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musl/src/time/__tz.c

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the big time handling overhaul this commit has two major user-visible parts: zoneinfo-format time zones are now supported, and overflow handling is intended to be complete in the sense that all functions return a correct result if and only if the result fits in the destination type, and otherwise return an error. also, some noticable bugs in the way DST detection and normalization worked have been fixed, and performance may be better than before, but it has not been tested.
2013-07-17 05:24:50 -04:00
#include "time_impl.h"
#include <stdint.h>
#include <limits.h>
#include <stdlib.h>
#include <string.h>
#include "libc.h"
long __timezone = 0;
int __daylight = 0;
char *__tzname[2] = { 0, 0 };
weak_alias(__timezone, timezone);
weak_alias(__daylight, daylight);
weak_alias(__tzname, tzname);
static char std_name[TZNAME_MAX+1];
static char dst_name[TZNAME_MAX+1];
fix strftime handling of time zone data this may need further revision in the future, since POSIX is rather unclear on the requirements, and is designed around the assumption of POSIX TZ specifiers which are not sufficiently powerful to represent real-world timezones (this is why zoneinfo support was added). the basic issue is that strftime gets the string and numeric offset for the timezone from the extra fields in struct tm, which are initialized when calling localtime/gmtime/etc. however, a conforming application might have created its own struct tm without initializing these fields, in which case using __tm_zone (a pointer) could crash. other zoneinfo-based implementations simply check for a null pointer, but otherwise can still crash of the field contains junk. simply ignoring __tm_zone and using tzname[] would "work" but would give incorrect results in time zones with more complex rules. I feel like this would lower the quality of implementation. instead, simply validate __tm_zone: unless it points to one of the zone name strings managed by the timezone system, assume it's invalid. this commit also fixes several other minor bugs with formatting: tm_isdst being negative is required to suppress printing of the zone formats, and %z was using the wrong format specifiers since the type of val was changed, resulting in bogus output.
2013-08-24 12:59:02 -04:00
const char __gmt[] = "GMT";
the big time handling overhaul this commit has two major user-visible parts: zoneinfo-format time zones are now supported, and overflow handling is intended to be complete in the sense that all functions return a correct result if and only if the result fits in the destination type, and otherwise return an error. also, some noticable bugs in the way DST detection and normalization worked have been fixed, and performance may be better than before, but it has not been tested.
2013-07-17 05:24:50 -04:00
static int dst_off;
static int r0[5], r1[5];
fix strftime handling of time zone data this may need further revision in the future, since POSIX is rather unclear on the requirements, and is designed around the assumption of POSIX TZ specifiers which are not sufficiently powerful to represent real-world timezones (this is why zoneinfo support was added). the basic issue is that strftime gets the string and numeric offset for the timezone from the extra fields in struct tm, which are initialized when calling localtime/gmtime/etc. however, a conforming application might have created its own struct tm without initializing these fields, in which case using __tm_zone (a pointer) could crash. other zoneinfo-based implementations simply check for a null pointer, but otherwise can still crash of the field contains junk. simply ignoring __tm_zone and using tzname[] would "work" but would give incorrect results in time zones with more complex rules. I feel like this would lower the quality of implementation. instead, simply validate __tm_zone: unless it points to one of the zone name strings managed by the timezone system, assume it's invalid. this commit also fixes several other minor bugs with formatting: tm_isdst being negative is required to suppress printing of the zone formats, and %z was using the wrong format specifiers since the type of val was changed, resulting in bogus output.
2013-08-24 12:59:02 -04:00
static const unsigned char *zi, *trans, *index, *types, *abbrevs, *abbrevs_end;
the big time handling overhaul this commit has two major user-visible parts: zoneinfo-format time zones are now supported, and overflow handling is intended to be complete in the sense that all functions return a correct result if and only if the result fits in the destination type, and otherwise return an error. also, some noticable bugs in the way DST detection and normalization worked have been fixed, and performance may be better than before, but it has not been tested.
