diff options
Diffstat (limited to 'contrib/tzcode/asctime.c')
| -rw-r--r-- | contrib/tzcode/asctime.c | 124 |
1 files changed, 68 insertions, 56 deletions
diff --git a/contrib/tzcode/asctime.c b/contrib/tzcode/asctime.c index ebb90a1cc84d..491d23bf73ac 100644 --- a/contrib/tzcode/asctime.c +++ b/contrib/tzcode/asctime.c @@ -7,38 +7,16 @@ /* ** Avoid the temptation to punt entirely to strftime; +** strftime can behave badly when tm components are out of range, and ** the output of strftime is supposed to be locale specific ** whereas the output of asctime is supposed to be constant. */ /*LINTLIBRARY*/ -#include "namespace.h" #include "private.h" -#include "un-namespace.h" #include <stdio.h> -/* -** All years associated with 32-bit time_t values are exactly four digits long; -** some years associated with 64-bit time_t values are not. -** Vintage programs are coded for years that are always four digits long -** and may assume that the newline always lands in the same place. -** For years that are less than four digits, we pad the output with -** leading zeroes to get the newline in the traditional place. -** The -4 ensures that we get four characters of output even if -** we call a strftime variant that produces fewer characters for some years. -** This conforms to recent ISO C and POSIX standards, which say behavior -** is undefined when the year is less than 1000 or greater than 9999. -*/ -static char const ASCTIME_FMT[] = "%s %s%3d %.2d:%.2d:%.2d %-4s\n"; -/* -** For years that are more than four digits we put extra spaces before the year -** so that code trying to overwrite the newline won't end up overwriting -** a digit within a year and truncating the year (operating on the assumption -** that no output is better than wrong output). -*/ -static char const ASCTIME_FMT_B[] = "%s %s%3d %.2d:%.2d:%.2d %s\n"; - enum { STD_ASCTIME_BUF_SIZE = 26 }; /* ** Big enough for something such as @@ -52,14 +30,24 @@ enum { STD_ASCTIME_BUF_SIZE = 26 }; */ static char buf_asctime[2*3 + 5*INT_STRLEN_MAXIMUM(int) + 7 + 2 + 1 + 1]; -/* A similar buffer for ctime. - C89 requires that they be the same buffer. - This requirement was removed in C99, so support it only if requested, - as support is more likely to lead to bugs in badly written programs. */ -#if SUPPORT_C89 -# define buf_ctime buf_asctime -#else -static char buf_ctime[sizeof buf_asctime]; +/* On pre-C99 platforms, a snprintf substitute good enough for us. */ +#if !HAVE_SNPRINTF +# include <stdarg.h> +ATTRIBUTE_FORMAT((printf, 3, 4)) static int +my_snprintf(char *s, size_t size, char const *format, ...) +{ + int n; + va_list args; + char stackbuf[sizeof buf_asctime]; + va_start(args, format); + n = vsprintf(stackbuf, format, args); + va_end (args); + if (0 <= n && n < size) + memcpy (s, stackbuf, n + 1); + return n; +} +# undef snprintf +# define snprintf my_snprintf #endif /* Publish asctime_r and ctime_r only when supporting older POSIX. */ @@ -84,14 +72,19 @@ asctime_r(struct tm const *restrict timeptr, char *restrict buf) "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" }; - const char * wn; - const char * mn; - char year[INT_STRLEN_MAXIMUM(int) + 2]; - char result[sizeof buf_asctime]; + register const char * wn; + register const char * mn; + int year, mday, hour, min, sec; + long long_TM_YEAR_BASE = TM_YEAR_BASE; + size_t bufsize = (buf == buf_asctime + ? sizeof buf_asctime : STD_ASCTIME_BUF_SIZE); if (timeptr == NULL) { + strcpy(buf, "??? ??? ?? ??:??:?? ????\n"); + /* Set errno now, since strcpy might change it in + POSIX.1-2017 and earlier. */ errno = EINVAL; - return strcpy(buf, "??? ??? ?? ??:??:?? ????\n"); + return buf; } if (timeptr->tm_wday < 0 || timeptr->tm_wday >= DAYSPERWEEK) wn = "???"; @@ -99,25 +92,41 @@ asctime_r(struct tm const *restrict timeptr, char *restrict buf) if (timeptr->tm_mon < 0 || timeptr->tm_mon >= MONSPERYEAR) mn = "???"; else mn = mon_name[timeptr->tm_mon]; - /* - ** Use strftime's %Y to generate the year, to avoid overflow problems - ** when computing timeptr->tm_year + TM_YEAR_BASE. - ** Assume that strftime is unaffected by other out-of-range members - ** (e.g., timeptr->tm_mday) when processing "%Y". - */ - strftime(year, sizeof year, "%Y", timeptr); - /* - ** We avoid using snprintf since it's not available on all systems. - */ - sprintf(result, - ((strlen(year) <= 4) ? ASCTIME_FMT : ASCTIME_FMT_B), - wn, mn, - timeptr->tm_mday, timeptr->tm_hour, - timeptr->tm_min, timeptr->tm_sec, - year); - if (strlen(result) < STD_ASCTIME_BUF_SIZE - || buf == buf_ctime || buf == buf_asctime) - return strcpy(buf, result); + + year = timeptr->tm_year; + mday = timeptr->tm_mday; + hour = timeptr->tm_hour; + min = timeptr->tm_min; + sec = timeptr->tm_sec; + + /* Vintage programs are coded for years that are always four bytes long + and may assume that the newline always lands in the same place. + For years that are less than four bytes, pad the output with + leading zeroes to get the newline in the traditional place. + For years longer than four bytes, put extra spaces before the year + so that vintage code trying to overwrite the newline + won't overwrite a digit within a year and truncate the year, + using the principle that no output is better than wrong output. + This conforms to ISO C and POSIX standards, which say behavior + is undefined when the year is less than 1000 or greater than 9999. + + Also, avoid overflow when formatting tm_year + TM_YEAR_BASE. */ + + if ((year <= LONG_MAX - TM_YEAR_BASE + ? snprintf (buf, bufsize, + ((-999 - TM_YEAR_BASE <= year + && year <= 9999 - TM_YEAR_BASE) + ? "%s %s%3d %.2d:%.2d:%.2d %04ld\n" + : "%s %s%3d %.2d:%.2d:%.2d %ld\n"), + wn, mn, mday, hour, min, sec, + year + long_TM_YEAR_BASE) + : snprintf (buf, bufsize, + "%s %s%3d %.2d:%.2d:%.2d %d%d\n", + wn, mn, mday, hour, min, sec, + year / 10 + TM_YEAR_BASE / 10, + year % 10)) + < bufsize) + return buf; else { errno = EOVERFLOW; return NULL; @@ -142,5 +151,8 @@ ctime_r(const time_t *timep, char *buf) char * ctime(const time_t *timep) { - return ctime_r(timep, buf_ctime); + /* Do not call localtime_r, as C23 requires ctime to initialize the + static storage that localtime updates. */ + struct tm *tmp = localtime(timep); + return tmp ? asctime(tmp) : NULL; } |