Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.c > #15762

struct alignment

Show all headers | View raw

Hello:

#define MAX_SIZE 8

enum my_enum
{
    VAL1 = 0;
    VAL2,
    VAL3,
    VAL4,
    VAL_MAX
};

struct my_struct
{
  enum my_enum e;
  int  w[MAX_SIZE];
};

Can a layout in such structure cause alignment issues on a target platform? 
I understand it much depends on a platform, but generally C compiler is 
allowed to do padding of structures, so for example on 32 bit machine, where 
'int' is 32 bit long:

struct my_struct
{
    int w[MAX_SIZE];
}

is aligned (as fas as I understand) so compiler probably won't be doing 
anything else with its layout, but adding 'enum my_enum' in the structure 
can poptentially get the structure un-aligned on such machine.  Should I be 
doing anything special to avoid this and should I be avoiding it at all ?

Would be very thankful for clarifications!

Mark 

Back to comp.lang.c | Previous | Next — Next in thread | Find similar | Unroll thread

Thread

struct alignment "Mark" <mark_cruzNOTFORSPAM@hotmail.com> - 2012-01-11 13:31 -0500
  Re: struct alignment Kleuske <kleuske@nowhere.net> - 2012-01-11 19:23 +0000
  Re: struct alignment "Scott Fluhrer" <sfluhrer@ix.netcom.com> - 2012-01-11 16:58 -0500
  Re: struct alignment Ralf Damaschke <rwspam@gmx.de> - 2012-01-11 22:08 +0000
  Re: struct alignment Keith Thompson <kst-u@mib.org> - 2012-01-11 14:42 -0800
    Re: struct alignment Dr Nick <3-nospam@temporary-address.org.uk> - 2012-01-12 06:56 +0000
      Re: struct alignment Ian Collins <ian-news@hotmail.com> - 2012-01-12 20:42 +1300
        Re: struct alignment Keith Thompson <kst-u@mib.org> - 2012-01-12 02:20 -0800
          Re: struct alignment Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-01-18 17:03 +0000
            Re: struct alignment Kaz Kylheku <kaz@kylheku.com> - 2012-01-18 17:21 +0000
              Re: struct alignment jgk@panix.com (Joe keane) - 2012-01-19 21:42 +0000
                Re: struct alignment blp@cs.stanford.edu (Ben Pfaff) - 2012-01-19 13:57 -0800
            Re: struct alignment Stephen Sprunk <stephen@sprunk.org> - 2012-01-18 11:57 -0600
              Re: struct alignment Keith Thompson <kst-u@mib.org> - 2012-01-18 14:28 -0800
            Re: struct alignment Robert Wessel <robertwessel2@yahoo.com> - 2012-01-18 13:10 -0600
              Re: struct alignment Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-01-19 11:34 +0000
                Re: struct alignment Robert Wessel <robertwessel2@yahoo.com> - 2012-01-19 14:50 -0600
                Re: struct alignment Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-01-21 11:49 +0000

csiph-web