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Subject: Re: [OMPI devel] flex warning from flex-2.5.4
From: Paul H. Hargrove (PHHargrove_at_[hidden])
Date: 2012-02-20 18:36:12


Ralph,

The change below removes the warning, but very slightly changes the
syntax that is parsed.
In the original, anything following the "[tag]" was considered trailing
context.
However that made inputs like "[tag]foo]" ambiguous to the parser (hence
the warning).
With the change below, both "]" will be in the matched string.
I am pretty sure that shouldn't ever happen in valid inputs anyway.
NOTE: I've not yet actually tested the resulting show_help utility [but
soon].

-Paul

Index: opal/util/show_help_lex.l
===================================================================
--- opal/util/show_help_lex.l (revision 25974)
+++ opal/util/show_help_lex.l (working copy)
@@ -62,7 +62,7 @@

  #.*\n ; /* comment line */

-^\[.+\]/.*\n { BEGIN(CHOMP); return OPAL_SHOW_HELP_PARSE_TOPIC; }
+^\[.+\]/[^\]\n]*\n { BEGIN(CHOMP); return OPAL_SHOW_HELP_PARSE_TOPIC; }

<CHOMP>.*\n { BEGIN(INITIAL); }

On 2/20/2012 3:26 PM, Ralph Castain wrote:
> My bad - didn't look closely enough. I'll take a look at it and see if there is anything we can do.
>
> On Feb 20, 2012, at 4:12 PM, Paul H. Hargrove wrote:
>
>> Ralph,
>>
>> Are you sure this is a flex-generated file?
>> I am looking at opal/util/show_help_lex.l in the svn trunk and it certainly looks human-generated to me.
>> Please clue me in if I am missing something.
>>
>> The warning is from flex when processing the .l file, NOT from the compilation of the flex-generated .c file.
>>
>> -Paul
>>
>> On 2/19/2012 7:55 PM, Ralph Castain wrote:
>>> We get that everywhere, unfortunately - it comes from flex and is outside our control as the file it complains about is actually generated by flex itself. Unfortunately, flex is no longer maintained, and so nothing has been done to correct it.
>>>
>>>
>>> On Feb 19, 2012, at 8:47 PM, Paul H. Hargrove wrote:
>>>
>>>> I've not checked any other systems, but building the trunk on OpenBSD and FreeBSD (w/ flex-2.5.4) I see the following:
>>>>> LEX show_help_lex.c
>>>>> "[srcdir]/opal/util/show_help_lex.l", line 65: warning, dangerous trailing context
>>>> I found this message in the flex documentation, and it mentions that the POSIX draft for LEX leaves such cases undefined.
>>>> http://flex.sourceforge.net/manual/Limitations.html
>>>>
>>>> -Paul
>>>>
>>>> --
>>>> Paul H. Hargrove PHHargrove_at_[hidden]
>>>> Future Technologies Group
>>>> HPC Research Department Tel: +1-510-495-2352
>>>> Lawrence Berkeley National Laboratory Fax: +1-510-486-6900
>>>>
>>>> _______________________________________________
>>>> devel mailing list
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>>>> http://www.open-mpi.org/mailman/listinfo.cgi/devel
>>> _______________________________________________
>>> devel mailing list
>>> devel_at_[hidden]
>>> http://www.open-mpi.org/mailman/listinfo.cgi/devel
>> --
>> Paul H. Hargrove PHHargrove_at_[hidden]
>> Future Technologies Group
>> HPC Research Department Tel: +1-510-495-2352
>> Lawrence Berkeley National Laboratory Fax: +1-510-486-6900
>>
>> _______________________________________________
>> devel mailing list
>> devel_at_[hidden]
>> http://www.open-mpi.org/mailman/listinfo.cgi/devel
>
> _______________________________________________
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> devel_at_[hidden]
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-- 
Paul H. Hargrove                          PHHargrove_at_[hidden]
Future Technologies Group
HPC Research Department                   Tel: +1-510-495-2352
Lawrence Berkeley National Laboratory     Fax: +1-510-486-6900