"""Implements the main interface for flow graph creation: build_flow().

"""

from inspect import CO_NEWLOCALS, isgeneratorfunction

from rpython.flowspace.model import checkgraph

from rpython.flowspace.bytecode import HostCode

from rpython.flowspace.flowcontext import (FlowContext, fixeggblocks)

from rpython.flowspace.generator import (tweak_generator_graph,

make_generator_entry_graph)

from rpython.flowspace.pygraph import PyGraph

def _assert_rpythonic(func):

"""Raise ValueError if ``func`` is obviously not RPython"""

try:

func.func_code.co_cellvars

except AttributeError:

raise ValueError("%r is not RPython: it is likely an unexpected "

"built-in function or type" % (func,))

if getattr(func, "_not_rpython_", False):

raise ValueError("%r is tagged as @not_rpython" % (func,))

if func.func_doc and func.func_doc.lstrip().startswith('NOT_RPYTHON'):

raise ValueError("%r is tagged as NOT_RPYTHON" % (func,))

if func.func_code.co_cellvars:

raise ValueError(

"""RPython functions cannot create closures

Possible causes:

Function is inner function

Function uses generator expressions

Lambda expressions

in %r""" % (func,))

if not (func.func_code.co_flags & CO_NEWLOCALS):

raise ValueError("The code object for a RPython function should have "

"the flag CO_NEWLOCALS set.")

def build_flow(func):

"""

Create the flow graph (in SSA form) for the function.

"""

_assert_rpythonic(func)

if (isgeneratorfunction(func) and

not hasattr(func, '_generator_next_method_of_')):

return make_generator_entry_graph(func)

code = HostCode._from_code(func.func_code)

graph = PyGraph(func, code)

ctx = FlowContext(graph, code)

ctx.build_flow()

fixeggblocks(graph)

if code.is_generator:

tweak_generator_graph(graph)

return graph