Add std::expected syscall wrappers and adopt them for fd creation - #25
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Introduce src/utils/sys.h: thin std::expected<UniqueFd, std::error_code> wrappers over the fd-creating syscalls (open, eventfd, signalfd, timerfd). A fallible call now hands back a [[nodiscard]], allocation-free error channel (errno mapped to std::generic_category()) with the fd already owned, instead of a bare -1 the caller must remember to check. This is the errno layer only, and it establishes the error-model convention for the project: syscalls -> std::expected<T, std::error_code>; D-Bus failures -> sdbus::Error exceptions (sdbus-c++'s model); absent-but-valid values -> std::optional. Each is the right tool for its layer. Adopted at the fd-creation sites: EventLoop's wake eventfd, SignalSource's signalfd, and the three controllers' hidraw open() (which now also logs the specific errno message). An opt-in unit test (sys_test) covers success, the ENOENT error path, and the eventfd/timerfd wrappers. Further adoption (e.g. the hidraw ioctl chain) can follow the same shape; this change lands the foundation and the reference call sites. Signed-off-by: Joel Winarske <[email protected]>
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Add std::expected syscall wrappers and adopt them for fd creation
Introduce src/utils/sys.h: thin std::expected<UniqueFd, std::error_code>
wrappers over the fd-creating syscalls (open, eventfd, signalfd, timerfd). A
fallible call now hands back a [[nodiscard]], allocation-free error channel
(errno mapped to std::generic_category()) with the fd already owned, instead of a bare -1 the caller must remember to check.
This is the errno layer only, and it establishes the error-model convention for
the project: syscalls -> std::expected<T, std::error_code>; D-Bus failures ->
sdbus::Error exceptions (sdbus-c++'s model); absent-but-valid values ->
std::optional. Each is the right tool for its layer.
Adopted at the fd-creation sites: EventLoop's wake eventfd, SignalSource's
signalfd, and the three controllers' hidraw open() (which now also logs the
specific errno message). An opt-in unit test (sys_test) covers success, the
ENOENT error path, and the eventfd/timerfd wrappers.
Further adoption (e.g. the hidraw ioctl chain) can follow the same shape; this
change lands the foundation and the reference call sites.