Setting class varibles goes through the ancestor list which can
contain iclasses. Iclasses share a lot of information with the
module they are made from, but not the frozen status.
Check the frozen status of the module instead of the iclass.
When `LANG=C`, dir is `UTF-8` and `base` is 'ASCII-8BIT` in `FileUtils::Entry_#join`.
So `Encoding::CompatibilityError` occurred and files are not removed.
https://rubyci.org/logs/rubyci.s3.amazonaws.com/arch/ruby-master/log/20200611T060002Z.fail.html.gz
```
1) Error:
WEBrick::TestFileHandler#test_cjk_in_path:
Errno::ENOTEMPTY: Directory not empty @ dir_s_rmdir - /home/chkbuild/chkbuild/tmp/build/20200611T060002Z/tmp/???20200611-1887828-3nn72a
/home/chkbuild/chkbuild/tmp/build/20200611T060002Z/ruby/lib/fileutils.rb:1460:in `rmdir'
/home/chkbuild/chkbuild/tmp/build/20200611T060002Z/ruby/lib/fileutils.rb:1460:in `block in remove_dir1'
/home/chkbuild/chkbuild/tmp/build/20200611T060002Z/ruby/lib/fileutils.rb:1471:in `platform_support'
/home/chkbuild/chkbuild/tmp/build/20200611T060002Z/ruby/lib/fileutils.rb:1459:in `remove_dir1'
/home/chkbuild/chkbuild/tmp/build/20200611T060002Z/ruby/lib/fileutils.rb:1452:in `remove'
/home/chkbuild/chkbuild/tmp/build/20200611T060002Z/ruby/lib/fileutils.rb:780:in `block in remove_entry'
/home/chkbuild/chkbuild/tmp/build/20200611T060002Z/ruby/lib/fileutils.rb:1509:in `ensure in postorder_traverse'
/home/chkbuild/chkbuild/tmp/build/20200611T060002Z/ruby/lib/fileutils.rb:1509:in `postorder_traverse'
/home/chkbuild/chkbuild/tmp/build/20200611T060002Z/ruby/lib/fileutils.rb:778:in `remove_entry'
/home/chkbuild/chkbuild/tmp/build/20200611T060002Z/ruby/lib/tmpdir.rb:97:in `mktmpdir'
/home/chkbuild/chkbuild/tmp/build/20200611T060002Z/ruby/test/webrick/test_filehandler.rb:292:in `test_cjk_in_path'
```
This callcache is on stack, must not be GCed. However its contents are
copied from other materials, which can be an ordinal object. Should
set a flag to make sure it is properly skipped by the GC.
For ZSUPER methods with no defined class for the method entry, start the next lookup at the superclass of the origin class of the method owner, instead of the superclass of the method owner.
Fixes [Bug #16942]
This reverts commit 02b216e5a70235f42f537e895d6f1afd05d8916a.
This reverts commit 9b8825b6f94696c9659f93f5da9bf02644625f67.
I found that combining sweep and move is not safe. I don't think that
we can do compaction concurrently with _anything_ unless there is a read
barrier installed.
Here is a simple example. A class object is freed, and during it's free
step, it tries to remove itself from its parent's subclass list.
