is more than one cycle AND
- elements of those cycles have rules in common. Even when this
- occurs it may not affect the code generated - but it might. It
- might also lead to undetected ambiguities.
-
- There were no changes in antlr or dlg output from the revised version.
-
- The following fragment demonstates the problem by giving different
- follow sets (option -pa) for var_access when built with k=1 and ck=2 on
- 1.33 vanilla and 1.33MR10:
-
- echo_statement : ECHO ( echo_expr )*
- ;
-
- echo_expr : ( command )?
- | expression
- ;
-
- command : IDENTIFIER
- { concat }
- ;
-
- expression : operand ( OPERATOR operand )*
- ;
-
- operand : value
- | START command END
- ;
-
- value : concat
- | TYPE operand
- ;
-
- concat : var_access { CONCAT value }
- ;
-
- var_access : IDENTIFIER { INDEX }
-
- ;
-#81. (Changed in 1.33MR10) C mode use of attributes and ASTs
-
- Reported by Isaac Clark (irclark@mindspring.com).
-
- C mode code ignores attributes returned by rules which are
- referenced using element labels when ASTs are enabled (-gt option).
-
- 1. start : r:rule t:Token <<$start=$r;>>
-
- The $r refrence will not work when combined with
- the -gt option.
-
- 2. start : t:Token <<$start=$t;>>
-
- The $t reference works in all cases.
-
- 3. start : rule <<$0=$1;>>
-
- Numeric labels work in all cases.
-
- With MR10 the user will receive an error message for case 1 when
- the -gt option is used.
-
-#80. (Fixed in 1.33MR10) (...)? as last alternative of block
-
- A construct like the following:
-
- rule : a
- | (b)?
- ;
-
- does not make sense because there is no alternative when
- the guess block fails. This is now reported as a warning
- to the user.
-
- Previously, there was a code generation error for this case:
- the guess block was not "closed" when the guess failed.
- This could cause an infinite loop or other problems. This
- is now fixed.
-
- Example problem:
-
- #header<<
- #include <stdio.h>
- #include "charptr.h"
- >>
-
- <<
- #include "charptr.c"
- main ()
- {
- ANTLR(start(),stdin);
- }
- >>
-
- #token "[\ \t]+" << zzskip(); >>
- #token "[\n]" << zzline++; zzskip(); >>
-
- #token Word "[a-z]+"
- #token Number "[0-9]+"
-
-
- start : (test1)?
- | (test2)?
- ;
- test1 : (Word Word Word Word)?
- | (Word Word Word Number)?
- ;
- test2 : (Word Word Number Word)?
- | (Word Word Number Number)?
- ;
-
- Test data which caused infinite loop:
-
- a 1 a a
-
-#79. (Changed in 1.33MR10) Use of -fh with multiple parsers
-
- Previously, antlr always used the pre-processor symbol
- STDPCCTS_H as a gate for the file stdpccts.h. This
- caused problems when there were multiple parsers defined
- because they used the same gate symbol.
-
- In 1.33MR10, the -fh filename is used to generate the
- gate file for stdpccts.h. For instance:
-
- antlr -fh std_parser1.h
-
- generates the pre-processor symbol "STDPCCTS_std_parser1_H".
-
- Reported by Ramanathan Santhanam (ps@kumaran.com).
-
-#78. (Changed in 1.33MR9) Guard predicates that refer to rules
-
- ------------------------
- Please refer to Item #87
- ------------------------
-
- Guard predicates are processed during an early phase
- of antlr (during parsing) before all data structures
- are completed.
-
- There is an apparent bug in earlier versions of 1.33
- which caused guard predicates which contained references
- to rules (rather than tokens) to reference a structure
- which hadn't yet been initialized.
-
- In some cases (perhaps all cases) references to rules
- in guard predicates resulted in the use of "garbage".
-
-#79. (Changed in 1.33MR9) Jeff Vincent (JVincent@novell.com)
-
- Previously, the maximum length file name was set
- arbitrarily to 300 characters in antlr, dlg, and sorcerer.
-
- The config.h file now attempts to define the maximum length
- filename using _MAX_PATH from stdlib.h before falling back
- to using the value 300.
-
-#78. (Changed in 1.33MR9) Jeff Vincent (JVincent@novell.com)
-
- Put #ifndef/#endif around definition of ZZLEXBUFSIZE in
- antlr.
