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------------------------------------------------------------
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The primary purpose for MR12 is to make quite clear that MR11 is
obsolete and to fix the bug related to predicate expressions.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 is 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 isTypeName() isn't on the leading edge
of typeName, so it 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.