* remove fancy but broken static LinuxVersion object.
  This means each usage of a EMPER_LINUX_* macro results in a syscall.
  But I think this is worth it when the result is a sound program.
  Users of those macros should store the result of the comparison anyway.
* fix that we skipped parsing the last part of a version string
* add a test for LinuxVersion
* IO_MUST_INVALIDATE_BROKEN_CHAIN can still be const

Deprecate IoContext submit broken chain logic

See merge request !248

[apps/Coordinator] return SUCCESS when exiting successful not FAILURE

See merge request !250

[io/tests] use our own ASSERT macro unaffected by NDEBUG

Closes #11

See merge request !251

This allows use to remove the current hack that the test are always
build without NDEBUG regardless of the meson buildtype.

Which is fact fixes the failing io tests in release builds.
Because Future.hpp and Future.cpp see the same version of NDEBUG.

[Debug] implement logging to a memory-mapped log file

See merge request !244

When setting the environment variable EMPER_LOG_FILE=<logfile> EMPER
will write its log messages to <logfile> instead of stderr.
This removes the need for the mutex protecting std::cerr as well as
multiple write calls to flush std:cerr.

To efficiently write log messages to the log file the algorithm uses
three memory 1MiB mapped views into <logfile> to store the log messages.
One buffer is active, one is new, and one is old.
The next buffer ensures that threads can write log messages even if the
active buffer would overflows.
The old buffer allows slower threads to still write safely while everyone
else uses the active buffer.
When a thread changes from the active buffer to the new buffer it
is responsible to renew the current old buffer and changing the semantic
of the buffers:

* active -> old
* next -> active
* old -> next

This buffer scheme allows wait-free logging.
But the approach is NOT sound because delayed thread may still use the
old buffer which gets renewed by the first thread touching the next buffer.
But the likeliness for this situation decreases with bigger sizes of the
buffers.

ATTENTION: Using SCHED_IDLE for the completer may break this likeliness
assumption.

Add new CI test job with mmaped log files.

This contains code cleanups
Suggested-By: Florian Schmaus <flow@cs.fau.de>

[PipeSleepStrategy] prevent the still present race to cqes with the completer

See merge request !249

The previous race which I tried but in fact can not be fixed alone with
waitInflight flag is now described in the code comment in
PipeSleepStrategy::sleep().

To completely prevent the completer and the worker racing to the
new work notifications cqes we repurpose the cq_lock to ensure the
completer is always observing and honoring the waitInflight flag.

Also add an onNewWorkNotification callback to keep most sleep related
code and logic in PipeSleepStrategy.

[Make] use tidy make target instead of the meson generated clang-tidy target

See merge request !247

[meson/liburing] switch to the official liburing wrap from meson wrapdb

See merge request !246

[IoContext] die when the completer threads reaps new work notifications

See merge request !245

The meson generated clang-tidy target uses compile_commands including
all code from subprojects and therefore fails due to code not in our control.
The gitlab CI also uses the tidy make target.

The PipeSleepStrategy uses the invariant that the completer thread
is not reaping IoContext of workers which have a read of the
sleep/notification pipe in flight.
This means that it can not reap CQEs resulting from such reads.
To esnure this invariant we DIE if the completer encounters completions
for such notifications.

[Debug] fix nanos in log timestamp

See merge request !242

The timestamp consists of <hour><minutes>.<nanos> but the calculation of
the nanos in the current minute was broken.
A minute are 60 * 10^9 nanoseconds and not 10^9.

[liburing] bump the used wrap

See merge request !241

Now EMPER builds using the liburing wrap succeed because they no longer
include liburing/src which contains a custom syscall header.

[Makefile] Make static-analysis depend on iwyu

See merge request !240

[build] Emit a message if liburing subproject is used

See merge request !239

The ninja 'iwyu' target does not depend nor generates
compile_commands_wo_subprojects/compile_commands.json. Hence iwyu
would fail if the database is not yet generated or run with an
outdated compile_commands.json.

Instead of iwyu being added to STATIC_ANALYSIS_NINJA_TARGETS, we now
have the static-analysis make target depend on iwyu. This ensures that
compile_commands_wo_subprojects/compile_commands.json is generated or
updated (if required) before iwyu is run.p

[IO] add shutdown(3) support

See merge request !190

Consume liburing as meson wrap if native is not recent enough

See merge request !238

[Future] Also log 'res' in LOGD of setCompletion(int32_t res)

See merge request !237

[GlobalIoContext] Add CompleterSchedParam option

See merge request !236

Generate a new compile_commands database in compile_commands_wo_subprojects/
without the files in subprojects/.
This new compile_commands database is than consumed by iwyu and clang-tidy.

Co-Authored-By: Florian Schmaus <schmaus@cs.fau.de>
Suggested--By: Florian Schmaus <schmaus@cs.fau.de>

It can't hurt to provide more information in log messages, especially
'res' is a good candidate in this case.

[IoContext] Add missing error handling in submitPreparedSqesAndWait()

See merge request !235

[IoContext] Remove duplicate CQE_BATCH_COUNT delcaration and definition

See merge request !233

This adds an option to make the scheduling parameters of the completer
thread configurable via a meson option.

Within the

do { reapAndScheduleCompletions() } while (io_uring_submit() == -EBUSY)

loop, the return value of io_uring_submit could be a negative value other
than EBUSY. In that case, we did not DIE.

Looking at the SubmitActor, where we have a very similar loop, the
error handling is correct. This changes the error handling in
IoContext to match the one of SubmitActor, even though it has a little
bit more overhead.