Given we already pass in a reference to the kernel that the shared
memory instance is created under, we can just use that to check the
current process, rather than using the global accessor functions.
This allows removing direct dependency on the system instance entirely.
The kernel allows restricting the total size of the handle table through
the process capability descriptors. Until now, this functionality wasn't
hooked up. With this, the process handle tables become properly restricted.
In the case of metadata-less executables, the handle table will assume
the maximum size is requested, preserving the behavior that existed
before these changes.
A fairly trivial change. Other sections of the codebase use nested
namespaces instead of separate namespaces here. This one must have just
been overlooked.
Gets rid of the largest set of mutable global state within the core.
This also paves a way for eliminating usages of GetInstance() on the
System class as a follow-up.
Note that no behavioral changes have been made, and this simply extracts
the functionality into a class. This also has the benefit of making
dependencies on the core timing functionality explicit within the
relevant interfaces.
Places all of the timing-related functionality under the existing Core
namespace to keep things consistent, rather than having the timing
utilities sitting in its own completely separate namespace.
A holdover from citra, the Horizon kernel on the switch has no
prominent kernel object that functions as a timer. At least not
to the degree of sophistication that this class provided.
As such, this can be removed entirely. This class also wasn't used at
all in any meaningful way within the core, so this was just code sitting
around doing nothing. This also allows removing a few things from the
main KernelCore class that allows it to use slightly less resources
overall (though very minor and not anything really noticeable).
No inheritors of the WaitObject class actually make use of their own
implementations of these functions, so they can be made non-virtual.
It's also kind of sketchy to allow overriding how the threads get added
to the list anyways, given the kernel itself on the actual hardware
doesn't seem to customize based off this.
Looking into the implementation of the C++ standard facilities that seem
to be within all modules, it appears that they use 7 as a break reason
to indicate an uncaught C++ exception.
This was primarily found via the third last function called within
Horizon's equivalent of libcxxabi's demangling_terminate_handler(),
which passes the value 0x80000007 to svcBreak.
This is a bounds check to ensure that the thread priority is within the
valid range of 0-64. If it exceeds 64, that doesn't necessarily mean
that an actual priority of 64 was expected (it actually means whoever
called the function screwed up their math).
Instead clarify the message to indicate the allowed range of thread
priorities.
Now that we handle the kernel capability descriptors we can correct
CreateThread to properly check against the core and priority masks
like the actual kernel does.
This makes the naming more closely match its meaning. It's just a
preferred core, not a required default core. This also makes the usages
of this term consistent across the thread and process implementations.
This function isn't a general purpose function that should be exposed to
everything, given it's specific to initializing the main thread for a
Process instance.
Given that, it's a tad bit more sensible to place this within
process.cpp, which keeps it visible only to the code that actually needs
it.
In all cases that these functions are needed, the VMManager can just be
retrieved and used instead of providing the same functions in Process'
interface.
This also makes it a little nicer dependency-wise, since it gets rid of
cases where the VMManager interface was being used, and then switched
over to using the interface for a Process instance. Instead, it makes
all accesses uniform and uses the VMManager instance for all necessary
tasks.
All the basic memory mapping functions did was forward to the Process'
VMManager instance anyways.
Similar to the service capability flags, however, we currently don't
emulate the GIC, so this currently handles all interrupts as being valid
for the time being.
Handles the priority mask and core mask flags to allow building up the
masks to determine the usable thread priorities and cores for a kernel
process instance.
We've had the old kernel capability parser from Citra, however, this is
unused code and doesn't actually map to how the kernel on the Switch
does it. This introduces the basic functional skeleton for parsing
process capabilities.
If a thread handle is passed to svcGetProcessId, the kernel attempts to
access the process ID via the thread's instance's owning process.
Technically, this function should also be handling the kernel debug
objects as well, however we currently don't handle those kernel objects
yet, so I've left a note via a comment about it to remind myself when
implementing it in the future.
