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Use thread-safe strftime_l() instead of strftime().

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This removes some setlocale() calls and a lot of commentary about how
dangerous that is.  strftime_l() is from POSIX 2008, and on Windows we
use _wcsftime_l().

While here, adjust error message for strftime_l() failure: it does not
in practice set errno (even though POSIX says it could), so no %m.

Author: Thomas Munro <thomas.munro@gmail.com>
Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Reviewed-by: Peter Eisentraut <peter@eisentraut.org>
Discussion: https://postgr.es/m/CA%2BhUKGJqVe0%2BPv9dvC9dSums_PXxGo9SWcxYAMBguWJUGbWz-A%40mail.gmail.com
This commit is contained in:
Peter Eisentraut
2025-03-28 07:13:43 +01:00
parent 474d7a1fd8
commit 890fc826c9
4 changed files with 29 additions and 90 deletions
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110
src/backend/utils/adt/pg_locale.c
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@@ -18,34 +18,13 @@
* LC_MESSAGES is settable at run time and will take effect
* immediately.
*
* The other categories, LC_MONETARY, LC_NUMERIC, and LC_TIME are also
* settable at run-time. However, we don't actually set those locale
* categories permanently. This would have bizarre effects like no
* longer accepting standard floating-point literals in some locales.
* Instead, we only set these locale categories briefly when needed,
* cache the required information obtained from localeconv() or
* strftime(), and then set the locale categories back to "C".
* The other categories, LC_MONETARY, LC_NUMERIC, and LC_TIME are
* permanentaly set to "C", and then we use temporary locale_t
* objects when we need to look up locale data based on the GUCs
* of the same name. Information is cached when the GUCs change.
* The cached information is only used by the formatting functions
* (to_char, etc.) and the money type. For the user, this should all be
* transparent.
*
* !!! NOW HEAR THIS !!!
*
* We've been bitten repeatedly by this bug, so let's try to keep it in
* mind in future: on some platforms, the locale functions return pointers
* to static data that will be overwritten by any later locale function.
* Thus, for example, the obvious-looking sequence
* save = setlocale(category, NULL);
* if (!setlocale(category, value))
* fail = true;
* setlocale(category, save);
* DOES NOT WORK RELIABLY: on some platforms the second setlocale() call
* will change the memory save is pointing at. To do this sort of thing
* safely, you *must* pstrdup what setlocale returns the first time.
*
* The POSIX locale standard is available here:
*
* http://www.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap07.html
*----------
*/
@@ -667,8 +646,8 @@ PGLC_localeconv(void)
* pg_strftime(), which isn't locale-aware and does not need to be replaced.
*/
static size_t
strftime_win32(char *dst, size_t dstlen,
const char *format, const struct tm *tm)
strftime_l_win32(char *dst, size_t dstlen,
const char *format, const struct tm *tm, locale_t locale)
{
size_t len;
wchar_t wformat[8]; /* formats used below need 3 chars */
@@ -684,7 +663,7 @@ strftime_win32(char *dst, size_t dstlen,
elog(ERROR, "could not convert format string from UTF-8: error code %lu",
GetLastError());
len = wcsftime(wbuf, MAX_L10N_DATA, wformat, tm);
len = _wcsftime_l(wbuf, MAX_L10N_DATA, wformat, tm, locale);
if (len == 0)
{
/*
@@ -705,8 +684,8 @@ strftime_win32(char *dst, size_t dstlen,
return len;
}