-
-#77. (Changed in 1.33MR9) Arithmetic overflow for very large grammars
-
- In routine HandleAmbiguities() antlr attempts to compute the
- number of possible elements in a set that is order of
- number-of-tokens raised to the number-of-lookahead-tokens power.
- For large grammars or large lookahead (e.g. -ck 7) this can
- cause arithmetic overflow.
-
- With 1.33MR9, arithmetic overflow in this computation is reported
- the first time it happens. The program continues to run and
- the program branches based on the assumption that the computed
- value is larger than any number computed by counting actual cases
- because 2**31 is larger than the number of bits in most computers.
-
- Before 1.33MR9 overflow was not reported. The behavior following
- overflow is not predictable by anyone but the original author.
-
- NOTE
-
- In 1.33MR10 the warning message is suppressed.
- The code which detects the overflow allows the
- computation to continue without an error. The
- error message itself made made users worry.
-
-#76. (Changed in 1.33MR9) Jeff Vincent (JVincent@novell.com)
-
- Jeff Vincent has convinced me to make ANTLRCommonToken and
- ANTLRCommonNoRefCountToken use variable length strings
- allocated from the heap rather than fixed length strings.
- By suitable definition of setText(), the copy constructor,
- and operator =() it is possible to maintain "copy" semantics.
- By "copy" semantics I mean that when a token is copied from
- an existing token it receives its own, distinct, copy of the
- text allocated from the heap rather than simply a pointer
- to the original token's text.
-
- ============================================================
- W * A * R * N * I * N * G
- ============================================================
-
- It is possible that this may cause problems for some users.
- For those users I have included the old version of AToken.h as
- pccts/h/AToken_traditional.h.
-
-#75. (Changed in 1.33MR9) Bruce Guenter (bruceg@qcc.sk.ca)
-
- Make DLGStringInput const correct. Since this is infrequently
- subclassed, it should affect few users, I hope.
-
-#74. (Changed in 1.33MR9) -o (output directory) option
-
- Antlr does not properly handle the -o output directory option
- when the filename of the grammar contains a directory part. For
- example:
-
- antlr -o outdir pccts_src/myfile.g
-
- causes antlr create a file called "outdir/pccts_src/myfile.cpp.
- It SHOULD create outdir/myfile.cpp
-
- The suggested code fix has been installed in antlr, dlg, and
- Sorcerer.
-
-#73. (Changed in 1.33MR9) Hoisting of semantic predicates and -mrhoist
-
- ============================================
- This has been rendered obsolete by Item #117
- ============================================
-
-#72. (Changed in 1.33MR9) virtual saveState()/restoreState()/guess_XXX
-
- The following methods in ANTLRParser were made virtual at
- the request of S. Bochnak (S.Bochnak@microTool.com.pl):
-
- saveState() and restoreState()
- guess(), guess_fail(), and guess_done()
-
-#71. (Changed in 1.33MR9) Access to omitted command line argument
-
- If a switch requiring arguments is the last thing on the
- command line, and the argument is omitted, antlr would core.
-
- antlr test.g -prc
-
- instead of
-
- antlr test.g -prc off
-
-#70. (Changed in 1.33MR9) Addition of MSVC .dsp and .mak build files
-
- The following MSVC .dsp and .mak files for pccts and sorcerer
- were contributed by Stanislaw Bochnak (S.Bochnak@microTool.com.pl)
- and Jeff Vincent (JVincent@novell.com)
-
- PCCTS Distribution Kit
- ----------------------
- pccts/PCCTSMSVC50.dsw
-
- pccts/antlr/AntlrMSVC50.dsp
- pccts/antlr/AntlrMSVC50.mak
-
- pccts/dlg/DlgMSVC50.dsp
- pccts/dlg/DlgMSVC50.mak
-
- pccts/support/msvc.dsp
-
- Sorcerer Distribution Kit
- -------------------------
- pccts/sorcerer/SorcererMSVC50.dsp
- pccts/sorcerer/SorcererMSVC50.mak
-
- pccts/sorcerer/lib/msvc.dsp
-
-#69. (Changed in 1.33MR9) Change "unsigned int" to plain "int"
-
- Declaration of max_token_num in misc.c as "unsigned int"
- caused comparison between signed and unsigned ints giving
- warning message without any special benefit.
