The intention behind the iterator was to avoid needing to allocate the
symbols, but in practice we need to allocate them anyway since we need
to reverse their order and don't have random access. The alternative
would be an N^2 algorithm.
In practice this isn't that bad, because even if the allocation fails,
we'll still end up printing the address, so the user still ends up with
the necessary information to reconstruct the crash. I don't think it's
worth it to try to set up some kind of ring buffer or return partial
results on failure, but may revisit this.
This fix reveals another bug--we need to display the inline site syms in
the reverse of the encoded order. The parent/child relationships are
actually encoded on the inline sites, but it's likely a bit fragile to
try to trace those, and also more complex. As long as there aren't
multiple matches this is fine, and if there are, tracing the parent/child
chain won't work anyway.
I hit an unexpected errno 30 on macos attempting to call createFile on a
directory in PATH. errno 30 is EROFS, this change propagates that error
as error.ReadOnlyFileSystem.
- delete std.Thread.Futex
- delete std.Thread.Mutex
- delete std.Thread.Semaphore
- delete std.Thread.Condition
- delete std.Thread.RwLock
- delete std.once
std.Thread.Mutex.Recursive remains... for now. it will be replaced with
a special purpose mechanism used only by panic logic.
std.Io.Threaded exposes mutexLock and mutexUnlock for the advanced case
when you need to call them directly.
- remove error.SharingViolation from all error sets since it has the
same meaning as FileBusy
- add error.FileBusy to CreateFileAtomicError and ReadLinkError
- update dirReadLinkWindows to use NtCreateFile and NtFsControlFile and
integrate with cancelation properly.
- move windows CTL_CODE constants to the proper namespace
- delete os.windows.ReadLink
The most interesting thing here is the replacement of the pthread futex
implementation with an implementation based on thread park/unpark APIs.
Thread parking tends to be the primitive provided by systems which do
not have a futex primitive, such as NetBSD, so this implementation is
far more efficient than the pthread one. It is also useful on Windows,
where `RtlWaitOnAddress` is itself a userland implementation based on
thread park/unpark; we can implement it ourselves including support for
features which Windows' implementation lacks, such as cancelation and
waking a number of waiters with 1<n<infinity.
Compared to the pthread implementation, this thread-parking-based one
also supports full robust cancelation. Thread parking also turns out to
be useful for implementing `sleep`, so is now used for that on Windows
and NetBSD.
This commit also introduces proper cancelation support for most Windows
operations. The most notable omission right now is DNS lookups through
`GetAddrInfoEx`, just because they're a little more work due to having
a unique cancelation mechanism---but the machinery is all there, so I'll
finish gluing it together soon.
As of this commit, there are very few parts of `Io.Threaded` which do
not support full robust cancelation. The only ones which actually really
matter (because they could block for a prolonged period of time) are DNS
lookups on Windows (as discussed above) and futex waits on WASM.
It's better to avoid references to this global variable, but, in the
cases where it's needed, such as in std.debug.print and collecting stack
traces, better to share the same instance.
https://github.com/ziglang/zig/issues/26027#issuecomment-3571227050
tracked some bad performance in `DebugAllocator` on macOS down to a
function in dyld which `std.debug.SelfInfo` was calling into. It turns
out `dladdr`'s symbol lookup logic is horrendously slow (looking at its
source code, it appears to be doing a *linear scan* over all symbols in
the image?!). However, we don't actually need the symbol, so we want to
try and avoid this logic.
Luckily, dyld has more precise APIs for what we need! Unluckily, Apple,
in their infinite wisdom, decided they should be deprecated in favour of
`dladdr`, despite the latter being several times slower (and by "several
times", I have measured a 50x slowdown on repeated calls to `dladdr`
compared to the other API). But luckily again, the deprecated APIs are
still exposed.
So, after a careful analysis of the situation (reading dyld code and
cursing Apple engineers), I think it makes sense to just use these
deprecated APIs for now. If they ever go away, we can write our own
cache for this data to bypass Apple's awfully slow code, but I suspect
these functions will stick around for the foreseeable future.
Uh, and if `_dyld_get_image_header_containing_address` goes away,
there's also `dyld_image_header_containing_address`, which is a
seemingly identical function, exported by dyld just the same, but with a
separate (functionally identical) implementation, and not documented in
the public header file. Apple work in mysterious ways, I guess.
This is relevant to PIEs, which are notably enabled by default on macOS.
The build system needs to only see virtual addresses, that is, those
which do not have the slide applied; but the fuzzer itself naturally
sees relocated addresses (i.e. with the slide applied). We just need to
subtract the slide when we communicate addresses to the build system.
Like ELF, we now have `std.debug.MachOFile` for the host-independent
parts, and `std.debug.SelfInfo.MachO` for logic requiring the file to
correspond to the running program.
restores code closer to master branch in hopes of avoiding a regression
that was introduced when this was based on openSelfExe rather than
GetModuleFileNameExW.
Mason Remaley