Starts the process ID counter off at 81, which is what the kernel itself
checks against internally when creating processes. It's actually
supposed to panic if the PID is less than 81 for a userland process.
Adds the barebones enumeration constants and functions in place to
handle memory attributes, while also essentially leaving the attribute
itself non-functional.
In the previous change, the memory writing was moved into the service
function itself, however it still had a problem, in that the entire
MemoryInfo structure wasn't being written out, only the first 32 bytes
of it were being written out. We still need to write out the trailing
two reference count members and zero out the padding bits.
Not doing this can result in wrong behavior in userland code in the following
scenario:
MemoryInfo info; // Put on the stack, not quaranteed to be zeroed out.
svcQueryMemory(&info, ...);
if (info.device_refcount == ...) // Whoops, uninitialized read.
This can also cause the wrong thing to happen if the user code uses
std::memcmp to compare the struct, with another one (questionable, but
allowed), as the padding bits are not guaranteed to be a deterministic
value. Note that the kernel itself also fully zeroes out the structure
before writing it out including the padding bits.
Moves the memory writes directly into QueryProcessMemory instead of
letting the wrapper function do it. It would be inaccurate to allow the
handler to do it because there's cases where memory shouldn't even be
written to. For example, if the given process handle is invalid.
HOWEVER, if the memory writing is within the wrapper, then we have no
control over if these memory writes occur, meaning in an error case, 68
bytes of memory randomly get trashed with zeroes, 64 of those being
written to wherever the memory info address points to, and the remaining
4 being written wherever the page info address points to.
One solution in this case would be to just conditionally check within
the handler itself, but this is kind of smelly, given the handler
shouldn't be performing conditional behavior itself, it's a behavior of
the managed function. In other words, if you remove the handler from the
equation entirely, does the function still retain its proper behavior?
In this case, no.
Now, we don't potentially trash memory from this function if an invalid
query is performed.
This would result in svcSetMemoryAttribute getting the wrong value for
its third parameter. This is currently fine, given the service function
is stubbed, however this will be unstubbed in a future change, so this
needs to change.
The kernel returns a memory info instance with the base address set to
the end of the address space, and the size of said block as
0 - address_space_end, it doesn't set both of said members to zero.
Gets the two structures out of an unrelated header and places them with
the rest of the memory management code.
This also corrects the structures. PageInfo appears to only contain a
32-bit flags member, and the extra padding word in MemoryInfo isn't
necessary.
Amends the MemoryState enum to use the same values like the actual
kernel does. Also provides the necessary operators to operate on them.
This will be necessary in the future for implementing
svcSetMemoryAttribute, as memory block state is checked before applying
the attribute.
The Process object kept itself alive indefinitely because its handle_table
contains a SharedMemory object which owns a reference to the same Process object,
creating a circular ownership scenario.
Break that up by storing only a non-owning pointer in the SharedMemory object.
This was only ever public so that code could check whether or not a
handle was valid or not. Instead of exposing the object directly and
allowing external code to potentially mess with the map contents, we
just provide a member function that allows checking whether or not a
handle is valid.
This makes all member variables of the VMManager class private except
for the page table.
While partially correct, this service call allows the retrieved event to
be null, as it also uses the same handle to check if it was referring to
a Process instance. The previous two changes put the necessary machinery
in place to allow for this, so we can simply call those member functions
here and be done with it.
Process instances can be waited upon for state changes. This is also
utilized by svcResetSignal, which will be modified in an upcoming
change. This simply puts all of the WaitObject related machinery in
place.
svcResetSignal relies on the event instance to have already been
signaled before attempting to reset it. If this isn't the case, then an
error code has to be returned.
This function simply does a handle table lookup for a writable event
instance identified by the given handle value. If a writable event
cannot be found for the given handle, then an invalid handle error is
returned. If a writable event is found, then it simply signals the
event, as one would expect.
svcCreateEvent operates by creating both a readable and writable event
and then attempts to add both to the current process' handle table.
