Modifying CMAKE_* related flags directly applies those changes to every
single CMake target. This includes even the targets we have in the
externals directory.
So, if we ever increased our warning levels, or enabled particular ones,
or enabled any other compilation setting, then this would apply to
externals as well, which is often not desirable.
This makes our compilation flag setup less error prone by only applying
our settings to our targets and leaving the externals alone entirely.
This also means we don't end up clobbering any provided flags on the
command line either, allowing users to specifically use the flags they
want.
We generally shouldn't be hijacking CMAKE_CXX_FLAGS, etc as a means to
append flags to the targets, since this adds the compilation flags to
everything, including our externals, which can result in weird issues
and makes the build hierarchy fragile.
Instead, we want to just apply these compilation flags to our targets,
and let those managing external libraries to properly specify their
compilation flags.
This also results in us not getting as many warnings, as we don't raise
the warning level on every external target.
Rather than make a global accessor for this sort of thing. We can make
it a part of the thread interface itself. This allows getting rid of a
hidden global accessor in the kernel code.
The previous code had some minor issues with it, really not a big deal,
but amending it is basically 'free', so I figured, "why not?".
With the standard container maps, when:
map[key] = thing;
is done, this can cause potentially undesirable behavior in certain
scenarios. In particular, if there's no value associated with the key,
then the map constructs a default initialized instance of the value
type.
In this case, since it's a std::shared_ptr (as a type alias) that is
the value type, this will construct a std::shared_pointer, and then
assign over it (with objects that are quite large, or actively heap
allocate this can be extremely undesirable).
We also make the function take the region by value, as we can avoid a
copy (and by extension with std::shared_ptr, a copy causes an atomic
reference count increment), in certain scenarios when ownership isn't a
concern (i.e. when ReserveGlobalRegion is called with an rvalue
reference, then no copy at all occurs). So, it's more-or-less a "free"
gain without many downsides.
With this, all kernel objects finally have all of their data members
behind an interface, making it nicer to reason about interactions with
other code (as external code no longer has the freedom to totally alter
internals and potentially messing up invariants).
Previously this was required, as BitField wasn't trivially copyable.
BitField has since been made trivially copyable, so now this isn't
required anymore.
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