WHen libyaml is not installed, make fails with the following cryptic
message:
```
gmake[2]: Entering directory '/home/chkbuild/chkbuild-crossruby/tmp/build/20220325T045825Z/ruby/ext/psych'
gmake[2]: *** No rule to make target 'yaml/yaml.h', needed by 'psych.o'. Stop.
gmake[2]: Leaving directory '/home/chkbuild/chkbuild-crossruby/tmp/build/20220325T045825Z/ruby/ext/psych'
```
I think it should give up building psych with a clear message.
Header file include/ruby/internal/abi.h contains RUBY_ABI_VERSION which
is the ABI version. This value should be bumped whenever an ABI
incompatible change is introduced.
When loading dynamic libraries, Ruby will compare its own
`ruby_abi_version` and the `ruby_abi_version` of the loaded library. If
these two values don't match it will raise a `LoadError`. This feature
can also be turned off by setting the environment variable
`RUBY_RUBY_ABI_CHECK=0`.
This feature will prevent cases where previously installed native gems
fail in unexpected ways due to incompatibility of changes in header
files. This will force the developer to recompile their gems to use the
same header files as the built Ruby.
In Ruby, the ABI version is exposed through
`RbConfig::CONFIG["ruby_abi_version"]`.
Inside ObjectSpace.reachable_objects_from we keep an internal identhash
in order to de-duplicate reachable objects when wrapping them as
InternalObject. Previously this hash was not hidden, making it possible
to leak references to those internal objects to Ruby if using
ObjectSpace.each_object.
This commit solves this by hiding the hash. To simplify collection of
values, we instead now just use the hash as a set of visited objects,
and collect an Array (not hidden) of values to be returned.
The gem doesn't even install on old rubies, but since the gemspec claims
it's supported, `gem install pathname` will try to install it and print
an error.
This commit doesn't fix the above issue. The only way to fix it would be
to restore support and release a new version that actually supports old
rubies. However, such a change has been proposed and ignored for a long
time.
So this issue proposes to leave that broken but at least bring the
gemspec manifest and the CI matrix in sync to hopefully avoid this issue
from happening again in the future.
https://github.com/ruby/pathname/commit/3ee010b538
It does not seem needed, and it's causing issues on Windows when
uninstalling `strscan`, because strscan's shared library being used when
RubyGems tries to remove it (because its loaded through Psych, which
RubyGems uses for loading configuration).
https://github.com/ruby/psych/commit/3911356ec1
