30 files changed, 535 insertions, 170 deletions
diff --git a/.github/workflows/windows.yml b/.github/workflows/windows.yml
index 6c8f09660d..fa3d2f659e 100644
--- a/.github/workflows/windows.yml
+++ b/.github/workflows/windows.yml
@@ -71,7 +71,7 @@ jobs:
           bundler: none
           windows-toolchain: none
 
-      - name: Install libraries with scoop
+      - name: Install tools with scoop
         run: |
           Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser
           iwr -useb get.scoop.sh | iex
diff --git a/NEWS.md b/NEWS.md
index 7fdc195653..b332164e25 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -14,6 +14,26 @@ Note that each entry is kept to a minimum, see links for details.
 
 Note: We're only listing outstanding class updates.
 
+* Kernel
+
+    * `Kernel#inspect` now checks for the existence of a `#instance_variables_to_inspect` method,
+      allowing control over which instance variables are displayed in the `#inspect` string:
+
+      ```ruby
+      class DatabaseConfig
+        def initialize(host, user, password)
+          @host = host
+          @user = user
+          @password = password
+        end
+
+        private def instance_variables_to_inspect = [:@host, :@user]
+      end
+
+      conf = DatabaseConfig.new("localhost", "root", "hunter2")
+      conf.inspect #=> #<DatabaseConfig:0x0000000104def350 @host="localhost", @user="root">
+      ```
+
 * Binding
 
     * `Binding#local_variables` does no longer include numbered parameters.
diff --git a/common.mk b/common.mk
index d76223e072..34287c5782 100644
--- a/common.mk
+++ b/common.mk
@@ -1562,18 +1562,6 @@ extract-gems$(sequential): PHONY
 
 extract-gems$(sequential): $(HAVE_GIT:yes=clone-bundled-gems-src)
 
-clone-bundled-gems-src: PHONY
-	$(Q) $(BASERUBY) -C "$(srcdir)" \
-	    -Itool/lib -rbundled_gem -answ \
-	    -e 'BEGIN {git = $$git}' \
-	    -e 'gem, _, repo, rev = *$$F' \
-	    -e 'next if !rev or /^#/=~gem' \
-	    -e 'gemdir = "gems/src/#{gem}"' \
-	    -e 'BundledGem.checkout(gemdir, repo, rev, git: git)' \
-	    -e 'BundledGem.dummy_gemspec("#{gemdir}/#{gem}.gemspec")' \
-	    -- -git="$(GIT)" \
-	    gems/bundled_gems
-
 outdate-bundled-gems: PHONY
 	$(Q) $(BASERUBY) $(tooldir)/[email protected] --make="$(MAKE)" --mflags="$(MFLAGS)" \
 	--ruby-platform=$(arch) --ruby-version=$(ruby_version) \
@@ -1623,7 +1611,8 @@ yes-install-for-test-bundled-gems: yes-update-default-gemspecs
 		"sinatra" "rack" "tilt" "mustermann" "base64" "compact_index" "rack-test" "logger" "kpeg" "tracer"
 
 test-bundled-gems-fetch: yes-test-bundled-gems-fetch
-yes-test-bundled-gems-fetch:
+yes-test-bundled-gems-fetch: clone-bundled-gems-src
+clone-bundled-gems-src: PHONY
 	$(Q) $(BASERUBY) -C $(srcdir)/gems ../tool/fetch-bundled_gems.rb BUNDLED_GEMS="$(BUNDLED_GEMS)" src bundled_gems
 no-test-bundled-gems-fetch:
 
diff --git a/defs/gmake.mk b/defs/gmake.mk
index 87fc8021b2..a81d82eadd 100644
--- a/defs/gmake.mk
+++ b/defs/gmake.mk
@@ -365,7 +365,7 @@ $(srcdir)/.bundle/.timestamp:
 define build-gem
 $(srcdir)/gems/src/$(1)/.git: | $(srcdir)/gems/src
 	$(ECHO) Cloning $(4)
-	$(Q) $(GIT) clone $(4) $$(@D)
+	$(Q) $(GIT) clone --depth=1 --no-tags $(4) $$(@D)
 
 $(bundled-gem-revision): \
 	$(if $(if $(wildcard $$(@)),$(filter $(3),$(shell cat $$(@)))),,PHONY) \
diff --git a/doc/globals.rdoc b/doc/globals.rdoc
index 9d9fc57e6e..9466005be7 100644
--- a/doc/globals.rdoc
+++ b/doc/globals.rdoc
@@ -137,7 +137,7 @@ English - <tt>$DEFAULT_INPUT</tt>.
 
