bpo-28604: Fix localeconv() for different LC_MONETARY (GH-10606)

locale.localeconv() now sets temporarily the LC_CTYPE locale to the
LC_MONETARY locale if the two locales are different and monetary
strings are non-ASCII. This temporary change affects other threads.

Changes:

* locale.localeconv() can now set LC_CTYPE to LC_MONETARY to decode
  monetary fields.
* Add LocaleInfo.grouping_buffer: copy localeconv() grouping string
  since it can be replaced anytime if a different thread calls
  localeconv().
* _Py_GetLocaleconvNumeric() now requires a "struct lconv *"
  structure, so locale.localeconv() now longer calls localeconv()
  twice. Moreover, the function now requires all arguments to be
  non-NULL.
* Rename STATIC_LOCALE_INFO_INIT to LocaleInfo_STATIC_INIT.
* Move _Py_GetLocaleconvNumeric() definition from fileutils.h
  to pycore_fileutils.h. pycore_fileutils.h now includes locale.h.
* The _locale module is now built with Py_BUILD_CORE defined.

2 files changed, 94 insertions, 17 deletions

diff --git a/Modules/Setup b/Modules/Setup
index e7b939d..11ddd0c 100644
--- a/Modules/Setup
+++ b/Modules/Setup
@@ -120,7 +120,7 @@ time -DPy_BUILD_CORE -I$(srcdir)/Include/internal timemodule.c	# -lm # time oper
 _thread -DPy_BUILD_CORE -I$(srcdir)/Include/internal _threadmodule.c	# low-level threading interface
 
 # access to ISO C locale support
-_locale _localemodule.c  # -lintl
+_locale -DPy_BUILD_CORE _localemodule.c  # -lintl
 
 # Standard I/O baseline
 _io -DPy_BUILD_CORE -I$(srcdir)/Include/internal -I$(srcdir)/Modules/_io _io/_iomodule.c _io/iobase.c _io/fileio.c _io/bytesio.c _io/bufferedio.c _io/textio.c _io/stringio.c
diff --git a/Modules/_localemodule.c b/Modules/_localemodule.c
index 3fdbc5e..4202cc4 100644
--- a/Modules/_localemodule.c
+++ b/Modules/_localemodule.c
@@ -11,6 +11,7 @@ This software comes with no warranty. Use at your own risk.
 
 #define PY_SSIZE_T_CLEAN
 #include "Python.h"
+#include "pycore_fileutils.h"
 
 #include <stdio.h>
 #include <locale.h>
@@ -128,6 +129,82 @@ PyLocale_setlocale(PyObject* self, PyObject* args)
     return result_object;
 }
 
+static int
+locale_is_ascii(const char *str)
+{
+    return (strlen(str) == 1 && ((unsigned char)str[0]) <= 127);
+}
+
+static int
+locale_decode_monetary(PyObject *dict, struct lconv *lc)
+{
+    int change_locale;
+    change_locale = (!locale_is_ascii(lc->int_curr_symbol)
+                     || !locale_is_ascii(lc->currency_symbol)
+                     || !locale_is_ascii(lc->mon_decimal_point)
+                     || !locale_is_ascii(lc->mon_thousands_sep));
+
+    /* Keep a copy of the LC_CTYPE locale */
+    char *oldloc = NULL, *loc = NULL;
+    if (change_locale) {
+        oldloc = setlocale(LC_CTYPE, NULL);
+        if (!oldloc) {
+            PyErr_SetString(PyExc_RuntimeWarning,
+                            "failed to get LC_CTYPE locale");
+            return -1;
+        }
+
+        oldloc = _PyMem_Strdup(oldloc);
+        if (!oldloc) {
+            PyErr_NoMemory();
+            return -1;
+        }
+
+        loc = setlocale(LC_MONETARY, NULL);
+        if (loc != NULL && strcmp(loc, oldloc) == 0) {
+            loc = NULL;
+        }
+
+        if (loc != NULL) {
+            /* Only set the locale temporarily the LC_CTYPE locale
+               to the LC_MONETARY locale if the two locales are different and
+               at least one string is non-ASCII. */
+            setlocale(LC_CTYPE, loc);
+        }
+    }
+
+    int res = -1;
+
+#define RESULT_STRING(ATTR) \
+    do { \
+        PyObject *obj; \
+        obj = PyUnicode_DecodeLocale(lc->ATTR, NULL); \
+        if (obj == NULL) { \
+            goto done; \
+        } \
+        if (PyDict_SetItemString(dict, Py_STRINGIFY(ATTR), obj) < 0) { \
+            Py_DECREF(obj); \
+            goto done; \
+        } \
+        Py_DECREF(obj); \
+    } while (0)
+
+    RESULT_STRING(int_curr_symbol);
+    RESULT_STRING(currency_symbol);
+    RESULT_STRING(mon_decimal_point);
+    RESULT_STRING(mon_thousands_sep);
+#undef RESULT_STRING
+
+    res = 0;
+
+done:
+    if (loc != NULL) {
+        setlocale(LC_CTYPE, oldloc);
+    }
+    PyMem_Free(oldloc);
+    return res;
+}
+
 PyDoc_STRVAR(localeconv__doc__,
 "() -> dict. Returns numeric and monetary locale-specific parameters.");
 
