[Buildroot] [Bug 15856] New: Using BR2_CONFIG= on a different file-system than O= (build outputs) fails with kconfig syncconfig error

[bugzilla@busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=15856

            Bug ID: 15856
           Summary: Using BR2_CONFIG= on a different file-system than O=
                    (build outputs) fails with kconfig syncconfig error
           Product: buildroot
           Version: 2023.08.3
          Hardware: All
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P5
         Component: Other
          Assignee: unassigned@buildroot.uclibc.org
          Reporter: ciprian.craciun@gmail.com
                CC: buildroot@uclibc.org
  Target Milestone: ---

If one has BuildRoot sources checked out on a file-system, but uses a build
outputs folder on a different file-system (via `make O=...`) and one also
specifies `BR2_CONFIG` on the first file-system (the one holding the sources),
the `make syncconfig` target fails with an `*** Error during update of the
configuration.` error.

`strace`-ing the `conf syncconfig` invocation leads me to the following
conclusion:

* something in the build system (perhaps `kconfig`) creates temporary files in
the parent folder of the configuration file (the one specified via
`BR2_CONFIG`);

* but then it tries to move it inside the outputs folder with a simple `rename`
syscall`;

* this fails because the rename is cross mount points;

The output of `strace` (here `/mnt/.../sources` where the sources and the
config are is a different mount point than `/mnt/.../volatile` where the
outputs are):
~~~~
rename("/mnt/.../sources/buildroot/!custom/.tmpconfig.h",
"/mnt/.../volatile/buildroot/build/build/buildroot-config/autoconf.h") = -1
EXDEV (Invalid cross-device link)
~~~~

-- 
You are receiving this mail because:
You are on the CC list for the bug.
_______________________________________________
buildroot mailing list
buildroot@buildroot.org
https://lists.buildroot.org/mailman/listinfo/buildroot