If adding either of the events to the handle table fails, then the
relevant error from the handle table is returned.
If adding the readable event after the writable event to the table
fails, then the writable event is removed from the handle table and the
relevant error from the handle table is returned.
Note that since we do not currently test resource limits, we don't check
the resource limit table yet.
Two kernel object should absolutely never have the same handle ID type.
This can cause incorrect behavior when it comes to retrieving object
types from the handle table. In this case it allows converting a
WritableEvent into a ReadableEvent and vice-versa, which is undefined
behavior, since the object types are not the same.
This also corrects ClearEvent() to check both kernel types like the
kernel itself does.
The kernel uses the handle table of the current process to retrieve the
process that should be used to retrieve certain information. To someone
not familiar with the kernel, this might raise the question of "Ok,
sounds nice, but doesn't this make it impossible to retrieve information
about the current process?".
No, it doesn't, because HandleTable instances in the kernel have the
notion of a "pseudo-handle", where certain values allow the kernel to
lookup objects outside of a given handle table. Currently, there's only
a pseudo-handle for the current process (0xFFFF8001) and a pseudo-handle
for the current thread (0xFFFF8000), so to retrieve the current process,
one would just pass 0xFFFF8001 into svcGetInfo.
The lookup itself in the handle table would be something like:
template <typename T>
T* Lookup(Handle handle) {
if (handle == PSEUDO_HANDLE_CURRENT_PROCESS) {
return CurrentProcess();
}
if (handle == PSUEDO_HANDLE_CURRENT_THREAD) {
return CurrentThread();
}
return static_cast<T*>(&objects[handle]);
}
which, as is shown, allows accessing the current process or current
thread, even if those two objects aren't actually within the HandleTable
instance.
Our implementation of svcGetInfo was slightly incorrect in that we
weren't doing proper error checking everywhere. Instead, reorganize it
to be similar to how the kernel seems to do it.
More hardware accurate. On the actual system, there is a differentiation between the signaler and signalee, they form a client/server relationship much like ServerPort and ClientPort.
The opposite of the getter functions, this function sets the limit value
for a particular ResourceLimit resource category, with the restriction
that the new limit value must be equal to or greater than the current
resource value. If this is violated, then ERR_INVALID_STATE is returned.
e.g.
Assume:
current[Events] = 10;
limit[Events] = 20;
a call to this service function lowering the limit value to 10 would be
fine, however, attempting to lower it to 9 in this case would cause an
invalid state error.
This kernel service function is essentially the exact same as
svcGetResourceLimitLimitValue(), with the only difference being that it
retrieves the current value for a given resource category using the
provided resource limit handle, rather than retrieving the limiting
value of that resource limit instance.
Given these are exactly the same and only differ on returned values, we
can extract the existing code for svcGetResourceLimitLimitValue() to
handle both values.
This kernel service function retrieves the maximum allowable value for
a provided resource category for a given resource limit instance. Given
we already have the functionality added to the resource limit instance
itself, it's sufficient to just hook it up.
The error scenarios for this are:
1. If an invalid resource category type is provided, then ERR_INVALID_ENUM is returned.
2. If an invalid handle is provided, then ERR_INVALID_HANDLE is returned (bad thing goes in, bad thing goes out, as one would expect).
If neither of the above error cases occur, then the out parameter is
provided with the maximum limit value for the given category and success
is returned.
This function simply creates a ResourceLimit instance and attempts to
create a handle for it within the current process' handle table. If the
kernal fails to either create the ResourceLimit instance or create a
handle for the ResourceLimit instance, it returns a failure code
(OUT_OF_RESOURCE, and HANDLE_TABLE_FULL respectively). Finally, it exits
by providing the output parameter with the handle value for the
ResourceLimit instance and returning that it was successful.
Note: We do not return OUT_OF_RESOURCE because, if yuzu runs out of
available memory, then new will currently throw. We *could* allocate the
kernel instance with std::nothrow, however this would be inconsistent
with how all other kernel objects are currently allocated.