@@ -135,7 +212,7 @@ static PyObject*
 PyLocale_localeconv(PyObject* self, PyObject *Py_UNUSED(ignored))
 {
     PyObject* result;
-    struct lconv *l;
+    struct lconv *lc;
     PyObject *x;
 
     result = PyDict_New();
@@ -144,7 +221,7 @@ PyLocale_localeconv(PyObject* self, PyObject *Py_UNUSED(ignored))
     }
 
     /* if LC_NUMERIC is different in the C library, use saved value */
-    l = localeconv();
+    lc = localeconv();
 
     /* hopefully, the localeconv result survives the C library calls
        involved herein */
@@ -162,22 +239,21 @@ PyLocale_localeconv(PyObject* self, PyObject *Py_UNUSED(ignored))
 
 #define RESULT_STRING(s)\
     do { \
-        x = PyUnicode_DecodeLocale(l->s, NULL); \
+        x = PyUnicode_DecodeLocale(lc->s, NULL); \
         RESULT(#s, x); \
     } while (0)
 
 #define RESULT_INT(i)\
     do { \
-        x = PyLong_FromLong(l->i); \
+        x = PyLong_FromLong(lc->i); \
         RESULT(#i, x); \
     } while (0)
 
-    /* Monetary information */
-    RESULT_STRING(int_curr_symbol);
-    RESULT_STRING(currency_symbol);
-    RESULT_STRING(mon_decimal_point);
-    RESULT_STRING(mon_thousands_sep);
-    x = copy_grouping(l->mon_grouping);
+    /* Monetary information: LC_MONETARY encoding */
+    if (locale_decode_monetary(result, lc) < 0) {
+        goto failed;
+    }
+    x = copy_grouping(lc->mon_grouping);
     RESULT("mon_grouping", x);
 
     RESULT_STRING(positive_sign);
@@ -191,12 +267,9 @@ PyLocale_localeconv(PyObject* self, PyObject *Py_UNUSED(ignored))
     RESULT_INT(p_sign_posn);
     RESULT_INT(n_sign_posn);
 
-    /* Numeric information */
+    /* Numeric information: LC_NUMERIC encoding */
     PyObject *decimal_point, *thousands_sep;
-    const char *grouping;
-    if (_Py_GetLocaleconvNumeric(&decimal_point,
-                                 &thousands_sep,
-                                 &grouping) < 0) {
+    if (_Py_GetLocaleconvNumeric(lc, &decimal_point, &thousands_sep) < 0) {
         goto failed;
     }
 
@@ -213,7 +286,7 @@ PyLocale_localeconv(PyObject* self, PyObject *Py_UNUSED(ignored))
     }
     Py_DECREF(thousands_sep);
 
-    x = copy_grouping(grouping);
+    x = copy_grouping(lc->grouping);
     RESULT("grouping", x);
 
     return result;
@@ -221,6 +294,10 @@ PyLocale_localeconv(PyObject* self, PyObject *Py_UNUSED(ignored))
   failed:
     Py_DECREF(result);
     return NULL;
+
+#undef RESULT
+#undef RESULT_STRING
+#undef RESULT_INT
 }
 
 #if defined(HAVE_WCSCOLL)