 An output stream, initially <tt>$stdout</tt>.
 
-English - <tt>$DEFAULT_OUTPUT
+English - <tt>$DEFAULT_OUTPUT</tt>
 
 === <tt>$.</tt> (Input Position)
 
diff --git a/enumerator.c b/enumerator.c
index faaa77cb49..b91b2eb940 100644
--- a/enumerator.c
+++ b/enumerator.c
@@ -162,10 +162,9 @@
  */
 VALUE rb_cEnumerator;
 static VALUE rb_cLazy;
-static ID id_rewind, id_new, id_to_enum, id_each_entry;
+static ID id_rewind, id_to_enum, id_each_entry;
 static ID id_next, id_result, id_receiver, id_arguments, id_memo, id_method, id_force;
-static ID id_begin, id_end, id_step, id_exclude_end;
-static VALUE sym_each, sym_cycle, sym_yield;
+static VALUE sym_each, sym_yield;
 
 static VALUE lazy_use_super_method;
 
@@ -3748,6 +3747,55 @@ enumerator_s_product(int argc, VALUE *argv, VALUE klass)
     return obj;
 }
 
+struct arith_seq {
+    struct enumerator enumerator;
+    VALUE begin;
+    VALUE end;
+    VALUE step;
+    bool exclude_end;
+};
+
+RUBY_REFERENCES(arith_seq_refs) = {
+    RUBY_REF_EDGE(struct enumerator, obj),
+    RUBY_REF_EDGE(struct enumerator, args),
+    RUBY_REF_EDGE(struct enumerator, fib),
+    RUBY_REF_EDGE(struct enumerator, dst),
+    RUBY_REF_EDGE(struct enumerator, lookahead),
+    RUBY_REF_EDGE(struct enumerator, feedvalue),
+    RUBY_REF_EDGE(struct enumerator, stop_exc),
+    RUBY_REF_EDGE(struct enumerator, size),
+    RUBY_REF_EDGE(struct enumerator, procs),
+
+    RUBY_REF_EDGE(struct arith_seq, begin),
+    RUBY_REF_EDGE(struct arith_seq, end),
+    RUBY_REF_EDGE(struct arith_seq, step),
+    RUBY_REF_END
+};
+
+static const rb_data_type_t arith_seq_data_type = {
+    "arithmetic_sequence",
+    {
+        RUBY_REFS_LIST_PTR(arith_seq_refs),
+        RUBY_TYPED_DEFAULT_FREE,
+        NULL, // Nothing allocated externally, so don't need a memsize function
+        NULL,
+    },
+    .parent = &enumerator_data_type,
+    .flags = RUBY_TYPED_FREE_IMMEDIATELY | RUBY_TYPED_WB_PROTECTED | RUBY_TYPED_DECL_MARKING | RUBY_TYPED_EMBEDDABLE
+};
+
+static VALUE
+arith_seq_allocate(VALUE klass)
+{
+    struct arith_seq *ptr;
+    VALUE enum_obj;
+
+    enum_obj = TypedData_Make_Struct(klass, struct arith_seq, &arith_seq_data_type, ptr);
+    ptr->enumerator.obj = Qundef;
+
+    return enum_obj;
+}
+
 /*
  * Document-class: Enumerator::ArithmeticSequence
  *
@@ -3765,12 +3813,16 @@ rb_arith_seq_new(VALUE obj, VALUE meth, int argc, VALUE const *argv,
                  rb_enumerator_size_func *size_fn,
                  VALUE beg, VALUE end, VALUE step, int excl)
 {
-    VALUE aseq = enumerator_init(enumerator_allocate(rb_cArithSeq),
+    VALUE aseq = enumerator_init(arith_seq_allocate(rb_cArithSeq),
                                  obj, meth, argc, argv, size_fn, Qnil, rb_keyword_given_p());
-    rb_ivar_set(aseq, id_begin, beg);
-    rb_ivar_set(aseq, id_end, end);
-    rb_ivar_set(aseq, id_step, step);
-    rb_ivar_set(aseq, id_exclude_end, RBOOL(excl));
+    struct arith_seq *ptr;
+    TypedData_Get_Struct(aseq, struct arith_seq, &enumerator_data_type, ptr);
+
+    RB_OBJ_WRITE(aseq, &ptr->begin, beg);
+    RB_OBJ_WRITE(aseq, &ptr->end, end);
+    RB_OBJ_WRITE(aseq, &ptr->step, step);
+    ptr->exclude_end = excl;
+
     return aseq;
 }
 
