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gh-86542: New C-APIs to simplify module attribute declaration #23286

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436c1b0
Define module constants in PyModuleDef
tiran Nov 14, 2020
d93f2da
Add PyModule_AddTypeFromSpec
tiran Nov 15, 2020
a1c8240
PyModule_AddNew* helpers
tiran Nov 15, 2020
a277939
Rename new API to PyModuleConst_
tiran Nov 16, 2020
22e4f7f
Use Py_mod_constants instead of PyModuleDef.m_constants
tiran Nov 16, 2020
31f8189
Revert "Use Py_mod_constants instead of PyModuleDef.m_constants"
tiran Nov 16, 2020
366e810
Remove PyModuleDef.m_constants again
tiran Nov 16, 2020
bb41d82
bpo-42376: New C-APIs to simplify module attribute declaration
tiran Nov 16, 2020
751c560
ULong, private types, add module to call
tiran Nov 18, 2020
c34a4df
Add CAPI tests
tiran Nov 18, 2020
3e50f44
Typo
tiran Nov 18, 2020
00236fe
Use single base class feature from bpo-42423
tiran Nov 22, 2020
8458120
It's a strong ref
tiran Nov 22, 2020
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ULong, private types, add module to call
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@tiran
tiran committed Apr 17, 2021
commit 751c560728b1e2f6559fd6c3c7f7be756f8dae1e
20 changes: 14 additions & 6 deletions Doc/c-api/module.rst
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Expand Up @@ -602,7 +602,7 @@ state:
Example::

static PyObject*
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@shihai1991 shihai1991 Nov 26, 2020

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nitpick: static PyObject * in here.

example_call(void *)
example_call(PyObject *module)
{
return PyBytes_FromString("23");
}
Expand All @@ -613,6 +613,7 @@ state:
static PyModuleConst_Def example_constants[] = {
PyModuleConst_None("none_value"),
PyModuleConst_Long("integer", 42),
PyModuleConst_ULong("unsigned", 42UL),
PyModuleConst_Bool("false_value", 0),
PyModuleConst_Bool("true_value", 1),
#ifdef Py_MATH_PI
Expand All @@ -628,7 +629,7 @@ state:
static int
example_init_constants(PyObject *module)
{
return PyModule_AddConstants(module, posix_constants);
return PyModule_AddConstants(module, example_constants);
}

static PyModuleDef_Slot example_slots[] = {
Expand Down Expand Up @@ -667,13 +668,19 @@ state:

.. c:macro:: PyModuleConst_Long(name, value)

Add an entry for an int constant.
Add an entry for an integer constant.

.. versionadded:: 3.10

.. c:macro:: PyModuleConst_Long(name, value)

Add an entry for an unsigned integer constant.

.. versionadded:: 3.10

.. c:macro:: PyModuleConst_Bool(name, value)

Add an entry for a bool constant.
Add an entry for a bool constant. ``0`` is false, ``1`` is true.

.. versionadded:: 3.10

Expand All @@ -689,9 +696,10 @@ state:

.. versionadded:: 3.10

.. c:macro:: PyModuleConst_Call(name, c_function)
.. c:macro:: PyModuleConst_Call(name, func)

Add an entry for a constant as returned by *c_function*.
Add an entry for a constant as returned by callback with signature
``PyObject* (*func)(PyObject *module)``.

.. versionadded:: 3.10

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34 changes: 19 additions & 15 deletions Include/moduleobject.h
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Expand Up @@ -75,40 +75,44 @@ typedef struct PyModuleDef_Slot{
struct PyModuleConst_Def;
#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x03100000
/* New in 3.10 */
enum PyModuleConst_type {
PyModuleConst_none_type = 1,
PyModuleConst_long_type = 2,
PyModuleConst_bool_type = 3,
PyModuleConst_double_type = 4,
PyModuleConst_string_type = 5,
PyModuleConst_call_type = 6,
enum _PyModuleConst_type {
_PyModuleConst_none_type = 1,
_PyModuleConst_long_type = 2,
_PyModuleConst_ulong_type = 3,
_PyModuleConst_bool_type = 4,
_PyModuleConst_double_type = 5,
_PyModuleConst_string_type = 6,
_PyModuleConst_call_type = 7,
};

typedef struct PyModuleConst_Def {
const char *name;
enum PyModuleConst_type type;
enum _PyModuleConst_type type;
union {
const char *m_str;
long m_long;
unsigned long m_ulong;
double m_double;
PyObject* (*m_call)(void);
PyObject* (*m_call)(PyObject *module);
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@vstinner vstinner Nov 23, 2020

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I'm not sure how to make this member future-proof in term of stable ABI.