-
-#68. (Changed in 1.33MR9) Add void return for dlg internal_error()
-
- Get rid of "no return value" message in internal_error()
- in file dlg/support.c and dlg/dlg.h.
-
-#67. (Changed in Sor) sor.g: lisp() has no return value
-
- Added a "void" for the return type.
-
-#66. (Added to Sor) sor.g: ZZLEXBUFSIZE enclosed in #ifndef/#endif
-
- A user needed to be able to change the ZZLEXBUFSIZE for
- sor. Put the definition of ZZLEXBUFSIZE inside #ifndef/#endif
-
-#65. (Changed in 1.33MR9) PCCTSAST::deepCopy() and ast_dup() bug
-
- Jeff Vincent (JVincent@novell.com) found that deepCopy()
- made new copies of only the direct descendents. No new
- copies were made of sibling nodes, Sibling pointers are
- set to zero by shallowCopy().
-
- PCCTS_AST::deepCopy() has been changed to make a
- deep copy in the traditional sense.
-
- The deepCopy() routine depends on the behavior of
- shallowCopy(). In all sor examples I've found,
- shallowCopy() zeroes the right and down pointers.
-
- Original Tree Original deepCopy() Revised deepCopy
- ------------- ------------------- ----------------
- a->b->c A A
- | | |
- d->e->f D D->E->F
- | | |
- g->h->i G G->H->I
- | |
- j->k J->K
-
- While comparing deepCopy() for C++ mode with ast_dup for
- C mode I found a problem with ast_dup().
-
- Routine ast_dup() has been changed to make a deep copy
- in the traditional sense.
-
- Original Tree Original ast_dup() Revised ast_dup()
- ------------- ------------------- ----------------
- a->b->c A->B->C A
- | | |
- d->e->f D->E->F D->E->F
- | | |
- g->h->i G->H->I G->H->I
- | | |
- j->k J->K J->K
-
-
- I believe this affects transform mode sorcerer programs only.
-
-#64. (Changed in 1.33MR9) anltr/hash.h prototype for killHashTable()
-
-#63. (Changed in 1.33MR8) h/charptr.h does not zero pointer after free
-
- The charptr.h routine now zeroes the pointer after free().
-
- Reported by Jens Tingleff (jensting@imaginet.fr)
-
-#62. (Changed in 1.33MR8) ANTLRParser::resynch had static variable
-
- The static variable "consumed" in ANTLRParser::resynch was
- changed into an instance variable of the class with the
- name "resynchConsumed".
-
- Reported by S.Bochnak@microTool.com.pl
-
-#61. (Changed in 1.33MR8) Using rule>[i,j] when rule has no return values
-
- Previously, the following code would cause antlr to core when
- it tried to generate code for rule1 because rule2 had no return
- values ("upward inheritance"):
-
- rule1 : <<int i; int j>>
- rule2 > [i,j]
- ;
-
- rule2 : Anything ;
-
- Reported by S.Bochnak@microTool.com.pl
-
- Verified correct operation of antlr MR8 when missing or extra
- inheritance arguments for all combinations. When there are
- missing or extra arguments code will still be generated even
- though this might cause the invocation of a subroutine with
- the wrong number of arguments.
-
-#60. (Changed in 1.33MR7) Major changes to exception handling
-
- There were significant problems in the handling of exceptions
- in 1.33 vanilla. The general problem is that it can only
- process one level of exception handler. For example, a named
- exception handler, an exception handler for an alternative, or
- an exception for a subrule always went to the rule's exception
- handler if there was no "catch" which matched the exception.
-
- In 1.33MR7 the exception handlers properly "nest". If an
- exception handler does not have a matching "catch" then the
- nextmost outer exception handler is checked for an appropriate
- "catch" clause, and so on until an exception handler with an
- appropriate "catch" is found.
-
- There are still undesirable features in the way exception
- handlers are implemented, but I do not have time to fix them
- at the moment:
-
- The exception handlers for alternatives are outside the
- block containing the alternative. This makes it impossible
- to access variables declared in a block or to resume the
- parse by "falling through". The parse can still be easily
- resumed in other ways, but not in the most natural fashion.
-
- This results in an inconsistentcy between named exception
- handlers and exception handlers for alternatives. When
- an exception handler for an alternative "falls through"
- it goes to the nextmost outer handler - not the "normal
- action".