@@ -3783,7 +3835,9 @@ rb_arith_seq_new(VALUE obj, VALUE meth, int argc, VALUE const *argv,
 static inline VALUE
 arith_seq_begin(VALUE self)
 {
-    return rb_ivar_get(self, id_begin);
+    struct arith_seq *ptr;
+    TypedData_Get_Struct(self, struct arith_seq, &enumerator_data_type, ptr);
+    return ptr->begin;
 }
 
 /*
@@ -3794,7 +3848,9 @@ arith_seq_begin(VALUE self)
 static inline VALUE
 arith_seq_end(VALUE self)
 {
-    return rb_ivar_get(self, id_end);
+    struct arith_seq *ptr;
+    TypedData_Get_Struct(self, struct arith_seq, &enumerator_data_type, ptr);
+    return ptr->end;
 }
 
 /*
@@ -3806,7 +3862,9 @@ arith_seq_end(VALUE self)
 static inline VALUE
 arith_seq_step(VALUE self)
 {
-    return rb_ivar_get(self, id_step);
+    struct arith_seq *ptr;
+    TypedData_Get_Struct(self, struct arith_seq, &enumerator_data_type, ptr);
+    return ptr->step;
 }
 
 /*
@@ -3817,13 +3875,17 @@ arith_seq_step(VALUE self)
 static inline VALUE
 arith_seq_exclude_end(VALUE self)
 {
-    return rb_ivar_get(self, id_exclude_end);
+    struct arith_seq *ptr;
+    TypedData_Get_Struct(self, struct arith_seq, &enumerator_data_type, ptr);
+    return RBOOL(ptr->exclude_end);
 }
 
 static inline int
 arith_seq_exclude_end_p(VALUE self)
 {
-    return RTEST(arith_seq_exclude_end(self));
+    struct arith_seq *ptr;
+    TypedData_Get_Struct(self, struct arith_seq, &enumerator_data_type, ptr);
+    return ptr->exclude_end;
 }
 
 int
@@ -4664,7 +4726,6 @@ void
 Init_Enumerator(void)
 {
     id_rewind = rb_intern_const("rewind");
-    id_new = rb_intern_const("new");
     id_next = rb_intern_const("next");
     id_result = rb_intern_const("result");
     id_receiver = rb_intern_const("receiver");
@@ -4674,12 +4735,7 @@ Init_Enumerator(void)
     id_force = rb_intern_const("force");
     id_to_enum = rb_intern_const("to_enum");
     id_each_entry = rb_intern_const("each_entry");
-    id_begin = rb_intern_const("begin");
-    id_end = rb_intern_const("end");
-    id_step = rb_intern_const("step");
-    id_exclude_end = rb_intern_const("exclude_end");
     sym_each = ID2SYM(id_each);
-    sym_cycle = ID2SYM(rb_intern_const("cycle"));
     sym_yield = ID2SYM(rb_intern_const("yield"));
 
     InitVM(Enumerator);
diff --git a/file.c b/file.c
index b38cd67199..322df6dbec 100644
--- a/file.c
+++ b/file.c
@@ -543,7 +543,7 @@ rb_stat_new(const struct stat *st)
     if (st) {
 #if RUBY_USE_STATX
 # define CP(m) .stx_ ## m = st->st_ ## m
-# define CP_32(m) .stx_ ## m = (__u32)st->st_ ## m
+# define CP_32(m) .stx_ ## m = (uint32_t)st->st_ ## m
 # define CP_TS(m) .stx_ ## m = stat_ ## m ## spec(st)
         rb_st->stat = (struct statx){
             .stx_mask = STATX_BASIC_STATS,
diff --git a/gc.c b/gc.c
index 5281e7fb49..05cefc739b 100644
--- a/gc.c
+++ b/gc.c
@@ -131,45 +131,45 @@
 #include "shape.h"
 
