This patch initiates the refactoring of Linux syscalls as described in
the RFC (https://discourse.llvm.org/t/rfc-linux-syscall-cleanup/87248/).
It introduces a new infrastructure in
`src/__support/OSUtil/linux/syscall_wrappers/` to house header-only
syscall wrappers. These wrappers utilize `ErrorOr` to provide a
consistent, type-safe interface for error handling across the library,
standardizing how syscall return values are converted into
errno-compatible Error objects.
Summary of changes:
- Created the `syscall_wrappers` directory and added `close.h`,
`read.h`, `write.h`, and `open.h`.
- Moved the existing `getrandom.h` into the new `syscall_wrappers`
directory and updated its callers (including HashTable/randomness.h).
- Refactored core entrypoints (`close`, `read`, `write`, `open`) to use
the new wrappers, removing direct `syscall_impl` logic and manual errno
setting.
- Updated `shm_open.cpp` to use the new `open` wrapper.
- Cleaned up `OSUtil/linux/fcntl.cpp` by removing redundant internal
implementations of `open` and `close`.
- Added a developer guide in `docs/dev/syscall_wrapper_refactor.rst`
outlining the established pattern for future migrations.
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Co-authored-by: Michael Jones <michaelrj@google.com>
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