strptime doesn't fill in tm_wday and tm_yday.

Peter Rosin
Wed May 11 14:52:00 GMT 2011


The following STC hints at a problem in strptime:

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

	/* seed tm with some garbage */
	struct tm tm = {
		0, 0, 0, /* s m h */
		0, 0, 0, /* d m y */
		290774, 2280577, 81
	const char date[] = "2011-05-11 14:06:11";

	if (!strptime(date, "%Y - %m - %d %T", &tm)) {
		fprintf(stderr, "strptime error\n");
		return 1;

	printf("%s", asctime(&tm));
	printf("tm_yday %d\n", tm.tm_yday);
	printf("tm_wday %d\n", tm.tm_wday);
	printf("tm_isdst %d\n", tm.tm_isdst);
	return 0;

I get this output with Cygwin 1.7.9-1:
 May 11 14:06:11 2011
tm_yday 2280577
tm_wday 290774
tm_isdst 81

I expect:
Wed May 11 14:06:11 2011
tm_yday 130
tm_wday 3
tm_isdst whatever

I get the expected output on the Linux host I tried (with tm_isdst=81),
but not on Solaris 10.

On Solaris 10 I get (for completeness):
Sun May 11 14:06:11 2011
tm_yday 0
tm_wday 0
tm_isdst 0

Opengroup has this to say about only filling in some fields:

	"It is unspecified whether multiple calls to strptime()
	using the same tm structure will update the current
	contents of the structure or overwrite all contents of
	the structure. Conforming applications should make a
	single call to strptime() with a format and all data
	needed to completely specify the date and time being

but I don't think it applies since indeed I do completely specify
the date in my strptime call.

In my "real" program, the call to asctime with the crippled tm
causes a seg-fault instead of "just" missing weekday output, I guess
it depends...


Problem reports:
Unsubscribe info:

More information about the Cygwin mailing list