[Scons-users] Scons none-deterministic behavior for incremental build

[Hua Yanghao]

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
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