Problem:
- C-style arrays do not automatically provide bounds checking and are
less type safe overall.
- `__builtin_memcmp` is not a constant expression in the current gcc.
Solution:
- Change private m_data to be AK::Array.
- Eliminate constructor from C-style array.
- Change users of the C-style array constructor to use the default
constructor.
- Change `operator==()` to be a hand-written comparison loop and let
the optimizer figure out to use `memcmp`.
Problem:
- `MACAddress` class is not usable in a compile-time context.
- `__builtin_memcpy` is not constexpr in gcc.
Solution:
- Decorate functions with `constexpr` keyword.
- Use default constructors and destructors.
- Change `__builtin_memcpy` to a hand-written `for` loop and let the
compiler's optimizer take care of it.
- Add tests to ensure compile-time capabilities.
This fixes an OOB access when the last read/written chunk is empty (as we _just_
started on a new chunk).
Also adds a test case to TestMemoryStream.
Found via human fuzzing in the shell:
```sh
for $(cat /dev/urandom) {
clear
match $it {
?* as (x) {
echo $x
sleep 1
}
}
}
```
would assert at some point.
Personally I found this unintuitive at first, but it is in line with
strtol(), Python's int() or JavaScript's parseInt(), so I guess it makes
sense.
Fixes#4097.
Problem:
- There are no unit tests for `MACAddress` class. This makes it
difficult to refactor and ensure the same behavior.
- `m_data` private member variable is uninitialized leading to undefined
behavior of `is_zero()`.
Solution:
- Add unit tests to cover basic functionality.
- Initialize `m_data`.
Problem:
- C++20 changes the way equality operators are generated. This results
in overload ambiguity as reported by clang.
Solution:
- Remove `AK::Vector::operator!=` because it will be automatically
generated in terms of `AK::Vector::operator==`.
- Change `AK::Vector::operator==` to be a function template so that
overload resolution is not confused about `a == b` vs `b == a`.
- Add tests to ensure the behavior works.
Notes:
- There is more info available at
https://brevzin.github.io/c++/2019/07/28/comparisons-cpp20/ for
deeper discussion about overload resolution, operator rewriting, and
generated functions.
Problem:
- `typedef` is a keyword which comes from C and carries with it old
syntax that is hard to read.
- Creating type aliases with the `using` keyword allows for easier
future maintenance because it supports template syntax.
- There is inconsistent use of `typedef` vs `using`.
Solution:
- Use `clang-tidy`'s checker called `modernize-use-using` to update
the syntax to use the newer syntax.
- Remove unused functions to make `clang-tidy` happy.
- This results in consistency within the codebase.
Problem:
- IPv4Address class cannot be used in a compile-time context.
- A union is used by initializing one of the members and reading the
non-active member. This is undefined behavior and not permitted in a
`constexpr` context.
Solution:
- Eliminate undefined behavior by changing to a simple `u32` for
storage instead of the union and performing mask/shift calculations
for obtaining the individual octets.
- Decorate functions with `constexpr` where possible. Currently string
formatting and optionals are not `constexpr`-capable so functions
using those are left out.
- Modify tests to validate functionality in a `constexpr` context in
addition to the run-time tests already being run. This ensures that
functionality is the same in both contexts.
This makes most operations thread safe, especially so that they
can safely be used in the Kernel. This includes obtaining a strong
reference from a weak reference, which now requires an explicit
call to WeakPtr::strong_ref(). Another major change is that
Weakable::make_weak_ref() may require the explicit target type.
Previously we used reinterpret_cast in WeakPtr, assuming that it
can be properly converted. But WeakPtr does not necessarily have
the knowledge to be able to do this. Instead, we now ask the class
itself to deliver a WeakPtr to the type that we want.
