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[3.14] gh-123681: Check NORMALIZE_CENTURY behavior at runtime; require C99 (GH-136022) (GH-137947)

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A runtime check is needed to support cross-compiling.

Remove the _Py_NORMALIZE_CENTURY macro.
Remove _pydatetime.py's _can_support_c99.
(cherry picked from commit 719e5c3f71)

Co-authored-by: Petr Viktorin <encukou@gmail.com>
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
This commit is contained in:
Miss Islington (bot) 2025-10-07 19:59:06 +02:00 • committed by GitHub
parent fad7bfc282
commit 7d9b2671c6
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GPG key ID: B5690EEEBB952194
8 changed files with 48 additions and 191 deletions
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13
Lib/_pydatetime.py
View file

@ -213,17 +213,6 @@ def _need_normalize_century():
_normalize_century = True
return _normalize_century
_supports_c99 = None
def _can_support_c99():
global _supports_c99
if _supports_c99 is None:
try:
_supports_c99 = (
_time.strftime("%F", (1900, 1, 1, 0, 0, 0, 0, 1, 0)) == "1900-01-01")
except ValueError:
_supports_c99 = False
return _supports_c99
# Correctly substitute for %z and %Z escapes in strftime formats.
def _wrap_strftime(object, format, timetuple):
# Don't call utcoffset() or tzname() unless actually needed.
@ -283,7 +272,7 @@ def _wrap_strftime(object, format, timetuple):
newformat.append(Zreplace)
# Note that datetime(1000, 1, 1).strftime('%G') == '1000' so
# year 1000 for %G can go on the fast path.
elif ((ch in 'YG' or ch in 'FC' and _can_support_c99()) and
elif ((ch in 'YG' or ch in 'FC') and
object.year < 1000 and _need_normalize_century()):
if ch == 'G':
year = int(_time.strftime("%G", timetuple))

38
Lib/test/datetimetester.py
View file

@ -1807,7 +1807,7 @@ def test_bool(self):
self.assertTrue(self.theclass.min)
self.assertTrue(self.theclass.max)
def test_strftime_y2k(self):
def check_strftime_y2k(self, specifier):
# Test that years less than 1000 are 0-padded; note that the beginning
# of an ISO 8601 year may fall in an ISO week of the year before, and
# therefore needs an offset of -1 when formatting with '%G'.
@ -1821,22 +1821,28 @@ def test_strftime_y2k(self):
(1000, 0),
(1970, 0),
)
specifiers = 'YG'
if _time.strftime('%F', (1900, 1, 1, 0, 0, 0, 0, 1, 0)) == '1900-01-01':
specifiers += 'FC'
for year, g_offset in dataset:
for specifier in specifiers:
with self.subTest(year=year, specifier=specifier):
d = self.theclass(year, 1, 1)
if specifier == 'G':
year += g_offset
if specifier == 'C':
expected = f"{year // 100:02d}"
else:
expected = f"{year:04d}"
if specifier == 'F':
expected += f"-01-01"
self.assertEqual(d.strftime(f"%{specifier}"), expected)
with self.subTest(year=year, specifier=specifier):
d = self.theclass(year, 1, 1)
if specifier == 'G':
year += g_offset
if specifier == 'C':
expected = f"{year // 100:02d}"
else:
expected = f"{year:04d}"
if specifier == 'F':
expected += f"-01-01"
self.assertEqual(d.strftime(f"%{specifier}"), expected)
def test_strftime_y2k(self):
self.check_strftime_y2k('Y')
self.check_strftime_y2k('G')
def test_strftime_y2k_c99(self):
# CPython requires C11; specifiers new in C99 must work.
# (Other implementations may want to disable this test.)
self.check_strftime_y2k('F')
self.check_strftime_y2k('C')
def test_replace(self):
cls = self.theclass

3
Misc/NEWS.d/next/Build/2025-01-03-13-02-06.gh-issue-123681.gQ67nK.rst Normal file
View file

@ -0,0 +1,3 @@
Check the ``strftime()`` behavior at runtime instead of at the compile time
to support cross-compiling.
Remove the internal macro ``_Py_NORMALIZE_CENTURY``.

26
Modules/_datetimemodule.c
View file

@ -1753,6 +1753,24 @@ format_utcoffset(char *buf, size_t buflen, const char *sep,
return 0;
}
/* Check whether year with century should be normalized for strftime. */
inline static int
normalize_century(void)
{
static int cache = -1;
if (cache < 0) {
char year[5];
struct tm date = {
.tm_year = -1801,
.tm_mon = 0,
.tm_mday = 1
};
cache = (strftime(year, sizeof(year), "%Y", &date) &&
strcmp(year, "0099") != 0);
}
return cache;
}
static PyObject *
make_somezreplacement(PyObject *object, char *sep, PyObject *tzinfoarg)
{
@ -1924,10 +1942,9 @@ wrap_strftime(PyObject *object, PyObject *format, PyObject *timetuple,
}
replacement = freplacement;
}
#ifdef _Py_NORMALIZE_CENTURY
else if (ch == 'Y' || ch == 'G'
|| ch == 'F' || ch == 'C'
) {
else if (normalize_century()
&& (ch == 'Y' || ch == 'G' || ch == 'F' || ch == 'C'))
{
/* 0-pad year with century as necessary */
PyObject *item = PySequence_GetItem(timetuple, 0);
if (item == NULL) {
@ -1978,7 +1995,6 @@ wrap_strftime(PyObject *object, PyObject *format, PyObject *timetuple,
}
continue;
}
#endif
else {
/* percent followed by something else */
continue;

1
Tools/c-analyzer/cpython/ignored.tsv
View file

@ -226,6 +226,7 @@ Modules/_datetimemodule.c datetime_isoformat specs -
Modules/_datetimemodule.c parse_hh_mm_ss_ff correction -
Modules/_datetimemodule.c time_isoformat specs -
Modules/_datetimemodule.c - capi_types -
Modules/_datetimemodule.c normalize_century cache -
Modules/_decimal/_decimal.c - cond_map_template -
Modules/_decimal/_decimal.c - dec_signal_string -
Modules/_decimal/_decimal.c - dflt_ctx -

Can't render this file because it has a wrong number of fields in line 4.

