[Scons-users] How to turn off source scanner

Thu Feb 7 15:04:07 EST 2019

Of course it doesn't work. Scanners are already hooked.
When you clone you're initializing with no scanners and thus no hooks.

On Wed, Feb 6, 2019 at 11:46 PM Jason Kenny <dragon512 at live.com> wrote:

> Hi Bill,
>
>
>
> Changing the code to:
>
>
>
> env2=env.Clone(SCANNERS=[])
>
> env2.Command(..
>
>
>
> seems to work.
>
>
>
> However
>
>
>
> env.Command(
>
>     […],
>
>     […],
>
>     "autoreconf -if && ./configure\
>
>      CC=${CC} CXX=${CXX}\
>
>      ",
>
>      SCANNERS=[]
>
> )
>
>
>
> Does not. I would have thought that the environment override would have
> worked here. It does not to my surprise
>
>
>
> It does looks like adding a
>
>
>
> env.Command(
>
>     […],
>
>     […],
>
>     "autoreconf -if && ./configure\
>
>      CC=${CC} CXX=${CXX}\
>
>      ",
>
>      source_scanner=Scanner(
>
>                 function = lambda *lst,**kw: [],
>
>                 )
>
> )
>
>
>
> Works.
>
>
>
> Thanks … moving on to the next issue.
>
>
>
> Jason
>
>
>
>
>
> *From:* Scons-users <scons-users-bounces at scons.org> * On Behalf Of *Bill
> Deegan
> *Sent:* Wednesday, February 6, 2019 9:40 PM
> *To:* SCons users mailing list <scons-users at scons.org>
> *Subject:* Re: [Scons-users] How to turn off source scanner
>
>
>
> From manpage:
>
> SCANNERS
>
> A list of the available implicit dependency scanners. New file scanners
> may be added by appending to this list, although the more flexible approach
> is to associate scanners with a specific Builder. See the sections "Builder
> Objects" and "Scanner Objects," below, for more information.
>
> Create a new environment and empty this variable? Use that environment for
> your command?
>
>
>
> Does that work?
>
>
>
> On Wed, Feb 6, 2019 at 9:31 PM Jason Kenny <dragon512 at live.com> wrote:
>
>
>
> Looking how to turn off a scanner for a build command.
>
>
>
> Simple reproducer..
>
>
>
> Run:
>
> Git clone https://github.com/libunwind/libunwind.git
> <https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Flibunwind%2Flibunwind.git&data=02%7C01%7C%7C2867dfe9f89a4a7b9fb708d68cae03a2%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636851076338526850&sdata=u%2BEbJu10%2Bi8DhnvCwJuiK%2FBDKMfmFxHi51fCLnmLSoc%3D&reserved=0>
>
>
>
> In the libunwind folder add a Sconstruct with this content
>
>
>
> env = Environment()
>
> env.Command(
>
>     ["Makefile"],
>
>     [
>
>         "include/compiler.h",
>
>         "include/dwarf-eh.h",
>
>         "include/dwarf.h",
>
>         "include/dwarf_i.h",
>
>         "include/libunwind-aarch64.h",
>
>         "include/libunwind-arm.h",
>
>         "include/libunwind-common.h.in
> <https://nam04.safelinks.protection.outlook.com/?url=http%3A%2F%2Flibunwind-common.h.in&data=02%7C01%7C%7C2867dfe9f89a4a7b9fb708d68cae03a2%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636851076338536860&sdata=eGTdDeMwFiS3IKq2hYb4lw16ZI032kvlgjmFo92754k%3D&reserved=0>
> ",
>
>         "include/libunwind-coredump.h",
>
>         "include/libunwind-dynamic.h",
>
>         "include/libunwind.h.in
> <https://nam04.safelinks.protection.outlook.com/?url=http%3A%2F%2Flibunwind.h.in&data=02%7C01%7C%7C2867dfe9f89a4a7b9fb708d68cae03a2%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636851076338546865&sdata=OXAhRrPx55EeUf9W1A%2FBPQuYVy5Xn2jnzfCMyCskJV4%3D&reserved=0>
> ",
>
>         "include/libunwind-hppa.h",
>
>         "include/libunwind-ia64.h",
>
>         "include/libunwind_i.h",
>
>         "include/libunwind-mips.h",
>
>         "include/libunwind-ppc32.h",
>
>         "include/libunwind-ppc64.h",
>
>         "include/libunwind-ptrace.h",
>
>         "include/libunwind-sh.h",
>
>         "include/libunwind-tilegx.h",
>
>         "include/libunwind-x86_64.h",
>
>         "include/libunwind-x86.h",
>
>         "include/mempool.h",
>
>         "include/remote.h",
>
>         "include/unwind.h",
>
>     ],
>
>     "autoreconf -if && ./configure\
>
>      CC=${CC} CXX=${CXX}\
>
>      "
>
> )
>
>
>
> Then run
>
> Scons
>
>
>
> Then run
>
> Scons –debug=explain -n
>
>
>
> You should see something as:
>
> …
>
> scons: Building targets ...
>
> scons: rebuilding `Makefile' because:
>
>            `include/config.h' is a new dependency
>
>            `include/libunwind.h' is a new dependency
>
>            `include/libunwind-common.h' is a new dependency
>
>            `include/tdep/libunwind_i.h' is a new dependency
>
> autoreconf -if && ./configure CC=gcc CXX=g++
>
> scons: done building targets.
>
>
>
> The reason for this is that the Commands source is a list of header files.
> These header files have a scanner running on them. When the configure logic
> is finished the config.h and other headers are generated. This cause a
> false rebuild to happen.
>
>
>
> I would like to prevent the false rebuild.
>
> The more complex case based on a function I am trying to define to make it
> easy to call autoconf project from scons to build a larger mega project.
> The issue I am having is that in case as this libunwind would be a “leaf
> component” that is needed by many other components. This rebuild of the
> Makefile causes a chain of build action that make for annoying and long
> builds on the second pass that are not needed. Technically the Makefile
> does not need to be rebuilt because config.h was added. However I have not
> found a way to get this fixed.
>
>
>
> I tired adding
>
>
>
> env.Ignore(['Makefile'],
>
>     [
>
>         'include/config.h',
>
>            'include/libunwind.h',
>
>            'include/libunwind-common.h',
>
>            'include/tdep/libunwind_i.h',
>
>     ]
>
> )
>
>
>
> But this results in a message of:
>
> scons: rebuilding `Makefile' because the dependency order changed:…
>
>
>
> Do you have thoughts on how to fix this? My main thought is to turn off
> the c\c++ scanner for this builder. However I am unaware of a method to do
> this.
>
>
>
> Jason
>
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>
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