(autoconf.info)Structures

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4.5 Structures
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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'.