104
configure generated vendored
View file

@ -28186,110 +28186,6 @@ printf "%s\n" "#define HAVE_STAT_TV_NSEC2 1" >>confdefs.h
fi
{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether year with century should be normalized for strftime" >&5
printf %s "checking whether year with century should be normalized for strftime... " >&6; }
if test ${ac_cv_normalize_century+y}
then :
printf %s "(cached) " >&6
else case e in #(
e)
if test "$cross_compiling" = yes
then :
ac_cv_normalize_century=yes
else case e in #(
e) cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h. */
#include <time.h>
#include <string.h>
int main(void)
{
char year[5];
struct tm date = {
.tm_year = -1801,
.tm_mon = 0,
.tm_mday = 1
};
if (strftime(year, sizeof(year), "%Y", &date) && !strcmp(year, "0099")) {
return 1;
}
return 0;
}
_ACEOF
if ac_fn_c_try_run "$LINENO"
then :
ac_cv_normalize_century=yes
else case e in #(
e) ac_cv_normalize_century=no ;;
esac
fi
rm -f core *.core core.conftest.* gmon.out bb.out conftest$ac_exeext \
conftest.$ac_objext conftest.beam conftest.$ac_ext ;;
esac
fi
;;
esac
fi
{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ac_cv_normalize_century" >&5
printf "%s\n" "$ac_cv_normalize_century" >&6; }
if test "$ac_cv_normalize_century" = yes
then
printf "%s\n" "#define _Py_NORMALIZE_CENTURY 1" >>confdefs.h
fi
{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether C99-compatible strftime specifiers are supported" >&5
printf %s "checking whether C99-compatible strftime specifiers are supported... " >&6; }
if test ${ac_cv_strftime_c99_support+y}
then :
printf %s "(cached) " >&6
else case e in #(
e)
if test "$cross_compiling" = yes
then :
ac_cv_strftime_c99_support=
else case e in #(
e) cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h. */
#include <time.h>
#include <string.h>
int main(void)
{
char full_date[11];
struct tm date = {
.tm_year = 0,
.tm_mon = 0,
.tm_mday = 1
};
if (strftime(full_date, sizeof(full_date), "%F", &date) && !strcmp(full_date, "1900-01-01")) {
return 0;
}
return 1;
}
_ACEOF
if ac_fn_c_try_run "$LINENO"
then :
ac_cv_strftime_c99_support=yes
else case e in #(
e) as_fn_error $? "Python requires C99-compatible strftime specifiers" "$LINENO" 5 ;;
esac
fi
rm -f core *.core core.conftest.* gmon.out bb.out conftest$ac_exeext \
conftest.$ac_objext conftest.beam conftest.$ac_ext ;;
esac
fi
;;
esac
fi
{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ac_cv_strftime_c99_support" >&5
printf "%s\n" "$ac_cv_strftime_c99_support" >&6; }
have_curses=no
have_panel=no

51
configure.ac
View file

@ -6792,57 +6792,6 @@ then
[Define if you have struct stat.st_mtimensec])
fi
AC_CACHE_CHECK([whether year with century should be normalized for strftime], [ac_cv_normalize_century], [
AC_RUN_IFELSE([AC_LANG_SOURCE([[
#include <time.h>
#include <string.h>
int main(void)
{
char year[5];
struct tm date = {
.tm_year = -1801,
.tm_mon = 0,
.tm_mday = 1
};
if (strftime(year, sizeof(year), "%Y", &date) && !strcmp(year, "0099")) {
return 1;
}
return 0;
}
]])],
[ac_cv_normalize_century=yes],
[ac_cv_normalize_century=no],
[ac_cv_normalize_century=yes])])
if test "$ac_cv_normalize_century" = yes
then
AC_DEFINE([_Py_NORMALIZE_CENTURY], [1],
[Define if year with century should be normalized for strftime.])
fi
AC_CACHE_CHECK([whether C99-compatible strftime specifiers are supported], [ac_cv_strftime_c99_support], [
AC_RUN_IFELSE([AC_LANG_SOURCE([[
#include <time.h>
#include <string.h>
int main(void)
{
char full_date[11];
struct tm date = {
.tm_year = 0,
.tm_mon = 0,
.tm_mday = 1
};
if (strftime(full_date, sizeof(full_date), "%F", &date) && !strcmp(full_date, "1900-01-01")) {
return 0;
}
return 1;
}
]])],
[ac_cv_strftime_c99_support=yes],
[AC_MSG_ERROR([Python requires C99-compatible strftime specifiers])],
[ac_cv_strftime_c99_support=])])
dnl check for ncursesw/ncurses and panelw/panel
dnl NOTE: old curses is not detected.
dnl have_curses=[no, yes]

3
pyconfig.h.in
View file

@ -2023,9 +2023,6 @@
/* HACL* library can compile SIMD256 implementations */
#undef _Py_HACL_CAN_COMPILE_VEC256
/* Define if year with century should be normalized for strftime. */
#undef _Py_NORMALIZE_CENTURY
/* Define to force use of thread-safe errno, h_errno, and other functions */
#undef _REENTRANT