emscripten and boost library: how to compile existing project for webassembly?

Question

I have an existing project written on C++ that I would like to compile for webassembly using emscripten. The code calls boost library:

#include <boost/program_options.hpp>

#include <iostream>
#include <string>
#include <exception>
#include <algorithm>
#include <iterator>
#include <boost/filesystem/fstream.hpp>
#include <boost/filesystem/exception.hpp>
#include <boost/filesystem/convenience.hpp>
#include <boost/thread/thread.hpp>
#include <boost/lexical_cast.hpp>
#include <boost/assign.hpp>

I have compiled the necessary parts of boost library using emscripten as static libraries and converted them from bc to a-files using emar. Now I'm trying to compile the project feeding the compiler with the precompiled libraries: (part of Makefile)

C_OPTIONS= -O3 -DNDEBUG -g \
           /home/hiisi/workspace/boost_libs/program_options/build/emscripten-1.38.38/release/link-static/threading-multi/libs/cmdline.bc.a \
           /home/hiisi/workspace/boost_libs/program_options/build/emscripten-1.38.38/release/link-static/threading-multi/libs/config_file.bc.a \
           /home/hiisi/workspace/boost_libs/program_options/build/emscripten-1.38.38/release/link-static/threading-multi/libs/convert.bc.a \
           /home/hiisi/workspace/boost_libs/program_options/build/emscripten-1.38.38/release/link-static/threading-multi/libs/libboost_program_options.bc.a \

However make still complains on the very first occurrence of boost in the code:

main.cpp:1:10: fatal error: 'boost/program_options.hpp' file not found
#include <boost/program_options.hpp>
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.
shared:ERROR: compiler frontend failed to generate LLVM bitcode, halting

The question may sound little bit naive, but how do I correctly do this? The project compiles perfectly fine with g++, but not em++

Answer 1

You have to add the include directories to use boost.

That would be an argument that look like this:

... -I/home/hiisi/workspace/boost_libs/include ...

Answer 2

All I had to do is to make sure that boost lib presents in emscripten include directory. In my case that was emsdk/fastcomp/emscripten/system/include/ I made a symlink to system' boost library there and everything worked like a charm.