gl_* check do nothing?

[Sam Steingold]

this part of my configure.in:

==========================
AC_FUNC_CHOWN
gl_FUNC_MKTIME
gl_FUNC_GNU_STRFTIME
gl_FUNC_STRPTIME
gl_TIME_MODULE_INDICATOR([strptime])
gl_GETDATE
gl_FUNC_STRVERSCMP
gl_STRING_MODULE_INDICATOR([strverscmp])
gl_FUNC_UNAME
gl_SYS_UTSNAME_MODULE_INDICATOR([uname])
gl_FUNC_STRERROR
gl_STRING_MODULE_INDICATOR([strerror])
AC_CHECK_DECLS([signgam],,,[#include <math.h>])
==========================

produces this output:
==========================
checking for working chown... yes
checking for working mktime... (cached) yes
checking for struct tm.tm_zone... (cached) yes
checking for strverscmp... (cached) yes
checking for uname... (cached) yes
checking whether signgam is declared... yes
==========================

i.e.,

==========================
gl_FUNC_GNU_STRFTIME
gl_FUNC_STRPTIME
gl_TIME_MODULE_INDICATOR([strptime])
gl_GETDATE
==========================

only prints

==========================
checking for struct tm.tm_zone... (cached) yes
==========================

while

==========================
gl_FUNC_STRERROR
gl_STRING_MODULE_INDICATOR([strerror])
==========================

print NOTHING.

So, does this mean that gnulib NEVER relies on the system-supplied strftime, 
strptime, getdate, strerror?
why?
this is a very current ubuntu so I expected that _none_ of the gnulib code 
would be used.
how do I get the full list of all functions which gnulib actually replaced in 
the current build?

thanks!
Sam.