gh-96512: Move int_max_str_digits setting to PyConfig

It had to live as a global outside of PyConfig for stable ABI reasons in the pre-3.12 backports. This removes the `_Py_global_config_int_max_str_digits` and gets rid of the equivalent field in the internal `struct _is PyInterpreterState` as code can just use the existing nested config struct within that.
python · gpshead · Oct 3, 2022 · Sep 20, 2022 · Sep 20, 2022 · Sep 20, 2022
commit cf20758bbb6f63cbfa6b6f64ee6fab0be48efd9e
@@ -828,6 +828,23 @@ PyConfig
 
       Default: ``0``.
 
+   .. c:member:: int int_max_str_digits
+
+      Configures the :ref:`integer string conversion length limitation
+      <int_max_str_digits>`.  ``-1`` means that
+      :data:`sys.int_info.default_max_str_digits` will be used.  No other
+      negative value is accepted.  ``0`` disables the limitation.  Values
+      greater than zero but less than ``_PY_LONG_MAX_STR_DIGITS_THRESHOLD``
+      (640) also known as :data:`sys.int_info.str_digits_check_threshold`
+      are unsupported and will produce an error.
+
+      Configured by the :option:`-X int_max_str_digits <-X>` command line
+      flag or the :envvar:`PYTHONINTMAXSTRDIGITS` environment varable.
+
+      Default: ``-1``.
+
+      .. versionadded:: 3.12
+
    .. c:member:: int isolated
 
       If greater than ``0``, enable isolated mode:

@@ -178,6 +178,7 @@ typedef struct PyConfig {
     wchar_t *check_hash_pycs_mode;
     int use_frozen_modules;
     int safe_path;
+    int int_max_str_digits;
 
     /* --- Path configuration inputs ------------ */
     int pathconfig_warnings;

@@ -170,8 +170,6 @@ extern void _Py_DumpPathConfig(PyThreadState *tstate);
 
 PyAPI_FUNC(PyObject*) _Py_Get_Getpath_CodeObject(void);
 
-extern int _Py_global_config_int_max_str_digits;  // TODO(gpshead): move this into PyConfig in 3.12 after the backports ship.
-
 
 /* --- Function used for testing ---------------------------------- */
 

@@ -175,8 +175,6 @@ struct _is {
     struct types_state types;
     struct callable_cache callable_cache;
 
-    int int_max_str_digits;
-
     /* The following fields are here to avoid allocation during init.
        The data is exposed through PyInterpreterState pointer fields.
        These fields should not be accessed directly outside of init.

diff --git a/Lib/test/test_embed.py b/Lib/test/test_embed.py
@@ -434,6 +434,7 @@ class InitConfigTests(EmbeddingTestsMixin, unittest.TestCase):
         'install_signal_handlers': 1,
         'use_hash_seed': 0,
         'hash_seed': 0,
+        'int_max_str_digits': 4300,
         'faulthandler': 0,
         'tracemalloc': 0,
         'perf_profiling': 0,
@@ -876,6 +877,7 @@ def test_init_from_config(self):
             'platlibdir': 'my_platlibdir',
             'module_search_paths': self.IGNORE_CONFIG,
             'safe_path': 1,
+            'int_max_str_digits': 31337,
 
