how to handle name clashes in linux/freebsd kernel sources ?

hi,
as part of the linux-kmod-compat code, and also SoC-KVM
work,
we are integrating some linux kernel source code with
FreeBSD source,
and there are a number of clashes in names (macros,
functions, etc.)
used in different ways in the two camps.

Any ideas on how to handle the conflict ? As a temporary
workaround we 
added a _compat suffix (in the source code) to the linux
names,
but this is of course undesirable, especially for widely
used names.

E.g. take these two examples:

msleep() - used to be a function in FreeBSD 6.x, but now it
is a macro    

  when it was a function we could make the linux source do
the following
        #include <sys/systm.h>          // bring in
the prototype
        #define msleep  linux_msleep    // override for
linux source
        // now reinclusion of sys/systm.h won't give
problems
  and then implement the linux function. However this breaks
with
  FreeBSD macros that call msleep, because they will be
expanded using
  linux msleep.

  With the macro version, we have not found a solution yet.

list manipulation macros
  these have the same names on linux and FreeBSD, but
different
  arguments, so they are not compatible. Here the
redefinition through
  a macro won't even work.

So... any ideas on how to handle this, short of renaming the
linux
macros ?

	cheers
	luigi
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This is related to the post attached at the end of this
email.

In this commit:

    CVS log for src/sys/sys/systm.h
    Revision 1.252: download - view: text, markup, annotated
- select for diffs
    Fri Mar 9 22:41:01 2007 UTC (3 months, 2 weeks ago) by
jhb

msleep() changed from a function to a macro wrapping
_sleep().

Being a macro, it is a lot harder to hide it in case of name
clashes
such as the one mentioned below.

This raises the question - what is the point in using
macros
in cases like this where we could use static inline function
and
probably even exploit better compiler checks ?

Would it be possible to revert msleep() to a real function
?

	cheers
	luigi

On Tue, Jun 26, 2007 at 04:07:58AM -0700, Luigi Rizzo
wrote:
> hi,
> as part of the linux-kmod-compat code, and also SoC-KVM
work,
> we are integrating some linux kernel source code with
FreeBSD source,
> and there are a number of clashes in names (macros,
functions, etc.)
> used in different ways in the two camps.
> 
> Any ideas on how to handle the conflict ? As a
temporary workaround we 
> added a _compat suffix (in the source code) to the
linux names,
> but this is of course undesirable, especially for
widely used names.
> 
> E.g. take these two examples:
> 
> msleep() - used to be a function in FreeBSD 6.x, but
now it is a macro    
> 
>   when it was a function we could make the linux source
do the following
>         #include <sys/systm.h>          // bring
in the prototype
>         #define msleep  linux_msleep    // override for
linux source
>         // now reinclusion of sys/systm.h won't give
problems
>   and then implement the linux function. However this
breaks with
>   FreeBSD macros that call msleep, because they will be
expanded using
>   linux msleep.
> 
>   With the macro version, we have not found a solution
yet.
> 
> list manipulation macros
>   these have the same names on linux and FreeBSD, but
different
>   arguments, so they are not compatible. Here the
redefinition through
>   a macro won't even work.
> 
> So... any ideas on how to handle this, short of
renaming the linux
> macros ?
> 
> 	cheers
> 	luigi
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On Tuesday 26 June 2007 03:31:30 pm Luigi Rizzo wrote:
> This is related to the post attached at the end of this
email.
> 
> In this commit:
> 
>     CVS log for src/sys/sys/systm.h
>     Revision 1.252: download - view: text, markup,
annotated - select for 
diffs
>     Fri Mar 9 22:41:01 2007 UTC (3 months, 2 weeks ago)
by jhb
> 
> msleep() changed from a function to a macro wrapping
_sleep().
> 
> Being a macro, it is a lot harder to hide it in case of
name clashes
> such as the one mentioned below.
> 
> This raises the question - what is the point in using
macros
> in cases like this where we could use static inline
function and
> probably even exploit better compiler checks ?
> 
> Would it be possible to revert msleep() to a real
function ?

FreeBSD already uses macros all over the place in sys/*.h. 
Go duke it out 
with bde.   You can
always #undef msleep and redefine it to something 
else.

-- 
John Baldwin
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