2013-07-17 05:24:50 -04:00
static size_t map_size;
static char old_tz_buf[32];
static char *old_tz = old_tz_buf;
static size_t old_tz_size = sizeof old_tz_buf;
static int lock[2];
static int getint(const char **p)
{
unsigned x;
for (x=0; **p-'0'<10U; (*p)++) x = **p-'0' + 10*x;
return x;
}
static int getsigned(const char **p)
{
if (**p == '-') {
++*p;
return -getint(p);
}
if (**p == '+') ++*p;
return getint(p);
}
static int getoff(const char **p)
{
int off = 3600*getsigned(p);
if (**p == ':') {
++*p;
off += 60*getint(p);
if (**p == ':') {
++*p;
off += getint(p);
}
}
return off;
}
static void getrule(const char **p, int rule[5])
{
int r = rule[0] = **p;
if (r!='M') {
if (r=='J') ++*p;
else rule[0] = 0;
rule[1] = getint(p);
} else {
++*p; rule[1] = getint(p);
++*p; rule[2] = getint(p);
++*p; rule[3] = getint(p);
}
if (**p=='/') {
++*p;
rule[4] = getoff(p);
} else {
rule[4] = 7200;
}
}
static void getname(char *d, const char **p)
{
int i;
if (**p == '<') {
++*p;
for (i=0; **p!='>' && i<TZNAME_MAX; i++)
d[i] = (*p)[i];
++*p;
} else {
for (i=0; ((*p)[i]|32)-'a'<26U && i<TZNAME_MAX; i++)
d[i] = (*p)[i];
}
*p += i;
d[i] = 0;
}
#define VEC(...) ((const unsigned char[]){__VA_ARGS__})
static uint32_t zi_read32(const unsigned char *z)
{
return (unsigned)z[0]<<24 | z[1]<<16 | z[2]<<8 | z[3];
}
static size_t zi_dotprod(const unsigned char *z, const unsigned char *v, size_t n)
{
size_t y;
uint32_t x;
for (y=0; n; n--, z+=4, v++) {
x = zi_read32(z);
y += x * *v;
}
return y;
}
int __munmap(void *, size_t);
static void do_tzset()
{
char buf[NAME_MAX+25], *pathname=buf+24;
allow zoneinfo-path-relative filenames with no slashes in TZ variable since the form TZ=name is reserved for POSIX-form time zone strings, TZ=:name needs to be used when the zoneinfo filename is in the top-level zoneinfo directory and therefore does not contain a slash. previously the leading colon was merely dropped, making it impossible to access such zones without a full absolute pathname. changes based on patch by Timo Teräs.
2014-04-21 18:11:42 -04:00
const char *try, *s, *p;
the big time handling overhaul this commit has two major user-visible parts: zoneinfo-format time zones are now supported, and overflow handling is intended to be complete in the sense that all functions return a correct result if and only if the result fits in the destination type, and otherwise return an error. also, some noticable bugs in the way DST detection and normalization worked have been fixed, and performance may be better than before, but it has not been tested.
2013-07-17 05:24:50 -04:00
const unsigned char *map = 0;
size_t i;
static const char search[] =
"/usr/share/zoneinfo/\0/share/zoneinfo/\0/etc/zoneinfo/\0";
s = getenv("TZ");
fix strftime handling of time zone data this may need further revision in the future, since POSIX is rather unclear on the requirements, and is designed around the assumption of POSIX TZ specifiers which are not sufficiently powerful to represent real-world timezones (this is why zoneinfo support was added). the basic issue is that strftime gets the string and numeric offset for the timezone from the extra fields in struct tm, which are initialized when calling localtime/gmtime/etc. however, a conforming application might have created its own struct tm without initializing these fields, in which case using __tm_zone (a pointer) could crash. other zoneinfo-based implementations simply check for a null pointer, but otherwise can still crash of the field contains junk. simply ignoring __tm_zone and using tzname[] would "work" but would give incorrect results in time zones with more complex rules. I feel like this would lower the quality of implementation. instead, simply validate __tm_zone: unless it points to one of the zone name strings managed by the timezone system, assume it's invalid. this commit also fixes several other minor bugs with formatting: tm_isdst being negative is required to suppress printing of the zone formats, and %z was using the wrong format specifiers since the type of val was changed, resulting in bogus output.
