Profiles use.mask
file
The use.mask
file can be used to mark USE
flags as unavailable on a
particular profile. This can be useful for various reasons:
-
Masking hardware-specific feature flags. For example,
mmx
andsse
are only available onx86
,altivec
is only available onppc
andvis
is only available onsparc
v9. -
Disabling unavailable soft dependencies. A simple hypothetical example — say
fooapp
works onmips
, but has an optional dependency (controlled by thebar
flag) uponlibbar
, which doesn't work onmips
. Then by adding thebar
flag toprofiles/arch/mips/use.mask
,fooapp
could be made available tomips
users with the unresolvable dependency forcibly disabled.
Note that use.mask
is a per-flag thing, not per package's use of a given
flag. This is one of the reasons that USE flags must have a specific well
defined purpose.
Updates to use.mask
should be handled via the relevant arch team. Any
additions are sorted chronologically, starting at the top of the file
(underneath any comment header blocks).
See noblah USE flags for more discussion.