Also, WeakLink is no longer specific to a target type. The reason
for this is that we want to be able to safely convert e.g. WeakPtr<T>
to WeakPtr<U>, and before this we just reinterpret_cast the internal
WeakLink<T> to WeakLink<U>, which is a bold assumption that it would
actually produce the correct code. Instead, WeakLink now operates
on just a raw pointer and we only make those constructors/operators
available if we can verify that it can be safely cast.
In order to guarantee thread safety, we now use the least significant
bit in the pointer for locking purposes. This also means that only
properly aligned pointers can be used.
Problem:
- There is no direct unit testing of the IPv4Address functionality
which makes refactoring difficult.
Solution:
- Add unit tests to cover the current functionality of
IPv4Address. This will allow future refactorings with confidence.
`AK::URL` will now check if the URL requires a port to be set using
`AK::URL.protocol_requires_port(protocol)`.
If the URL does not specify a port, and no default port for the URL
protocol is found with `AK::URL.default_port_for_protocol(protocol)`,
the URL is considered to be invalid.
Problem:
- `constexpr_sum` is implemented using `Array` which means the
function needs to be a function template so that the size can be
deduced.
Solution:
- Change the `Array` function argument to a `Span` since `Span` now is
`constexpr`.
Problem:
- Hash functions can be `constexpr`, but are not.
Solution:
- Change `inline` keyword to `constexpr`.
- Add `static_assert` tests to ensure the hash functions work in a
`constexpr` context.
Problem:
- The hash functions have no associated tests, so there is nothing
binding their behavior.
Solution:
- Bind the hash function behavior by adding tests.
- Use the existing behavior as "correct".
Problem:
- `Checked` is not `constexpr`-aware.
Solution:
- Decorate member functions with `constexpr` keyword.
- Add tests to ensure the functionality where possible.
Problem:
- There is no test which guarantees the CircularQueue does not
construct any objects of the value type. The goal is to have
uninitialized memory which can be used.
Solution:
- Add a test requiring that the constructor of the value type is never
called.
This commit also removes a few functions like raw_out and vwarn. If we
want to write raw output, we can do this as follows:
out("{}", "Hello, World!");
The vout stuff isn't really public API anyways, so no need for another
vwarn.
Problem:
- It is not possible to perform a binary search at compile-time
because `binary_search` is not `constexpr`-aware.
Solution:
- Add `constexpr` support.
Problem:
- `Span` is not `constexpr` aware.
Solution:
- Add `constexpr` support for all parts that do not require
`reinterpret_cast`.
- Modify tests which use the `constexpr` functions.
Problem:
- Output of decode and encode grow as the decode and encode
happen. This is inefficient because a large size will require many
reallocations.
- `const` qualifiers are missing on variables which are not intended
to change.
Solution:
- Since the size of the decoded or encoded message is known prior to
starting, calculate the size and set the output to that size
immediately. All appends will not incur the reallocation overhead.
- Add `const` qualifiers to show intent.
Problem:
- Constructors and conversion operators are not `constexpr`,
but they can be.
- `constexpr` is needed here so that other classes can add `constexpr`
evaluation.
Solution:
- Add the `constexpr` keyword to the constructors and
conversion operators.
- Add `static_assert` tests which ensure the capability works.
String literals are just pointers to a constant character. It should be
possible to format them as such. (The default is to print them as
strings still.)
When we write the format specifier '{:#08x}' we are asking for eight
significant digits, zero padding and the prefix '0x'.
However, previously we got only six significant digits because the
prefix counted towards the width. (The number '8' here is the total
width and not the number of significant digits.)
Both fmtlib and printf shared this behaviour. However, I am introducing
a special case here because when we do zero padding we really only care
about the digits and not the width.
Notice that zero padding is a special case anyways, because zero padding
goes after the prefix as opposed to any other padding which goes before
it.
It's now save to pass a signed integer as parameter and then use it as
replacement field (previously, this would just cast it to size_t which
would be bad.)
I put this into the <AK/PrintfImplementation.h> header in the hope that
it could be re-used by the printf implementation. That would not be
super trivial though, so I am not doing that now.