2013-08-24 12:59:02 -04:00
if (!s || !*s) s = __gmt;
the big time handling overhaul this commit has two major user-visible parts: zoneinfo-format time zones are now supported, and overflow handling is intended to be complete in the sense that all functions return a correct result if and only if the result fits in the destination type, and otherwise return an error. also, some noticable bugs in the way DST detection and normalization worked have been fixed, and performance may be better than before, but it has not been tested.
2013-07-17 05:24:50 -04:00
if (old_tz && !strcmp(s, old_tz)) return;
if (zi) __munmap((void *)zi, map_size);
/* Cache the old value of TZ to check if it has changed. Avoid
* free so as not to pull it into static programs. Growth
* strategy makes it so free would have minimal benefit anyway. */
i = strlen(s);
fix handling of overly-long TZ environment variable values the rest of the code is not prepared to handle an empty TZ string, so falling back to __gmt ("GMT"), just as if TZ had been blank or unset, is the preferable action.
2013-11-08 20:50:59 -05:00
if (i > PATH_MAX+1) s = __gmt, i = 3;
the big time handling overhaul this commit has two major user-visible parts: zoneinfo-format time zones are now supported, and overflow handling is intended to be complete in the sense that all functions return a correct result if and only if the result fits in the destination type, and otherwise return an error. also, some noticable bugs in the way DST detection and normalization worked have been fixed, and performance may be better than before, but it has not been tested.
2013-07-17 05:24:50 -04:00
if (i >= old_tz_size) {
old_tz_size *= 2;
if (i >= old_tz_size) old_tz_size = i+1;
if (old_tz_size > PATH_MAX+2) old_tz_size = PATH_MAX+2;
old_tz = malloc(old_tz_size);
}
if (old_tz) memcpy(old_tz, s, i+1);
/* Non-suid can use an absolute tzfile pathname or a relative
* pathame beginning with "."; in secure mode, only the
* standard path will be searched. */
allow zoneinfo-path-relative filenames with no slashes in TZ variable since the form TZ=name is reserved for POSIX-form time zone strings, TZ=:name needs to be used when the zoneinfo filename is in the top-level zoneinfo directory and therefore does not contain a slash. previously the leading colon was merely dropped, making it impossible to access such zones without a full absolute pathname. changes based on patch by Timo Teräs.
2014-04-21 18:11:42 -04:00
if (*s == ':' || ((p=strchr(s, '/')) && !memchr(s, ',', p-s))) {
if (*s == ':') s++;
if (*s == '/' || *s == '.') {
if (!libc.secure) map = __map_file(s, &map_size);
} else {
size_t l = strlen(s);
if (l <= NAME_MAX && !strchr(s, '.')) {
the big time handling overhaul this commit has two major user-visible parts: zoneinfo-format time zones are now supported, and overflow handling is intended to be complete in the sense that all functions return a correct result if and only if the result fits in the destination type, and otherwise return an error. also, some noticable bugs in the way DST detection and normalization worked have been fixed, and performance may be better than before, but it has not been tested.
2013-07-17 05:24:50 -04:00
memcpy(pathname, s, l+1);
pathname[l] = 0;
timezone parser: fix iteration over search dir paths try+l points to \0, so only one iteration was ever tried.
2013-11-04 17:07:28 +00:00
for (try=search; !map && *try; try+=l+1) {
the big time handling overhaul this commit has two major user-visible parts: zoneinfo-format time zones are now supported, and overflow handling is intended to be complete in the sense that all functions return a correct result if and only if the result fits in the destination type, and otherwise return an error. also, some noticable bugs in the way DST detection and normalization worked have been fixed, and performance may be better than before, but it has not been tested.
