What's wrong with this code?

John Levine johnl at iecc.com
Tue Dec 13 05:39:24 UTC 2011

This tiny routine is in a .so loadable module I use.  (It's part of the mailfront
SMTP daemon.)

static const char* date_string(void)
  static char datebuf[64];
  time_t now = time(0);
  struct tm* tm = gmtime(&now);
  strftime(datebuf, sizeof datebuf - 1, "%d %b %Y %H:%M:%S -0000", tm);
  return datebuf;

I was getting bogus dates.  Running it under GDB, time() is returning
-1, and setting errno to 22, which is EINVAL.  Changing the call to
time to time(NULL) or time(&now) made no difference.

I changed it to a call to gettimeofday(), which works fine.  But what
could the problem have been?  When I splice this routine into a tiny
test program that calls it and prints out the result, it works fine.

The obvious problem, since it's in a .so, is that it's linking to something other than
the system library time() function, but I did an nm on the .so, and it said this,
which sure looks like the system time() function to me:

                 U time@@FBSD_1.0

Setting a breakpoint in gdb gets a complaint about trying to set a breakpoint in /lib/libc.so.7.

Any ideas what the problem was?


More information about the freebsd-questions mailing list