-
- A major difference between 1.33MR7 and 1.33 vanilla is
- the default action after an exception is caught:
-
- 1.33 Vanilla
- ------------
- In 1.33 vanilla the signal value is set to zero ("NoSignal")
- and the code drops through to the code following the exception.
- For named exception handlers this is the "normal action".
- For alternative exception handlers this is the rule's handler.
-
- 1.33MR7
- -------
- In 1.33MR7 the signal value is NOT automatically set to zero.
-
- There are two cases:
-
- For named exception handlers: if the signal value has been
- set to zero the code drops through to the "normal action".
-
- For all other cases the code branches to the nextmost outer
- exception handler until it reaches the handler for the rule.
-
- The following macros have been defined for convenience:
-
- C/C++ Mode Name
- --------------------
- (zz)suppressSignal
- set signal & return signal arg to 0 ("NoSignal")
- (zz)setSignal(intValue)
- set signal & return signal arg to some value
- (zz)exportSignal
- copy the signal value to the return signal arg
-
- I'm not sure why PCCTS make a distinction between the local
- signal value and the return signal argument, but I'm loathe
- to change the code. The burden of copying the local signal
- value to the return signal argument can be given to the
- default signal handler, I suppose.
-
-#59. (Changed in 1.33MR7) Prototypes for some functions
-
- Added prototypes for the following functions to antlr.h
-
- zzconsumeUntil()
- zzconsumeUntilToken()
-
-#58. (Changed in 1.33MR7) Added defintion of zzbufsize to dlgauto.h
-
-#57. (Changed in 1.33MR7) Format of #line directive
-
- Previously, the -gl directive for line 1234 would
- resemble: "# 1234 filename.g". This caused problems
- for some compilers/pre-processors. In MR7 it generates
- "#line 1234 filename.g".
-
-#56. (Added in 1.33MR7) Jan Mikkelsen <janm@zeta.org.au>
-
- Move PURIFY macro invocaton to after rule's init action.
-
-#55. (Fixed in 1.33MR7) Unitialized variables in ANTLRParser
-
- Member variables inf_labase and inf_last were not initialized.
- (See item #50.)
-
-#54. (Fixed in 1.33MR6) Brad Schick (schick@interacess.com)
-
- Previously, the following constructs generated the same
- code:
-
- rule1 : (A B C)?
- | something-else
- ;
-
- rule2 : (A B C)? ()
- | something-else
- ;
-
- In all versions of pccts rule1 guesses (A B C) and then
- consume all three tokens if the guess succeeds. In MR6
- rule2 guesses (A B C) but consumes NONE of the tokens
- when the guess succeeds because "()" matches epsilon.
-
-#53. (Explanation for 1.33MR6) What happens after an exception is caught ?
-
- The Book is silent about what happens after an exception
- is caught.
-
- The following code fragment prints "Error Action" followed
- by "Normal Action".
-
- test : Word ex:Number <<printf("Normal Action\n");>>
- exception[ex]
- catch NoViableAlt:
- <<printf("Error Action\n");>>
- ;
-
- The reason for "Normal Action" is that the normal flow of the
- program after a user-written exception handler is to "drop through".
- In the case of an exception handler for a rule this results in
- the exection of a "return" statement. In the case of an
- exception handler attached to an alternative, rule, or token
- this is the code that would have executed had there been no
- exception.
-
- The user can achieve the desired result by using a "return"
- statement.
-
- test : Word ex:Number <<printf("Normal Action\n");>>
- exception[ex]
- catch NoViableAlt:
- <<printf("Error Action\n"); return;>>
- ;
-
- The most powerful mechanism for recovery from parse errors
- in pccts is syntactic predicates because they provide
- backtracking. Exceptions allow "return", "break",
- "consumeUntil(...)", "goto _handler", "goto _fail", and
- changing the _signal value.
-
-#52. (Fixed in 1.33MR6) Exceptions without syntactic predicates
-
- The following generates bad code in 1.33 if no syntactic
- predicates are present in the grammar.
-
- test : Word ex:Number <<printf("Normal Action\n");>>
- exception[ex]
- catch NoViableAlt:
- <<printf("Error Action\n");>>
-
- There is a reference to a guess variable. In C mode
- this causes a compiler error. In C++ mode it generates
- an extraneous check on member "guessing".
-
- In MR6 correct code is generated for both C and C++ mode.
-
-#51. (Added to 1.33MR6) Exception operator "@" used without exceptions
-
- In MR6 added a warning when the exception operator "@" is
- used and no exception group is defined. This is probably
- a case where "\@" or "@" is meant.