             'check_hash_pycs_mode': 'always',
             'pathconfig_warnings': 0,

diff --git a/Objects/longobject.c b/Objects/longobject.c
@@ -1767,7 +1767,7 @@ long_to_decimal_string_internal(PyObject *aa,
     if (size_a >= 10 * _PY_LONG_MAX_STR_DIGITS_THRESHOLD
                   / (3 * PyLong_SHIFT) + 2) {
         PyInterpreterState *interp = _PyInterpreterState_GET();
-        int max_str_digits = interp->int_max_str_digits;
+        int max_str_digits = interp->config.int_max_str_digits;
         if ((max_str_digits > 0) &&
             (max_str_digits / (3 * PyLong_SHIFT) <= (size_a - 11) / 10)) {
             PyErr_Format(PyExc_ValueError, _MAX_STR_DIGITS_ERROR_FMT_TO_STR,
@@ -1837,7 +1837,7 @@ long_to_decimal_string_internal(PyObject *aa,
     }
     if (strlen > _PY_LONG_MAX_STR_DIGITS_THRESHOLD) {
         PyInterpreterState *interp = _PyInterpreterState_GET();
-        int max_str_digits = interp->int_max_str_digits;
+        int max_str_digits = interp->config.int_max_str_digits;
         Py_ssize_t strlen_nosign = strlen - negative;
         if ((max_str_digits > 0) && (strlen_nosign > max_str_digits)) {
             Py_DECREF(scratch);
@@ -2514,7 +2514,7 @@ digit beyond the first.
         /* Limit the size to avoid excessive computation attacks. */
         if (digits > _PY_LONG_MAX_STR_DIGITS_THRESHOLD) {
             PyInterpreterState *interp = _PyInterpreterState_GET();
-            int max_str_digits = interp->int_max_str_digits;
+            int max_str_digits = interp->config.int_max_str_digits;
             if ((max_str_digits > 0) && (digits > max_str_digits)) {
                 PyErr_Format(PyExc_ValueError, _MAX_STR_DIGITS_ERROR_FMT_TO_INT,
                              max_str_digits, digits);
@@ -6196,10 +6196,6 @@ _PyLong_InitTypes(PyInterpreterState *interp)
             return _PyStatus_ERR("can't init int info type");
         }
     }
-    interp->int_max_str_digits = _Py_global_config_int_max_str_digits;
-    if (interp->int_max_str_digits == -1) {
-        interp->int_max_str_digits = _PY_LONG_DEFAULT_MAX_STR_DIGITS;
-    }
 
     return _PyStatus_OK();
 }

diff --git a/Programs/_testembed.c b/Programs/_testembed.c
@@ -683,6 +683,9 @@ static int test_init_from_config(void)
 
     config._isolated_interpreter = 1;
 
+    putenv("PYTHONINTMAXSTRDIGITS=6666");
+    config.int_max_str_digits = 31337;
+
     init_from_config_clear(&config);
 
     dump_config();

diff --git a/Python/clinic/sysmodule.c.h b/Python/clinic/sysmodule.c.h
@@ -695,6 +695,7 @@ config_check_consistency(const PyConfig *config)
     assert(config->pathconfig_warnings >= 0);
     assert(config->_is_python_build >= 0);
     assert(config->safe_path >= 0);
+    assert(config->int_max_str_digits >= 0);
     // config->use_frozen_modules is initialized later
     // by _PyConfig_InitImportConfig().
     return 1;
@@ -789,14 +790,11 @@ _PyConfig_InitCompatConfig(PyConfig *config)
     config->use_frozen_modules = 1;
 #endif
     config->safe_path = 0;
+    config->int_max_str_digits = -1;
     config->_is_python_build = 0;
     config->code_debug_ranges = 1;
 }
 
-/* Excluded from public struct PyConfig for backporting reasons. */
-/* default to unconfigured, _PyLong_InitTypes() does the rest */
-int _Py_global_config_int_max_str_digits = -1;
-
 
 static void
 config_init_defaults(PyConfig *config)
@@ -1021,6 +1019,7 @@ _PyConfig_Copy(PyConfig *config, const PyConfig *config2)
     COPY_ATTR(safe_path);
     COPY_WSTRLIST(orig_argv);
     COPY_ATTR(_is_python_build);
+    COPY_ATTR(int_max_str_digits);
 
 #undef COPY_ATTR
 #undef COPY_WSTR_ATTR
@@ -1128,6 +1127,7 @@ _PyConfig_AsDict(const PyConfig *config)
     SET_ITEM_INT(use_frozen_modules);
     SET_ITEM_INT(safe_path);
     SET_ITEM_INT(_is_python_build);
+    SET_ITEM_INT(int_max_str_digits);
 
     return dict;
 
@@ -1317,6 +1317,12 @@ _PyConfig_FromDict(PyConfig *config, PyObject *dict)
         } \
         CHECK_VALUE(#KEY, config->KEY >= 0); \
     } while (0)
+#define GET_INT(KEY) \
+    do { \
+        if (config_dict_get_int(dict, #KEY, &config->KEY) < 0) { \
+            return -1; \
+        } \
+    } while (0)
 #define GET_WSTR(KEY) \
     do { \
         if (config_dict_get_wstr(dict, #KEY, config, &config->KEY) < 0) { \
@@ -1415,9 +1421,11 @@ _PyConfig_FromDict(PyConfig *config, PyObject *dict)
     GET_UINT(use_frozen_modules);
     GET_UINT(safe_path);
     GET_UINT(_is_python_build);
+    GET_INT(int_max_str_digits);
 
