Date: Mon, 21 Mar 2005 17:06:20 +0100 From: =?ISO-8859-1?Q?Ra=FAl_Izquierdo_Castanedo?= <raul.izquierdo@gmail.com> To: davidxu@viatech.com.cn, ports@FreeBSD.org Subject: FreeBSD Port: byaccj-1.1 Message-ID: <f2e121f505032108067a20bddf@mail.gmail.com>
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Hello,
I'm Ra=FAl, Professor at University of Oviedo (Spain) where I teach
Compiler Construction.
After using PCLex/Pcyacc during many years I decided to change them
and after checking several tools I decided to use byaccJ.
I write you because I think something goes wrong when generating the
parser in Java (no problem in C++).
First of all I assure you that I've tried to solve the problem for myself:
- I have checked the samples generating C/C++ with byacc and with
other LR tools. All of them where right with the same input grammar
except ByaccJ.
- I've searched in Google for a solution. Nothing found.
=BFCould this be a bug?
-------------
1) The first sample is (I include a ZIP with complete files to run)
inicio: expr { System.out.println($1.ival); }
;
expr: '+' CTE expr { $$.ival =3D $2.ival + $3.ival; }
| {$$.ival =3D 0; }
;
When I run it a "Null pointer exception" is throw. When it tries to
access the stack to get the semantic values ($n) it seems to get a
null pointer from the stack.
---------------------
2) The second sample is:
inicio: expr { System.out.println($1.ival); }
;
expr: CTE moreTerms { $$.ival =3D $1.ival + $2.ival; }
;
moreTerms: '+' CTE moreTerms { $$.ival =3D $2.ival + $3.ival;
System.out.println($2 =3D=3D $3); }
| { $$.ival =3D 0; }
;
I think it's another view of the same bug. Now the program runs
without exceptions, but the final result is wrong. There is a problem
with the $s.
Sometimes $2 and $3 reference the same ParserVal instance (see the
System.out.println($2 =3D=3D $3) ).
Could you please help me? If I don't find a solution I will have to
select another tool and I think it byaccJ is the best.
Thanks in advance
Ra=FAl
Ps: I assure you that this translation from spanish hasn't been made
automatically by Google. ;)
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