-
-#50. (Fixed in 1.33MR6) Gunnar Rxnning (gunnar@candleweb.no)
- http://www.candleweb.no/~gunnar/
-
- Routines zzsave_antlr_state and zzrestore_antlr_state don't
- save and restore all the data needed when switching states.
-
- Suggested patch applied to antlr.h and err.h for MR6.
-
-#49. (Fixed in 1.33MR6) Sinan Karasu (sinan@boeing.com)
-
- Generated code failed to turn off guess mode when leaving a
- (...)+ block which contained a guess block. The result was
- an infinite loop. For example:
-
- rule : (
- (x)?
- | y
- )+
-
- Suggested code fix implemented in MR6. Replaced
-
- ... else if (zzcnt>1) break;
-
- with:
-
- C++ mode:
- ... else if (zzcnt>1) {if (!zzrv) zzGUESS_DONE; break;};
- C mode:
- ... else if (zzcnt>1) {if (zzguessing) zzGUESS_DONE; break;};
-
-#48. (Fixed in 1.33MR6) Invalid exception element causes core
-
- A label attached to an invalid construct can cause
- pccts to crash while processing the exception associated
- with the label. For example:
-
- rule : t:(B C)
- exception[t] catch MismatchedToken: <<printf(...);>>
-
- Version MR6 generates the message:
-
- reference in exception handler to undefined label 't'
-
-#47. (Fixed in 1.33MR6) Manuel Ornato
-
- Under some circumstances involving a k >1 or ck >1
- grammar and a loop block (i.e. (...)* ) pccts will
- fail to detect a syntax error and loop indefinitely.
- The problem did not exist in 1.20, but has existed
- from 1.23 to the present.
-
- Fixed in MR6.
-
- ---------------------------------------------------
- Complete test program
- ---------------------------------------------------
- #header<<
- #include <stdio.h>
- #include "charptr.h"
- >>
-
- <<
- #include "charptr.c"
- main ()
- {
- ANTLR(global(),stdin);
- }
- >>
-
- #token "[\ \t]+" << zzskip(); >>
- #token "[\n]" << zzline++; zzskip(); >>
-
- #token B "b"
- #token C "c"
- #token D "d"
- #token E "e"
- #token LP "\("
- #token RP "\)"
-
- #token ANTLREOF "@"
-
- global : (
- (E liste)
- | liste
- | listed
- ) ANTLREOF
- ;
-
- listeb : LP ( B ( B | C )* ) RP ;
- listec : LP ( C ( B | C )* ) RP ;
- listed : LP ( D ( B | C )* ) RP ;
- liste : ( listeb | listec )* ;
-
- ---------------------------------------------------
- Sample data causing infinite loop
- ---------------------------------------------------
- e (d c)
- ---------------------------------------------------
-
-#46. (Fixed in 1.33MR6) Robert Richter
- (Robert.Richter@infotech.tu-chemnitz.de)
-
- This item from the list of known problems was
- fixed by item #18 (below).
-
-#45. (Fixed in 1.33MR6) Brad Schick (schick@interaccess.com)
-
- The dependency scanner in VC++ mistakenly sees a
- reference to an MPW #include file even though properly
- #ifdef/#endif in config.h. The suggested workaround
- has been implemented:
-
- #ifdef MPW
- .....
- #define MPW_CursorCtl_Header <CursorCtl.h>
- #include MPW_CursorCtl_Header
- .....
- #endif
-
-#44. (Fixed in 1.33MR6) cast malloc() to (char *) in charptr.c
-
- Added (char *) cast for systems where malloc returns "void *".
-
-#43. (Added to 1.33MR6) Bruce Guenter (bruceg@qcc.sk.ca)
-
- Add setLeft() and setUp methods to ASTDoublyLinkedBase
- for symmetry with setRight() and setDown() methods.
-
-#42. (Fixed in 1.33MR6) Jeff Katcher (jkatcher@nortel.ca)
-
- C++ style comment in antlr.c corrected.
-
-#41. (Added in 1.33MR6) antlr -stdout
-
- Using "antlr -stdout ..." forces the text that would
- normally go to the grammar.c or grammar.cpp file to
- stdout.
