I have had Xen 4.2-Unstable compiled a week or so ago and it all went 
fine and running, but i forget what revision i compiled now.

When i ran the *xl create /etc/xen/win7.cfg* to create a VM, i got an 
error about libxl and running "*sudo xl list*" shows the newly created 
VM, SO i just ignored that error for now. That error message was:

*libxl: error: libxl.c:3117:libxl_sched_credit_domain_set: Cpu weight 
out of range, valid values are within range from 1 to 65535
*
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SO, I noticed on the xen-unstable.hg tree that there have been a lot of 
updates to the libxl lately SO just out of curiosity, i wanted to get 
the latest revision 25374 of xen-unstable as of today 5/20/2012, and 
compile it. BUT, i cannot compile Xen anymore as the compile stops with 
warnings and error messages.

Upon scrolling up in the terminal window, i noticed these warning or 
error messages:

*node-select.c:57:6: warning: function declaration isn't a prototype 
[-Wstrict-prototypes]
node-select.c: In function 'vchan_wr':
node-select.c:60:2: warning: ISO C90 forbids mixed declarations and code 
[-Wdeclaration-after-statement]
node-select.c: At top level:
node-select.c:71:6: warning: function declaration isn't a prototype 
[-Wstrict-prototypes]
node-select.c: In function 'stdout_wr':
node-select.c:74:2: warning: ISO C90 forbids mixed declarations and code 
[-Wdeclaration-after-statement]*

*The error log from compiling the libSDL test is:
/tmp/qemu-conf--3330-.c:1:17: fatal error: SDL.h: No such file or directory*

*../xen-unstable.hg/tools/qemu-xen-traditional-dir/hw/eepro100.c:1232:5: 
warning: 'val' may be used uninitialized in this function [-Wuninitialized]*


_I also get like a dozen warnings about this:_
*../tools/xenstore/compat/xs.h:1:2: warning: #warning xs.h is deprecated 
use xenstore.h instead [-Wcpp]*


_AND finally the compilations stops with these messages:_
*libxl.c: In function 'libxl_primary_console_exec':
libxl.c:1233:9: error: case value '4294967295' not in enumerated type 
'libxl_domain_type' [-Werror=switch]

cc1: all warnings being treated as errors
make[3]: *** [libxl.o] Error 1
make[3]: *** Waiting for unfinished jobs....
make[3]: Leaving directory 
`/home/xyber/Desktop/KERNEL_BUILD/Xen/xen-unstable.hg/tools/libxl'
make[2]: *** [subdir-install-libxl] Error 2
make[2]: Leaving directory 
`/home/xyber/Desktop/KERNEL_BUILD/Xen/xen-unstable.hg/tools'
make[1]: *** [subdirs-install] Error 2
make[1]: Leaving directory 
`/home/xyber/Desktop/KERNEL_BUILD/Xen/xen-unstable.hg/tools'
make: *** [install-tools] Error 2*

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All of these messages appear at different times during compile, but 
these where the ones i found thru a quick glance at the terminal window 
output. I have also tried to compile the latest Xen 4.2 THREE different 
times now, and in all cases it seems to end with a similar error about 
*libxl.c*.

Each time i tried to compile, i booted into non-Xen kernel, ran "*sudo 
make uninstall*" of my current Xen 4.2-unstable and ran "*sudo dpkg -r 
xen-upstream-4.2-unstable*", AND twice now i cloned a fresh copy of the 
xen-unstable.hg before compile.