Revert "Do not load file with same realpath twice when requiring"

This reverts commit ddb85c5d2b.

This commit causes unexpected warnings in TestTranscode#test_loading_race
occasionally in CI.

load.c

@@ -152,12 +152,6 @@ get_loaded_features(void)
     return GET_VM()->loaded_features;
 }
 
-static VALUE
-get_loaded_features_realpaths(void)
-{
-    return GET_VM()->loaded_features_realpaths;
-}
-
 static VALUE
 get_LOADED_FEATURES(ID _x, VALUE *_y)
 {
@@ -323,9 +317,6 @@ get_loaded_features_index(void)
 	/* The sharing was broken; something (other than us in rb_provide_feature())
 	   modified loaded_features.  Rebuild the index. */
 	st_foreach(vm->loaded_features_index, loaded_features_index_clear_i, 0);
-
-        VALUE realpaths = vm->loaded_features_realpaths;
-        rb_hash_clear(realpaths);
 	features = vm->loaded_features;
 	for (i = 0; i < RARRAY_LEN(features); i++) {
 	    VALUE entry, as_str;
@@ -337,15 +328,6 @@ get_loaded_features_index(void)
 	    features_index_add(as_str, INT2FIX(i));
 	}
 	reset_loaded_features_snapshot();
-
-        features = rb_ary_dup(vm->loaded_features_snapshot);
-        long j = RARRAY_LEN(features);
-        for (i = 0; i < j; i++) {
-            VALUE as_str = rb_ary_entry(features, i);
-            VALUE realpath = rb_check_realpath(Qnil, as_str, NULL);
-            if (NIL_P(realpath)) realpath = as_str;
-            rb_hash_aset(realpaths, rb_fstring(realpath), Qtrue);
-        }
     }
     return vm->loaded_features_index;
 }
@@ -1081,8 +1063,6 @@ require_internal(rb_execution_context_t *ec, VALUE fname, int exception)
     char *volatile ftptr = 0;
     VALUE path;
     volatile VALUE saved_path;
-    VALUE realpath = 0;
-    VALUE realpaths = get_loaded_features_realpaths();
     volatile bool reset_ext_config = false;
     struct rb_ext_config prev_ext_config;
 
@@ -1110,10 +1090,6 @@ require_internal(rb_execution_context_t *ec, VALUE fname, int exception)
 	    else if (!*ftptr) {
 		result = TAG_RETURN;
 	    }
-            else if (RTEST(rb_hash_aref(realpaths,
-                                        realpath = rb_realpath_internal(Qnil, path, 1)))) {
-                result = 0;
-            }
 	    else {
 		switch (found) {
 		  case 'r':
@@ -1165,12 +1141,7 @@ require_internal(rb_execution_context_t *ec, VALUE fname, int exception)
         rb_exc_raise(ec->errinfo);
     }
 
-    if (result == TAG_RETURN) {
+    if (result == TAG_RETURN) rb_provide_feature(path);
-        rb_provide_feature(path);
-        if (realpath) {
-            rb_hash_aset(realpaths, rb_fstring(realpath), Qtrue);
-        }
-    }
     ec->errinfo = saved.errinfo;
 
     RUBY_DTRACE_HOOK(REQUIRE_RETURN, RSTRING_PTR(fname));
@@ -1370,8 +1341,6 @@ Init_load(void)
     vm->loaded_features = rb_ary_new();
     vm->loaded_features_snapshot = rb_ary_tmp_new(0);
     vm->loaded_features_index = st_init_numtable();
-    vm->loaded_features_realpaths = rb_hash_new();
-    rb_obj_hide(vm->loaded_features_realpaths);
 
     rb_define_global_function("load", rb_f_load, -1);
     rb_define_global_function("require", rb_f_require, 1);

test/ruby/test_require.rb

@@ -434,32 +434,6 @@ class TestRequire < Test::Unit::TestCase
     }
   end
 
-  def test_relative_symlink_realpath
-    Dir.mktmpdir {|tmp|
-      Dir.chdir(tmp) {
-        Dir.mkdir "a"
-        File.open("a/a.rb", "w") {|f| f.puts 'require_relative "b"' }
-        File.open("a/b.rb", "w") {|f| f.puts '$t += 1' }
-        Dir.mkdir "b"
-        File.binwrite("c.rb", <<~RUBY)
-          $t = 0
-          $:.unshift(File.expand_path('../b', __FILE__))
-          require "b"
-          require "a"
-          print $t
-        RUBY
-        begin
-          File.symlink("../a/a.rb", "b/a.rb")
-          File.symlink("../a/b.rb", "b/b.rb")
-          result = IO.popen([EnvUtil.rubybin, "c.rb"], &:read)
-          assert_equal("1", result, "bug17885 [ruby-core:104010]")
-        rescue NotImplementedError, Errno::EACCES
-          skip "File.symlink is not implemented"
-        end
-      }
-    }
-  end
-
   def test_frozen_loaded_features
     bug3756 = '[ruby-core:31913]'
     assert_in_out_err(['-e', '$LOADED_FEATURES.freeze; require "ostruct"'], "",
@@ -737,8 +711,8 @@ class TestRequire < Test::Unit::TestCase
       assert_in_out_err([{"RUBYOPT" => nil}, "-", script.path], "#{<<~"begin;"}\n#{<<~"end;"}", %w(:ok), [], bug7530, timeout: 60)
       begin;
         PATH = ARGV.shift
-        THREADS = 30
+        THREADS = 4
-        ITERATIONS_PER_THREAD = 300
+        ITERATIONS_PER_THREAD = 1000
 
         THREADS.times.map {
           Thread.new do

vm.c

@@ -2486,7 +2486,6 @@ rb_vm_update_references(void *ptr)
         vm->expanded_load_path = rb_gc_location(vm->expanded_load_path);
         vm->loaded_features = rb_gc_location(vm->loaded_features);
         vm->loaded_features_snapshot = rb_gc_location(vm->loaded_features_snapshot);
-        vm->loaded_features_realpaths = rb_gc_location(vm->loaded_features_realpaths);
         vm->top_self = rb_gc_location(vm->top_self);
         vm->orig_progname = rb_gc_location(vm->orig_progname);
 
@@ -2574,7 +2573,6 @@ rb_vm_mark(void *ptr)
         rb_gc_mark_movable(vm->expanded_load_path);
         rb_gc_mark_movable(vm->loaded_features);
         rb_gc_mark_movable(vm->loaded_features_snapshot);
-        rb_gc_mark_movable(vm->loaded_features_realpaths);
         rb_gc_mark_movable(vm->top_self);
         rb_gc_mark_movable(vm->orig_progname);
         RUBY_MARK_MOVABLE_UNLESS_NULL(vm->coverages);

vm_core.h

@@ -631,7 +631,6 @@ typedef struct rb_vm_struct {
     VALUE expanded_load_path;
     VALUE loaded_features;
     VALUE loaded_features_snapshot;
-    VALUE loaded_features_realpaths;
     struct st_table *loaded_features_index;
     struct st_table *loading_table;