The build system declared `rev_target` to be a dependency of
libdav1d instead of libdav1dentrypoint. This causes initial builds
to fail, as it is `src/lib.c` from libdav1dentrypoint that includes
this file. Move the dependency to libdav1dentrypoint to fix this.

This is a fix for

    ERROR:  Unknown variable "stackrealign_flag"

when configuring for x86 on compilers that do not support any of the
checked stackalign flags.

Since some code is still taken from there

Always use the compatibility layer.
Fix #28

Since we don't want to probe for winpthreads anymore, this macro isn't
usefull anymore

Also a tiny fix to ensure that frame-difference is always evaluated
in the correct wraparound order.

Downshift all the constants by one, and reduce the rounding shift by one.
This is mathematically equivalent since all constants are a multiple of two,
but allows for using 16-bit intermediates in the 1st pass of the 8-tap filter.

Marvin Scholz authored 6 years ago and Jean-Baptiste Kempf committed 6 years ago

This library is just a helper and should not be built by default as it
is only used to extract the objects and has no use as stand-alone
library for uses to link to.

This makes the function thread safe, to call, for example,
from multiple transient dependecies or threads.

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>

This function will be required to make dav1d_init threadsafe.

Full erro checking support is included in this implementation,
for completeness, even though dav1d_init cannot fail, and thus
will ignore the return value of pthread_once.

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>

These were all allocated with aligned malloc().

This prevents leaving the caller with a dangling pointer.

They are not valid out of a function in ISO C

It is not valid in ISO C and doesn't differ from __func__

As it is forbidden by ISO C

Removes undefined-behavior when primary_ref_frame is 7

Meson before 0.45 did not honor the meson version arg in the build file,
so there will be no proper error when using the wrong version.

Fix #24

Fixes mismatch in issue #14.

Fixes hang from sample in issue #14.

Fix for issue #20