-
-#40. (Added in 1.33MR6) antlr -tab to change tab stops
-
- Using "antlr -tab number ..." changes the tab stops
- for the grammar.c or grammar.cpp file. The number
- must be between 0 and 8. Using 0 gives tab characters,
- values between 1 and 8 give the appropriate number of
- space characters.
-
-#39. (Fixed in 1.33MR5) Jan Mikkelsen <janm@zeta.org.au>
-
- Commas in function prototype still not correct under
- some circumstances. Suggested code fix installed.
-
-#38. (Fixed in 1.33MR5) ANTLRTokenBuffer constructor
-
- Have ANTLRTokenBuffer ctor initialize member "parser" to null.
-
-#37. (Fixed in 1.33MR4) Bruce Guenter (bruceg@qcc.sk.ca)
-
- In ANTLRParser::FAIL(int k,...) released memory pointed to by
- f[i] (as well as f itself. Should only free f itself.
-
-#36. (Fixed in 1.33MR3) Cortland D. Starrett (cort@shay.ecn.purdue.edu)
-
- Neglected to properly declare isDLGmaxToken() when fixing problem
- reported by Andreas Magnusson.
-
- Undo "_retv=NULL;" change which caused problems for return values
- from rules whose return values weren't pointers.
-
- Failed to create bin directory if it didn't exist.
-
-#35. (Fixed in 1.33MR2) Andreas Magnusson
-(Andreas.Magnusson@mailbox.swipnet.se)
-
- Repair bug introduced by 1.33MR1 for #tokdefs. The original fix
- placed "DLGmaxToken=9999" and "DLGminToken=0" in the TokenType enum
- in order to fix a problem with an aggresive compiler assigning an 8
- bit enum which might be too narrow. This caused #tokdefs to assume
- that there were 9999 real tokens. The repair to the fix causes antlr to
- ignore TokenTypes "DLGmaxToken" and "DLGminToken" in a #tokdefs file.
-
-#34. (Added to 1.33MR1) Add public DLGLexerBase::set_line(int newValue)
-
- Previously there was no public function for changing the line
- number maintained by the lexer.
-
-#33. (Fixed in 1.33MR1) Franklin Chen (chen@adi.com)
-
- Accidental use of EXIT_FAILURE rather than PCCTS_EXIT_FAILURE
- in pccts/h/AParser.cpp.
-
-#32. (Fixed in 1.33MR1) Franklin Chen (chen@adi.com)
-
- In PCCTSAST.cpp lines 405 and 466: Change
-
- free (t)
- to
- free ( (char *)t );
-
- to match prototype.
-
-#31. (Added to 1.33MR1) Pointer to parser in ANTLRTokenBuffer
- Pointer to parser in DLGLexerBase
-
- The ANTLRTokenBuffer class now contains a pointer to the
- parser which is using it. This is established by the
- ANTLRParser constructor calling ANTLRTokenBuffer::
- setParser(ANTLRParser *p).
-
- When ANTLRTokenBuffer::setParser(ANTLRParser *p) is
- called it saves the pointer to the parser and then
- calls ANTLRTokenStream::setParser(ANTLRParser *p)
- so that the lexer can also save a pointer to the
- parser.
-
- There is also a function getParser() in each class
- with the obvious purpose.
-
- It is possible that these functions will return NULL
- under some circumstances (e.g. a non-DLG lexer is used).
-
-#30. (Added to 1.33MR1) function tokenName(int token) standard
-
- The generated parser class now includes the
- function:
-
- static const ANTLRChar * tokenName(int token)
-
- which returns a pointer to the "name" corresponding
- to the token.
-
- The base class (ANTLRParser) always includes the
- member function:
-
- const ANTLRChar * parserTokenName(int token)
-
- which can be accessed by objects which have a pointer
- to an ANTLRParser, but do not know the name of the
- parser class (e.g. ANTLRTokenBuffer and DLGLexerBase).
-
-#29. (Added to 1.33MR1) Debugging DLG lexers
-
- If the pre-processor symbol DEBUG_LEXER is defined
- then DLexerBase will include code for printing out
- key information about tokens which are recognized.