<random> isn't necesary directly within the header and can be placed in
the cpp file where its needed. Avoids propagating random generation
utilities via a header file.
Cleans out the citra/3DS-specific implementation details that don't
apply to the Switch. Sets the stage for implementing ResourceLimit
instances properly.
While we're at it, remove the erroneous checks within CreateThread() and
SetThreadPriority(). While these are indeed checked in some capacity,
they are not checked via a ResourceLimit instance.
In the process of moving out Citra-specifics, this also replaces the
system ResourceLimit instance's values with ones from the Switch.
Both member functions assume the passed in target process will not be
null. Instead of making this assumption implicit, we can change the
functions to be references and enforce this at the type-system level.
Makes the interface nicer to use in terms of 64-bit code, as it makes it
less likely for one to get truncation warnings (and also makes sense in
the context of the rest of the interface where 64-bit types are used for
sizes and offsets
Similar to PR 1706, which cleans up the error codes for the filesystem
code, but done for the kernel error codes. This removes the ErrCodes
namespace and specifies the errors directly. This also fixes up any
straggling lines of code that weren't using the named error codes where
applicable.
* svcBreak now dumps information from the debug buffer passed
info1 and info2 seem to somtimes hold an address to a buffer, this is usually 4 bytes or the size of the int and contains an error code. There's other circumstances where it can be something different so we hexdump these to examine them at a later date.
* Addressed comments
* get rid of boost::optional
* Remove optional references
* Use std::reference_wrapper for optional references
* Fix clang format
* Fix clang format part 2
* Adressed feedback
* Fix clang format and MacOS build
Now that we've gotten the innaccurate error codes out of the way, we can
finally toss away a bunch of these, trimming down the error codes to
ones that are actually used and knocking out two TODO comments.
All priority checks are supposed to occur before checking the validity
of the thread handle, we're also not supposed to return
ERR_NOT_AUTHORIZED here.
In the kernel, there isn't a singular handle table that everything gets
tossed into or used, rather, each process gets its own handle table that
it uses. This currently isn't an issue for us, since we only execute one
process at the moment, but we may as well get this out of the way so
it's not a headache later on.
This should be comparing against the queried process' vma_map, not the
current process'. The only reason this hasn't become an issue yet is we
currently only handle one process being active at any time.
Now that the changes clarifying the address spaces has been merged, we
can wrap the checks that the kernel performs when mapping shared memory
(and other forms of memory) into its own helper function and then use
those within MapSharedMemory and UnmapSharedMemory to complete the
sanitizing checks that are supposed to be done.
So, one thing that's puzzled me is why the kernel seemed to *not* use
the direct code address ranges in some cases for some service functions.
For example, in svcMapMemory, the full address space width is compared
against for validity, but for svcMapSharedMemory, it compares against
0xFFE00000, 0xFF8000000, and 0x7FF8000000 as upper bounds, and uses
either 0x200000 or 0x8000000 as the lower-bounds as the beginning of the
compared range. Coincidentally, these exact same values are also used in
svcGetInfo, and also when initializing the user address space, so this
is actually retrieving the ASLR extents, not the extents of the address
space in general.
This should help diagnose crashes easier and prevent many users thinking that a game is still running when in fact it's just an audio thread still running(this is typically not killed when svcBreak is hit since the game expects us to do this)
A fairly basic service function, which only appears to currently support
retrieving the process state. This also alters the ProcessStatus enum to
contain all of the values that a kernel process seems to be able of
reporting with regards to state.
These only exist to ferry data into a Process instance and end up going
out of scope quite early. Because of this, we can just make it a plain
struct for holding things and just std::move it into the relevant
function. There's no need to make this inherit from the kernel's Object
type.
Regular value initialization is adequate here for zeroing out data. It
also has the benefit of not invoking undefined behavior if a non-trivial
type is ever added to the struct for whatever reason.
