[Scons-users] Scons none-deterministic behavior for incremental build
Hua Yanghao
huayanghao at gmail.com
Wed Dec 5 03:38:27 EST 2018
Alright, I have figured out a way to bypass/stub most of the python3
code and can confirm this *ONLY* happens in python3. And python3.6.x
and python3.7.x doesn't make a difference.
But I think the problem is clearly that the previously stored md5sum
and currently computed md5sum is not reliable, seems scons computation
of md5sum of a dependency does not only depends on the file content.
On Wed, Dec 5, 2018 at 9:23 AM Hua Yanghao <huayanghao at gmail.com> wrote:
>
> It is impossible to run on python2.7 within a reasonable time as a
> huge list of python3-only syntax/modules needs to be adapted ...
> On Wed, Dec 5, 2018 at 12:15 AM Bill Deegan <bill at baddogconsulting.com> wrote:
> >
> > Does this happen if you use python 2.7?
> >
> > On Tue, Dec 4, 2018 at 6:00 PM Hua Yanghao <huayanghao at gmail.com> wrote:
> >>
> >> Apparently the MD5 signature is taking *turns* some how.
> >>
> >> You can see below the old md5 and new md5 checksum is somehow
> >> alternating between two fixed value ...
> >> How is scons calculating the md5 value? is it only depends on the file content?
> >> The md5sum of the "arch_init.c" is:
> >> md5sum firmware/arch/armv7/arch_init.c
> >> db624fbb365812d7ba58c87d49f44b6f firmware/arch/armv7/arch_init.c
> >>
> >> First build:
> >> e494890ea1b6e36acf275f3698a3f3f9
> >> c706a016770a7c85ac42f16f79456797
> >> Returning True
> >> in self.changed ... 2
> >> return not r: False
> >> ['build/configs/qemu_arm_vexpress/arm3/firmware/arch/armv7/arch_init.o']
> >> <SCons.Script.Main.BuildTask object at 0x7fdc934c7fd0>
> >> ______CC build/configs/qemu_arm_vexpress/arm3/firmware/arch/armv7/arch_init.o
> >>
> >> Second build:
> >> c706a016770a7c85ac42f16f79456797
> >> e494890ea1b6e36acf275f3698a3f3f9
> >> Returning True
> >> in self.changed ... 2
> >> return not r: False
> >> ['build/configs/qemu_arm_vexpress/arm3/firmware/arch/armv7/arch_init.o']
> >> <SCons.Script.Main.BuildTask object at 0x7f3fca5e4fd0>
> >> ______CC build/configs/qemu_arm_vexpress/arm3/firmware/arch/armv7/arch_init.o
> >> On Tue, Dec 4, 2018 at 11:54 PM Hua Yanghao <huayanghao at gmail.com> wrote:
> >> >
> >> > That is generated by sconstruct, not from shell. Any potential issue
> >> > here? (It was working for a very long time before and only breaks
> >> > recently when I added some new features).
> >> >
> >> > In the meantime I have isolated the issue to be in Node.Node.changed()
> >> > call, where scons old & new signature for the C files seems not
> >> > matching (print("###### 3.1") is executed in error case):
> >> > 1463 if self.has_builder():
> >> > |3
> >> > 1464 print("####### 3")
> >> > |3
> >> > 1465 import SCons.Util
> >> > |3
> >> > 1466 newsig = SCons.Util.MD5signature(contents)
> >> > |3
> >> > 1467 if bi.bactsig != newsig:
> >> > |3
> >> > 1468 if t: Trace(': bactsig %s != newsig %s' %
> >> > (bi.bactsig, newsig)) |3
> >> > 1469 print("####### 3.1")
> >> > |3
> >> > 1470 result = True
> >> > On Tue, Dec 4, 2018 at 11:24 PM Bill Deegan <bill at baddogconsulting.com> wrote:
> >> > >
> >> > > Generated by logic in your sconstruct/sconscripts? or do you shell out and run a script/program to generate it.
> >> > >
> >> > >
> >> > > On Tue, Dec 4, 2018 at 4:37 PM Hua Yanghao <huayanghao at gmail.com> wrote:
> >> > >>
> >> > >> Hi Bill,
> >> > >> config.h is generated file, not checked in, it is generated in the
> >> > >> build folder only.
> >> > >> Well at least I see scons is very odering-sensitive. For example, if
> >> > >> the order of SConscript processing changes (in the case of a set()),
> >> > >> even if there is no dependency actually changed, scons thinks the
> >> > >> target need to be rebuilt.