 unsigned int
-rb_gc_vm_lock(void)
+rb_gc_vm_lock(const char *file, int line)
 {
     unsigned int lev = 0;
-    RB_VM_LOCK_ENTER_LEV(&lev);
+    rb_vm_lock_enter(&lev, file, line);
     return lev;
 }
 
 void
-rb_gc_vm_unlock(unsigned int lev)
+rb_gc_vm_unlock(unsigned int lev, const char *file, int line)
 {
-    RB_VM_LOCK_LEAVE_LEV(&lev);
+    rb_vm_lock_leave(&lev, file, line);
 }
 
 unsigned int
-rb_gc_cr_lock(void)
+rb_gc_cr_lock(const char *file, int line)
 {
     unsigned int lev;
-    RB_VM_LOCK_ENTER_CR_LEV(GET_RACTOR(), &lev);
+    rb_vm_lock_enter_cr(GET_RACTOR(), &lev, file, line);
     return lev;
 }
 
 void
-rb_gc_cr_unlock(unsigned int lev)
+rb_gc_cr_unlock(unsigned int lev, const char *file, int line)
 {
-    RB_VM_LOCK_LEAVE_CR_LEV(GET_RACTOR(), &lev);
+    rb_vm_lock_leave_cr(GET_RACTOR(), &lev, file, line);
 }
 
 unsigned int
-rb_gc_vm_lock_no_barrier(void)
+rb_gc_vm_lock_no_barrier(const char *file, int line)
 {
     unsigned int lev = 0;
-    RB_VM_LOCK_ENTER_LEV_NB(&lev);
+    rb_vm_lock_enter_nb(&lev, file, line);
     return lev;
 }
 
 void
-rb_gc_vm_unlock_no_barrier(unsigned int lev)
+rb_gc_vm_unlock_no_barrier(unsigned int lev, const char *file, int line)
 {
-    RB_VM_LOCK_LEAVE_LEV_NB(&lev);
+    rb_vm_lock_leave_nb(&lev, file, line);
 }
 
 void
@@ -1783,9 +1783,9 @@ generate_next_object_id(void)
     // 64bit atomics are available
     return SIZET2NUM(RUBY_ATOMIC_SIZE_FETCH_ADD(object_id_counter, 1) * OBJ_ID_INCREMENT);
 #else
-    unsigned int lock_lev = rb_gc_vm_lock();
+    unsigned int lock_lev = RB_GC_VM_LOCK();
     VALUE id = ULL2NUM(++object_id_counter * OBJ_ID_INCREMENT);
-    rb_gc_vm_unlock(lock_lev);
+    RB_GC_VM_UNLOCK(lock_lev);
     return id;
 #endif
 }
@@ -1867,7 +1867,7 @@ class_object_id(VALUE klass)
 {
     VALUE id = RUBY_ATOMIC_VALUE_LOAD(RCLASS(klass)->object_id);
     if (!id) {
-        unsigned int lock_lev = rb_gc_vm_lock();
+        unsigned int lock_lev = RB_GC_VM_LOCK();
         id = generate_next_object_id();
         VALUE existing_id = RUBY_ATOMIC_VALUE_CAS(RCLASS(klass)->object_id, 0, id);
         if (existing_id) {
@@ -1876,7 +1876,7 @@ class_object_id(VALUE klass)
         else if (RB_UNLIKELY(id2ref_tbl)) {
             st_insert(id2ref_tbl, id, klass);
         }
-        rb_gc_vm_unlock(lock_lev);
+        RB_GC_VM_UNLOCK(lock_lev);
     }
     return id;
 }
@@ -1946,9 +1946,9 @@ object_id(VALUE obj)
     }
 
     if (UNLIKELY(rb_gc_multi_ractor_p() && rb_ractor_shareable_p(obj))) {
-        unsigned int lock_lev = rb_gc_vm_lock();
+        unsigned int lock_lev = RB_GC_VM_LOCK();
         VALUE id = object_id0(obj);
-        rb_gc_vm_unlock(lock_lev);
+        RB_GC_VM_UNLOCK(lock_lev);
         return id;
     }
 
@@ -1983,7 +1983,7 @@ object_id_to_ref(void *objspace_ptr, VALUE object_id)
 {
     rb_objspace_t *objspace = objspace_ptr;
 
