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(autoconf.info)Structures

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Structures
==========

   The following macros check for certain structures or structure
members.  To check structures not listed here, use `AC_EGREP_CPP'
(Note: Examining Declarations) or `AC_TRY_COMPILE' (Note: Examining
Syntax).

 - Macro: AC_HEADER_STAT
     If the macros `S_ISDIR', `S_ISREG' et al. defined in `sys/stat.h'
     do not work properly (returning false positives), define
     `STAT_MACROS_BROKEN'.  This is the case on Tektronix UTekV, Amdahl
     UTS and Motorola System V/88.

 - Macro: AC_HEADER_TIME
     If a program may include both `time.h' and `sys/time.h', define
     `TIME_WITH_SYS_TIME'.  On some older systems, `sys/time.h'
     includes `time.h', but `time.h' is not protected against multiple
     inclusion, so programs should not explicitly include both files.
     This macro is useful in programs that use, for example, `struct
     timeval' or `struct timezone' as well as `struct tm'.  It is best
     used in conjunction with `HAVE_SYS_TIME_H', which can be checked
     for using `AC_CHECK_HEADERS(sys/time.h)'.

          #if TIME_WITH_SYS_TIME
          # include <sys/time.h>
          # include <time.h>
          #else
          # if HAVE_SYS_TIME_H
          #  include <sys/time.h>
          # else
          #  include <time.h>
          # endif
          #endif

 - Macro: AC_STRUCT_ST_BLKSIZE
     If `struct stat' contains an `st_blksize' member, define
     `HAVE_ST_BLKSIZE'.

 - Macro: AC_STRUCT_ST_BLOCKS
     If `struct stat' contains an `st_blocks' member, define
     `HAVE_ST_BLOCKS'.  Otherwise, add `fileblocks.o' to the output
     variable `LIBOBJS'.

 - Macro: AC_STRUCT_ST_RDEV
     If `struct stat' contains an `st_rdev' member, define
     `HAVE_ST_RDEV'.

 - 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'.

 - Macro: AC_STRUCT_TIMEZONE
     Figure out how to get the current timezone.  If `struct tm' has a
     `tm_zone' member, define `HAVE_TM_ZONE'.  Otherwise, if the
     external array `tzname' is found, define `HAVE_TZNAME'.