/* redefine strftime() */
#define strftime(a,b,c,d) strftime_win32(a,b,c,d)
/* redefine strftime_l() */
#define strftime_l(a,b,c,d,e) strftime_l_win32(a,b,c,d,e)
#endif /* WIN32 */
/*
@@ -748,10 +727,7 @@ cache_locale_time(void)
bool strftimefail = false;
int encoding;
int i;
char *save_lc_time;
#ifdef WIN32
char *save_lc_ctype;
#endif
locale_t locale;
/* did we do this already? */
if (CurrentLCTimeValid)
@@ -759,39 +735,16 @@ cache_locale_time(void)
elog(DEBUG3, "cache_locale_time() executed; locale: \"%s\"", locale_time);
/*
* As in PGLC_localeconv(), it's critical that we not throw error while
* libc's locale settings have nondefault values. Hence, we just call
* strftime() within the critical section, and then convert and save its
* results afterwards.
*/
/* Save prevailing value of time locale */
save_lc_time = setlocale(LC_TIME, NULL);
if (!save_lc_time)
elog(ERROR, "setlocale(NULL) failed");
save_lc_time = pstrdup(save_lc_time);
errno = ENOENT;
#ifdef WIN32
/*
* On Windows, it appears that wcsftime() internally uses LC_CTYPE, so we
* must set it here. This code looks the same as what PGLC_localeconv()
* does, but the underlying reason is different: this does NOT determine
* the encoding we'll get back from strftime_win32().
*/
/* Save prevailing value of ctype locale */
save_lc_ctype = setlocale(LC_CTYPE, NULL);
if (!save_lc_ctype)
elog(ERROR, "setlocale(NULL) failed");
save_lc_ctype = pstrdup(save_lc_ctype);
/* use lc_time to set the ctype */
setlocale(LC_CTYPE, locale_time);
locale = _create_locale(LC_ALL, locale_time);
if (locale == (locale_t) 0)
_dosmaperr(GetLastError());
#else
locale = newlocale(LC_ALL_MASK, locale_time, (locale_t) 0);
#endif
setlocale(LC_TIME, locale_time);
if (!locale)
report_newlocale_failure(locale_time);
/* We use times close to current time as data for strftime(). */
timenow = time(NULL);
@@ -814,10 +767,10 @@ cache_locale_time(void)
for (i = 0; i < 7; i++)
{
timeinfo->tm_wday = i;
if (strftime(bufptr, MAX_L10N_DATA, "%a", timeinfo) <= 0)
if (strftime_l(bufptr, MAX_L10N_DATA, "%a", timeinfo, locale) <= 0)
strftimefail = true;
bufptr += MAX_L10N_DATA;
if (strftime(bufptr, MAX_L10N_DATA, "%A", timeinfo) <= 0)
if (strftime_l(bufptr, MAX_L10N_DATA, "%A", timeinfo, locale) <= 0)
strftimefail = true;
bufptr += MAX_L10N_DATA;
}
@@ -827,37 +780,26 @@ cache_locale_time(void)
{
timeinfo->tm_mon = i;
timeinfo->tm_mday = 1; /* make sure we don't have invalid date */
if (strftime(bufptr, MAX_L10N_DATA, "%b", timeinfo) <= 0)
if (strftime_l(bufptr, MAX_L10N_DATA, "%b", timeinfo, locale) <= 0)
strftimefail = true;
bufptr += MAX_L10N_DATA;
if (strftime(bufptr, MAX_L10N_DATA, "%B", timeinfo) <= 0)
if (strftime_l(bufptr, MAX_L10N_DATA, "%B", timeinfo, locale) <= 0)
strftimefail = true;
bufptr += MAX_L10N_DATA;
}
/*
* Restore the prevailing locale settings; as in PGLC_localeconv(),
* failure to do so is fatal.
*/
#ifdef WIN32
if (!setlocale(LC_CTYPE, save_lc_ctype))
elog(FATAL, "failed to restore LC_CTYPE to \"%s\"", save_lc_ctype);
_free_locale(locale);
#else
freelocale(locale);
#endif
if (!setlocale(LC_TIME, save_lc_time))
elog(FATAL, "failed to restore LC_TIME to \"%s\"", save_lc_time);
/*
* At this point we've done our best to clean up, and can throw errors, or
* call functions that might throw errors, with a clean conscience.
*/
if (strftimefail)
elog(ERROR, "strftime() failed: %m");
/* Release the pstrdup'd locale names */
pfree(save_lc_time);
#ifdef WIN32
pfree(save_lc_ctype);
#endif
elog(ERROR, "strftime_l() failed");
#ifndef WIN32