Re: Hypervisor build can't work without `python` (Was: Re: Xen commit 9b0bc91b3 possibly removed too much info from README)

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 17/04/2019 12:03, Wei Liu wrote:
> On Wed, Apr 17, 2019 at 11:58:49AM +0100, Andrew Cooper wrote:
>> On 17/04/2019 11:57, Wei Liu wrote:
>>> On Wed, Apr 17, 2019 at 11:44:36AM +0100, Andrew Cooper wrote:
>>>> On 17/04/2019 11:41, Wei Liu wrote:
>>>>> On Wed, Apr 17, 2019 at 10:56:57AM +0100, Wei Liu wrote:
>>>>>>> Here's what i did having pulled the master at commit cb70a26
>>>>>>>
>>>>>>> tar xf /path/to/xen-cb70a26.tar.gz
>>>>>>>
>>>>>>> cd xen-master/
>>>>>>>
>>>>>>> PYTHON=/usr/bin/python3 ./configure --prefix=/usr   \
>>>>>>>    --disable-seabios   \
>>>>>>>    --disable-qemu-traditional  \
>>>>>>>    --disable-rombios     \
>>>>>>>    --disable-stubdom 2>&1 | tee ../config.log
>>>>>>>
>>>>>>> make EFI_DIR=/usr/lib/efi world 2>&1 | tee ../make_world_3.out
>>>>>>>
>>>>>>>
>>>>>>> ...
>>>>>>> gcc -Wp,-MD,tools/kconfig/.zconf.tab.o.d    -D_GNU_SOURCE
>>>>>>> -D_DEFAULT_SOURCE -DCURSES_LOC="<ncurses.h>" -DNCURSES_WIDECHAR=1
>>>>>>> -DLOCALE  -Itools/kconfig -c -o tools/kconfig/zconf.tab.o
>>>>>>> tools/kconfig/zconf.tab.c
>>>>>>> gcc  -o tools/kconfig/conf tools/kconfig/conf.o tools/kconfig/zconf.tab.o
>>>>>>> tools/kconfig/conf -s --silentoldconfig Kconfig
>>>>>>> make[3]: Leaving directory '/usr/src/xen/xen-master/xen'
>>>>>>> make -f Rules.mk _install
>>>>>>> make[3]: Entering directory '/usr/src/xen/xen-master/xen'
>>>>>>> make -C tools
>>>>>>> make[4]: Entering directory '/usr/src/xen/xen-master/xen/tools'
>>>>>>> make symbols
>>>>>>> make[5]: Entering directory '/usr/src/xen/xen-master/xen/tools'
>>>>>>> gcc -Wall -Werror -Wstrict-prototypes -O2 -fomit-frame-pointer
>>>>>>> -fno-strict-aliasing -Wdeclaration-after-statement -o symbols
>>>>>>> symbols.c
>>>>>>> make[5]: Leaving directory '/usr/src/xen/xen-master/xen/tools'
>>>>>>> make[4]: Leaving directory '/usr/src/xen/xen-master/xen/tools'
>>>>>>> make -f /usr/src/xen/xen-master/xen/Rules.mk include/xen/compile.h
>>>>>>> make[4]: Entering directory '/usr/src/xen/xen-master/xen'
>>>>>>>  Xen 4.13-unstable
>>>>>>> /bin/sh: python: command not found
>>>>>>> make[4]: *** [Makefile:169: include/xen/compile.h] Error 127
>>>>>> Here. The PYTHON invocation is from the hypervisor build, not the tools
>>>>>> build.
>>>>>>
>>>>>> Thanks for the log.  I will have a closer look.
>>>>>>
>>>>>>> make[4]: Leaving directory '/usr/src/xen/xen-master/xen'
>>>>>>> make[3]: *** [Makefile:137: /usr/src/xen/xen-master/xen/xen] Error 2
>>>>>>> make[3]: Leaving directory '/usr/src/xen/xen-master/xen'
>>>>>>> make[2]: *** [Makefile:45: install] Error 2
>>>>>>> make[2]: Leaving directory '/usr/src/xen/xen-master/xen'
>>>>>>> make[1]: *** [Makefile:123: install-xen] Error 2
>>>>>>> make[1]: Leaving directory '/usr/src/xen/xen-master'
>>>>>>> make: *** [Makefile:165: world] Error 2
>>>>>>>
>>>>>>>
>>>>>>> Note the
>>>>>>>
>>>>>>> /bin/sh: python: command not found
>>>>>>>
>>>>> The issue here is on LFS there is no /usr/bin/python. So the hypervisor
>>>>> build is broken because xen/include/compile.h invokes
>>>>>
>>>>>  @$(PYTHON) tools/fig-to-oct.py < .banner >> $@.new
>>>>>
>>>>> There are other appearances of PYTHON in hypervisor build, which are
>>>>> equally broken.
>>>>>
>>>>> We had / have a policy to avoid making hypervisor build dependent on
>>>>> configure. I have CC'ed more people on their opinions.
>>>> Where has $(PYTHON) got lost?  It was specified correctly to begin with.
>>> Where is it specified?
>> Oh - I see now.
>>
>> It is specified for ./configure, but not for make.
> Right.
>
> It works for tools because tools build includes config/Tools.mk which
> contains the correct python path. Tools.mk is generated by configure.
>  
> Obviously hypervisor build shouldn't include Tools.mk. Furthermore, the
> policy of "hv shouldn't depend on configure" makes this route a no-go.
>
> Either we change the policy, or we document the deficiency, or we come
> up with some clever trick to probe.

Given the shebang in all of our scripts, would `env python` be
sufficiently clever trickery, or is that a can of worms we'd prefer not
to open?

~Andrew

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