-    unsigned int lev = rb_gc_vm_lock();
+    unsigned int lev = RB_GC_VM_LOCK();
 
     if (!id2ref_tbl) {
         rb_gc_vm_barrier(); // stop other ractors
@@ -2007,7 +2007,7 @@ object_id_to_ref(void *objspace_ptr, VALUE object_id)
     VALUE obj;
     bool found = st_lookup(id2ref_tbl, object_id, &obj) && !rb_gc_impl_garbage_object_p(objspace, obj);
 
-    rb_gc_vm_unlock(lev);
+    RB_GC_VM_UNLOCK(lev);
 
     if (found) {
         return obj;
@@ -4093,7 +4093,8 @@ vm_weak_table_gen_fields_foreach(st_data_t key, st_data_t value, st_data_t data)
             );
         }
         else {
-            for (uint32_t i = 0; i < fields_tbl->as.shape.fields_count; i++) {
+            uint32_t fields_count = RSHAPE_LEN(RBASIC_SHAPE_ID((VALUE)key));
+            for (uint32_t i = 0; i < fields_count; i++) {
                 if (SPECIAL_CONST_P(fields_tbl->as.shape.fields[i])) continue;
 
                 int ivar_ret = iter_data->callback(fields_tbl->as.shape.fields[i], iter_data->data);
diff --git a/gc/README.md b/gc/README.md
index 102b24e24e..cb71357973 100644
--- a/gc/README.md
+++ b/gc/README.md
@@ -15,12 +15,17 @@ Two GC implementations are included in Ruby:
 > [!IMPORTANT]
 > Ruby's modular GC feature is experimental and subject to change. There may be bugs or performance impacts. Use at your own risk.
 
+### Building Ruby with Modular GC
+
 1. Configure Ruby with the `--with-modular-gc=<dir>` option, where `dir` is the directory you want to place the built GC libraries into.
 2. Build Ruby as usual.
-3. Build your desired GC implementation with `make install-modular-gc MODULAR_GC=<impl>`. This will build the GC implementation and place the built library into the `dir` specified in step 1. `impl` can be one of:
+
+### Building GC implementations shipped with Ruby
+
+1. Build your desired GC implementation with `make install-modular-gc MODULAR_GC=<impl>`. This will build the GC implementation and place the built library into the `dir` specified in step 1. `impl` can be one of:
     - `default`: The default GC that Ruby ships with.
     - `mmtk`: The GC that uses [MMTk](https://www.mmtk.io/) as the back-end. See Ruby-specific details in the [ruby/mmtk](https://github.com/ruby/mmtk) repository.
-4. Run your desired GC implementation by setting the `RUBY_GC_LIBRARY=<lib>` environment variable, where `lib` could be `default`, `mmtk`, or your own implementation (as long as you place it in the `dir` specified in step 1).
+2. Run your desired GC implementation by setting the `RUBY_GC_LIBRARY=<lib>` environment variable, where `lib` could be `default`, `mmtk`, or your own implementation (as long as you place it in the `dir` specified in step 1).
 
 ## Modular GC API
 
diff --git a/gc/default/default.c b/gc/default/default.c
index 5664b3dd90..40d39d6f17 100644
--- a/gc/default/default.c
+++ b/gc/default/default.c
@@ -1229,7 +1229,7 @@ check_rvalue_consistency_force(rb_objspace_t *objspace, const VALUE obj, int ter
 {
     int err = 0;
 
-    int lev = rb_gc_vm_lock_no_barrier();
+    int lev = RB_GC_VM_LOCK_NO_BARRIER();
     {
         if (SPECIAL_CONST_P(obj)) {
             fprintf(stderr, "check_rvalue_consistency: %p is a special const.\n", (void *)obj);
@@ -1319,7 +1319,7 @@ check_rvalue_consistency_force(rb_objspace_t *objspace, const VALUE obj, int ter
             }
         }
     }
-    rb_gc_vm_unlock_no_barrier(lev);
+    RB_GC_VM_UNLOCK_NO_BARRIER(lev);
 
     if (err > 0 && terminate) {
         rb_bug("check_rvalue_consistency_force: there is %d errors.", err);
@@ -2140,7 +2140,7 @@ newobj_init(VALUE klass, VALUE flags, int wb_protected, rb_objspace_t *objspace,
 #if RGENGC_CHECK_MODE
     newobj_fill(obj, 0, 0, 0);
 
