Problem:
- Using regular functions rather than function templates results in
the arguments not being deduced. This then requires the same
function to be written multiple times and for `move` to be used
rather than `forward`.
Solution:
- Collapse multiple function overloads to a single function template
with a deduced argument. This allows the argument to be a forwarding
reference and bind to either an l-value or r-value and forward the
value.
Note:
- `append` is not being changed because there are several overloads
for appending single values and concatenating vectors. This
conflation needs to be addressed first.
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`.
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.
Much like with Vector::append(), you may want to append multiple items in one
go. It's actually more important to do this for prepending, because you don't
want to copy the rest of items further each time.
first_matching returns the first item in the vector that matches
the given condition.
last_matching returns the last item in the vector that matches
the given condition.
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.
I originally defined the bytes() method for the String class, because it
made it obvious that it's a span of bytes instead of span of characters.
This commit makes this more consistent by defining a bytes() method when
the type of the span is known to be u8.
Additionaly, the cast operator to Bytes is overloaded for ByteBuffer and
such.
The symbol name insertion scheme is different from objdump -d's.
Compare the output on Build/Userland/id:
* disasm:
...
_start (08048305-0804836b):
08048305 push ebp
...
08048366 call 0x0000df56
0804836b o16 nop
0804836d o16 nop
0804836f nop
(deregister_tm_clones (08048370-08048370))
08048370 mov eax, 0x080643e0
...
_ZN2AK8Utf8ViewC1ERKNS_6StringE (0805d9b2-0805d9b7):
_ZN2AK8Utf8ViewC2ERKNS_6StringE (0805d9b2-0805d9b7):
0805d9b2 jmp 0x00014ff2
0805d9b7 nop
* objdump -d:
08048305 <_start>:
8048305: 55 push %ebp
...
8048366: e8 9b dc 00 00 call 8056006 <exit>
804836b: 66 90 xchg %ax,%ax
804836d: 66 90 xchg %ax,%ax
804836f: 90 nop
08048370 <deregister_tm_clones>:
8048370: b8 e0 43 06 08 mov $0x80643e0,%eax
...
0805d9b2 <_ZN2AK8Utf8ViewC1ERKNS_6StringE>:
805d9b2: e9 eb f6 ff ff jmp 805d0a2 <_ZN2AK10StringViewC1ERKNS_6StringE>
805d9b7: 90 nop
Differences:
1. disasm can show multiple symbols that cover the same instructions.
I've only seen this happen for C1/C2 (and D1/D2) ctor/dtor pairs,
but it could conceivably happen with ICF as well.
2. disasm separates instructions that do not belong to a symbol with
a newline, so that nop padding isn't shown as part of a function
when it technically isn't.
3. disasm shows symbols that are skipped (due to having size 0)
in parenthesis, separated from preceding and following instructions.
Use the AK version of std::initializer_list in AK::Vector, but only
when in serenity. When building AK for a non-serenity target, the header
<initializer_list> should be always available.
We can use __builtin_memset() without including <string.h>.
This is pretty neat, as it will allow us to reduce the header deps
of AK templates a bit, if applied consistently.
Note that this is an enabling change for an upcoming #include removal.
You can now #include <AK/Forward.h> to get most of the AK types as
forward declarations.
Header dependency explosion is one of the main contributors to compile
times at the moment, so this is a step towards smaller include graphs.
Previously, when deallocating a range of VM, we would sort and merge
the range list. This was quite slow for large processes.
This patch optimizes VM deallocation in the following ways:
- Use binary search instead of linear scan to find the place to insert
the deallocated range.
- Insert at the right place immediately, removing the need to sort.
- Merge the inserted range with any adjacent range(s) in-line instead
of doing a separate merge pass into a list copy.
- Add Traits<Range> to inform Vector that Range objects are trivial
and can be moved using memmove().
I've also added an assertion that deallocated ranges are actually part
of the RangeAllocator's initial address range.
I've benchmarked this using g++ to compile Kernel/Process.cpp.
With these changes, compilation goes from ~41 sec to ~35 sec.