2013-07-17 05:24:50 -04:00
l = strlen(try);
memcpy(pathname-l, try, l);
map = __map_file(pathname-l, &map_size);
}
}
}
do not try to interpret implementation specific strings as tz definition
2014-04-22 21:55:20 +03:00
if (!map) s = __gmt;
the big time handling overhaul this commit has two major user-visible parts: zoneinfo-format time zones are now supported, and overflow handling is intended to be complete in the sense that all functions return a correct result if and only if the result fits in the destination type, and otherwise return an error. also, some noticable bugs in the way DST detection and normalization worked have been fixed, and performance may be better than before, but it has not been tested.
2013-07-17 05:24:50 -04:00
}
perform minimal sanity checks on zoneinfo files loaded via TZ variable previously, setting TZ to the pathname of a file which was not a valid zoneinfo file would usually cause programs using local time zone based operations to crash. the new code checks the file size and magic at the beginning of the file, which seems sufficient to prevent accidental misconfiguration from causing crashes. attempting to make fully-robust validation would be futile unless we wanted to drop use of mmap (shared zoneinfo) and instead read it into a local buffer, since such validation would be subject to race conditions with modification of the file.
2014-04-22 20:09:56 -04:00
if (map && (map_size < 44 || memcmp(map, "TZif", 4))) {
__munmap((void *)map, map_size);
map = 0;
s = __gmt;
}
the big time handling overhaul this commit has two major user-visible parts: zoneinfo-format time zones are now supported, and overflow handling is intended to be complete in the sense that all functions return a correct result if and only if the result fits in the destination type, and otherwise return an error. also, some noticable bugs in the way DST detection and normalization worked have been fixed, and performance may be better than before, but it has not been tested.
2013-07-17 05:24:50 -04:00
zi = map;
if (map) {
int scale = 2;
if (sizeof(time_t) > 4 && map[4]=='2') {
fix timezone parser code crashing on 64bit sys if sizeof(time_t) == 8, this code path was missing the correct offset into the zoneinfo file, using the header magic to do offset calculations. the 6 32bit fields to be read start at offset 20.
2013-11-04 15:13:21 +00:00
size_t skip = zi_dotprod(zi+20, VEC(1,1,8,5,6,1), 6);
timezone parser: fix offset to transition table in 64bit code path we need to skip to the second TZif header, which starts at skip+44, and then skip another header (20 bytes) plus the following 6 32bit values.
2013-11-04 15:57:51 +00:00
trans = zi+skip+44+44;
the big time handling overhaul this commit has two major user-visible parts: zoneinfo-format time zones are now supported, and overflow handling is intended to be complete in the sense that all functions return a correct result if and only if the result fits in the destination type, and otherwise return an error. also, some noticable bugs in the way DST detection and normalization worked have been fixed, and performance may be better than before, but it has not been tested.
2013-07-17 05:24:50 -04:00
scale++;
} else {
trans = zi+44;
}
index = trans + (zi_read32(trans-12) << scale);
types = index + zi_read32(trans-12);
abbrevs = types + 6*zi_read32(trans-8);
fix strftime handling of time zone data this may need further revision in the future, since POSIX is rather unclear on the requirements, and is designed around the assumption of POSIX TZ specifiers which are not sufficiently powerful to represent real-world timezones (this is why zoneinfo support was added). the basic issue is that strftime gets the string and numeric offset for the timezone from the extra fields in struct tm, which are initialized when calling localtime/gmtime/etc. however, a conforming application might have created its own struct tm without initializing these fields, in which case using __tm_zone (a pointer) could crash. other zoneinfo-based implementations simply check for a null pointer, but otherwise can still crash of the field contains junk. simply ignoring __tm_zone and using tzname[] would "work" but would give incorrect results in time zones with more complex rules. I feel like this would lower the quality of implementation. instead, simply validate __tm_zone: unless it points to one of the zone name strings managed by the timezone system, assume it's invalid. this commit also fixes several other minor bugs with formatting: tm_isdst being negative is required to suppress printing of the zone formats, and %z was using the wrong format specifiers since the type of val was changed, resulting in bogus output.