However, during the sweep step, the parent class was moved and the
"currently being freed" class didn't have references updated yet. So we
get a segv like this:
```
(lldb) bt
* thread #1, name = 'ruby', stop reason = signal SIGSEGV
* frame #0: 0x0000560763e344cb ruby`rb_st_lookup at st.c:320:43
frame #1: 0x0000560763e344cb ruby`rb_st_lookup(tab=0x2f7469672f6e6f72, key=3809, value=0x0000560765bf2270) at st.c:1010
frame #2: 0x0000560763e8f16a ruby`rb_search_class_path at variable.c:99:9
frame #3: 0x0000560763e8f141 ruby`rb_search_class_path at variable.c:145
frame #4: 0x0000560763e8f141 ruby`rb_search_class_path(klass=94589785585880) at variable.c:191
frame #5: 0x0000560763ec744e ruby`rb_vm_bugreport at vm_dump.c:996:17
frame #6: 0x0000560763f5b958 ruby`rb_bug_for_fatal_signal at error.c:675:5
frame #7: 0x0000560763e27dad ruby`sigsegv(sig=<unavailable>, info=<unavailable>, ctx=<unavailable>) at signal.c:955:5
frame #8: 0x00007f8b891d33c0 libpthread.so.0`___lldb_unnamed_symbol1$$libpthread.so.0 + 1
frame #9: 0x0000560763efa8bb ruby`rb_class_remove_from_super_subclasses(klass=94589790314280) at class.c:93:56
frame #10: 0x0000560763d10cb7 ruby`gc_sweep_step at gc.c:2674:2
frame #11: 0x0000560763d1187b ruby`gc_sweep at gc.c:4540:2
frame #12: 0x0000560763d101f0 ruby`gc_start at gc.c:6797:6
frame #13: 0x0000560763d15153 ruby`rb_gc_compact at gc.c:7479:12
frame #14: 0x0000560763eb4eb8 ruby`vm_exec_core at vm_insnhelper.c:5183:13
frame #15: 0x0000560763ea9bae ruby`rb_vm_exec at vm.c:1953:22
frame #16: 0x0000560763eac08d ruby`rb_yield at vm.c:1132:9
frame #17: 0x0000560763edb4f2 ruby`rb_ary_collect at array.c:3186:9
frame #18: 0x0000560763e9ee15 ruby`vm_call_cfunc_with_frame at vm_insnhelper.c:2575:12
frame #19: 0x0000560763eb2e66 ruby`vm_exec_core at vm_insnhelper.c:4177:11
frame #20: 0x0000560763ea9bae ruby`rb_vm_exec at vm.c:1953:22
frame #21: 0x0000560763eac08d ruby`rb_yield at vm.c:1132:9
frame #22: 0x0000560763edb4f2 ruby`rb_ary_collect at array.c:3186:9
frame #23: 0x0000560763e9ee15 ruby`vm_call_cfunc_with_frame at vm_insnhelper.c:2575:12
frame #24: 0x0000560763eb2e66 ruby`vm_exec_core at vm_insnhelper.c:4177:11
frame #25: 0x0000560763ea9bae ruby`rb_vm_exec at vm.c:1953:22
frame #26: 0x0000560763ceee01 ruby`rb_ec_exec_node(ec=0x0000560765afa530, n=0x0000560765b088e0) at eval.c:296:2
frame #27: 0x0000560763cf3b7b ruby`ruby_run_node(n=0x0000560765b088e0) at eval.c:354:12
frame #28: 0x0000560763cee4a3 ruby`main(argc=<unavailable>, argv=<unavailable>) at main.c:50:9
frame #29: 0x00007f8b88e560b3 libc.so.6`__libc_start_main + 243
frame #30: 0x0000560763cee4ee ruby`_start + 46
(lldb) f 9
frame #9: 0x0000560763efa8bb ruby`rb_class_remove_from_super_subclasses(klass=94589790314280) at class.c:93:56
90
91 *RCLASS_EXT(klass)->parent_subclasses = entry->next;
92 if (entry->next) {
-> 93 RCLASS_EXT(entry->next->klass)->parent_subclasses = RCLASS_EXT(klass)->parent_subclasses;
94 }
95 xfree(entry);
96 }
(lldb) command script import -r misc/lldb_cruby.py
lldb scripts for ruby has been installed.
(lldb) rp entry->next->klass
(struct RMoved) $1 = (flags = 30, destination = 94589792806680, next = 94589784369160)
(lldb)
```
We don't need to resolve symbols when freeing cc tables, so this commit
just changes the id table iterator to look at values rather than keys
and values.