-
- The debug feature of the lexer is controlled by:
-
- int previousDebugValue=lexer.debugLexer(newValue);
-
- a value of 0 disables output
- a value of 1 enables output
-
- Even if the lexer debug code is compiled into DLexerBase
- it must be enabled before any output is generated. For
- example:
-
- DLGFileInput in(stdin);
- MyDLG lexer(&in,2000);
-
- lexer.setToken(&aToken);
-
- #if DEBUG_LEXER
- lexer.debugLexer(1); // enable debug information
- #endif
-
-#28. (Added to 1.33MR1) More control over DLG header
-
- Version 1.33MR1 adds the following directives to PCCTS
- for C++ mode:
-
- #lexprefix <<source code>>
-
- Adds source code to the DLGLexer.h file
- after the #include "DLexerBase.h" but
- before the start of the class definition.
-
- #lexmember <<source code>>
-
- Adds source code to the DLGLexer.h file
- as part of the DLGLexer class body. It
- appears immediately after the start of
- the class and a "public: statement.
-
-#27. (Fixed in 1.33MR1) Comments in DLG actions
-
- Previously, DLG would not recognize comments as a special case.
- Thus, ">>" in the comments would cause errors. This is fixed.
-
-#26. (Fixed in 1.33MR1) Removed static variables from error routines
-
- Previously, the existence of statically allocated variables
- in some of the parser's member functions posed a danger when
- there was more than one parser active.
-
- Replaced with dynamically allocated/freed variables in 1.33MR1.
-
-#25. (Fixed in 1.33MR1) Use of string literals in semantic predicates
-
- Previously, it was not possible to place a string literal in
- a semantic predicate because it was not properly "stringized"
- for the report of a failed predicate.
-
-#24. (Fixed in 1.33MR1) Continuation lines for semantic predicates
-
- Previously, it was not possible to continue semantic
- predicates across a line because it was not properly
- "stringized" for the report of a failed predicate.
-
- rule : <<ifXYZ()>>?[ a very
- long statement ]
-
-#23. (Fixed in 1.33MR1) {...} envelope for failed semantic predicates
-
- Previously, there was a code generation error for failed
- semantic predicates:
-
- rule : <<xyz()>>?[ stmt1; stmt2; ]
-
- which generated code which resembled:
-
- if (! xyz()) stmt1; stmt2;
-
- It now puts the statements in a {...} envelope:
-
- if (! xyz()) { stmt1; stmt2; };
-
-#22. (Fixed in 1.33MR1) Continuation of #token across lines using "\"
-
- Previously, it was not possible to continue a #token regular
- expression across a line. The trailing "\" and newline caused
- a newline to be inserted into the regular expression by DLG.
-
- Fixed in 1.33MR1.
-
-#21. (Fixed in 1.33MR1) Use of ">>" (right shift operator in DLG actions
-
- It is now possible to use the C++ right shift operator ">>"
- in DLG actions by using the normal escapes:
-
- #token "shift-right" << value=value \>\> 1;>>
-
-#20. (Version 1.33/19-Jan-97 Karl Eccleson <karle@microrobotics.co.uk>
- P.A. Keller (P.A.Keller@bath.ac.uk)
-
- There is a problem due to using exceptions with the -gh option.
-
- Suggested fix now in 1.33MR1.
-
-#19. (Fixed in 1.33MR1) Tom Piscotti and John Lilley
-
- There were problems suppressing messages to stdin and stdout
- when running in a window environment because some functions
- which uses fprint were not virtual.
-
- Suggested change now in 1.33MR1.
-
- I believe all functions containing error messages (excluding those
- indicating internal inconsistency) have been placed in functions
- which are virtual.
-
-#18. (Version 1.33/ 22-Nov-96) John Bair (jbair@iftime.com)
-
- Under some combination of options a required "return _retv" is
- not generated.
-
- Suggested fix now in 1.33MR1.
-
-#17. (Version 1.33/3-Sep-96) Ron House (house@helios.usq.edu.au)
-
- The routine ASTBase::predorder_action omits two "tree->"
- prefixes, which results in the preorder_action belonging
- to the wrong node to be invoked.
-
- Suggested fix now in 1.33MR1.
-
-#16. (Version 1.33/7-Jun-96) Eli Sternheim <eli@interhdl.com>
-
- Routine consumeUntilToken() does not check for end-of-file
- condition.
-
- Suggested fix now in 1.33MR1.
-
-#15. (Version 1.33/8 Apr 96) Asgeir Olafsson <olafsson@cstar.ac.com>
-
- Problem with tree duplication of doubly linked ASTs in ASTBase.cpp.
-
- Suggested fix now in 1.33MR1.
