The following macros check for certain structures or structure members.
Perform all the actions of AC_HEADER_DIRENT (see Particular Header Checks). Then, if struct dirent contains a d_ino
member, define HAVE_STRUCT_DIRENT_D_INO.
HAVE_STRUCT_DIRENT_D_INO indicates only the presence of
d_ino, not whether its contents are always reliable.
Traditionally, a zero d_ino indicated a deleted directory entry,
though current systems hide this detail from the user and never return
zero d_ino values.
Many current systems report an incorrect d_ino for a directory
entry that is a mount point.
Perform all the actions of AC_HEADER_DIRENT (see Particular Header Checks). Then, if struct dirent contains a d_type
member, define HAVE_STRUCT_DIRENT_D_TYPE.
If struct stat contains an st_blocks member, define
HAVE_STRUCT_STAT_ST_BLOCKS. Otherwise, require an
AC_LIBOBJ replacement of ‘fileblocks’. The former name,
HAVE_ST_BLOCKS is to be avoided, as its support will cease in the
future.
This macro caches its result in the ac_cv_member_struct_stat_st_blocks
variable.
If time.h does not define struct tm, define
TM_IN_SYS_TIME, which means that including sys/time.h
had better define struct tm.
This macro is obsolescent, as time.h defines struct tm in
current systems. New programs need not use this macro.
Figure out how to get the current timezone. If struct tm has a
tm_zone member, define HAVE_STRUCT_TM_TM_ZONE (and the
obsoleted HAVE_TM_ZONE). Otherwise, if the external array
tzname is found, define HAVE_TZNAME; if it is declared,
define HAVE_DECL_TZNAME.