lib/55436: strptime does not process %G or %V

[jklowden%schemamania.org@localhost]

>Number:         55436
>Category:       lib
>Synopsis:       strptime does not process %G or %V
>Confidential:   no
>Severity:       serious
>Priority:       low
>Responsible:    lib-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Jun 30 19:45:00 +0000 2020
>Originator:     jklowden
>Release:        NetBSD 7.0
>Organization:
self
>Environment:
System: NetBSD oak.schemamania.org 7.0 NetBSD 7.0 (GENERIC.201509250726Z) amd64
Architecture: x86_64
Machine: amd64
>Description:
	strptime(3) claims to honor %G and %V for ISO dates.  In fact, both metacharacters are processed but ignored.  strptime returns a pointer indicating the input was accepted, but the tm structure is unchanged. 
>How-To-Repeat:
	The attached program accepts three arguments: strptime format, strftime format, and a datestring.  It prints the contents of the strptime struct tm output, and the strftime output from that tm. One example use:

  $ t/strpftime W%V %D  W26
    tm = {
      tm_sec = 0, 
      tm_min = 0, 
      tm_hour = 0, 
      tm_mday = 0, 
      tm_mon = 0, 
      tm_year = 0, 
      tm_wday = 0, 
      tm_yday = 0, 
      tm_isdst = 0 }
  01/00/00 ('' unparsed)

It is perhaps interesting that the GNU strptime exhibits similar behavior. 

>Fix:
No fix.  Demonstration program:
[snip]
#include <ctype.h>
#include <err.h>
#include <getopt.h>
#include <libgen.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

#include <sys/types.h>

extern char *optarg;

int
main(int argc, char *argv[]) {
  char output[80];
  struct tm tm = {};

  if( argc < 4 ) {
    errx(EXIT_FAILURE, "syntax %s: strptime_fmt strftime_fmt datetime", argv[0]);
  }

  const char *ifmt = argv[1], *pend;
  const char *ofmt = argv[2];
  const char *input = argv[3];

  if( (pend = strptime(input, ifmt, &tm)) == NULL ) {
    errx(EXIT_FAILURE, "could not parse '%s' with '%s'", input, ifmt);
  }

  const char fmt[] =
    "  tm = {\n"
    "    tm_sec = %d, \n"
    "    tm_min = %d, \n"
    "    tm_hour = %d, \n"
    "    tm_mday = %d, \n"
    "    tm_mon = %d, \n"
    "    tm_year = %d, \n"
    "    tm_wday = %d, \n"
    "    tm_yday = %d, \n"
    "    tm_isdst = %d }\n";

  printf(fmt,    
	 tm.tm_sec, 
	 tm.tm_min, 
	 tm.tm_hour, 
	 tm.tm_mday, 
	 tm.tm_mon, 
	 tm.tm_year, 
	 tm.tm_wday, 
	 tm.tm_yday, 
	 tm.tm_isdst);

  strftime(output, sizeof(output), ofmt, &tm);
  printf("%s ('%s' unparsed)\n", output, pend);

  return EXIT_SUCCESS;
}
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