2013-08-24 12:59:02 -04:00
abbrevs_end = abbrevs + zi_read32(trans-4);
the big time handling overhaul this commit has two major user-visible parts: zoneinfo-format time zones are now supported, and overflow handling is intended to be complete in the sense that all functions return a correct result if and only if the result fits in the destination type, and otherwise return an error. also, some noticable bugs in the way DST detection and normalization worked have been fixed, and performance may be better than before, but it has not been tested.
2013-07-17 05:24:50 -04:00
if (zi[map_size-1] == '\n') {
for (s = (const char *)zi+map_size-2; *s!='\n'; s--);
s++;
} else {
properly fill in tzname[] for old (pre-64-bit-format) zoneinfo files in this case, the first standard-time and first daylight-time rules should be taken as the "default" ones to expose.
2013-08-24 13:11:18 -04:00
const unsigned char *p;
__tzname[0] = __tzname[1] = 0;
__daylight = __timezone = dst_off = 0;
for (i=0; i<5; i++) r0[i] = r1[i] = 0;
for (p=types; p<abbrevs; p+=6) {
if (!p[4] && !__tzname[0]) {
__tzname[0] = (char *)abbrevs + p[5];
__timezone = -zi_read32(p);
}
if (p[4] && !__tzname[1]) {
__tzname[1] = (char *)abbrevs + p[5];
dst_off = -zi_read32(p);
__daylight = 1;
}
}
if (!__tzname[0]) __tzname[0] = __tzname[1];
if (!__tzname[0]) __tzname[0] = (char *)__gmt;
if (!__daylight) {
__tzname[1] = __tzname[0];
dst_off = __timezone;
}
return;
the big time handling overhaul this commit has two major user-visible parts: zoneinfo-format time zones are now supported, and overflow handling is intended to be complete in the sense that all functions return a correct result if and only if the result fits in the destination type, and otherwise return an error. also, some noticable bugs in the way DST detection and normalization worked have been fixed, and performance may be better than before, but it has not been tested.
2013-07-17 05:24:50 -04:00
}
}
fix strftime handling of time zone data this may need further revision in the future, since POSIX is rather unclear on the requirements, and is designed around the assumption of POSIX TZ specifiers which are not sufficiently powerful to represent real-world timezones (this is why zoneinfo support was added). the basic issue is that strftime gets the string and numeric offset for the timezone from the extra fields in struct tm, which are initialized when calling localtime/gmtime/etc. however, a conforming application might have created its own struct tm without initializing these fields, in which case using __tm_zone (a pointer) could crash. other zoneinfo-based implementations simply check for a null pointer, but otherwise can still crash of the field contains junk. simply ignoring __tm_zone and using tzname[] would "work" but would give incorrect results in time zones with more complex rules. I feel like this would lower the quality of implementation. instead, simply validate __tm_zone: unless it points to one of the zone name strings managed by the timezone system, assume it's invalid. this commit also fixes several other minor bugs with formatting: tm_isdst being negative is required to suppress printing of the zone formats, and %z was using the wrong format specifiers since the type of val was changed, resulting in bogus output.
2013-08-24 12:59:02 -04:00
if (!s) s = __gmt;
the big time handling overhaul this commit has two major user-visible parts: zoneinfo-format time zones are now supported, and overflow handling is intended to be complete in the sense that all functions return a correct result if and only if the result fits in the destination type, and otherwise return an error. also, some noticable bugs in the way DST detection and normalization worked have been fixed, and performance may be better than before, but it has not been tested.