-    int lev = rb_gc_vm_lock_no_barrier();
+    int lev = RB_GC_VM_LOCK_NO_BARRIER();
     {
         check_rvalue_consistency(objspace, obj);
 
@@ -2151,7 +2151,7 @@ newobj_init(VALUE klass, VALUE flags, int wb_protected, rb_objspace_t *objspace,
 
         if (RVALUE_REMEMBERED(objspace, obj)) rb_bug("newobj: %s is remembered.", rb_obj_info(obj));
     }
-    rb_gc_vm_unlock_no_barrier(lev);
+    RB_GC_VM_UNLOCK_NO_BARRIER(lev);
 #endif
 
     if (RB_UNLIKELY(wb_protected == FALSE)) {
@@ -2363,7 +2363,7 @@ newobj_cache_miss(rb_objspace_t *objspace, rb_ractor_newobj_cache_t *cache, size
     bool unlock_vm = false;
 
     if (!vm_locked) {
-        lev = rb_gc_cr_lock();
+        lev = RB_GC_CR_LOCK();
         unlock_vm = true;
     }
 
@@ -2387,7 +2387,7 @@ newobj_cache_miss(rb_objspace_t *objspace, rb_ractor_newobj_cache_t *cache, size
     }
 
     if (unlock_vm) {
-        rb_gc_cr_unlock(lev);
+        RB_GC_CR_UNLOCK(lev);
     }
 
     if (RB_UNLIKELY(obj == Qfalse)) {
@@ -2416,7 +2416,7 @@ newobj_slowpath(VALUE klass, VALUE flags, rb_objspace_t *objspace, rb_ractor_new
     VALUE obj;
     unsigned int lev;
 
-    lev = rb_gc_cr_lock();
+    lev = RB_GC_CR_LOCK();
     {
         if (RB_UNLIKELY(during_gc || ruby_gc_stressful)) {
             if (during_gc) {
@@ -2438,7 +2438,7 @@ newobj_slowpath(VALUE klass, VALUE flags, rb_objspace_t *objspace, rb_ractor_new
         obj = newobj_alloc(objspace, cache, heap_idx, true);
         newobj_init(klass, flags, wb_protected, objspace, obj);
     }
-    rb_gc_cr_unlock(lev);
+    RB_GC_CR_UNLOCK(lev);
 
     return obj;
 }
@@ -2753,7 +2753,7 @@ rb_gc_impl_define_finalizer(void *objspace_ptr, VALUE obj, VALUE block)
 
     RBASIC(obj)->flags |= FL_FINALIZE;
 
-    int lev = rb_gc_vm_lock();
+    int lev = RB_GC_VM_LOCK();
 
     if (st_lookup(finalizer_table, obj, &data)) {
         table = (VALUE)data;
@@ -2766,7 +2766,7 @@ rb_gc_impl_define_finalizer(void *objspace_ptr, VALUE obj, VALUE block)
             for (i = 0; i < len; i++) {
                 VALUE recv = RARRAY_AREF(table, i);
                 if (rb_equal(recv, block)) {
-                    rb_gc_vm_unlock(lev);
+                    RB_GC_VM_UNLOCK(lev);
                     return recv;
                 }
             }
@@ -2780,7 +2780,7 @@ rb_gc_impl_define_finalizer(void *objspace_ptr, VALUE obj, VALUE block)
         st_add_direct(finalizer_table, obj, table);
     }
 
-    rb_gc_vm_unlock(lev);
+    RB_GC_VM_UNLOCK(lev);
 
     return block;
 }
@@ -2794,9 +2794,9 @@ rb_gc_impl_undefine_finalizer(void *objspace_ptr, VALUE obj)
 
     st_data_t data = obj;
 
-    int lev = rb_gc_vm_lock();
+    int lev = RB_GC_VM_LOCK();
     st_delete(finalizer_table, &data, 0);
-    rb_gc_vm_unlock(lev);
+    RB_GC_VM_UNLOCK(lev);
 
     FL_UNSET(obj, FL_FINALIZE);
 }
@@ -2810,7 +2810,7 @@ rb_gc_impl_copy_finalizer(void *objspace_ptr, VALUE dest, VALUE obj)
 
     if (!FL_TEST(obj, FL_FINALIZE)) return;
 