As suggested by Joshua, this commit adds the 2-clause BSD license as a
comment block to the top of every source file.
For the first pass, I've just added myself for simplicity. I encourage
everyone to add themselves as copyright holders of any file they've
added or modified in some significant way. If I've added myself in
error somewhere, feel free to replace it with the appropriate copyright
holder instead.
Going forward, all new source files should include a license header.
This removes an item at an index without preserving the sort order of
the Vector.
This enables constant-time removal from unsorted Vectors, as it avoids
shifting all of the entries following the removed one.
This can definitely be improved with better trivial type detection and
by using the TypedTransfer template in more places.
It's a bit annoying that we can't get <type_traits> in Vector.h since
it's included in the toolchain compilation before we have libstdc++.
This is a complement to append() that works by constructing the new
element in-place via placement new and forwarded constructor arguments.
The STL calls this emplace_back() which looks ugly, so I'm inventing
a nice word for it instead. :^)
It's not possible to grow one of these vectors beyond what's already in them
since it's not possible to default-construct Nonnull{Own,Ref}Ptr.
Add Vector::shrink() which can be used when you want to shrink the Vector
and delete resize() from the specialized Vectors.
This allows you to do things like:
vector.insert_before_matching(value, [](auto& entry) {
return value < entry;
});
Basically it scans until it finds an element that matches the condition
callback and then inserts the new value before the matching element.
This is prep work for supporting HashMap with NonnullRefPtr<T> as values.
It's currently not possible because many HashTable functions require being
able to default-construct the value type.
The LibC build is a bit complicated, since the toolchain depends on it.
During the toolchain bootstrap, after we've built parts of GCC, we have
to stop and build Serenity's LibC, so that the rest of GCC can use it.
This means that during that specific LibC build, we don't yet have access
to things like std::initializer_list.
For now we solve this by defining SERENITY_LIBC_BUILD during the LibC
build and excluding the Vector/initializer_list support inside LibC.
This is a slot-in convenience replacement for Vector<NonnullRefPtr<T>> that
makes accessors return T& instead of NonnullRefPtr<T>&.
Since NonnullRefPtr guarantees non-nullness, this allows you to access these
vector elements using dot (.) rather than arrow (->). :^)
Put together a pretty well-performing queue using a Vector and an offset.
By using the new Vector::shift_left(int) instead of Vector::take_first()
we can avoid shifting the vector contents every time and instead only
do it every so often.
Maybe this could be generalized into a separate class, I'm not sure if it's
the best algorithm though, it's just what I came up with right now. :^)
Also run it across the whole tree to get everything using the One True Style.
We don't yet run this in an automated fashion as it's a little slow, but
there is a snippet to do so in makeall.sh.
It was depressing not being able to capture anything when passing a lambda
to qsort_r() so let's just have our own QuickSort. I was gonna have to do
this eventually anyway. :^)
It forgot to clear out the moved-from vector. It's easy to see where this bug
came from: I assumed m_impl was an OwnPtr. It would be comfy if move() on some
arbitrary T* would also null it out but alas that's not how things work.
I feel like this concept might be useful in more places. It's very naive
right now and uses dynamically growing buffers. It should really use static
size buffers and never kmalloc().
I was surprised to find that dup()'ed fds don't share the close-on-exec flag.
That means it has to be stored separately from the FileDescriptor object.
This was the fix:
-process.m_page_directory[0] = m_kernel_page_directory[0];
-process.m_page_directory[1] = m_kernel_page_directory[1];
+process.m_page_directory->entries[0] = m_kernel_page_directory->entries[0];
+process.m_page_directory->entries[1] = m_kernel_page_directory->entries[1];
I spent a good two hours scratching my head, not being able to figure out why
user process page directories felt they had ownership of page tables in the
kernel page directory.
It was because I was copying the entire damn kernel page directory into
the process instead of only sharing the two first PDE's. Dang!
This shows some info about the MM. Right now it's just the zone count
and the number of free physical pages. Lots more can be added.
Also added "exit" to sh so we can nest shells and exit from them.
I also noticed that we were leaking all the physical pages, so fixed that.
