Here's my latest effort at asctime.c. In this version, asctime itself never returns NULL which I trust makes folks happy. Given kre's points about avoiding breaking existing code, the format of what asctime returns is not always standard conforming which I trust makes some folks unhappy. Feedback welcome. --ado /* ** This file is in the public domain, so clarified as of ** 1996-06-05 by Arthur David Olson (arthur_david_olson@nih.gov). */ #ifndef lint #ifndef NOID static char elsieid[] = "@(#)asctime.c 7.16"; #endif /* !defined NOID */ #endif /* !defined lint */ /*LINTLIBRARY*/ #include "private.h" #include "tzfile.h" #if STRICTLY_STANDARD_ASCTIME #define ASCTIME_FMT "%.3s %.3s%3d %.2d:%.2d:%.2d %d\n" #define ASCTIME_FMT_B ASCTIME_FMT #else /* !STRICTLY_STANDARD_ASCTIME */ /* ** Some systems only handle "%.2d"; others only handle "%02d"; ** "%02.2d" makes (most) everybody happy. */ /* ** 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 ** spaces before the newline to get the newline in the traditional place. */ #define ASCTIME_FMT "%.3s %.3s%3d %02.2d:%02.2d:%02.2d %-4ld\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). */ #define ASCTIME_FMT_B "%.3s %.3s%3d %02.2d:%02.2d:%02.2d %ld\n" #endif /* !STRICTLY_STANDARD_ASCTIME */ #define STD_ASCTIME_BUF_SIZE 26 /* ** Big enough for something such as ** ??? ???-2147483648 -2147483648:-2147483648:-2147483648 -2147483648\n ** (two three-character abbreviations, five strings denoting integers, ** seven explicit spaces, two explicit colons, a newline, ** and a trailing ASCII nul). ** The values above are for systems where an int is 32 bits and are provided ** as an example; the define below calculates the maximum for system at hand. */ #define MAX_ASCTIME_BUF_SIZE (2*3+5*INT_STRLEN_MAXIMUM(int)+7+2+1+1) static char buf_asctime[MAX_ASCTIME_BUF_SIZE]; /* ** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition. */ char * asctime_r(timeptr, buf) register const struct tm * timeptr; char * buf; { static const char wday_name[][3] = { "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat" }; static const char mon_name[][3] = { "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" }; register const char * wn; register const char * mn; long year; char result[MAX_ASCTIME_BUF_SIZE]; if (timeptr->tm_wday < 0 || timeptr->tm_wday >= DAYSPERWEEK) wn = "???"; else wn = wday_name[timeptr->tm_wday]; if (timeptr->tm_mon < 0 || timeptr->tm_mon >= MONSPERYEAR) mn = "???"; else mn = mon_name[timeptr->tm_mon]; year = timeptr->tm_year + (long) TM_YEAR_BASE; /* ** We avoid using snprintf since it's not available on all systems. */ (void) sprintf(result, ((year >= -999 && year <= 9999) ? 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_asctime) { (void) strcpy(buf, result); return buf; } else { errno = EOVERFLOW; return NULL; } } /* ** A la ISO/IEC 9945-1, ANSI/IEEE Std 1003.1, 2004 Edition. */ char * asctime(timeptr) register const struct tm * timeptr; { return asctime_r(timeptr, buf_asctime); }