2013-07-17 05:24:50 -04:00
getname(std_name, &s);
__tzname[0] = std_name;
__timezone = getoff(&s);
getname(dst_name, &s);
__tzname[1] = dst_name;
if (dst_name[0]) {
__daylight = 1;
if (*s == '+' || *s=='-' || *s-'0'<10U)
dst_off = getoff(&s);
else
dst_off = __timezone - 3600;
} else {
__daylight = 0;
dst_off = 0;
}
if (*s == ',') s++, getrule(&s, r0);
if (*s == ',') s++, getrule(&s, r1);
}
/* Search zoneinfo rules to find the one that applies to the given time,
* and determine alternate opposite-DST-status rule that may be needed. */
static size_t scan_trans(long long t, int local, size_t *alt)
{
int scale = 3 - (trans == zi+44);
uint64_t x;
int off = 0;
size_t a = 0, n = (index-trans)>>scale, m;
if (!n) {
if (alt) *alt = 0;
return 0;
}
/* Binary search for 'most-recent rule before t'. */
while (n > 1) {
m = a + n/2;
x = zi_read32(trans + (m<<scale));
if (scale == 3) x = x<<32 | zi_read32(trans + (m<<scale) + 4);
else x = (int32_t)x;
if (local) off = (int32_t)zi_read32(types + 6 * index[m-1]);
if (t - off < (int64_t)x) {
n /= 2;
} else {
a = m;
n -= n/2;
}
}
/* First and last entry are special. First means to use lowest-index
* non-DST type. Last means to apply POSIX-style rule if available. */
n = (index-trans)>>scale;
if (a == n-1) return -1;
if (a == 0) {
x = zi_read32(trans + (a<<scale));
if (scale == 3) x = x<<32 | zi_read32(trans + (a<<scale) + 4);
else x = (int32_t)x;
if (local) off = (int32_t)zi_read32(types + 6 * index[a-1]);
if (t - off < (int64_t)x) {
for (a=0; a<(abbrevs-types)/6; a++) {
if (types[6*a+4] != types[4]) break;
}
if (a == (abbrevs-types)/6) a = 0;
if (types[6*a+4]) {
*alt = a;
return 0;
} else {
*alt = 0;
return a;
}
}
}
/* Try to find a neighboring opposite-DST-status rule. */
if (alt) {
if (a && types[6*index[a-1]+4] != types[6*index[a]+4])
*alt = index[a-1];
else if (a+1<n && types[6*index[a+1]+4] != types[6*index[a]+4])
*alt = index[a+1];
else
*alt = index[a];
}
return index[a];
}
static int days_in_month(int m, int is_leap)
{
if (m==2) return 28+is_leap;
else return 30+((0xad5>>(m-1))&1);
}
/* Convert a POSIX DST rule plus year to seconds since epoch. */
static long long rule_to_secs(const int *rule, int year)
{
int is_leap;
long long t = __year_to_secs(year, &is_leap);
int x, m, n, d;
if (rule[0]!='M') {
x = rule[1];
if (rule[0]=='J' && (x < 60 || !is_leap)) x--;
t += 86400 * x;
} else {
m = rule[1];
n = rule[2];
d = rule[3];
t += __month_to_secs(m-1, is_leap);
int wday = (int)((t + 4*86400) % (7*86400)) / 86400;
int days = d - wday;
if (days < 0) days += 7;
if (n == 5 && days+28 >= days_in_month(m, is_leap)) n = 4;
t += 86400 * (days + 7*(n-1));
}
t += rule[4];
return t;
}
/* Determine the time zone in effect for a given time in seconds since the
* epoch. It can be given in local or universal time. The results will
* indicate whether DST is in effect at the queried time, and will give both
* the GMT offset for the active zone/DST rule and the opposite DST. This
* enables a caller to efficiently adjust for the case where an explicit
* DST specification mismatches what would be in effect at the time. */
void __secs_to_zone(long long t, int local, int *isdst, long *offset, long *oppoff, const char **zonename)
{
LOCK(lock);
do_tzset();
if (zi) {
size_t alt, i = scan_trans(t, local, &alt);
if (i != -1) {
*isdst = types[6*i+4];
*offset = -(int32_t)zi_read32(types+6*i);
*zonename = (const char *)abbrevs + types[6*i+5];
if (oppoff) *oppoff = -(int32_t)zi_read32(types+6*alt);
UNLOCK(lock);
return;
}
}
if (!__daylight) goto std;
/* FIXME: may be broken if DST changes right at year boundary?