This adds the missing address range checking that the service functions
do before attempting to map or unmap memory. Given that both service
functions perform the same set of checks in the same order, we can wrap
these into a function and just call it from both functions, which
deduplicates a little bit of code.
There's no real need to use a shared pointer in these cases, and only
makes object management more fragile in terms of how easy it would be to
introduce cycles. Instead, just do the simple thing of using a regular
pointer. Much of this is just a hold-over from citra anyways.
It also doesn't make sense from a behavioral point of view for a
process' thread to prolong the lifetime of the process itself (the
process is supposed to own the thread, not the other way around).
When loading NROs, svcBreak is called to signal to the debugger that a new "module" is loaded. As no debugger is technically attached we shouldn't be killing the programs execution.
This was the result of a typo accidentally introduced in
e51d715700. This restores the previous
correct behavior.
The behavior with the reference was incorrect and would cause some games
to fail to boot.
Conceptually, it doesn't make sense for a thread to be able to persist
the lifetime of a scheduler. A scheduler should be taking care of the
threads; the threads should not be taking care of the scheduler.
If the threads outlive the scheduler (or we simply don't actually
terminate/shutdown the threads), then it should be considered a bug
that we need to fix.
Attributing this to balika011, as they opened #1317 to attempt to fix
this in a similar way, but my refactoring of the kernel code caused
quite a few conflicts.
Many of the member variables of the thread class aren't even used
outside of the class itself, so there's no need to make those variables
public. This change follows in the steps of the previous changes that
made other kernel types' members private.
The main motivation behind this is that the Thread class will likely
change in the future as emulation becomes more accurate, and letting
random bits of the emulator access data members of the Thread class
directly makes it a pain to shuffle around and/or modify internals.
Having all data members public like this also makes it difficult to
reason about certain bits of behavior without first verifying what parts
of the core actually use them.
Everything being public also generally follows the tendency for changes
to be introduced in completely different translation units that would
otherwise be better introduced as an addition to the Thread class'
public interface.
Now that we have all of the rearranging and proper structure sizes in
place, it's fairly trivial to implement svcGetThreadContext(). In the
64-bit case we can more or less just write out the context as is, minus
some minor value sanitizing. In the 32-bit case we'll need to clear out
the registers that wouldn't normally be accessible from a 32-bit
AArch32 exectuable (or process).
This will be necessary for the implementation of svcGetThreadContext(),
as the kernel checks whether or not the process that owns the thread
that has it context being retrieved is a 64-bit or 32-bit process.
If the process is 32-bit, then the upper 15 general-purpose registers
and upper 16 vector registers are cleared to zero (as AArch32 only has
15 GPRs and 16 128-bit vector registers. not 31 general-purpose
registers and 32 128-bit vector registers like AArch64).
Makes the public interface consistent in terms of how accesses are done
on a process object. It also makes it slightly nicer to reason about the
logic of the process class, as we don't want to expose everything to
external code.
boost::static_pointer_cast for boost::intrusive_ptr (what SharedPtr is),
takes its parameter by const reference. Given that, it means that this
std::move doesn't actually do anything other than obscure what the
function's actual behavior is, so we can remove this. To clarify, this
would only do something if the parameter was either taking its argument
by value, by non-const ref, or by rvalue-reference.
The locations of these can actually vary depending on the address space
layout, so we shouldn't be using these when determining where to map
memory or be using them as offsets for calculations. This keeps all the
memory ranges flexible and malleable based off of the virtual memory
manager instance state.
Previously, these were reporting hardcoded values, but given the regions
can change depending on the requested address spaces, these need to
report the values that the memory manager contains.
Rather than hard-code the address range to be 36-bit, we can derive the
parameters from supplied NPDM metadata if the supplied exectuable
supports it. This is the bare minimum necessary for this to be possible.
The following commits will rework the memory code further to adjust to
this.
