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

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 17/04/2019 12:16, Wei Liu wrote:
> On Wed, Apr 17, 2019 at 12:15:04PM +0100, Andrew Cooper wrote:
>> 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?
> I already tried env python -- it didn't work. I think it searches PATHS
> just like a shell would.

So this particular use of python is completely trivial.  It is an octal
conversion on the banner string, to feed into a string for XEN_BANNER

It exists because I removed a fork of figlet[1] from Xen's source tree
with this script, but its probably just as easy to do with awk or
something similar.

~Andrew

[1] Yes - Xen did use to carry a fork of figlet which differed solely by
being able to output an octal-escaped string.  No - I have no words
which can possibly be used to defend this...

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