<section id='package-ebuild-eapi-4-slot-abi'>
<title>EAPI 4-slot-abi</title>
<section id='package-ebuild-eapi-4-slot-abi-metadata'>
<title>Metadata</title>
<section id='package-ebuild-eapi-4-slot-abi-metadata-slot-sub-slot-abi'>
<title>SLOT Supports Optional "sub-slot" ABI part</title>
<para>
In order to represent cases in which an upgrade to a new version of a package
requires reverse dependencies to be rebuilt, the SLOT variable may contain an
optional "sub-slot" ABI part that is delimited by a '/' character.
</para>
<para>
For
example, the package 'dev-libs/glib-2.30.2' may set SLOT="2/2.30" in order to
indicate a sub-slot value of "2.30". This package will be matched by
dependency atoms such as 'dev-libs/glib:2' or 'dev-libs/glib:2/2.30', where
the sub-slot part of the atom is optional.
</para>
<para>
If SLOT does not contain a sub-slot
part, then it is considered to have an implicit sub-slot that is equal to the
SLOT value. For example, SLOT="0" is implicitly equal to SLOT="0/0".
</para>
<para>
Refer to the
<link linkend="package-ebuild-eapi-4-slot-abi-metadata-dependency-atom-slot-abi-equal-operator">
:= operator </link> documentation for more information about sub-slot usage.
</para>
</section>
<section id='package-ebuild-eapi-4-slot-abi-metadata-dependency-atom-slot-abi-equal-operator'>
<title>Dependency Atom slot/sub-slot := Operator</title>
<para>
Dependency atom syntax now supports slot/sub-slot := operators which allow the
specific slot/sub-slot that a package is built against to be recorded, so that it's
possible to automatically determine when a package needs to be rebuilt due to
having a dependency upgraded to a different slot/sub-slot.
</para>
<para>
For example, if a package is built
against the package 'dev-libs/glib-2.30.2' with SLOT="2/2.30", then dependency
atoms such as 'dev-libs/glib:=' or 'dev-libs/glib:2=' will be rewritten at
build time to be recorded as 'dev-libs/glib:2/2.30='.
</para>
<para>
For another example, if
a package is built against the package 'sys-libs/db-4.8.30' with SLOT="4.8",
then a dependency atom such as 'sys-libs/db:=' will be rewritten at build time
to be recorded as 'sys-libs/db:4.8/4.8='. In this case, since SLOT="4.8" does
not contain a sub-slot part, the sub-slot is considered to be implicitly equal
to "4.8".
</para>
<para>
When dependencies are rewritten as described above, the slot/sub-slot recorded in
the atom is always equal to that of the highest matched version that is
installed at build time.
</para>
</section>
<section id='package-ebuild-eapi-4-slot-abi-metadata-dependency-atom-slot-abi-asterisk-operator'>
<title>Dependency Atom slot/sub-slot :* Operator</title>
<para>
The new :* operator is used to express dependencies that can change versions
at runtime without requiring reverse dependencies to be rebuilt. For example,
a dependency atom such as 'dev-libs/glib:*' can be used to match any slot of
the 'dev-libs/glib' package, and dependency atom such as 'dev-libs/glib:2*'
can be used to specifically match slot '2' of the same package (ignoring its
sub-slot).
</para>
</section>
</section>
</section>