[Buildroot] [Bug 8771] New: make savedefconfig modifies sources

[Buildroot] [Bug 8771] New: make savedefconfig modifies sources

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=8771

            Bug ID: 8771
           Summary: make savedefconfig modifies sources
           Product: buildroot
           Version: unspecified
          Hardware: All
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P5
         Component: Other
          Assignee: unassigned at buildroot.uclibc.org
          Reporter: geoff at infradead.org
                CC: buildroot at uclibc.org
  Target Milestone: ---

When building out of the source tree 'make savedefconfig' will modify the
sources in some situations.  This is problematic when the sources are on
read-only media.  It should write to the file defconfig in the build directory.

  mkdir /tmp/out
  make O=/tmp/out qemu_aarch64_virt_defconfig
  cd /tmp/out
  make savedefconfig

In this case qemu_aarch64_virt_defconfig in the sources gets modified.

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[Buildroot] [Bug 8771] make savedefconfig modifies sources

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=8771

Thomas Petazzoni <thomas.petazzoni@free-electrons.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |WORKSFORME
             Status|NEW                         |RESOLVED

--- Comment #1 from Thomas Petazzoni <thomas.petazzoni@free-electrons.com> ---
This is the expected behavior. I personally don't like it (since it deviates
from how the Linux kernel handles defconfig, and also because it's look weird),
but that's the way it's supposed to work in Buildroot.

Basically, the defconfig is stored to the file pointed by BR2_DEFCONFIG. By
default, this option is set to $(CONFIG_DIR)/defconfig, which would do what you
want, i.e save the defconfig next to the .config file.

However, when you run "make <foobar>_defconfig", we set BR2_DEFCONFIG to
"configs/<foobar>_defconfig". The original intent is to make things
"transparent": if you start from a defconfig, the assumption is that you want
changes made to this configuration to be saved back to the same defconfig.

You can override this at any time by changing BR2_DEFCONFIG in
menuconfig/xconfig/nconfig, or simply on the command line by passing
BR2_DEFCONFIG="/some/place".

As I said, I personally don't really like this behavior, and I got confused
several times. The fact that the source tree is modified is indeed another
drawback of this behavior. However, I didn't find this to be too problematic to
really argue against the contributors who wanted this feature.

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[Buildroot] [Bug 8771] make savedefconfig modifies sources

[Arnout Vandecappelle]

[Taking this discussion to the list]

On 03/07/16 21:23, bugzilla at busybox.net wrote:
> https://bugs.busybox.net/show_bug.cgi?id=8771
>
> Thomas Petazzoni <thomas.petazzoni@free-electrons.com> changed:
>
>             What    |Removed                     |Added
> ----------------------------------------------------------------------------
>           Resolution|---                         |WORKSFORME
>               Status|NEW                         |RESOLVED
>
> --- Comment #1 from Thomas Petazzoni <thomas.petazzoni@free-electrons.com> ---
> This is the expected behavior. I personally don't like it (since it deviates
> from how the Linux kernel handles defconfig, and also because it's look weird),
> but that's the way it's supposed to work in Buildroot.
>
> Basically, the defconfig is stored to the file pointed by BR2_DEFCONFIG. By
> default, this option is set to $(CONFIG_DIR)/defconfig, which would do what you
> want, i.e save the defconfig next to the .config file.
>
> However, when you run "make <foobar>_defconfig", we set BR2_DEFCONFIG to
> "configs/<foobar>_defconfig". The original intent is to make things
> "transparent": if you start from a defconfig, the assumption is that you want
> changes made to this configuration to be saved back to the same defconfig.

  I think we do agree that it is weird for the in-tree defconfigs. In the past, 
there was no way to distinguish between the upstream in-tree defconfigs, and the 
defconfigs that you add to your custom buildroot tree for internal use. But now 
we could say that you're supposed to use BR2_EXTERNAL, So we could reset 
BR2_DEFCONFIG for in-tree configs.

  Of course, at the moment we still point to the in-tree 
configs/<boardname>_defconfig in the manual, so that would have to change first...

  Regards,
  Arnout


>
> You can override this at any time by changing BR2_DEFCONFIG in
> menuconfig/xconfig/nconfig, or simply on the command line by passing
> BR2_DEFCONFIG="/some/place".
>
> As I said, I personally don't really like this behavior, and I got confused
> several times. The fact that the source tree is modified is indeed another
> drawback of this behavior. However, I didn't find this to be too problematic to
> really argue against the contributors who wanted this feature.
>


-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium           BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
GPG fingerprint:  7493 020B C7E3 8618 8DEC 222C 82EB F404 F9AC 0DDF

[Buildroot] [Bug 8771] make savedefconfig modifies sources

[Thomas Petazzoni]

Arnout,

On Tue, 8 Mar 2016 00:39:46 +0100, Arnout Vandecappelle wrote:

>   I think we do agree that it is weird for the in-tree defconfigs. In the past, 
> there was no way to distinguish between the upstream in-tree defconfigs, and the 
> defconfigs that you add to your custom buildroot tree for internal use. But now 
> we could say that you're supposed to use BR2_EXTERNAL, So we could reset 
> BR2_DEFCONFIG for in-tree configs.

