C++17 introduced aligned versions of `new` and `delete`, which are
automatically called by the compiler when allocating over-aligned
objects. As with the regular allocator functions, these are generally
thin wrappers around LibC.
We did not have support for aligned allocations in LibC, so this was not
possible. While libstdc++ has a fallback implementation, libc++ does
not, so the aligned allocation function was disabled internally. This
made building the LLVM port with Clang impossible.
Note that while the Microsoft docs say that aligned_malloc and
_aligned_free are declared in `malloc.h`, libc++ doesn't #include that
file, but instead relies on the definition coming from `stdlib.h`.
Therefore, I chose to declare it in that file instead of creating a new
LibC header.
I chose not to implement the more Unix-y `memalign`, `posix_memalign`,
or the C11 `aligned_alloc`, because that would require us to
significantly alter the memory allocator's internals. See the comment in
malloc.cpp.
We always use UTF-8, meaning that a single `wchar_t` might be converted
into up to 4 `char`s. This would cause a buffer overflow if something
actually relied on this being the right value.
This implements the macOS API malloc_good_size() which returns the
true allocation size for a given requested allocation size. This
allows us to make use of all the available memory in a malloc chunk.
For example, for a malloc request of 35 bytes our malloc would
internally use a chunk of size 64, however the remaining 29 bytes
would be unused.
Knowing the true allocation size allows us to request more usable
memory that would otherwise be wasted and make that available for
Vector, HashTable and potentially other callers in the future.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
Just ignore all these environment flags if the AT_SECURE flag is set in
the program's auxiliary vector.
This prevents a user from tricking set-uid programs into dumping debug
information via environment flags.