The owning process of a thread is required to exist before the thread,
so we can enforce this API-wise by using a reference. We can also avoid
the reliance on the system instance by using that parameter to access
the page table that needs to be set.
This can just be a regular function, getting rid of the need to also
explicitly undef the define at the end of the file. Given FuncReturn()
was already converted into a function, it's #undef can also be removed.
This modifies the CPU interface to more accurately match an
AArch64-supporting CPU as opposed to an ARM11 one. Two of the methods
don't even make sense to keep around for this interface, as Adv Simd is
used, rather than the VFP in the primary execution state. This is
essentially a modernization change that should have occurred from the
get-go.
The kernel does the equivalent of the following check before proceeding:
if (address + 0x8000000000 < 0x7FFFE00000) {
return ERR_INVALID_MEMORY_STATE;
}
which is essentially what our IsKernelVirtualAddress() function does. So
we should also be checking for this.
The kernel also checks if the given input addresses are 4-byte aligned,
however our Mutex::TryAcquire() and Mutex::Release() functions already
handle this, so we don't need to add code for this case.
The kernel caps the size limit of shared memory to 8589930496 bytes (or
(1GB - 512 bytes) * 8), so approximately 8GB, where every GB has a 512
byte sector taken off of it.
It also ensures the shared memory is created with either read or
read/write permissions for both permission types passed in, allowing the
remote permissions to also be set as "don't care".
Part of the checking done by the kernel is to check if the given
address and size are 4KB aligned, as well as checking if the size isn't
zero. It also only allows mapping shared memory as readable or
read/write, but nothing else, and so we shouldn't allow mapping as
anything else either.
Previously, these were sitting outside of the Kernel namespace, which
doesn't really make sense, given they're related to the Thread class
which is within the Kernel namespace.
While unlikely, it does avoid constructing a std::string and
unnecessarily calling into the memory code if a game or executable
decides to be really silly about their logging.
Given we now have the kernel as a class, it doesn't make sense to keep
the current process pointer within the System class, as processes are
related to the kernel.
This also gets rid of a subtle case where memory wouldn't be freed on
core shutdown, as the current_process pointer would never be reset,
causing the pointed to contents to continue to live.
Now that we have a class representing the kernel in some capacity, we
now have a place to put the named port map, so we move it over and get
rid of another piece of global state within the core.
The follow-up to e2457418da, which
replaces most of the includes in the core header with forward declarations.
This makes it so that if any of the headers the core header was
previously including change, then no one will need to rebuild the bulk
of the core, due to core.h being quite a prevalent inclusion.
This should make turnaround for changes much faster for developers.
As means to pave the way for getting rid of global state within core,
This eliminates kernel global state by removing all globals. Instead
this introduces a KernelCore class which acts as a kernel instance. This
instance lives in the System class, which keeps its lifetime contained
to the lifetime of the System class.
This also forces the kernel types to actually interact with the main
kernel instance itself instead of having transient kernel state placed
all over several translation units, keeping everything together. It also
has a nice consequence of making dependencies much more explicit.
This also makes our initialization a tad bit more correct. Previously we
were creating a kernel process before the actual kernel was initialized,
which doesn't really make much sense.
The KernelCore class itself follows the PImpl idiom, which allows
keeping all the implementation details sealed away from everything else,
which forces the use of the exposed API and allows us to avoid any
unnecessary inclusions within the main kernel header.
We can make this error code an alias of the resource limit exceeded
error code, allowing us to get rid of the lingering 3DS error code of
the same type.
We already have the variable itself set up to perform this task, so we
can just return its value from the currently executing process instead
of always stubbing it to zero.
Allows querying the inverse of IsDomain() to make things more readable.
This will likely also be usable in the event of implementing
ConvertDomainToSession().
Despite being covered by a global mutex, we should still ensure that the
class handles its reference counts properly. This avoids potential
shenanigans when it comes to data races.