-    int lev = rb_gc_vm_lock();
+    int lev = RB_GC_VM_LOCK();
     if (RB_LIKELY(st_lookup(finalizer_table, obj, &data))) {
         table = rb_ary_dup((VALUE)data);
         RARRAY_ASET(table, 0, rb_obj_id(dest));
@@ -2820,7 +2820,7 @@ rb_gc_impl_copy_finalizer(void *objspace_ptr, VALUE dest, VALUE obj)
     else {
         rb_bug("rb_gc_copy_finalizer: FL_FINALIZE set but not found in finalizer_table: %s", rb_obj_info(obj));
     }
-    rb_gc_vm_unlock(lev);
+    RB_GC_VM_UNLOCK(lev);
 }
 
 static VALUE
@@ -2864,7 +2864,7 @@ finalize_list(rb_objspace_t *objspace, VALUE zombie)
         next_zombie = RZOMBIE(zombie)->next;
         page = GET_HEAP_PAGE(zombie);
 
-        int lev = rb_gc_vm_lock();
+        int lev = RB_GC_VM_LOCK();
 
         run_final(objspace, zombie);
         {
@@ -2878,7 +2878,7 @@ finalize_list(rb_objspace_t *objspace, VALUE zombie)
             heap_page_add_freeobj(objspace, page, zombie);
             page->heap->total_freed_objects++;
         }
-        rb_gc_vm_unlock(lev);
+        RB_GC_VM_UNLOCK(lev);
 
         zombie = next_zombie;
     }
@@ -3247,7 +3247,7 @@ read_barrier_handler(uintptr_t address)
         rb_bug("read_barrier_handler: segmentation fault at %p", (void *)address);
     }
 
-    int lev = rb_gc_vm_lock();
+    int lev = RB_GC_VM_LOCK();
     {
         unlock_page_body(objspace, page_body);
 
@@ -3255,7 +3255,7 @@ read_barrier_handler(uintptr_t address)
 
         invalidate_moved_page(objspace, GET_HEAP_PAGE(address));
     }
-    rb_gc_vm_unlock(lev);
+    RB_GC_VM_UNLOCK(lev);
 }
 #endif
 
@@ -5180,7 +5180,7 @@ gc_verify_internal_consistency(void *objspace_ptr)
 {
     rb_objspace_t *objspace = objspace_ptr;
 
-    unsigned int lev = rb_gc_vm_lock();
+    unsigned int lev = RB_GC_VM_LOCK();
     {
         rb_gc_vm_barrier(); // stop other ractors
 
@@ -5191,7 +5191,7 @@ gc_verify_internal_consistency(void *objspace_ptr)
         }
         during_gc = prev_during_gc;
     }
-    rb_gc_vm_unlock(lev);
+    RB_GC_VM_UNLOCK(lev);
 }
 
 static void
@@ -5952,11 +5952,11 @@ gc_writebarrier_generational(VALUE a, VALUE b, rb_objspace_t *objspace)
 
     /* mark `a' and remember (default behavior) */
     if (!RVALUE_REMEMBERED(objspace, a)) {
-        int lev = rb_gc_vm_lock_no_barrier();
+        int lev = RB_GC_VM_LOCK_NO_BARRIER();
         {
             rgengc_remember(objspace, a);
         }
-        rb_gc_vm_unlock_no_barrier(lev);
+        RB_GC_VM_UNLOCK_NO_BARRIER(lev);
 
         gc_report(1, objspace, "gc_writebarrier_generational: %s (remembered) -> %s\n", rb_obj_info(a), rb_obj_info(b));
     }
@@ -6029,7 +6029,7 @@ rb_gc_impl_writebarrier(void *objspace_ptr, VALUE a, VALUE b)
     else {
         bool retry = false;
         /* slow path */
-        int lev = rb_gc_vm_lock_no_barrier();
+        int lev = RB_GC_VM_LOCK_NO_BARRIER();
         {
             if (is_incremental_marking(objspace)) {
                 gc_writebarrier_incremental(a, b, objspace);
@@ -6038,7 +6038,7 @@ rb_gc_impl_writebarrier(void *objspace_ptr, VALUE a, VALUE b)
                 retry = true;
             }
         }
-        rb_gc_vm_unlock_no_barrier(lev);
+        RB_GC_VM_UNLOCK_NO_BARRIER(lev);
 
         if (retry) goto retry;
     }
@@ -6057,7 +6057,7 @@ rb_gc_impl_writebarrier_unprotect(void *objspace_ptr, VALUE obj)
         gc_report(2, objspace, "rb_gc_writebarrier_unprotect: %s %s\n", rb_obj_info(obj),
                   RVALUE_REMEMBERED(objspace, obj) ? " (already remembered)" : "");
 
