There is no straightforward way for the Zig team to access the Solaris system
headers; to do this, one has to create an Oracle account, accept their EULA to
download the installer ISO, and finally install it on a machine or VM. We do not
have to jump through hoops like this for any other OS that we support, and no
one on the team has expressed willingness to do it.
As a result, we cannot audit any Solaris contributions to std.c or other
similarly sensitive parts of the standard library. The best we would be able to
do is assume that Solaris and illumos are 100% compatible with no way to verify
that assumption. But at that point, the solaris and illumos OS tags would be
functionally identical anyway.
For Solaris especially, any contributions that involve APIs introduced after the
OS was made closed-source would also be inherently more risky than equivalent
contributions for other proprietary OSs due to the case of Google LLC v. Oracle
America, Inc., wherein Oracle clearly demonstrated its willingness to pursue
legal action against entities that merely copy API declarations.
Finally, Oracle laid off most of the Solaris team in 2017; the OS has been in
maintenance mode since, presumably to be retired completely sometime in the 2030s.
For these reasons, this commit removes all Oracle Solaris support.
Anyone who still wishes to use Zig on Solaris can try their luck by simply using
illumos instead of solaris in target triples - chances are it'll work. But there
will be no effort from the Zig team to support this use case; we recommend that
people move to illumos instead.
If these ever get allocated, it's most likely going to be for things that don't
matter to us anyway, so completely abandoning DWARF unwinding just because we
see these doesn't seem justified. We will still do so if we're actually asked to
read from such a register, which is the only actually problematic case; see
c23a5ccd19 for more details.
I made a couple of decisions for this based on the fact that we don't expose the
signal_ucontext_t type outside of the file:
* Adding all the floating point and vector state to every ucontext_t and
mcontext_t variant was way, way too much work, especially when we don't even
use the stuff. So I deleted all that and kept only the bare minimum needed to
reach into general-purpose registers.
* There is no particularly compelling reason to stick to the naming and struct
nesting used in the system headers. So we can actually unify the access
patterns for almost all of these variants by taking some liberties here; as a
result, fromPosixSignalContext() is now much nicer to read and extend.
For unwinding purposes, we don't care about unsupported registers. Yet because
we added these rules to the cache entry, we'd later try to evaluate them and
thus fail the unwind attempt for no good reason. They'd also take up cache rule
slots that would be better spent on actually relevant registers.
Note that any attempt to read unsupported registers during unwinding will still
fail the unwind attempt as expected.
There were only a few dozen lines of common logic, and they frankly
introduced more complexity than they eliminated. Instead, let's accept
that the implementations of `SelfInfo` are all pretty different and want
to track different state. This probably fixes some synchronization and
memory bugs by simplifying a bunch of stuff. It also improves the DWARF
unwind cache, making it around twice as fast in a debug build with the
self-hosted x86_64 backend, because we no longer have to redundantly go
through the hashmap lookup logic to find the module. Unwinding on
Windows will also see a slight performance boost from this change,
because `RtlVirtualUnwind` does not need to know the module whatsoever,
so the old `SelfInfo` implementation was doing redundant work. Lastly,
this makes it even easier to implement `SelfInfo` on freestanding
targets; there is no longer a need to emulate a real module system,
since the user controls the whole implementation!
There are various other small refactors here in the `SelfInfo`
implementations as well as in the DWARF unwinding logic. This change
turned out to make a lot of stuff simpler!
