So, this works to set RD_TRACE:
perl -MParse::RecDescent -s - -RD_TRACE grammar NewMakepp::Grammar
Unfortunately, it looks like the path taken by the precompilation fails to
actually check for undefined rules. This may be a bug, or may have been
intentional, I'll have to follow up with Damian.
Even if this were fixed, I'm not sure how useful the '-s' command line option
is, as -RD_AUTOSTUB will set $::RD_AUTOSTUB to '1'. An undocumented feature of
$::RD_AUTOSTUB is that if it has a boolean-true value, an undefined rule named
'foo' will not get the production
foo: 'foo'
but instead get the production:
foo: $::RD_AUTOSTUB
Which, for -s -RD_AUTOSTUB, will generate:
foo: '1'
1: '1'
Which probably isn't what you wanted in the first place.
Long story short, RD_AUTOSTUB doesn't currently work with precompilation of
parsers. You'll have to either not precompile, or define your own stub
productions.
Please file a ticket for this issue. I'm out of town for the next week, but
will try to get this into a bugfix release next week. I've included details on
the issue below, feel free to include them in the bug. You can find the ticket
tracker for Parse::RecDescent here:
https://rt.cpan.org/Public/Dist/Display.html?Name=Parse-RecDescent
Note that this isn't unique to the command line, but appears to be a problem with the Precompile method. The callstack is something like:
script: Parse::RecDescent->Precompile($grammar, $class, $sourcefile)
Precompile: $self = Parse::RecDescent->new($grammar,1,$class)
new: $self->Replace($grammar, 1, $class)
Replace: _generate($self, $grammar, 1(fromsplice), 1, $class);
_generate: my ($self, $grammar, $replace, $isimplicit, $isleftop) =
(@_, 0);
So, the '1' added to @_ from Precompile in the call to new() ends up becoming
$isimplicit.
$isimplicit prevents $self->_check_grammar() from being called, which is the
function that does the RD_AUTOSTUB checking/generation. I'll have to look into
why _check_grammar is skipped for $isimplicit cases.
There also appears to be another bug here, where the $class parameter gets
incorrectly propagated from Precompile into $isleftop inside of _generate,
which is probably not correct. Unless I've misread the code somewhere.
On 1/12/2012 10:01 AM, Yuri Shtil wrote:
Well, I found as much myself, tried all I could and it did not work.
-----Original Message-----
From: jtbr...@cpan.org [mailto:jtbr...@cpan.org]
Sent: Thursday, January 12, 2012 9:53 AM
To: recdescent@perl.org
Subject: Re: How to build parser with autostubbing
Consult the section on '-s' at http://perldoc.perl.org/perlrun.html:
-s
enables rudimentary switch parsing for switches on the command line
after the program name but before any filename arguments (or before
an argument of --). Any switch found there is removed from @ARGV and
sets the corresponding variable in the Perl program. The following
program prints "1" if the program is invoked with a -xyz switch, and
"abc" if it is invoked with -xyz=abc.
#!/usr/bin/perl -s
if ($xyz) { print "$xyz\n" }
Do note that a switch like --help creates the variable ${-help} ,
which is not compliant with use strict "refs" . Also, when using
this option on a script with warnings enabled you may get a lot of
spurious "used only once" warnings.
So this is probably what you want:
perl -MParse::RecDescent -s -RD_AUTOSTUB - grammar NewMakepp::Grammar
Untested, you may need to move -s, '-RD_AUTOSTUB and the '- grammar ...'
arguments around to make it work.
On 1/12/2012 9:39 AM, Yuri Shtil wrote:
The documentation is a little unclear
I use perl -MParse::RecDescent - grammar NewMakepp::Grammar to create a parser
module.
What do I do in order to generate stubs for undefined rules?
How do I pass RD_AUTOSTUB?
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