Nullifying Recently Introduced Xen Headers Check

["John L. Poole" <johnlpoole@xxxxxxxxx>]

Greetings,

Gentoo Linux maintains two packages for Xen:

   1) app-emulation/xen-tools ("xen-tools")
   2) app-emulation/xen ("xen")

xen-tools is a prerequisite to xen.  So a failure
to install xen-tools will preclude any attempt to install xen.
I acknowledge that building xen-tools before building xen
is backwards and/or runs contrary to your project's way of
building, but that is what the Gentoo paradigm has been.

In trying to troubleshoot why a Gentoo 4.18.0 ebuild fails,
I ended up downloading your archive and successfully building it.
I then decided to compare the products built to see where
they varied in processing order.  The Xen Project builds xen first,
then the tools.

To see a visualization of the to build systems and the object
files they create matched in chronological order, see:

https://salemdata.us/xen/gentoo-4.18.0/comparison_of_build_orders_Xen_4.18.xhtml
     or the LibreOffice workbook I created the comparison in:
https://salemdata.us/xen/gentoo-4.18.0/comparison_of_build_orders_Xen_4.18.ods

In March 2023, this commit added some sort of headers check:

https://xenbits.xen.org/gitweb/?p=qemu-xen.git;a=commit;f=include/hw/xen/xen_native.h;h=e2abfe5ec67b69fb310fbeaacf7e68d61d16609e

Specifically, the lines 4-6 in [qemu-xen.git] / include / hw / xen /
xen_native.h:

    4 #ifdef __XEN_INTERFACE_VERSION__
    5 #error In Xen native files, include xen_native.h before other Xen
headers
    6 #endif

cause Gentoo's build to error out.  See line 24790:

    5 | #error In Xen native files, include xen_native.h before other
Xen headers

at https://salemdata.us/xen/xen_tools_20240128_Sun_174740.script.html.

What I have done is create a patch for a draft Gentoo ebuild which nullifies
lines 4-6 by wrapping them in a comment:

     --- a/tools/qemu-xen/include/hw/xen/xen_native.h
     +++ b/tools/qemu-xen/include/hw/xen/xen_native.h
     @@ -1,9 +1,9 @@
      #ifndef QEMU_HW_XEN_NATIVE_H
      #define QEMU_HW_XEN_NATIVE_H

     -#ifdef __XEN_INTERFACE_VERSION__
     +/* #ifdef __XEN_INTERFACE_VERSION__
      #error In Xen native files, include xen_native.h before other Xen
headers
     -#endif
     +#endif */

This patch allows the Gentoo xen-tools ebuild to successfully build.

Question: is there a risk nullifying the above 3 lines in xen_native.h
given Gentoo's backward build paradigm?

Thank you.

John Poole