We should try to put a max_align_t inside, but this type requires C11. GCC defines it with:

typedef struct {
  long long __max_align_ll __attribute__((__aligned__(__alignof__(long long))));
  long double __max_align_ld __attribute__((__aligned__(__alignof__(long double))));
  /* _Float128 is defined as a basic type, so max_align_t must be
     sufficiently aligned for it.  This code must work in C++, so we
     use __float128 here; that is only available on some
     architectures, but only on i386 is extra alignment needed for
     __float128.  */
#ifdef __i386__
  __float128 __max_align_f128 __attribute__((__aligned__(__alignof(__float128))));
#endif
} max_align_t;

Maybe we can at least put long long and long double:

// Unused members added to make PyModuleConst_Def large enough
// to get a stable ABI and support future additions.
long long m_long_long;
long double m_long_double;

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@encukou encukou Nov 24, 2020

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This is the only issue I found here :)
The stable ABI doesn't have a good story around evolving structs, and I think we should design a general mechanism for that rather than try to future-proof individual structs.
To move this PR forward, could we exclude PyModule_AddConstants & co. from the limited API for the time being?

} value;
} PyModuleConst_Def;

PyAPI_FUNC(int) PyModule_AddConstants(PyObject *, PyModuleConst_Def *);

#define PyModuleConst_None(name) \
{(name), PyModuleConst_none_type, {.m_long=0}}
{(name), _PyModuleConst_none_type, {.m_long=0}}
#define PyModuleConst_Long(name, value) \
{(name), PyModuleConst_long_type, {.m_long=(value)}}
{(name), _PyModuleConst_long_type, {.m_long=(value)}}
#define PyModuleConst_ULong(name, value) \
{(name), _PyModuleConst_ulong_type, {.m_ulong=(value)}}
#define PyModuleConst_Bool(name, value) \
{(name), PyModuleConst_bool_type, {.m_long=(value)}}
{(name), _PyModuleConst_bool_type, {.m_long=(value)}}
#define PyModuleConst_Double(name, value) \
{(name), PyModuleConst_double_type, {.m_double=(value)}}
{(name), _PyModuleConst_double_type, {.m_double=(value)}}
#define PyModuleConst_String(name, value) \
{(name), PyModuleConst_string_type, {.m_string=(value)}}
{(name), _PyModuleConst_string_type, {.m_str=(value)}}
#define PyModuleConst_Call(name, value) \
{(name), PyModuleConst_call_type, {.m_call=(value)}}
{(name), _PyModuleConst_call_type, {.m_call=(value)}}

#define PyModuleConst_LongMacro(m) PyModuleConst_Long(#m, m)
#define PyModuleConst_StringMacro(m) PyModuleConst_String(#m, m)
Expand Down
4 changes: 2 additions & 2 deletions Modules/mathmodule.c
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Expand Up @@ -271,7 +271,7 @@ m_inf(void)
}

static PyObject*
m_inf_o(void)
m_inf_o(PyObject *module)
{
return PyFloat_FromDouble(m_inf());
}
Expand All @@ -292,7 +292,7 @@ m_nan(void)
}

static PyObject*
m_nan_o(void)
m_nan_o(PyObject *module)
{
return PyFloat_FromDouble(m_nan());
}
Expand Down
17 changes: 10 additions & 7 deletions Objects/moduleobject.c
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Expand Up @@ -190,24 +190,27 @@ PyModule_AddConstants(PyObject *module, PyModuleConst_Def *def)

for (cur_def = def; cur_def && cur_def->name; cur_def++) {
switch(cur_def->type) {
case PyModuleConst_none_type:
case _PyModuleConst_none_type:
v = Py_None;
Py_INCREF(v);
break;
case PyModuleConst_long_type:
case _PyModuleConst_long_type:
v = PyLong_FromLong(cur_def->value.m_long);
break;
case PyModuleConst_bool_type:
case _PyModuleConst_ulong_type:
v = PyLong_FromUnsignedLong(cur_def->value.m_ulong);
break;
case _PyModuleConst_bool_type:
v = PyBool_FromLong(cur_def->value.m_long);
break;
case PyModuleConst_double_type:
case _PyModuleConst_double_type:
v = PyFloat_FromDouble(cur_def->value.m_double);
break;
case PyModuleConst_string_type:
case _PyModuleConst_string_type:
v = PyUnicode_FromString(cur_def->value.m_str);
break;
case PyModuleConst_call_type:
v = cur_def->value.m_call();
case _PyModuleConst_call_type:
v = cur_def->value.m_call(module);
break;
default:
v = NULL;
Expand Down