* Also, this could be more efficient.*/
long long y = t / 31556952 + 70;
while (__year_to_secs(y, 0) > t) y--;
while (__year_to_secs(y+1, 0) < t) y++;
long long t0 = rule_to_secs(r0, y);
long long t1 = rule_to_secs(r1, y);
if (t0 < t1) {
if (!local) {
t0 += __timezone;
t1 += dst_off;
}
if (t >= t0 && t < t1) goto dst;
goto std;
} else {
if (!local) {
t1 += __timezone;
t0 += dst_off;
}
if (t >= t1 && t < t0) goto std;
goto dst;
}
std:
*isdst = 0;
*offset = __timezone;
if (oppoff) *oppoff = dst_off;
*zonename = __tzname[0];
UNLOCK(lock);
return;
dst:
*isdst = 1;
*offset = dst_off;
if (oppoff) *oppoff = __timezone;
*zonename = __tzname[1];
UNLOCK(lock);
}
void __tzset()
{
LOCK(lock);
do_tzset();
UNLOCK(lock);
}
weak_alias(__tzset, tzset);
fix strftime handling of time zone data this may need further revision in the future, since POSIX is rather unclear on the requirements, and is designed around the assumption of POSIX TZ specifiers which are not sufficiently powerful to represent real-world timezones (this is why zoneinfo support was added). the basic issue is that strftime gets the string and numeric offset for the timezone from the extra fields in struct tm, which are initialized when calling localtime/gmtime/etc. however, a conforming application might have created its own struct tm without initializing these fields, in which case using __tm_zone (a pointer) could crash. other zoneinfo-based implementations simply check for a null pointer, but otherwise can still crash of the field contains junk. simply ignoring __tm_zone and using tzname[] would "work" but would give incorrect results in time zones with more complex rules. I feel like this would lower the quality of implementation. instead, simply validate __tm_zone: unless it points to one of the zone name strings managed by the timezone system, assume it's invalid. this commit also fixes several other minor bugs with formatting: tm_isdst being negative is required to suppress printing of the zone formats, and %z was using the wrong format specifiers since the type of val was changed, resulting in bogus output.
2013-08-24 12:59:02 -04:00
const char *__tm_to_tzname(const struct tm *tm)
{
const void *p = tm->__tm_zone;
LOCK(lock);
do_tzset();
minor fix to tz name checking if a zoneinfo file is not (or is no longer) in use, don't check the abbrevs pointers, which may be invalid.
2013-08-24 13:10:01 -04:00
if (p != __gmt && p != __tzname[0] && p != __tzname[1] &&
(!zi || (uintptr_t)p-(uintptr_t)abbrevs >= abbrevs_end - abbrevs))
fix strftime handling of time zone data this may need further revision in the future, since POSIX is rather unclear on the requirements, and is designed around the assumption of POSIX TZ specifiers which are not sufficiently powerful to represent real-world timezones (this is why zoneinfo support was added). the basic issue is that strftime gets the string and numeric offset for the timezone from the extra fields in struct tm, which are initialized when calling localtime/gmtime/etc. however, a conforming application might have created its own struct tm without initializing these fields, in which case using __tm_zone (a pointer) could crash. other zoneinfo-based implementations simply check for a null pointer, but otherwise can still crash of the field contains junk. simply ignoring __tm_zone and using tzname[] would "work" but would give incorrect results in time zones with more complex rules. I feel like this would lower the quality of implementation. instead, simply validate __tm_zone: unless it points to one of the zone name strings managed by the timezone system, assume it's invalid. this commit also fixes several other minor bugs with formatting: tm_isdst being negative is required to suppress printing of the zone formats, and %z was using the wrong format specifiers since the type of val was changed, resulting in bogus output.
2013-08-24 12:59:02 -04:00
p = "";
UNLOCK(lock);
return p;
}
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