To be honest, I don't see the difference between in-tree defconfigs,
and defconfigs in your BR2_EXTERNAL tree. In both cases, if
BR2_DEFCONFIG points to such defconfigs, when you run "make
savedefconfig", you will modify version-controlled source code, which
IMO isn't nice.

But again, this is really a matter of taste, and I did understand the
idea of having make savedefconfig "automagically" save back to the
defconfig the configuration was started from.

I simply believe that:

 - It deviates from what the kernel does, which is a bit in violation
   of our principle "our configuration system is like the kernel"

 - It modifies version-controlled source code.

>   Of course, at the moment we still point to the in-tree 
> configs/<boardname>_defconfig in the manual, so that would have to change first...

I'm not sure what you mean by "we still point to". In which place of
the manual?

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

[Buildroot] [Bug 8771] make savedefconfig modifies sources

[Peter Korsgaard]

>>>>> "Thomas" == Thomas Petazzoni <thomas.petazzoni@free-electrons.com> writes:

Hi,

 > To be honest, I don't see the difference between in-tree defconfigs,
 > and defconfigs in your BR2_EXTERNAL tree. In both cases, if
 > BR2_DEFCONFIG points to such defconfigs, when you run "make
 > savedefconfig", you will modify version-controlled source code, which
 > IMO isn't nice.

It is a tradeoff. When developing on a project using BR you want to keep
the config under configuration control, and you normally want to commit
minimal (savedefconfig) defconfigs, so making the steps needed to do so
as few as possible is imho a very nice thing.

If on the other hand you are just trying out stuff it doesn't make much
sense (but why are you running make savedefconfig in the first place
then?)

 > I simply believe that:

 >  - It deviates from what the kernel does, which is a bit in violation
 >    of our principle "our configuration system is like the kernel"

True.

 >  - It modifies version-controlled source code.

This can be seen both as a + and a -.

-- 
Bye, Peter Korsgaard

[Buildroot] [Bug 8771] make savedefconfig modifies sources

[Steve Calfee]

On Tue, Mar 8, 2016 at 12:06 AM, Thomas Petazzoni
<thomas.petazzoni@free-electrons.com> wrote:
>  - It deviates from what the kernel does, which is a bit in violation
>    of our principle "our configuration system is like the kernel"
>
>  - It modifies version-controlled source code.
>
I use BR2_EXTERNAL and my custom stuff is in a git tree. So modifying
my external config is good. I can see what changed using git difftool,
revert it easily or commit an improved config.

It may deviate from a kernel savedefconfig does, but in buildroot the
kernel linux-savedefconfig does exactly the same thing as buildroot
savedefconfig. (if you configure the buildroot kernel for an external
config.)

Personally I find the maintenance of output/.br_external as more
bizarre and confusing. It does allow me to not have to remember to set
BR2_EXTERNAL when make is invoked, but it gets cleaned on make clean.
So using an external tree requires either a shell variable or using my
unreliable wet-ware memory.

But what we have works and changing this kind of stuff breaks user
habits, which cannot be easily corrected by documentation.

Regards, Steve

[Buildroot] [Bug 8771] make savedefconfig modifies sources

[Arnout Vandecappelle]

On 03/08/16 18:01, Steve Calfee wrote:
> Personally I find the maintenance of output/.br_external as more
> bizarre and confusing. It does allow me to not have to remember to set
> BR2_EXTERNAL when make is invoked, but it gets cleaned on make clean.

  That _is_ a bug IMHO. output/.br_external shouldn't be removed on 'make 
clean'. However, AFAICS it shouldn't be cleaned, only by distclean, and there it 
is appropriate of course.

  Regards,
  Arnout

-- 
Arnout Vandecappelle      arnout dot vandecappelle at essensium dot com
Senior Embedded Software Architect . . . . . . +32-478-010353 (mobile)
Essensium, Mind division . . . . . . . . . . . . . . http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium . . . . . BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
GPG fingerprint:  7493 020B C7E3 8618 8DEC 222C 82EB F404 F9AC 0DDF

[Buildroot] [Bug 8771] make savedefconfig modifies sources

[Steve Calfee]

On Tue, Mar 8, 2016 at 9:38 AM, Arnout Vandecappelle <arnout@mind.be> wrote:
>
>
> On 03/08/16 18:01, Steve Calfee wrote:
>>
>> Personally I find the maintenance of output/.br_external as more
>> bizarre and confusing. It does allow me to not have to remember to set
>> BR2_EXTERNAL when make is invoked, but it gets cleaned on make clean.
>
>
>  That _is_ a bug IMHO. output/.br_external shouldn't be removed on 'make
> clean'. However, AFAICS it shouldn't be cleaned, only by distclean, and
> there it is appropriate of course.
>
>  Regards,
>  Arnout
>

Hi Arnout,

I just went back and tried and make clean does not clear the
.br_external I guess I was just confused when trying earlier (I am
still on 2015.11). Sorry about the noise, no bug.

Regards, Steve