Using boost wave - c++

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.