BUG: mktime() May Cause R6003 "integer divide by 0" Error

The information in this article applies to:

• The C Run-time (CRT), included with: Microsoft Visual C++ for Windows, versions 1.0 and 1.5

SYMPTOMS

When you call mktime() with any time between 00:00:00 and 01:00:00 on 1/1/1970, with the TZ environment variable set to LOC000000 (Greenwich Mean Time), the following error messages display:

Under MS-DOS:

       run-time error
       - integer divide by 0

       Application Error
       - integer divide by 0

STATUS

Microsoft has confirmed this to be a bug in the products listed above. We are researching this bug and will post new information here in the Microsoft Knowledge Base as it becomes available.

This is not a problem in the Visual C++ 32-bit Edition.

MORE INFORMATION

The following sample code demonstrates how to reproduce this problem:

Sample Code

/*
/*  COMMAND LINE:
/*  DESCRIPTION: mktime() gives r6003 for time < 01:00:00 Jan. 1, 1970
/*            Be sure that environment variable TZ=LOC000000 GMT
/*

   #include <stdio.h>
   #include <time.h>

   #define START_TIME 3605L

   void main(void)
   {
     time_t reference;
     struct tm tblk;
     char buf[40];

     /* get current TZ environment variable
        (TZ=LOC000000 on my system: GMT) */
     _tzset();

     /* init reference time to 01/01/1970 at 01:00:05 */
     reference = START_TIME;

     /* assign daylight savings time value */
     tblk.tm_isdst = _daylight;

     /* loop downwards from initial reference time */
     for (reference = START_TIME;reference >= 0L; reference--)
     {
        tblk = *localtime(&reference);

        strftime(buf, 39, "%c", &tblk);
        printf("struct tm contents from localtime(): %s\n", buf);

        /* NOTE: mktime() generates divide by 0 error for reference
           seconds less than 3600 */
        reference = mktime(&tblk);
        printf("seconds from struct tm using mktime(): %ld\n", reference);
     }

   }