`__xl_a` is just a global variable containing a null function pointer. There's
nothing magical about it or its name at all.
The section names used on `__xl_a` and `__xl_b` (`.CRT$XLA` and `.CRT$XLZ`) are
the real magic here. The compiler emits TLS variables into `.CRT$XL<x>`
sections, where `x` is an uppercase letter between A and Z (exclusive). The
linker then sorts those sections alphabetically (due to the `$`), and the result
is a neat array of TLS initialization callbacks between `__xl_a` and `__xl_z`.
That array is null-terminated, though! Normally, `__xl_z` serves as the null
terminator; however, by pointing `AddressesOfCallBacks` to `__xl_a`, which just
contains a null function pointer, we've effectively made it so that the PE
loader will just immediately stop invoking TLS callbacks. Fix that by pointing
to the first actual TLS callback instead (or `__xl_z` if there are none).
There are two concepts here: one for whether dwarf supports unwinding on
that target, and another for whether the Zig standard library
implements it yet.
...which have a ucontext_t but not a PC register. The current stack
unwinding implementation does not yet support this architecture.
Also fix name of `std.debug.SelfInfo.openSelf` to remove redundancy.
Also removed this hook into root providing an "openSelfDebugInfo"
function. Sorry, this debugging code is not of sufficient quality to
offer a plugin API right now.
After this commit:
`std.debug.SelfInfo` is a cross-platform abstraction for the current
executable's own debug information, with a goal of minimal code bloat
and compilation speed penalty.
`std.debug.Dwarf` does not assume the current executable is itself the
thing being debugged, however, it does assume the debug info has the
same CPU architecture and OS as the current executable. It is planned to
remove this limitation.
This code has the hard-coded goal of supporting the executable's own
debug information and makes design choices along that goal, such as
memory-mapping the inputs, using dl_iterate_phdr, and doing conditional
compilation on the host target.
A more general-purpose implementation of debug information may be able
to share code with this, but there are some fundamental
incompatibilities. For example, the "SelfInfo" implementation wants to
avoid bloating the binary with PDB on POSIX systems, and likewise DWARF
on Windows systems, while a general-purpose implementation needs to
support both PDB and DWARF from the same binary. It might, for example,
inspect the debug information from a cross-compiled binary.
`SourceLocation` now lives at `std.debug.SourceLocation` and is
documented.
Deprecate `std.debug.runtime_safety` because it returns the optimization
mode of the standard library, when the caller probably wants to use the
optimization mode of their own module.
`std.pdb.Pdb` is moved to `std.debug.Pdb`, mirroring the recent
extraction of `std.debug.Dwarf` from `std.dwarf`.
I have no idea why we have both Module (with a Windows-specific
definition) and WindowsModule. I left some passive aggressive doc
comments to express my frustration.
std.debug.Dwarf is the parsing/decoding logic. std.dwarf remains the
unopinionated types and bits alone.
If you look at this diff you can see a lot less redundancy in
namespaces.
I pointed a fuzzer at the tokenizer and it crashed immediately. Upon
inspection, I was dissatisfied with the implementation. This commit
removes several mechanisms:
* Removes the "invalid byte" compile error note.
* Dramatically simplifies tokenizer recovery by making recovery always
occur at newlines, and never otherwise.
* Removes UTF-8 validation.
* Moves some character validation logic to `std.zig.parseCharLiteral`.
Removing UTF-8 validation is a regression of #663, however, the existing
implementation was already buggy. When adding this functionality back,
it must be fuzz-tested while checking the property that it matches an
independent Unicode validation implementation on the same file. While
we're at it, fuzzing should check the other properties of that proposal,
such as no ASCII control characters existing inside the source code.
Other changes included in this commit:
* Deprecate `std.unicode.utf8Decode` and its WTF-8 counterpart. This
function has an awkward API that is too easy to misuse.
* Make `utf8Decode2` and friends use arrays as parameters, eliminating a
runtime assertion in favor of using the type system.
After this commit, the crash found by fuzzing, which was
"\x07\xd5\x80\xc3=o\xda|a\xfc{\x9a\xec\x91\xdf\x0f\\\x1a^\xbe;\x8c\xbf\xee\xea"
no longer causes a crash. However, I did not feel the need to add this
test case because the simplified logic eradicates most crashes of this
nature.
This is a fairly small hobby OS that has not seen development in 2 years. Our
current policy is that hobby OSs should use the `other` tag.
https://github.com/zhmu/ananas
What is `sparcel`, you might ask? Good question!
If you take a peek in the SPARC v8 manual, §2.2, it is quite explicit that SPARC
v8 is a big-endian architecture. No little-endian or mixed-endian support to be
found here.
On the other hand, the SPARC v9 manual, in §3.2.1.2, states that it has support
for mixed-endian operation, with big-endian mode being the default.
Ok, so `sparcel` must just be referring to SPARC v9 running in little-endian
mode, surely?
Nope:
* 40b4fd7a3e/llvm/lib/Target/Sparc/SparcTargetMachine.cpp (L226)
* 40b4fd7a3e/llvm/lib/Target/Sparc/SparcTargetMachine.cpp (L104)
So, `sparcel` in LLVM is referring to some sort of fantastical little-endian
SPARC v8 architecture. I've scoured the internet and I can find absolutely no
evidence that such a thing exists or has ever existed. In fact, I can find no
evidence that a little-endian implementation of SPARC v9 ever existed, either.
Or any SPARC version, actually!
The support was added here: https://reviews.llvm.org/D8741
Notably, there is no mention whatsoever of what CPU this might be referring to,
and no justification given for the "but some are little" comment added in the
patch.
My best guess is that this might have been some private exercise in creating a
little-endian version of SPARC that never saw the light of day. Given that SPARC
v8 explicitly doesn't support little-endian operation (let alone little-endian
instruction encoding!), and no CPU is known to be implemented as such, I think
it's very reasonable for us to just remove this support.
