Add "nogil" option for BOOST_PYTHON_MODULE_INIT.

Implement optional arguments for BOOST_PYTHON_MODULE_INIT and allow the
boost::python::mod_gil_not_used() option.  This sets the
Py_MOD_GIL_NOT_USED flag for the extension module.

To define a module that supports free-threaded Python, define it
like this:

    BOOST_PYTHON_MODULE(my_module, boost::python::mod_gil_not_used())
    {
        ...
    }

include/boost/python/module_init.hpp

@@ -11,11 +11,41 @@
 
 # ifndef BOOST_PYTHON_MODULE_INIT
 
-namespace boost { namespace python { namespace detail {
+namespace boost { namespace python {
+
+#ifdef HAS_CXX11
+// Use to activate the Py_MOD_GIL_NOT_USED flag.
+class mod_gil_not_used {
+public:
+    explicit mod_gil_not_used(bool flag = true) : flag_(flag) {}
+    bool flag() const { return flag_; }
+
+private:
+    bool flag_;
+};
+
+namespace detail {
+
+inline bool gil_not_used_option() { return false; }
+template <typename F, typename... O>
+bool gil_not_used_option(F &&, O &&...o);
+template <typename... O>
+inline bool gil_not_used_option(mod_gil_not_used f, O &&...o) {
+    return f.flag() || gil_not_used_option(o...);
+}
+template <typename F, typename... O>
+inline bool gil_not_used_option(F &&, O &&...o) {
+    return gil_not_used_option(o...);
+}
+
+}
+#endif // HAS_CXX11
+
+namespace detail {
 
 #  if PY_VERSION_HEX >= 0x03000000
 
-BOOST_PYTHON_DECL PyObject* init_module(PyModuleDef&, void(*)());
+BOOST_PYTHON_DECL PyObject* init_module(PyModuleDef&, void(*)(), bool gil_not_used = false);
 
 #else
 
@@ -27,7 +57,37 @@ BOOST_PYTHON_DECL PyObject* init_module(char const* name, void(*)());
 
 #  if PY_VERSION_HEX >= 0x03000000
 
-#   define _BOOST_PYTHON_MODULE_INIT(name) \
+#   ifdef HAS_CXX11
+#    define _BOOST_PYTHON_MODULE_INIT(name, ...) \
+  PyObject* BOOST_PP_CAT(PyInit_, name)()  \
+  { \
+    static PyModuleDef_Base initial_m_base = { \
+        PyObject_HEAD_INIT(NULL) \
+        0, /* m_init */ \
+        0, /* m_index */ \
+        0 /* m_copy */ };  \
+    static PyMethodDef initial_methods[] = { { 0, 0, 0, 0 } }; \
+ \
+    static struct PyModuleDef moduledef = { \
+        initial_m_base, \
+        BOOST_PP_STRINGIZE(name), \
+        0, /* m_doc */ \
+        -1, /* m_size */ \
+        initial_methods, \
+        0,  /* m_reload */ \
+        0, /* m_traverse */ \
+        0, /* m_clear */ \
+        0,  /* m_free */ \
+    }; \
+ \
+    return boost::python::detail::init_module( \
+        moduledef, BOOST_PP_CAT(init_module_, name), \
+        boost::python::detail::gil_not_used_option(__VA_ARGS__) ); \
+  } \
+  void BOOST_PP_CAT(init_module_, name)()
+
+#   else // !HAS_CXX11
+#    define _BOOST_PYTHON_MODULE_INIT(name) \
   PyObject* BOOST_PP_CAT(PyInit_, name)()  \
   { \
     static PyModuleDef_Base initial_m_base = { \
@@ -53,6 +113,7 @@ BOOST_PYTHON_DECL PyObject* init_module(char const* name, void(*)());
         moduledef, BOOST_PP_CAT(init_module_, name) ); \
   } \
   void BOOST_PP_CAT(init_module_, name)()
+#   endif // HAS_CXX11
 
 #  else
 
@@ -66,9 +127,15 @@ BOOST_PYTHON_DECL PyObject* init_module(char const* name, void(*)());
 
 #  endif
 
-#  define BOOST_PYTHON_MODULE_INIT(name)                       \
+#  ifdef HAS_CXX11
+#   define BOOST_PYTHON_MODULE_INIT(name, ...)                  \
+  void BOOST_PP_CAT(init_module_,name)();                      \
+extern "C" BOOST_SYMBOL_EXPORT _BOOST_PYTHON_MODULE_INIT(name, __VA_ARGS__)
+#  else
+#   define BOOST_PYTHON_MODULE_INIT(name)                       \
   void BOOST_PP_CAT(init_module_,name)();                      \
 extern "C" BOOST_SYMBOL_EXPORT _BOOST_PYTHON_MODULE_INIT(name)
+#  endif // HAS_CXX11
 
 # endif
 

src/module.cpp

@@ -38,11 +38,12 @@ BOOST_PYTHON_DECL void scope_setattr_doc(char const* name, object const& x, char
 
 #if PY_VERSION_HEX >= 0x03000000
 
-BOOST_PYTHON_DECL PyObject* init_module(PyModuleDef& moduledef, void(*init_function)())
+BOOST_PYTHON_DECL PyObject* init_module(PyModuleDef& moduledef,
+    void(*init_function)(), bool gil_not_used)
 {
     PyObject *mod = PyModule_Create(&moduledef);
 #ifdef Py_GIL_DISABLED
-    if (mod != NULL) {
+    if (mod != NULL && gil_not_used) {
         PyUnstable_Module_SetGIL(mod, Py_MOD_GIL_NOT_USED);
     }
 #endif

test/fabscript

@@ -68,6 +68,7 @@ for t in [('injected',),
           ('raw_ctor',),
           ('exception_translator',),
           ('module_init_exception',),
+          ('module_nogil',),
           ('test_enum', ['enum_ext']),
           ('test_cltree', ['cltree']),
           ('newtest', ['m1', 'm2']),

test/module_nogil.cpp

@@ -0,0 +1,25 @@
+// Test for BOOST_PYTHON_MODULE with optional mod_gil_not_used argument
+
+#include <boost/python/module.hpp>
+#include <boost/python/def.hpp>
+
+// Simple function to export
+int get_value() {
+    return 1234;
+}
+
+#ifdef HAS_CXX11
+// C++11 build: test with mod_gil_not_used option
+BOOST_PYTHON_MODULE(module_nogil_ext, boost::python::mod_gil_not_used())
+{
+    using namespace boost::python;
+    def("get_value", get_value);
+}
+#else
+// C++98 build: test without optional arguments
+BOOST_PYTHON_MODULE(module_nogil_ext)
+{
+    using namespace boost::python;
+    def("get_value", get_value);
+}
+#endif

test/module_nogil.py

@@ -0,0 +1,29 @@
+"""
+>>> from module_nogil_ext import *
+>>> get_value()
+1234
+>>> import sys, sysconfig
+>>> Py_GIL_DISABLED = bool(sysconfig.get_config_var('Py_GIL_DISABLED'))
+>>> if Py_GIL_DISABLED and sys._is_gil_enabled():
+...    print('GIL is enabled and should not be')
+... else:
+...    print('okay')
+okay
+"""
+
+from __future__ import print_function
+
+def run(args = None):
+    import sys
+    import doctest
+
+    if args is not None:
+        sys.argv = args
+    return doctest.testmod(sys.modules.get(__name__))
+
+if __name__ == '__main__':
+    print("running...")
+    import sys
+    status = run()[0]
+    if (status == 0): print("Done.")
+    sys.exit(status)