Clarify and explain loaded_feature_path and rb_feature_p

* load.c (loaded_feature_path): clarify and briefly comment
  function.  These clarifications have no effect on the behavior
  of the function.

* load.c (rb_feature_p): explain the search loop.  Especially
  useful because the logic is complicated as described in the
  second paragraph.
  Patch by Greg Price.
  [ruby-core:47970] [Bug #7158]

git-svn-id: http://svn.ruby-lang.org/repos/ruby/trunk@37477 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
Expose whether two arrays are shared

* array.c (rb_ary_shared_with_p): new function.
  Expose whether two arrays are shared (read-only, C only).

* include/ruby/intern.h (rb_ary_shared_with_p): declare.
  Patch by Greg Price.
  [ruby-core:47970] [Bug #7158]

git-svn-id: http://svn.ruby-lang.org/repos/ruby/trunk@37478 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2012-11-06

git-svn-id: http://svn.ruby-lang.org/repos/ruby/trunk@37479 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
Index $LOADED_FEATURES so that require isn't so slow

* load.c (rb_feature_p, rb_provide_feature): index $LOADED_FEATURES
  so that require isn't so slow.

* load.c (rb_provide_feature, get_loaded_features_index): ensure
  that $LOADED_FEATURES entries are frozen strings.  The user
  must mutate $LOADED_FEATURES itself rather than its individual
  entries.

* load.c (reset_loaded_features_snapshot): add a new function to reset
  vm->loaded_features_snapshot.

* load.c (get_loaded_features_index_raw): add a new function to get
  the loaded-features index.

* load.c (features_index_add_single): add a new function to add to the
  loaded-features index a single feature.

* load.c (features_index_add): add a new function to add to the
  loaded-features index all the required entries for `feature`.

* vm_core.h (rb_vm_struct): add fields.

* vm.c (rb_vm_mark): mark new fields.

* include/ruby/intern.h (rb_hash_clear): declare function.

* hash.c (rb_hash_clear): make function non-static.
  Patch by Greg Price.
  [ruby-core:47970] [Bug #7158]

git-svn-id: http://svn.ruby-lang.org/repos/ruby/trunk@37480 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
Cache the expanded load path

* load.c (rb_get_expanded_load_path): cache the expanded load
  path.  This saves 4KB of allocation and some stats for every
  element of the load path (so nearly a MB in my Rails app)
  on every require.

* load.c (rb_construct_expanded_load_path): ensure that $LOAD_PATH
  entries are frozen strings.  The user must mutate $LOAD_PATH
  itself rather than its individual entries.

* vm_core.h (rb_vm_struct): add fields.

* vm.c (rb_vm_mark): mark new fields.

* ruby.c (process_options): modify $LOAD_PATH directly rather than
  its elements.
  Patch by Greg Price.
  [ruby-core:47970] [Bug #7158]

git-svn-id: http://svn.ruby-lang.org/repos/ruby/trunk@37481 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
Fix compatibility of cached expanded load path

* file.c (rb_get_path_check_to_string): extract from
  rb_get_path_check(). We change the spec not to call to_path of
  String object.

* file.c (rb_get_path_check_convert): extract from rb_get_path_check().

* file.c (rb_get_path_check): follow the above change.

* file.c (rb_file_expand_path_fast): remove check_expand_path_args().
  Instead we call it in load.c.

* file.c (rb_find_file_ext_safe): use rb_get_expanded_load_path() to
  reduce expand cost.

* file.c (rb_find_file_safe): ditto.

* internal.h (rb_get_expanded_load_path): add a declaration.

* internal.h (rb_get_path_check_to_string, rb_get_path_check_convert):
  add declarations.

* load.c (rb_construct_expanded_load_path): fix for compatibility.
  Same checks in rb_get_path_check() are added. We don't replace
  $LOAD_PATH and ensure that String object of $LOAD_PATH are frozen.
  We don't freeze non String object and expand it every times. We add
  arguments for expanding load path partially and checking if load path
  have relative paths or non String objects.

* load.c (load_path_getcwd): get current working directory for checking
  if it's changed when getting load path.

* load.c (rb_get_expanded_load_path): fix for rebuilding cache properly.
  We check if current working directory is changed and rebuild expanded
  load path cache. We expand paths which start with ~ (User HOME) and
  non String objects every times for compatibility. We make this
  accessible from other source files.

* load.c (rb_feature_provided): call rb_get_path() since we changed
  rb_file_expand_path_fast() not to call it.

* load.c (Init_load): initialize vm->load_path_check_cache.

* vm.c (rb_vm_mark): mark vm->load_path_check_cache for GC.

* vm_core.h (rb_vm_struct): add vm->load_path_check_cache to store data
  to check load path cache validity.

* test/ruby/test_require.rb (TestRequire): add tests for require
  compatibility related to cached expanded load path.
  [ruby-core:47970] [Bug #7158]

git-svn-id: http://svn.ruby-lang.org/repos/ruby/trunk@37482 b2dd03c8-39d4-4d8f-98ff-823fe69b080e