-
-#14. (Version 1.33/28-Feb-96) Andreas.Magnusson@mailbox.swipnet.se
-
- Problem with definition of operator = (const ANTLRTokenPtr rhs).
-
- Suggested fix now in 1.33MR1.
-
-#13. (Version 1.33/13-Feb-96) Franklin Chen (chen@adi.com)
-
- Sun C++ Compiler 3.0.1 can't compile testcpp/1 due to goto in
- block with destructors.
-
- Apparently fixed. Can't locate "goto".
-
-#12. (Version 1.33/10-Nov-95) Minor problems with 1.33 code
-
- The following items have been fixed in 1.33MR1:
-
- 1. pccts/antlr/main.c line 142
-
- "void" appears in classic C code
-
- 2. no makefile in support/genmk
-
- 3. EXIT_FAILURE/_SUCCESS instead of PCCTS_EXIT_FAILURE/_SUCCESS
-
- pccts/h/PCCTSAST.cpp
- pccts/h/DLexerBase.cpp
- pccts/testcpp/6/test.g
-
- 4. use of "signed int" isn't accepted by AT&T cfront
-
- pccts/h/PCCTSAST.h line 42
-
- 5. in call to ANTLRParser::FAIL the var arg err_k is passed as
- "int" but is declared "unsigned int".
-
- 6. I believe that a failed validation predicate still does not
- get put in a "{...}" envelope, despite the release notes.
-
- 7. The #token ">>" appearing in the DLG grammar description
- causes DLG to generate the string literal "\>\>" which
- is non-conforming and will cause some compilers to
- complain (scan.c function act10 line 143 of source code).
-
-#11. (Version 1.32b6) Dave Kuhlman (dkuhlman@netcom.com)
-
- Problem with file close in gen.c. Already fixed in 1.33.
-
-#10. (Version 1.32b6/29-Aug-95)
-
- pccts/antlr/main.c contains a C++ style comments on lines 149
- and 176 which causes problems for most C compilers.
-
- Already fixed in 1.33.
-
-#9. (Version 1.32b4/14-Mar-95) dlgauto.h #include "config.h"
-
- The file pccts/h/dlgauto.h should probably contain a #include
- "config.h" as it uses the #define symbol __USE_PROTOS.
-
- Added to 1.33MR1.
-
-#8. (Version 1.32b4/6-Mar-95) Michael T. Richter (mtr@igs.net)
-
- In C++ output mode anonymous tokens from in-line regular expressions
- can create enum values which are too wide for the datatype of the enum
- assigned by the C++ compiler.
-
- Fixed in 1.33MR1.
-
-#7. (Version 1.32b4/6-Mar-95) C++ does not imply __STDC__
-
- In err.h the combination of # directives assumes that a C++
- compiler has __STDC__ defined. This is not necessarily true.
-
- This problem also appears in the use of __USE_PROTOS which
- is appropriate for both Standard C and C++ in antlr/gen.c
- and antlr/lex.c
-
- Fixed in 1.33MR1.
-
-#6. (Version 1.32 ?/15-Feb-95) Name conflict for "TokenType"
-
- Already fixed in 1.33.
-
-#5. (23-Jan-95) Douglas_Cuthbertson.JTIDS@jtids_qmail.hanscom.af.mil
-
- The fail action following a semantic predicate is not enclosed in
- "{...}". This can lead to problems when the fail action contains
- more than one statement.
-
- Fixed in 1.33MR1.
-
-#4 . (Version 1.33/31-Mar-96) jlilley@empathy.com (John Lilley)
-
- Put briefly, a semantic predicate ought to abort a guess if it fails.
-
- Correction suggested by J. Lilley has been added to 1.33MR1.
-
-#3 . (Version 1.33) P.A.Keller@bath.ac.uk
-
- Extra commas are placed in the K&R style argument list for rules
- when using both exceptions and ASTs.
-
- Fixed in 1.33MR1.
-
-#2. (Version 1.32b6/2-Oct-95) Brad Schick <schick@interaccess.com>
-
- Construct #[] generates zzastnew() in C++ mode.
-
- Already fixed in 1.33.
-
-#1. (Version 1.33) Bob Bailey (robert@oakhill.sps.mot.com)
-
- Previously, config.h assumed that all PC systems required
- "short" file names. The user can now override that
- assumption with "#define LONGFILENAMES".
-
- Added to 1.33MR1.
|