* fix ringbuffer thread safety on ARM. fix #715 #388

This patch addresses the thread safety problem of `jack_ringbuffer_t`
mentioned in #715 and #388. The overbound read bug caused by this problem
is impossible to reproduce on x86 due to its strong memory ordering, but
it is a problem on ARM and other weakly ordered architectures.

Basically, the main problem is that, on a weakly ordered architecture,
it is possible that the pointer increment after `memcpy` becomes visible
to the other thread before `memcpy` finishes:

	memcpy (&(rb->buf[rb->write_ptr]), src, n1);
	// vvv can be visible to reading thread before memcpy finishes
	rb->write_ptr = (rb->write_ptr + n1) & rb->size_mask;

If this happens, the other thread can read the remaining garbage values
in `rb->buf` due to be overwritten by the unfinished `memcpy`.

To fix this, an explicit pair of release/acquire memory fences [1] is
used to ensure the copy on the other thread *happens after* the `memcpy`
finishes so no garbage values can be read.

[1]: https://preshing.com/20130922/acquire-and-release-fences/

* remove volatile qualifier on ringbuf r/w pointers

The volatile constraints are excess when compiler barriers are present.
It generates unnecessary `mov` instructions when pointers aren't going
to be updated.

* simplify read/write space calculations

This optimization is possible because the buffer size is always a power
of 2. See [1] for details.

[1]: https://github.com/drobilla/zix/pull/1#issuecomment-1212687196

* move acq fences to separate lines

Since doxygen 1.8.16, opening and closing a group must not be done as
C comment but as doxygen command. In other words, not one but two
asterisk characters are required so that doxygen finds a group.

* Add jack_position_t::tick_double, and flags around it

Signed-off-by: falkTX <falktx@falktx.com>

* s/precision/resolution/

Signed-off-by: falkTX <falktx@falktx.com>

Found via `codespell -q 3 -L capela,nd,numer,parm`

This reverts commit f3e8a6bc6b.

See https://github.com/jackaudio/jack2/issues/646 for the reason.
As the old headers are already widely used, it is too late now.

jack_port_get_latency_range only returns meaningful values after ports get
connected, and that is signalled via the latency callback. Saying that it's
normally used in callbacks is too soft, the docs should make it clear that the
function is not very useful outside of the callback, because you don't know
whether the port is connected / whether the latency values changed.

jack_port_get_latency_range only returns meaningful values after ports get
connected, and that is signalled via the latency callback. Saying that it's
normally used in callbacks is too soft, the docs should make it clear that the
function is not very useful outside of the callback, because you don't know
whether the port is connected / whether the latency values changed.

to ensure that it is not modified by any client.

const have internal linkage unless marked by extern

Change-Id: Ife1def2feb43aead32164f479e39ee3fd71b2ba0
Signed-off-by: Adam Miartus <external.Adam.Miartus@de.bosch.com>
Signed-off-by: Timo Wischer <twischer@de.adit-jv.com>

Signed-off-by: falkTX <falktx@falktx.com>

Fixes the following errors:

C:\vcpkg\installed\x64-windows-static-md\include\jack/systemdeps.h(73): error C2371: 'int8_t': redefinition; different basic types
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.23.28105\include\stdint.h(14): note: see declaration of 'int8_t'
C:\vcpkg\installed\x64-windows-static-md\include\jack/systemdeps.h(77): error C2371: 'int32_t': redefinition; different basic types
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.23.28105\include\stdint.h(16): note: see declaration of 'int32_t'
C:\vcpkg\installed\x64-windows-static-md\include\jack/systemdeps.h(78): error C2371: 'uint32_t': redefinition; different basic types
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.23.28105\include\stdint.h(20): note: see declaration of 'uint32_t'

Signed-off-by: falkTX <falktx@falktx.com>

Also document this usecase

Signed-off-by: falkTX <falktx@falktx.com>

Signed-off-by: falkTX <falktx@falktx.com>

Found via `codespell -q 3`

Signed-off-by: falkTX <falktx@falktx.com>

See https://github.com/jackaudio/jack2/issues/413

Signed-off-by: falkTX <falktx@gmail.com>

Flagged by the Debian QA tool.

Mostly automatic search-n-replace of the mistakes flagged.

Fixes #288

Thanks to Timo Wischer for the initial work

Forwarded from
<https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=728710>

JACK2 added this function first, but the int return has been always wrong.
When JACK1 added JackPortRenameCallback it used the proper return.

Now that JACK1 supports port renames, devs will start to use it.
(previously it didn't work properly because of the missing jack_client_t* arg)

Some code might be broken because of this, but it's a very simple change,
and existing code would have been broken when changing JACK1 to JACK2.

Finally, JACK2 code never uses the int return value of this callback.
So there's no real reason to NOT change this.

For instance, if compiling with gcc and the option --stc=c++11, WIN32 is not defined.
See http://webcache.googleusercontent.com/search?q=cache:amvfgAUCdsgJ:sourceforge.net/p/mingw-w64/mailman/message/31850993/+&cd=4&hl=en&ct=clnk&gl=no
http://sourceforge.net/p/mingw-w64/mailman/message/31850993/

This reverts commit 23f5919c62.