 #undef CHECK_VALUE
 #undef GET_UINT
+#undef GET_INT
 #undef GET_WSTR
 #undef GET_WSTR_OPT
     return 0;
@@ -1779,7 +1787,7 @@ static PyStatus
 config_init_int_max_str_digits(PyConfig *config)
 {
     int maxdigits;
-    int valid = 0;
+    bool valid = 0;
 
     const char *env = config_get_env(config, "PYTHONINTMAXSTRDIGITS");
     if (env) {
@@ -1794,7 +1802,7 @@ config_init_int_max_str_digits(PyConfig *config)
                     STRINGIFY(_PY_LONG_MAX_STR_DIGITS_THRESHOLD)
                     " or 0 for unlimited.");
         }
-        _Py_global_config_int_max_str_digits = maxdigits;
+        config->int_max_str_digits = maxdigits;
     }
 
     const wchar_t *xoption = config_get_xoption(config, L"int_max_str_digits");
@@ -1813,7 +1821,13 @@ config_init_int_max_str_digits(PyConfig *config)
 #undef _STRINGIFY
 #undef STRINGIFY
         }
-        _Py_global_config_int_max_str_digits = maxdigits;
+        config->int_max_str_digits = maxdigits;
+    }
+    if (config->int_max_str_digits < -1) {
+        return _PyStatus_ERR("invalid value: PyConfig.int_max_str_digits < -1.");
+    }
+    if (config->int_max_str_digits == -1) {
+        config->int_max_str_digits = _PY_LONG_DEFAULT_MAX_STR_DIGITS;
     }
     return _PyStatus_OK();
 }
@@ -1881,7 +1895,7 @@ config_read_complex_options(PyConfig *config)
         }
     }
 
-    if (_Py_global_config_int_max_str_digits < 0) {
+    if (config->int_max_str_digits < 0) {
         status = config_init_int_max_str_digits(config);
         if (_PyStatus_EXCEPTION(status)) {
             return status;

@@ -1717,24 +1717,29 @@ sys_get_int_max_str_digits_impl(PyObject *module)
 /*[clinic end generated code: output=0042f5e8ae0e8631 input=8dab13e2023e60d5]*/
 {
     PyInterpreterState *interp = _PyInterpreterState_GET();
-    return PyLong_FromSsize_t(interp->int_max_str_digits);
+    return PyLong_FromLong(interp->config.int_max_str_digits);
 }
 
 /*[clinic input]
 sys.set_int_max_str_digits
 
-    maxdigits: int
+    maxdigits: long
 
 Set the maximum string digits limit for non-binary int<->str conversions.
 [clinic start generated code]*/
 
 static PyObject *
-sys_set_int_max_str_digits_impl(PyObject *module, int maxdigits)
-/*[clinic end generated code: output=734d4c2511f2a56d input=d7e3f325db6910c5]*/
+sys_set_int_max_str_digits_impl(PyObject *module, long maxdigits)
+/*[clinic end generated code: output=40ea5d33a82c5c44 input=657c61a1822f6bcf]*/
 {
     PyThreadState *tstate = _PyThreadState_GET();
     if ((!maxdigits) || (maxdigits >= _PY_LONG_MAX_STR_DIGITS_THRESHOLD)) {
-        tstate->interp->int_max_str_digits = maxdigits;
+        if (maxdigits > INT_MAX) {
+            /* Silently cap our range; already effectively unlimited as no
+             * computation this large can finish. */
+            maxdigits = INT_MAX;
+        }
+        tstate->interp->config.int_max_str_digits = maxdigits;
         Py_RETURN_NONE;
     } else {
         PyErr_Format(
@@ -2810,7 +2815,8 @@ set_flags_from_config(PyInterpreterState *interp, PyObject *flags)
     SetFlag(preconfig->utf8_mode);
     SetFlag(config->warn_default_encoding);
     SetFlagObj(PyBool_FromLong(config->safe_path));
-    SetFlag(_Py_global_config_int_max_str_digits);
+    SetFlag(config->int_max_str_digits == _PY_LONG_DEFAULT_MAX_STR_DIGITS ?
+            -1 : config->int_max_str_digits);
 #undef SetFlagObj
 #undef SetFlag
     return 0;