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5.8.1 Particular Structure Checks
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The following macros check for certain structures or structure members.

 -- Macro: AC_STRUCT_DIRENT_D_INO
     Perform all the actions of ‘AC_HEADER_DIRENT’ (*note Particular
     Headers::).  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.

 -- Macro: AC_STRUCT_DIRENT_D_TYPE
     Perform all the actions of ‘AC_HEADER_DIRENT’ (*note Particular
     Headers::).  Then, if ‘struct dirent’ contains a ‘d_type’ member,
     define ‘HAVE_STRUCT_DIRENT_D_TYPE’.

 -- Macro: AC_STRUCT_ST_BLOCKS
     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.

 -- Macro: AC_STRUCT_TM
     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.

 -- Macro: AC_STRUCT_TIMEZONE
     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’.