[Buildroot] [git commit] Makefile: don't recreate staging symlink if it exists

Peter Korsgaard peter at korsgaard.com
Sat Mar 14 13:22:59 UTC 2020


>>>>> "Thomas" == Thomas Petazzoni <thomas.petazzoni at bootlin.com> writes:

 > commit: https://git.buildroot.net/buildroot/commit/?id=9b824423142697bf8715d3c3a230559b551b98f6
 > branch: https://git.buildroot.net/buildroot/commit/?id=refs/heads/master

 > Create the staging symlink the same way as the host symlink. This means
 > using a make dependency rather than recreating it every time.

 > In coreutils versions below 8.27, re-creation of symbolic links was not
 > atomic. This means that there is a period in time where the existing link is
 > removed, before the new one is created. In coreutils 8.27 this was fixed,
 > see [1]. Note that CentOS 7 ships with coreutils 8.22.

 > In the following scenario, this is a problem:

 > - an application is compiled using the sysroot prepared by Buildroot and
 >   links against Xenomai userspace libraries, but its build process is steered
 >   from outside of Buildroot
 > - to know the correct flags, the application makefile uses the 'xeno-config'
 >   file to request them, and passes DESTDIR=/buildroot/output/staging
 > - the xeno-config responds with flags based on the path
 >   '/buildroot/output/staging/...'
 > - while the application build is ongoing, a 'make' happens in Buildroot,
 >   causing the 'staging' symlink to be recreated (even though it already
 >   existed)
 > - when exactly at this time, the application calls the compiler with -I
 >   flags pointing to output/staging, the build fails with:

 >   -I/buildroot/output/staging/usr/include/xenomai/mercury: Error:  ^ is not a directory
 >   -I/buildroot/output/staging/usr/include/xenomai: Error:  ^ is not a directory
 >   -I/buildroot/output/staging/usr/include/xenomai/xenomai: Error:  ^ is not a directory
 >   -I/buildroot/output/staging/usr/include/xenomai/psos: Error:  ^ is not a directory
 >   Failed: ** ^ *

 > Work around this problem by only creating the staging symlink once, similar
 > to how the host symlink (if any) is created.

 > See also commit d0f4f95e390bcb1c953efa125f5277a8a235396e which changed the
 > way these symlinks are made. The reasoning in this commit is to move away
 > from the 'dirs' target.

 > [1] https://github.com/coreutils/coreutils/commit/376967889ed7ed561e46ff6d88a66779db62737a

 > Signed-off-by: Thomas De Schampheleire <thomas.de_schampheleire at nokia.com>
 > Signed-off-by: Thomas Petazzoni <thomas.petazzoni at bootlin.com>

Committed to 2019.02.x and 2019.11.x, thanks.

-- 
Bye, Peter Korsgaard


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