Using boost wave

Question

I'm trying to get my head around boost wave, and so far, I'm not having much luck.

I tried the sample code from the site. It is below:

#include <iostream>
#include <iomanip>
#include <fstream>
#include <string>
#include <vector>

///////////////////////////////////////////////////////////////////////////////
//  Include Wave itself
#include <boost/wave.hpp>

///////////////////////////////////////////////////////////////////////////////
// Include the lexer stuff
#include <boost/wave/cpplexer/cpp_lex_token.hpp>    // token class
#include <boost/wave/cpplexer/cpp_lex_iterator.hpp> // lexer class

int main () {
    // The following preprocesses a given input file.
    // Open the file and read it into a string variable
    std::ifstream instream("lex_infile");
    std::string input(
        std::istreambuf_iterator<char>(instream.rdbuf()),
        std::istreambuf_iterator<char>());

    // The template boost::wave::cpplexer::lex_token<> is the  
    // token type to be used by the Wave library.
    // This token type is one of the central types throughout 
    // the library, because it is a template parameter to some 
    // of the public classes and templates and it is returned 
    // from the iterators.
    // The template boost::wave::cpplexer::lex_iterator<> is
    // the lexer iterator to use as the token source for the
    // preprocessing engine. In this case this is parametrized
    // with the token type.
    typedef boost::wave::cpplexer::lex_iterator<
            boost::wave::cpplexer::lex_token<> >
        lex_iterator_type;
    typedef boost::wave::context<
            std::string::iterator, lex_iterator_type>
        context_type;

    context_type ctx(input.begin(), input.end(), "lex_infile");

    // At this point you may want to set the parameters of the
    // preprocessing as include paths and/or predefined macros.
        //ctx.add_include_path("...");
        //ctx.add_macro_definition(...);

    // Get the preprocessor iterators and use them to generate 
    // the token sequence.
    context_type::iterator_type first = ctx.begin();
    context_type::iterator_type last = ctx.end();

    std::cout << "HERE" << std::endl;

    // The input stream is preprocessed for you during iteration
    // over [first, last)
        while (first != last) {
            std::cout << (*first).get_value() << std::endl;
            ++first;
        }
}

It compiles ok, but when I feed a file into it, I get the following error:

terminate called after throwing an instance of 'boost::exception_detail::clone_impl >'
what(): boost::wave::preprocess_exception
Aborted

The code I'm trying to 'preprocess' is in a file called lex_infile, with the following contents:

#include <oglre>
#include <light>
#include <material>

in vec3 in_Position;
in vec2 in_Texture;
in vec3 in_Normal;

out vec2 textureCoord;
out vec4 pass_Color;




void main() {
    gl_Position = pvmMatrix * vec4(in_Position, 1.0);

    textureCoord = in_Texture;


    vec3 normalDirection = normalize(normalMatrix * in_Normal);
    vec3 lightDirection = normalize(vec3(lightSources[0].direction));

    vec3 diffuseReflection = vec3(lightSources[0].diffuse) * vec3(mymaterial.diffuse) * max(0.0, dot(normalDirection, lightDirection));

    /*
    float bug = 0.0;
    bvec3 result = equal( diffuseReflection, vec3(0.0, 0.0, 0.0) );
    if(result[0]) bug = 1.0;

    diffuseReflection.x += bug;
    */

    pass_Color = vec4(diffuseReflection, 1.0);
}

I imagine I need to define the include locations....how would i even do that?

Sorry if this is simple stuff, I'm just a little lost.

Answer 1

Figured it out.

I need to extend the class public wave::context_policies::default_preprocessing_hooks, and then override the method found_unknown_directive.

Once that was done, I needed to pass my new preprocessing hooks class into typedef boost::wave::context as a template parameter.

It looks like this:

typedef boost::wave::context<
                std::string::iterator, 
                lex_iterator_type,
                load_file_to_string,
                custom_directives_hooks
            > context_type;

and

class custom_directives_hooks
:   public wave::context_policies::default_preprocessing_hooks
{
public:

    template <typename ContextT, typename ContainerT>
    bool
    found_unknown_directive(ContextT const& ctx, ContainerT const& line, 
        ContainerT& pending)
    {
        typedef typename ContainerT::const_iterator iterator_type;
        iterator_type it = line.begin();
        wave::token_id id = wave::util::impl::skip_whitespace(it, line.end());

        if (id != wave::T_IDENTIFIER)
            return false;       // nothing we could do

        if (it->get_value() == "version" || it->get_value() == "extension") {
            // Handle #version and #extension directives
            std::copy(line.begin(), line.end(), std::back_inserter(pending));
            return true;
        }

        if (it->get_value() == "type") {
            // Handle type directive
            return true;
        }

        // Unknown directive
        return false;
    }
};

Hope that helps anyone else having this problem.