Re: Predefine _M_IX86 in gcc

On Tue, 17 Dec 2002, Danny Smith wrote:

> > Adding "defined(__GCC__)" was a quick and effective fix for me.
> However,
> > I think that _M_IX86 should be predefined when compiling a Win32/Intel
> > program, regardless of the compiler used.
>
> Those defines are done for you if you include windows.h.
> _M_IX86 is defined in winnt.h
> CALLBACK is defined in windef.h

Right, but this is not the point.

I merely showed you an example where the pre-definition of _M_IX86 might
be desirable. The example is meant to make <GL/glut.h> work without
including <windows.h>.

The purpose of GLUT is to achieve platform independence, and this includes
the avoidance of <win*.h>.

I see that one may include <winnt.h>, or <windows.h> for that matter,
but AFAIK the purpose of MinGW is to assure a smooth transition of the
programs that compile with MSC-Win and/or gcc-othersys.

In the _very_particular_ example I gave you, the author of GLUT wanted to
provide CALLBACK and other things defined by <windows.h> and required by
<GL/gl.h> and <GL/glu.h>, *but* without including <windows.h>. The purpose
was to avoid the useless namespace pollution, since <windows.h> was not
necessary for any other reason.


Now let's go back to the general reason:


As pre-defined by both MSC and Borland C, _M_IX86 has a purpose similar
to __i386__, __i686__ etc, and the user should not be required to do
an extra task (such as including <windows.h>, or defining the symbol in
the makefile) in order to get it right with GCC.
Actually, _M_IX86 should be the Win32-portable equivalent of __i386__
and its friends.

Here is a little more _M_IX86 advocacy that I will throw in:

  #ifdef _M_IX86
is better than
  #if defined(__i386__) || defined(__i486__) || defined...  // for GCC
or even
  #if defined(__i386__) || ... || defined(_M_IX86)  // for GCC and others
while
  #if _M_IX86==500
is still as good as
  #ifdef __i586__


I've just looked into the mingw specs, and I saw in the long line
  "... march=i486:-D__i486 -D__i486__ ..."
which can go into
  "... march=i486:-D__i486 -D__i486__ -D_M_IX86=400 ..."

However, if you do not wish to predefine _M_IX86 for some reason,
I understand.

Cosmin



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