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 on x86,altivec
is only available onppc
andvis
is only available on sparc 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.
See noblah USE Flags for more discussion.