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gh-123681: Check the strftime() behavior at runtime instead of at the compile time #128444

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gh-123681: Check the strftime() behavior at runtime instead of at the compile time #128444

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0d17190
gh-123681: Check the strftime() behavior at runtime instead of at the…
serhiy-storchaka Jan 3, 2025
695f58f
Merge branch 'main' into strftime-runtime-checks
serhiy-storchaka Apr 8, 2025
26441f9
Add static variables to ignored.tsv.
serhiy-storchaka Apr 8, 2025
65cf376
Merge branch 'main' into strftime-runtime-checks
serhiy-storchaka Apr 9, 2025
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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Build/2025-01-03-13-02-06.gh-issue-123681.gQ67nK.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Check the ``strftime()`` behavior at runtime instead of at the compile time
to support cross-compiling. Remove macros Py_NORMALIZE_CENTURY and
Py_STRFTIME_C99_SUPPORT.
44 changes: 39 additions & 5 deletions Modules/_datetimemodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1757,6 +1757,42 @@ 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;
}

/* Check whether C99-specific strftime specifiers are supported. */
inline static int
strftime_c99_support(void)
{
static int cache = -1;
if (cache < 0) {
char full_date[11];
struct tm date = {
.tm_year = 0,
.tm_mon = 0,
.tm_mday = 1
};
cache = (strftime(full_date, sizeof(full_date), "%F", &date) &&
strcmp(full_date, "1900-01-01") == 0);
}
return cache;
}

static PyObject *
make_somezreplacement(PyObject *object, char *sep, PyObject *tzinfoarg)
{
Expand Down Expand Up @@ -1928,10 +1964,9 @@ 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' ||
(strftime_c99_support() && (ch == 'F' || ch == 'C'))))
{
/* 0-pad year with century as necessary */
PyObject *item = PySequence_GetItem(timetuple, 0);
if (item == NULL) {
Expand Down Expand Up @@ -1982,7 +2017,6 @@ wrap_strftime(PyObject *object, PyObject *format, PyObject *timetuple,
}
continue;
}
#endif
else {
/* percent followed by something else */
continue;
Expand Down
2 changes: 2 additions & 0 deletions Tools/c-analyzer/cpython/ignored.tsv
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Original file line number Diff line number Diff line change
Expand Up @@ -224,6 +224,8 @@ 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/_datetimemodule.c strftime_c99_support cache -
Modules/_decimal/_decimal.c - cond_map_template -
Modules/_decimal/_decimal.c - dec_signal_string -
Modules/_decimal/_decimal.c - dflt_ctx -
Expand Down
104 changes: 0 additions & 104 deletions configure
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51 changes: 0 additions & 51 deletions configure.ac
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Original file line number Diff line number Diff line change
Expand Up @@ -6670,57 +6670,6 @@ 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]
Expand Down
3 changes: 0 additions & 3 deletions pyconfig.h.in
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Original file line number Diff line number Diff line change
Expand Up @@ -1715,9 +1715,6 @@
/* Defined if _Complex C type is available. */
#undef Py_HAVE_C_COMPLEX

/* Define if year with century should be normalized for strftime. */
#undef Py_NORMALIZE_CENTURY

/* Define if you want to enable remote debugging support. */
#undef Py_REMOTE_DEBUG

Expand Down
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