[antlr-interest] ANTLR Option warnWhenFollowAmbig

[Terence Parr]

Hi David,

If you are certain that there is no problem, you can use the option 
that shuts all warnings off.  Perhaps you should try "greedy=true" 
instead.

Ter

On Wednesday, December 18, 2002, at 08:50  AM, David Wigg wrote:

> We have been converting a grammar file from using PCCTS to using
> ANTLR 2.7.1.
>
> I am now trying to remove ALL warnings resulting from generation
> of the grammar file, but I don't seem to be able to get rid of
> the one shown below using "options {warnWhenFollowAmbig =
> false;}:" in class_specifier rule shown below.
>
> As you will see, I have replaced "#pragma approx" outside the
> brackets with "options {warnWhenFollowAmbig = false;}:" within
> the brackets which seems to work elsewhere.
>
> However, having read
> http://www.antlr.org/doc/options.html#warnWhenFollowAmbig
> I am beginning to wonder if it is always possible to turn
> unwanted warnings off as it may depend on the structure of the
> rule. I hope not, as I think we should be able to remove all
> unwanted warnings.
>
> Please could someone clarify the situation and, if at all
> possible, let me know how I could get this warning turned off.
>
> Thanks.
>
> David.
>
> CPP_parser.g:697: warning: nondeterminism upon
> CPP_parser.g:697: 	k==1:ID
> CPP_parser.g:697: 	k==2:COLON
> CPP_parser.g:697: 	between alts 1 and 3 of block
>
> class_specifier[DeclSpecifier ds] returns
> [CPPParser::TypeSpecifier ts]
> {char *saveClass;}
> 	:	("struct"	{ts=tsSTRUCT;}
> 		|"union"	{ts=tsUNION;}
> 		|"class" 	{ts=tsCLASS;classDefinition= 1;in_class_def = true;}
> 		)
> 		//#pragma approx // indicate that ambig between alts 1 and 3 is ok
> 		(options {warnWhenFollowAmbig = false;}:
> 			(id:ID
> 			{saveClass = enclosingClass;
> 			enclosingClass =
> symbols->strdup(const_cast<char*>((id->getText()).data()));
> 			}
> 			( base_clause )?
> 			LCURLY	
> 			{beginClassDefinition(ts, (id->getText()).data());
> in_class_def = true;}
> 			(member_declaration)*
> 			{endClassDefinition();in_class_def = false;}
> 			RCURLY
> 			{enclosingClass = saveClass;struct_flag = 1;}
> 			)
> 		|
> 			(LCURLY	
> 			{saveClass = enclosingClass; enclosingClass = "__anonymous";}
> 			{beginClassDefinition(ts, "anonymous");}
> 			(member_declaration)*
> 			{endClassDefinition();}
> 			RCURLY
> 			{enclosingClass = saveClass;struct_flag = 1;}
> 			)
> 		|	(
> 			tag:ID
> 			(options {warnWhenFollowAmbig = false;}:
> 			LESSTHAN template_argument_list GREATERTHAN
> 			)?
> 			{id_type = ID_VAR_NAME; // DW 3/4/01
> 			classForwardDeclaration(ts, ds, (tag->getText()).data());
> 			})
> 		)
> 	;
>
>
>
>
>
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>
--
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Creator, ANTLR Parser Generator: http://www.antlr.org
Lecturer in Comp. Sci., University of San Francisco


 

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