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

Groups > comp.lang.c > #57129

Re: porting from 32-bit to 64-bit with fine-tooth comb?

Show all headers | View raw

mbjorn@y7mail.com wrote:
> I got this in a mailing list for a FOSS package that I use:
 
> "Another thing to note when running old code on 64-bit platforms is to
> inspect the struct definitions that are used directly to store or read
> binary data. There's no standard way to guarantee compatibility but
> gcc has a "packed" pragma which should do the right thing combined
> with explicit padding where needed,"
 
> Is this a problem, that different word lengths can screw up 
> structures?  Can unsigned int, for example, change length going from
> a 32-bit system to 64?

It depends on your meaning of "system".

For the usual compile-link-run methodology, it depends on the 
properties and options of the compiler. It is usual for 64 bit
systems (that is, operating systems) to be able to run 32 bit 
programs, and run them exactly the same is on 32 bit OSs.

It is usual, but not required, that compiling for a 64 bit OS
will use 64 bit pointers. Other types may or may not change size.

You might even find some 32 bit systems that have a 64 bit int.

But if you recompile a program on a different system, even if both
are 32 bit or both 64 bit, it is possible for some sizes to change
and struct data not to match up.

-- glen

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

Thread

porting from 32-bit to 64-bit with fine-tooth comb? mbjorn@y7mail.com - 2015-02-07 15:33 -0800
  Re: porting from 32-bit to 64-bit with fine-tooth comb? wssimms@gmail.com - 2015-02-07 16:56 -0800
  Re: porting from 32-bit to 64-bit with fine-tooth comb? jt@toerring.de (Jens Thoms Toerring) - 2015-02-08 00:59 +0000
    Re: porting from 32-bit to 64-bit with fine-tooth comb? Keith Thompson <kst-u@mib.org> - 2015-02-07 17:22 -0800
      Re: porting from 32-bit to 64-bit with fine-tooth comb? jt@toerring.de (Jens Thoms Toerring) - 2015-02-08 01:43 +0000
        Re: porting from 32-bit to 64-bit with fine-tooth comb? raltbos@xs4all.nl (Richard Bos) - 2015-02-08 16:16 +0000
  Re: porting from 32-bit to 64-bit with fine-tooth comb? Richard Damon <Richard@Damon-Family.org> - 2015-02-07 20:02 -0500
  Re: porting from 32-bit to 64-bit with fine-tooth comb? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-02-08 02:18 +0000
  Re: porting from 32-bit to 64-bit with fine-tooth comb? Bartc <bc@freeuk.com> - 2015-02-08 11:08 +0000
  Re: porting from 32-bit to 64-bit with fine-tooth comb? Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-02-09 21:20 +0000
  Re: porting from 32-bit to 64-bit with fine-tooth comb? Nobody <nobody@nowhere.invalid> - 2015-02-09 21:35 +0000
  Re: porting from 32-bit to 64-bit with fine-tooth comb? Lőrinczy Zsigmond <nospam@for.me> - 2015-04-03 16:07 +0200
    Re: porting from 32-bit to 64-bit with fine-tooth comb? James Kuyper <jameskuyper@verizon.net> - 2015-04-03 11:21 -0400
    Re: porting from 32-bit to 64-bit with fine-tooth comb? Barry Schwarz <schwarzb@dqel.com> - 2015-04-03 09:36 -0700
      Re: porting from 32-bit to 64-bit with fine-tooth comb? Lőrinczy Zsigmond <nospam@for.me> - 2015-04-03 19:10 +0200
  Re: porting from 32-bit to 64-bit with fine-tooth comb? Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-04-04 21:05 +0000
    Re: porting from 32-bit to 64-bit with fine-tooth comb? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-04-04 23:13 -0700
      Re: porting from 32-bit to 64-bit with fine-tooth comb? Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-04-11 04:19 +0000
        Re: porting from 32-bit to 64-bit with fine-tooth comb? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-04-10 23:53 -0700
          Re: porting from 32-bit to 64-bit with fine-tooth comb? Richard Damon <Richard@Damon-Family.org> - 2015-04-11 10:54 -0400
          Re: porting from 32-bit to 64-bit with fine-tooth comb? Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-04-11 15:59 +0000

csiph-web