python + pythran spec -> c++ code
    returns a PythonModule object and an error checker

    the error checker can be used to print more detailed info on the origin of
    a compile error (e.g. due to bad typing)

def generate_cxx(module_name, code, specs=None, optimizations=None,
                 module_dir=None):
    '''python + pythran spec -> c++ code
    returns a PythonModule object and an error checker

    the error checker can be used to print more detailed info on the origin of
    a compile error (e.g. due to bad typing)

    '''

    pm, ir, renamings, docstrings = front_middle_end(module_name, code,
                                                     optimizations, module_dir)

    # back-end
    content = pm.dump(Cxx, ir)

    # instantiate the meta program
    if specs is None:

        class Generable(object):
            def __init__(self, content):
                self.content = content

            def __str__(self):
                return str(self.content)

            generate = __str__

        mod = Generable(content)

        def error_checker():
            tog.typecheck(ir)

    else:

        # uniform typing
        if isinstance(specs, dict):
            specs = Spec(specs, {})

        def error_checker():
            types = tog.typecheck(ir)
            check_specs(specs, renamings, types)

        specs.to_docstrings(docstrings)
        check_exports(ir, specs, renamings)

        if isinstance(code, bytes):
            code_bytes = code
        else:
            code_bytes = code.encode('ascii', 'ignore')
        metainfo = {'hash': hashlib.sha256(code_bytes).hexdigest(),
                    'version': __version__,
                    'date': datetime.now()}

        mod = PythonModule(module_name, docstrings, metainfo)
        mod.add_to_includes(
            Include("pythonic/core.hpp"),
            Include("pythonic/python/core.hpp"),
            # FIXME: only include these when needed
            Include("pythonic/types/bool.hpp"),
            Include("pythonic/types/int.hpp"),
            Line("#ifdef _OPENMP\n#include <omp.h>\n#endif")
        )
        mod.add_to_includes(*[Include(inc) for inc in
                              _extract_specs_dependencies(specs)])
        mod.add_to_includes(*content.body)
        mod.add_to_includes(
            Include("pythonic/python/exception_handler.hpp"),
        )

        def warded(module_name, internal_name):
            return pythran_ward + '{0}::{1}'.format(module_name, internal_name)

        for function_name, signatures in specs.functions.items():
            internal_func_name = renamings.get(function_name,
                                               function_name)
            # global variables are functions with no signatures :-)
            if not signatures:
                mod.add_global_var(function_name,
                                   "{}()()".format(warded(module_name,
                                                          internal_func_name)))

            for sigid, signature in enumerate(signatures):
                numbered_function_name = "{0}{1}".format(internal_func_name,
                                                         sigid)
                arguments_types = [pytype_to_ctype(t) for t in signature]
                arguments_names = HasArgument(internal_func_name).visit(ir)
                arguments = [n for n, _ in
                             zip(arguments_names, arguments_types)]
                name_fmt = pythran_ward + "{0}::{1}::type{2}"
                args_list = ", ".join(arguments_types)
                specialized_fname = name_fmt.format(module_name,
                                                    internal_func_name,
                                                    "<{0}>".format(args_list)
                                                    if arguments_names else "")
                result_type = "typename %s::result_type" % specialized_fname
                mod.add_pyfunction(
                    FunctionBody(
                        FunctionDeclaration(
                            Value(
                                result_type,
                                numbered_function_name),
                            [Value(t + '&&', a)
                             for t, a in zip(arguments_types, arguments)]),
                        Block([Statement("""
                            PyThreadState *_save = PyEval_SaveThread();
                            try {{
                                auto res = {0}()({1});
                                PyEval_RestoreThread(_save);
                                return res;
                            }}
                            catch(...) {{
                                PyEval_RestoreThread(_save);
                                throw;
                            }}
                            """.format(warded(module_name,
                                              internal_func_name),
                                       ', '.join(arguments)))])
                    ),
                    function_name,
                    arguments_types,
                    signature
                )

        for function_name, signature in specs.capsules.items():
            internal_func_name = renamings.get(function_name,
                                               function_name)

            arguments_types = [pytype_to_ctype(t) for t in signature]
            arguments_names = HasArgument(internal_func_name).visit(ir)
            arguments = [n for n, _ in
                         zip(arguments_names, arguments_types)]
            name_fmt = pythran_ward + "{0}::{1}::type{2}"
            args_list = ", ".join(arguments_types)
            specialized_fname = name_fmt.format(module_name,
                                                internal_func_name,
                                                "<{0}>".format(args_list)
                                                if arguments_names else "")
            result_type = "typename %s::result_type" % specialized_fname
            docstring = spec_to_string(function_name, signature)
            mod.add_capsule(
                FunctionBody(
                    FunctionDeclaration(
                        Value(result_type, function_name),
                        [Value(t, a)
                         for t, a in zip(arguments_types, arguments)]),
                    Block([ReturnStatement("{0}()({1})".format(
                        warded(module_name, internal_func_name),
                        ', '.join(arguments)))])
                ),
                function_name,
                docstring
            )

    return mod, error_checker