> >> > >>
> >> > >> any progress on these similar issues already? :)
> >> > >>
> >> > >> Best Regards,
> >> > >> Yanghao
> >> > >> On Tue, Dec 4, 2018 at 10:15 PM Bill Deegan <bill at baddogconsulting.com> wrote:
> >> > >> >
> >> > >> > Is "build/configs/qemu_arm_vexpress/arm3/config/config.h" a generated file? Or checked in?
> >> > >> >
> >> > >> > It's very unlikely to be set ordering. set's should only be used for membership checks not iteration in the SCons codebase.
> >> > >> >
> >> > >> > We're actively debugging similar issue.
> >> > >> >
> >> > >> > -Bill
> >> > >> >
> >> > >> > On Tue, Dec 4, 2018 at 3:23 PM Hua Yanghao <huayanghao at gmail.com> wrote:
> >> > >> >>
> >> > >> >> I does that a lot ... but a quick try to make sure no
> >> > >> >> LIBS/LIBPATH/CPPPATH etc. is touched after Object() is being called,
> >> > >> >> still shows the same 50~70% rebuild of the entire project.
> >> > >> >> I am not using any parallel build, and somehow scons is having a very
> >> > >> >> none-deterministic behavior.
> >> > >> >>
> >> > >> >> Actually I fixed partially the issue (e.g. in simpler build the
> >> > >> >> incremental builds now works fine), due to python set() is having a
> >> > >> >> random order for every run. I am thinking maybe scons is somehow also
> >> > >> >> depends on the ordering of a set()? And when it happens to be the same
> >> > >> >> order then no rebuild?
> >> > >> >> On Tue, Dec 4, 2018 at 9:00 PM Oscar Anson <oscar at solidangle.com> wrote:
> >> > >> >> >
> >> > >> >> > Hi,
> >> > >> >> >
> >> > >> >> > Not sure if this could be related, but a similar issue happened to me where I get a relink of a shared library without changing anything in the project. It happened that I was setting the environment LIBS and LIBPATH after calling the builder of the library.
> >> > >> >> >
> >> > >> >> > El mar., 4 dic. 2018 20:55, Hua Yanghao <huayanghao at gmail.com> escribió:
> >> > >> >> >>
> >> > >> >> >> Dear Scons Experts,
> >> > >> >> >> I recently hit on a very strange problem where scons incremental
> >> > >> >> >> builds sometimes OK, sometimes the entire project is re-built.
> >> > >> >> >>
> >> > >> >> >> scons: 3.0.1
> >> > >> >> >> python: 3.6.7
> >> > >> >> >>
> >> > >> >> >> --debug=explain gives below example trace:
> >> > >> >> >> scons: rebuilding
> >> > >> >> >> `build/configs/qemu_arm_vexpress/arm3/config/config.h' because
> >> > >> >> >> AlwaysBuild() is specified
> >> > >> >> >> __CONFIG build/configs/qemu_arm_vexpress/arm3/config/config.h
> >> > >> >> >> scons: rebuilding
> >> > >> >> >> `build/configs/qemu_arm_vexpress/arm3/firmware/arch/armv7/arch_init.o'
> >> > >> >> >> because:
> >> > >> >> >> `firmware/arch/armv7/arch_init.c' is no longer a dependency
> >> > >> >> >> `firmware/arch/armv7/arch_init.c' is a new dependency
> >> > >> >> >>
> >> > >> >> >> It seems some how the C file itself is removed and re-added as the
> >> > >> >> >> Object() dependency, and causes rebuild. However this is *NOT*
> >> > >> >> >> *always* the case. Sometime the rebuild doesn't happen.
> >> > >> >> >>
> >> > >> >> >> I failed to create a minimal example that can show this issue so far,
> >> > >> >> >> but in the production environment it is about 50% full-rebuild and 50%
> >> > >> >> >> incremental re-build.
> >> > >> >> >>
> >> > >> >> >> Any thoughts or hints?
> >> > >> >> >>
> >> > >> >> >> Thanks,
> >> > >> >> >> Yanghao
> >> > >> >> >> _______________________________________________
> >> > >> >> >> Scons-users mailing list
> >> > >> >> >> Scons-users at scons.org
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> >> > >> >> >
> >> > >> >> > _______________________________________________
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> >> > >> >
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