Implement the five interfaces openkal 0.8 adds

[Sunrisepeak]

openkal.terminal upon the kernel's terminal ioctls, openkal.net and openkal.datagram upon its socket calls, openkal.space upon clone, and openkal.timeout upon ppoll and a bounded wait for a child.

Paired with mcpplibs/openkal#13, which this branch follows by name.

Each is written on the kernel's own calling convention and names no facility a program above might also define. That property has held since version 0.5 and CI asserts it by examining the undefined symbols of the produced objects.

What writing the implementation established about the interface

Two changes went into the specification rather than into this repository, and both were found on the first run rather than by reading.

openkal.space is one operation because the kernel's primitive is one act. clone copies the address space and begins execution in the copy; there is no form that does the first without the second. An implementation asked to separate them would have to park a started context and build a channel by which to tell it what to run, which clause 7.1 excludes.

openkal.net yields an owned connection and a borrowed stream, for the same reason kal_file and kal_fs_stream are separate here: the owned handle carries a generation so that a released one stops being valid, and a stream handle is the bare descriptor because that is what the transfer operations take. The first form packed the connection into the handle scheme and kal_stream_read took the packed word as a descriptor, so the transfer read nothing.

Details worth stating

The terminal mode is read, modified and written rather than written alone. The kernel's structure carries input flags, output flags, a baud rate and the control characters, none of which the interface names; composing one from the mode word would discard all of them silently.

kal_terminal_props asks TIOCGWINSZ rather than deriving the answer from TCGETS. A pseudo terminal answers both and a serial line answers only the first, so a word derived from one would claim a facility the next call refuses — the disagreement clause 6.2 exists to prevent.

The endpoint conversion is shared between net and datagram because the type is, and either interface may be provided without the other. A length the implementation does not know is refused rather than read as one it does.

An interrupted bounded wait is reported as an expiry rather than retried with the whole bound again. Retrying would make the bound restart at every signal, leaving a program waiting without end while appearing to be bounded.

kal_timeout_wait_process polls with WNOHANG because the kernel has no bounded wait for a child. The alternative is a SIGCHLD handler, which is process-wide state an implementation would be taking away from the program above it.

kal_datagram_props does not claim broadcast. The kernel provides it only after SO_BROADCAST has been set and this interface has no operation that would set it.

Verification

mcpp test	7 passed, 0 failed
conformance suite	100 observations held, 0 did not hold
terminal	interactive path observed under a real pty, not only the refusal path

tests/conformance_v08.cpp is the C++ half of clause 4.3 for the new interfaces: the specification repository checks the C form against SURFACE.txt, and the module form is checked here, where a build of the modules already exists. It found a real omission on its first run — kal_endpoint was declared by the C form and not exported by the module form.

The observations are of behaviour and not only of existence. A test that named each entity and did nothing with it would compile against an implementation whose every operation returned an error, and would report that as conformance.