None of them are specific to the YASM assembler.

Previously, all link-time dependencies were added for all libraries,
resulting in bogus link-time dependencies since not all dependencies
are shared across libraries. Also, in some cases like libavutil, not
all dependencies were taken into account, resulting in some cases of
underlinking.

To address all this mess a machinery is added for tracking which
dependency belongs to which library component and then leveraged
to determine correct dependencies for all individual libraries.

This unclutters the top-level directory and groups related files together.

This moves work from the configure to the Make stage where it can
be parallelized and ensures that pkgconfig files are updated when
library versions change.

Bug-Id: 449

This moves work from the configure to the Make stage where it can
be parallelized and ensures that shared libraries are built with
the right version number in the filename.

This unclutters the top-level directory and groups related files together.

This makes naming more consistent and simplifies extralibs-related changes.

Otherwise builds without explicit target result in silent no-ops.

The library versions are stored in the config.mak file and are used
to derive shared library names.

EXTRALIBS contains general and platform-specific extra libraries
that should be part of all linker commands.

Supporting the system was a nice joke for the 9 release, but it has
run its course. Nowadays Plan 9 receives no testing and has no
practical usefulness.

Since avversion.h is a generated header it must be created before
dependencies can be determined as a side effect of compilation.
Otherwise Make stops and restarts the build process to generate
avversion.h and produces related error messages.

It didn't take into account the new pattern used for bitstream filters
and protocols.

The variable needs to be reset for each subdirectory.

And move the asm recipe to the top-level Makefile next to the other
local pattern rules for .o files.

Generate the files in a single postprocessing step w/o intermediate files.

Split version files into one line per symbol/directive to allow compatibility
with the Solaris linker without preprocessing and eliminate $ from version file
templates to simplify the postprocessing shell command.

Restore alphabetical order in lists, break overly long lines, do some
prettyprinting, add some explanatory section comments, group parts
together that belong together logically.

Signed-off-by: Anton Khirnov <anton@khirnov.net>

Assume that the default C compiler and the default ObjC compiler match
(default for OSX).

Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

The versioning facility in the Solaris linker differs from Linux in 3 ways:

1. It does not support globs in linker scripts for
symbol versioning -- this is a GNU extension.

2. The linker argument is '-M', instead of '--version-script'.

3. It is picky about line endings.
Each symbol or directive must be on a line of it's own.

Let's use make_sunver.pl from GCC to generate a version script that works
correctly with the Solaris linker. It's function is to correctly expand the
globs in the original generated version script.

Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

Checkasm needs to use internal symbols that should not be made public.

This returns something like "v12_dev0-1332-g333a27c". This is much more
useful than the individual library versions, of which there are too
many, and which are very hard to map back to releases or git commits.

Signed-off-by: Janne Grunau <janne-libav@jannau.net>

The options is useful to build position-independent executables on
hardened systems (e.g. Android L and Gentoo Hardened).

It has not been properly maintained for years and there is little hope
of that changing in the future.
It appears simpler to write a new replacement from scratch than
unbreaking it.

avcodec might depend on avresample and with --as-needed required symbols
might be get removed if avresample is linked before avcodec.
Fixes link failures of avprobe and avplay on aarch64 with
--enable-neon-clobber-test.

Signed-off-by: Luca Barbato <lu_zero@gentoo.org>