Given this is the root object that drives quite a bit of the kernel
object hierarchy, ensuring we always have the correct behavior (and no
races) is a good thing.
The current core may have nothing to do with the core where the new thread was scheduled to run. In case it's the same core, then the following PrepareReshedule call will take care of that.
WakeAfterDelay might be called from any host thread, so err on the side of caution and use the thread-safe CoreTiming::ScheduleEventThreadsafe.
Note that CoreTiming is still far from thread-safe, there may be more things we have to work on for it to be up to par with what we want.
Exit from AddMutexWaiter early if the thread is already waiting for a mutex owned by the owner thread.
This accounts for the possibility of a thread that is waiting on a condition variable being awakened twice in a row.
Also added more validation asserts.
This should fix one of the random crashes in Breath Of The Wild.
These members don't need to be entirely exposed, we can instead expose
an API to operate on them without directly needing to mutate them
We can also guard against overflow/API misuse this way as well, given
active_sessions is an unsigned value.
This amends cases where crashes can occur that were missed due to the
odd way the previous code was set up (using 3DS memory regions that
don't exist).
Using member variables for referencing the segments array increases the
size of the class in memory for little benefit. The same behavior can be
achieved through the use of accessors that just return the relevant
segment.
Avoids using a u32 to compare against a range of size_t, which can be a
source of warnings. While we're at it, compress a std::tie into a
structured binding.
General moving to keep kernel object types separate from the direct
kernel code. Also essentially a preliminary cleanup before eliminating
global kernel state in the kernel code.
This introduces a slightly more generic variant of WriteBuffer().
Notably, this variant doesn't constrain the arguments to only accepting
std::vector instances. It accepts whatever adheres to the
ContiguousContainer concept in the C++ standard library.
This essentially means, std::array, std::string, and std::vector can be
used directly with this interface. The interface no longer forces you to
solely use containers that dynamically allocate.
To ensure our overloads play nice with one another, we only enable the
container-based WriteBuffer if the argument is not a pointer, otherwise
we fall back to the pointer-based one.
The reason this would never be true is that ideal_processor is a u8 and
THREADPROCESSORID_DEFAULT is an s32. In this case, it boils down to how
arithmetic conversions are performed before performing the comparison.
If an unsigned value has a lesser conversion rank (aka smaller size)
than the signed type being compared, then the unsigned value is promoted
to the signed value (i.e. u8 -> s32 happens before the comparison). No
sign-extension occurs here either.
An alternative phrasing:
Say we have a variable named core and it's given a value of -2.
u8 core = -2;
This becomes 254 due to the lack of sign. During integral promotion to
the signed type, this still remains as 254, and therefore the condition
will always be true, because no matter what value the u8 is given it
will never be -2 in terms of 32 bits.
Now, if one type was a s32 and one was a u32, this would be entirely
different, since they have the same bit width (and the signed type would
be converted to unsigned instead of the other way around) but would
still have its representation preserved in terms of bits, allowing the
comparison to be false in some cases, as opposed to being true all the
time.
---
We also get rid of two signed/unsigned comparison warnings while we're
at it.
Previously, the buffer_index parameter was unused, causing all writes to
use the buffer index of zero, which is not necessarily what is wanted
all the time.
Thankfully, all current usages don't use a buffer index other than zero,
so this just prevents a bug before it has a chance to spring.
This would result in a lot of allocations and related object
construction, just to toss it all away immediately after the call.
These are definitely not intentional, and it was intended that all of
these should have been accessing the static function GetInstance()
through the name itself, not constructed instances.
This situation may happen like so:
Thread 1 with low priority calls WaitProcessWideKey with timeout.
Thread 2 with high priority calls WaitProcessWideKey without timeout.
Thread 3 calls SignalProcessWideKey
- Thread 2 acquires the lock and awakens.
- Thread 1 can't acquire the lock and is put to sleep with the lock owner being Thread 2.
Thread 1's timeout expires, with the lock owner still being set to Thread 2.
