Problem:
- Many constructors are defined as `{}` rather than using the ` =
default` compiler-provided constructor.
- Some types provide an implicit conversion operator from `nullptr_t`
instead of requiring the caller to default construct. This violates
the C++ Core Guidelines suggestion to declare single-argument
constructors explicit
(https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#c46-by-default-declare-single-argument-constructors-explicit).
Solution:
- Change default constructors to use the compiler-provided default
constructor.
- Remove implicit conversion operators from `nullptr_t` and change
usage to enforce type consistency without conversion.
Problem:
- The implementation of `find` is coupled to the implementation of
`SinglyLinkedList`.
Solution:
- Decouple the implementation of `find` from the class by using a
generic `find` algorithm.
Problem:
- The implementation of `find` is coupled to the implementation of
`DoublyLinkedList`.
- `append` and `prepend` are implemented multiple times so that
r-value references can be moved from into the new node. This is
probably not called very often because a pr-value or x-value needs
to be used here.
Solution:
- Decouple the implementation of `find` from the class by using a
generic `find` algorithm.
- Make `append` and `prepend` be function templates so that they can
have binding references which can be forwarded.
Problem:
- The implementation of `find` is coupled to the implementation of `Vector`.
- `Vector::find` takes the predicate by value which might be expensive.
Solution:
- Decouple the implementation of `find` from `Vector` by using a
generic `find` algorithm.
- Change the name of `find` with a predicate to `find_if` so that a
binding reference can be used and the predicate can be forwarded to
avoid copies.
- Change all the `find(pred)` call sites to use `find_if`.
Problem:
- `find` is implemented inside of each container. This coupling
requires that each container needs to individually provide `find`.
Solution:
- Decouple the `find` functionality from the container. This allows
provides a `find` algorithm which can work with all
containers. Containers can still provide their own `find` in the
case where it can be optimized.
- This also allows for searching sub-ranges of a container rather than
the entire container as some of the container-specific member
functions enforced.
Note:
- @davidstone's talk from 2015 C++Now conference entitled "Functions
Want to be Free" encourages this style:
(https://www.youtube.com/watch?v=_lVlC0xzXDc), but it does come at
the cost of composability.
- A logical follow-on to this is to provide a mechanism to use a
short-hand function which automatically searches the entire
container. This could automatically use the container-provided
version if available so that functions which provide their own
optimized version get the benefit.
Problem:
- Clang ToT fails to build `AK/Tests/TestTypeTraits.cpp` because
`nullptr_t` is missing the `std` namespace qualifier.
Solution:
- Prepend the namespace qualifier.
Let's adapt this class a bit better to how it's actually being used.
Instead of having valid/invalid states and storing an error in case
it's invalid, a MappedFile is now always valid, and the factory
function that creates it will return an OSError if mapping fails.
This enable using global raw pointers rather than Singleton objects,
which solves some problems because global Singleton object could
be deleted when destructors are run.
This is useful for collecting statistics, e.g.
Atomic<unsigned, MemoryOrder::memory_order_relaxed> would allow
using operators such as ++ to use relaxed semantics throughout
without having to explicitly call fetch_add with the memory order.
Add a specialization for a void ValueType. This is useful if a generic
function wants to return a Result<T, E> where the user might not
actually care abut the T, and default it to void. In this case it
basically becomes Unexpected<E> instead of Result, but hey, it works :)
Now that we have RTTI in userspace, we can do away with all this manual
hackery and use dynamic_cast.
We keep the is<T> and downcast<T> helpers since they still provide good
readability improvements. Note that unlike dynamic_cast<T>, downcast<T>
does not fail in a recoverable way, but will assert if the object being
casted is not a T.
Compared to version 10 this fixes a bunch of formatting issues, mostly
around structs/classes with attributes like [[gnu::packed]], and
incorrect insertion of spaces in parameter types ("T &"/"T &&").
I also removed a bunch of // clang-format off/on and FIXME comments that
are no longer relevant - on the other hand it tried to destroy a couple of
neatly formatted comments, so I had to add some as well.
Since RefPtr<T> decrements the ref counter to 0 and after that starts
destructing the object, there is a window where the ref count is 0
and the weak references have not been revoked.
Also change WeakLink to be able to obtain a strong reference
concurrently and block revoking instead, which should happen a lot
less often.
Fixes a problem observed in #4621
Add requires clauses to constraints on InputStream and OutputStream
operator<< / operator>>. Make the constraint on String::number a
requires clause instead of SFINAE. Also, fix some unecessary IsSame in
Trie where specialized traits exist for the given use cases.
Use SFINAE to enforce the fact that it's supposed to only be called for
Arithmetic types, rather than counting on the linker to tell us that an
instantiation of String::number(my_arg) was not found. This also adds
String::number for floating point types as a side-effect.
Use TypeLists to add test for IsIntegral, IsFloatingPoint, IsVoid,
IsNullPointer, IsArithmetic, IsFundamental, and AddConst type traits.
More can "easily" be added once the TypeList and macro magic is squinted
at for long enough :).
Also add IndexSequence and associated helpers. The TypeList class can be
queried for what type is at a certain index, and there are two helper
functions: for_each_type, and for_each_type_zipped.
for_each_type will invoke a lambda with a TypeWrapper object for
each type in the type list. The original type can be obtained by
extracting the ::Type from the type of your generic lambda's one
argument.
for_each_type_zipped will walk two TypeLists in lockstep and pass a
TypeWrapper object for the current index in each list to a generic
lambda. The original type from the TypeList can again be extracted via
the ::Type of the generic lambda's two parameters.
Seems Rust and OpenJDK both had issues with getting accurate stack size
for the main thread with MacOS Maverick and above. Apply a variant of
their workarounds. We could probably assume 8MB in all cases just to
be safe, as the only user of AK::StackInfo right now is lib JS's heap
for determining possible pointer candidates. But, this approach should
work if userspace apps start trying to add custom guard pages, as well.
I ran into this exact but at least twenty times in Serenity alone. The
C++ Standard dictates that 'unsigned long' and 'unsigned long long' are
distinct types even though on most platforms they are usually both 64
bit integers.
Also it wasn't possible to evaluate IsIntegral<T> for types that were
not integers since it used MakeUnsigned<T> internally.
This was causing WindowServer and Taskbar to crash sometimes when the
stars aligned and we tried cutting off a string ending with "..." right
on top of an emoji. :^)
A future patch could do some MacOS specific things for
set_volatile/set_nonvolatile. For now, swap out the defined(__linux__)
branches for simple not __serenity__ branches.
Create macros for the byte swap operations one would expect to be in
endian.h or byteswap.h in AK/Endian.h. It's likely a similar/different
change will be needed for BSDs, but there's no github action for those
added to the project yet.
The coarse clocks in time.h are a linux extension that we've adopted.
MacOS and the BSDs don't have it, so we need an alias in a platform
header for Lagom builds.
It's not an error to create a Userspace<T> that points to kernel memory
as the point of Userspace<T> is not to validate the address, but rather
to choose safe overloads that do validation before any data transfer
takes place.
Fixes#4581.
clang trunk with -std=c++20 doesn't seem to properly look for an
aggregate initializer here when the type being constructed is a simple
aggregate (e.g. `struct Thing { int a; int b; };`). This template fails
to compile in a usage added 12/16/2020 in `AK/Trie.h`.
Both forms of initialization are supposed to call the
aggregate-initializers but direct-list-initialization delegating to
aggregate initializers is a new addition in c++20 that might not be
implemented yet.
