[Bug fortran/47175] no predefined macros __amd64, __amd64__, __x86_64 __x86_64__ in prepocessor

["hjl.tools at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47175

--- Comment #5 from H.J. Lu <hjl.tools at gmail dot com> 2011-01-05 15:17:50 UTC ---
(In reply to comment #4)
> (In reply to comment #3)
> > (In reply to comment #2)
> > > (In reply to comment #1)
> > > > Checking __amd64, __amd64__, __x86_64 __x86_64__ for
> > > > pointer size is wrong since pointer size may be
> > > > 32bit on x86-64.
> > > No, it can't be. The macros are set in dependence of the target platform (m32
> > > or m64). That means, if m32 is given the macro __i686 is set instead of
> > > __amd64. On the other hand, if m64 is given the macro __amd64 is set. I don't
> > > want to know the really underlying platform. I (or Matlab) want to know the
> > > target platform. So it is right to check the __amd64 macro. You can try it with
> > > the gcc-4.4. Only with gfortran-4.4 the macro is missed.
> > 
> > See
> > 
> > http://www.kernel.org/pub/linux/devel/binutils/ilp32/abi.pdf
> > 
> > where pointer size is 32bit.
> 
> As far as I understood means ILP32 a 32bit application in a 64bit environment

No. ILP32 is a 32bit environment with 64bit instruction sets.

> and LP64 a 64bit application in 64bit environment. Am I Right? The predefined
> preprocessor macro __amd64 is true if I compile with -m64 (default on Linux)
> and it is not true if I compile with -m32. So why I can't check against this
> macro, as far it is supported (as in gcc)? Please correct me if I'm totally
> wrong. Or do you want to tell me that a 64bit application could use 32bit
> pointers, or the other way round? If so, how is it possible?

ILP32 will define both __amd64 and __ILP32__. __amd64 is ISA, which
can have 32bit or 64bit pointer sizes.