[svlug] Structure Field Offset Measurement

[J C Lawrence]

On Sat, 6 Jan 2001 23:21:29 -0800 
Karen Shaeffer <shaeffer at best.com> wrote:

> On Sat, Jan 06, 2001 at 10:16:16PM -0800, Anmol Khirbat wrote:

> At least not in this instance with gcc.
...
> I assure you it's not a problem--it works. It is actual code from
> <stddef.h> If point #4 was a factor here--then that MACRO would
> fail. Think about it.

Which clearly deliniates the flaw in the thread:

  You have are attempting to discuss how a specific implementation,
  to whit GCC on X86 when running against a Linux target, works.

  We have been attempting to discuss what the standard defines
  as as required behaviour as versus what it leaves as either
  implementation defined or as undefined (which are critically
  different).

This was not clear in your initial context-less query of a macro
definition, or in the early stages of the thread (my initial
response stated that I was commenting on the spec, not the
compiler).  In fact there was good evidence from you to think that
we were discussing the same thing, then.  What a particular compiler
does in a well defined environment ia barely interesting at best
whereas what an arbitrary compiler on an arbitrary platform platform
when compiling for an arbitrary target will necessarily do with
given code is a far more interesting thing -- tho my biases may be
showing slightly here.

'Specing the entire computing world as latter day Vaxen smells a
whole lot of the same sorts of narrow minded "we define the
computing universe" that autocracy that MS is regularly accused of.
Just what are you going to do with your first one's complement
machine which also happens to have the following?

  sizeof (byte) == sizeof(char) == sizeof(short) == sizeof(int) \
  == sizeof(long) == 64bits

Such machines exist today, and are even quite popular within certain
circles.

-- 
J C Lawrence                                       claw at kanga.nu
---------(*)                          http://www.kanga.nu/~claw/
--=| A man is as sane as he is dangerous to his environment |=--