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.

1 files changed, 21 insertions, 7 deletions

diff --git a/Python/formatter_unicode.c b/Python/formatter_unicode.c
index ba09cc6..e12ba49 100644
--- a/Python/formatter_unicode.c
+++ b/Python/formatter_unicode.c
@@ -3,6 +3,7 @@
    of int.__float__, etc., that take and return unicode objects */
 
 #include "Python.h"
+#include "pycore_fileutils.h"
 #include <locale.h>
 
 /* Raises an exception about an unknown presentation type for this
@@ -396,9 +397,10 @@ typedef struct {
     PyObject *decimal_point;
     PyObject *thousands_sep;
     const char *grouping;
+    char *grouping_buffer;
 } LocaleInfo;
 
-#define STATIC_LOCALE_INFO_INIT {0, 0, 0}
+#define LocaleInfo_STATIC_INIT {0, 0, 0, 0}
 
 /* describes the layout for an integer, see the comment in
    calc_number_widths() for details */
@@ -705,11 +707,22 @@ get_locale_info(enum LocaleType type, LocaleInfo *locale_info)
 {
     switch (type) {
     case LT_CURRENT_LOCALE: {
-        if (_Py_GetLocaleconvNumeric(&locale_info->decimal_point,
-                                     &locale_info->thousands_sep,
-                                     &locale_info->grouping) < 0) {
+        struct lconv *lc = localeconv();
+        if (_Py_GetLocaleconvNumeric(lc,
+                                     &locale_info->decimal_point,
+                                     &locale_info->thousands_sep) < 0) {
             return -1;
         }
+
+        /* localeconv() grouping can become a dangling pointer or point
+           to a different string if another thread calls localeconv() during
+           the string formatting. Copy the string to avoid this risk. */
+        locale_info->grouping_buffer = _PyMem_Strdup(lc->grouping);
+        if (locale_info->grouping_buffer == NULL) {
+            PyErr_NoMemory();
+            return -1;
+        }
+        locale_info->grouping = locale_info->grouping_buffer;
         break;
     }
     case LT_DEFAULT_LOCALE:
@@ -743,6 +756,7 @@ free_locale_info(LocaleInfo *locale_info)
 {
     Py_XDECREF(locale_info->decimal_point);
     Py_XDECREF(locale_info->thousands_sep);
+    PyMem_Free(locale_info->grouping_buffer);
 }
 
 /************************************************************************/
@@ -855,7 +869,7 @@ format_long_internal(PyObject *value, const InternalFormatSpec *format,
 
     /* Locale settings, either from the actual locale or
        from a hard-code pseudo-locale */
-    LocaleInfo locale = STATIC_LOCALE_INFO_INIT;
+    LocaleInfo locale = LocaleInfo_STATIC_INIT;
 
     /* no precision allowed on integers */
     if (format->precision != -1) {
@@ -1027,7 +1041,7 @@ format_float_internal(PyObject *value,
 
     /* Locale settings, either from the actual locale or
        from a hard-code pseudo-locale */
-    LocaleInfo locale = STATIC_LOCALE_INFO_INIT;
+    LocaleInfo locale = LocaleInfo_STATIC_INIT;
 
     if (format->precision > INT_MAX) {
         PyErr_SetString(PyExc_ValueError, "precision too big");
@@ -1190,7 +1204,7 @@ format_complex_internal(PyObject *value,
 
     /* Locale settings, either from the actual locale or
        from a hard-code pseudo-locale */
-    LocaleInfo locale = STATIC_LOCALE_INFO_INIT;
+    LocaleInfo locale = LocaleInfo_STATIC_INIT;
 
     if (format->precision > INT_MAX) {
         PyErr_SetString(PyExc_ValueError, "precision too big");