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Preprocess Verilog files

Verilog::Preproc - Preprocess Verilog files


Verilog::Preproc - Preprocess Verilog files


    use Verilog::Getopt;

    my $vp = Verilog::Preproc->new(I<parameters>);


    my $line = $vp->getline();


    # This is a complete verilog pre-parser!

    # For a command line version, see vppp

    use Verilog::Getopt;

    use Verilog::Preproc;

    my $opt = new Verilog::Getopt;

    @ARGV = $opt->parameter(@ARGV);

    my $vp = Verilog::Preproc->new(options=>$opt,);


    while (defined (my $line = $vp->getline())) {

       print $line;



Verilog::Preproc reads Verilog files, and preprocesses them according to the SystemVerilog 2005 specification. Programs can be easily converted from reading a IO::File into reading preprocessed output from Verilog::Preproc.

See the ``Which Package'' section of the Verilog::Language manpage if you are unsure which parsing package to use for a new application.


Returns true at the end of the file.

Returns the filename of the most recently returned getline(). May not match the filename passed on the command line, as `line directives are honored.

Return the next line of text. Returns undef at EOF. (Just like IO::File->getline().)

Returns the line number of the last getline(). Note that the line number may change several times between getline(), for example when traversing multiple include files.

Creates a new preprocessor. See the PARAMETERS section for the options that may be passed to new.

Opens the specified file. If called before a file is completely parsed, the new file will be parsed completely before returning to the previously open file. (As if it was an include file.)

Open may also be called without named parameters, in which case the only argument is the filename.

Insert text into the input stream at the given point. The text will not be parsed, just returned to the application. This lets comment() callbacks insert special code into the output stream.


The following named parameters may be passed to the new constructor.

With include_open_nonfatal set to one, ignore any include files that do not exist.

With keep_comments set to zero, strip all comments. When set to one (the default), insert comments in output streams. When set to 'sub', call the comment() function so that meta-comments can be processed outside of the output stream. Note that some programs use meta-comments to embed useful information (synthesis and lint), so use this with caution if feeding to tools other than your own. Defaults to 1.

With keep_whitespace set to zero, compress all whitespace to a single space or newline. When set to one (the default), retain whitespace. Defaults to 1.

With line_directives set to zero, suppress ```line'' comments which indicate filename and line number changes. Use the lineno() and filename() methods instead to retrieve this information. Defaults true.

options=>Verilog::Getopt object
Specifies the object to be used for resolving filenames and defines. Other classes may be used, as long as their interface matches that of Getopt.

With pedantic set, rigorously obey the Verilog pedantic. This disables the `__FILE__ and `__LINE__ features, and may disable other features that are not specified in the language pedantic. Defaults false.


Default callbacks are implemented that are suitable for most applications. Derived classes may override these callbacks as needed.

Called with each comment, when keep_comments=>'sub' is used. Defaults to do nothing.

Called with each `undef. Defaults to use options object.

$self->define(defname, value, params)
Called with each `define. Defaults to use options object.

Called to determine if the define exists. Return true if the define exists, or argument list with leading parenthesis if the define has arguments. Defaults to use options object.

Called to return value to substitute for specified define. Defaults to use options object.

Called on errors, with the error message as an argument. Defaults to die.

Specifies a include file has been found. Defaults to call $self->open after resolving the filename with the options parameter.


The preprocessor supports the constructs defined in the Verilog 2005 and SystemVerilog 2005 standards.

Verilog::Preproc adds the following features (unless the pedantic parameter is set.):

`__FILE__ will be replaced by the current filename. (Like C++ __FILE__.)

`__LINE__ will be replaced by the current line number. (Like C++ __LINE__.)

`error ``string''
`error will be reported whenever it is encountered. (Like C++ #error.)

These are useful for error macros, similar to assert() in C++.


Verilog-Perl is part of the free Verilog EDA software tool suite. The latest version is available from CPAN and from

Copyright 2000-2007 by Wilson Snyder. This package is free software; you can redistribute it and/or modify it under the terms of either the GNU Lesser General Public License or the Perl Artistic License.


Wilson Snyder <>


Verilog-Perl, the Verilog::Language manpage, the Verilog::Getopt manpage

the IO::File manpage

This package is layered on a C++ interface which may be found in the kit.