`$RPM_BUILD_ROOT` is no longer an absolute path if `%_builddir` is configured relative

[dmnks]

If %_builddir is a relative path configured externally (e.g. .), when we internally override it with the newly created per-package subdirectory, it's still a relative path (e.g. ./test-1-build). That, in turn, ends up in $RPM_BUILD_ROOT at build scriptlet execution time which is initialized from the new %_builddir.

This is of course sane but it happens to break the expectation of at least one macro config which we ship in Fedora via redhat-rpm-config, namely:

#---------------------------------------------------------------------
#       Expanded at beginning of %install scriptlet.
#

%__spec_install_pre %{___build_pre}\
    [ "$RPM_BUILD_ROOT" != "/" ] && rm -rf "${RPM_BUILD_ROOT}"\
    mkdir -p "`dirname "$RPM_BUILD_ROOT"`"\
    mkdir "$RPM_BUILD_ROOT"\
    %{?_auto_set_build_flags:%{set_build_flags}}\
%{nil}

As a result, when you build a package with such a relative builddir set, another subdirectory will be created in the %install stage and cded into which breaks the rest of the script.

As mentioned, this is not necessarily a bug per se, however it may result in random breakage wherever relative paths are configured in %_builddir.

If we don't choose to fix this, we might want to at least add a compatibility note to the 4.20 release notes.

[dmnks]

Thinking about it again, the word "sane" perhaps isn't entirely right, this actually isn't desired :smile: Even though we don't claim for $RPM_BUILD_ROOT to be an absolute path, it kinda makes sense for it to be, or we shouldn't at least regress here...

[dmnks]

Just for completeness, this issue was found thanks to the following test: https://src.fedoraproject.org/rpms/redhat-rpm-config/blob/rawhide/f/tests/auto-set-build-flags/runtest.sh

[pmatilai]

We never supported relative %_builddir and whatnot, that they happened to work in some cases was more like a lucky incident.

[dmnks]

Ack, in that case, let's just close (we can always include a note in the RN).

[pmatilai]

Let's leave it open for a bit, we might want to make an explicit check for absolute path instead.