-        unsigned int lev = rb_gc_vm_lock_no_barrier();
+        unsigned int lev = RB_GC_VM_LOCK_NO_BARRIER();
         {
             if (RVALUE_OLD_P(objspace, obj)) {
                 gc_report(1, objspace, "rb_gc_writebarrier_unprotect: %s\n", rb_obj_info(obj));
@@ -6079,7 +6079,7 @@ rb_gc_impl_writebarrier_unprotect(void *objspace_ptr, VALUE obj)
             RB_DEBUG_COUNTER_INC(obj_wb_unprotect);
             MARK_IN_BITMAP(GET_HEAP_WB_UNPROTECTED_BITS(obj), obj);
         }
-        rb_gc_vm_unlock_no_barrier(lev);
+        RB_GC_VM_UNLOCK_NO_BARRIER(lev);
     }
 }
 
@@ -6292,7 +6292,7 @@ garbage_collect(rb_objspace_t *objspace, unsigned int reason)
 {
     int ret;
 
-    int lev = rb_gc_vm_lock();
+    int lev = RB_GC_VM_LOCK();
     {
 #if GC_PROFILE_MORE_DETAIL
         objspace->profile.prepare_time = getrusage_time();
@@ -6306,7 +6306,7 @@ garbage_collect(rb_objspace_t *objspace, unsigned int reason)
 
         ret = gc_start(objspace, reason);
     }
-    rb_gc_vm_unlock(lev);
+    RB_GC_VM_UNLOCK(lev);
 
     return ret;
 }
@@ -6590,7 +6590,7 @@ gc_clock_end(struct timespec *ts)
 static inline void
 gc_enter(rb_objspace_t *objspace, enum gc_enter_event event, unsigned int *lock_lev)
 {
-    *lock_lev = rb_gc_vm_lock();
+    *lock_lev = RB_GC_VM_LOCK();
 
     switch (event) {
       case gc_enter_event_rest:
@@ -6629,7 +6629,7 @@ gc_exit(rb_objspace_t *objspace, enum gc_enter_event event, unsigned int *lock_l
     gc_report(1, objspace, "gc_exit: %s [%s]\n", gc_enter_event_cstr(event), gc_current_status(objspace));
     during_gc = FALSE;
 
-    rb_gc_vm_unlock(*lock_lev);
+    RB_GC_VM_UNLOCK(*lock_lev);
 }
 
 #ifndef MEASURE_GC
@@ -9106,7 +9106,7 @@ gc_verify_compaction_references(int argc, VALUE* argv, VALUE self)
     /* Clear the heap. */
     rb_gc_impl_start(objspace, true, true, true, false);
 
-    unsigned int lev = rb_gc_vm_lock();
+    unsigned int lev = RB_GC_VM_LOCK();
     {
         gc_rest(objspace);
 
@@ -9162,7 +9162,7 @@ gc_verify_compaction_references(int argc, VALUE* argv, VALUE self)
             objspace->rcompactor.compare_func = compare_free_slots;
         }
     }
-    rb_gc_vm_unlock(lev);
+    RB_GC_VM_UNLOCK(lev);
 
     rb_gc_impl_start(rb_gc_get_objspace(), true, true, true, true);
 
diff --git a/gc/gc.h b/gc/gc.h
index df709426de..c12498f033 100644
--- a/gc/gc.h
+++ b/gc/gc.h
@@ -35,6 +35,13 @@ enum rb_gc_vm_weak_tables {
     RB_GC_VM_WEAK_TABLE_COUNT
 };
 
+#define RB_GC_VM_LOCK() rb_gc_vm_lock(__FILE__, __LINE__)
+#define RB_GC_VM_UNLOCK(lev) rb_gc_vm_unlock(lev, __FILE__, __LINE__)
+#define RB_GC_CR_LOCK() rb_gc_cr_lock(__FILE__, __LINE__)
+#define RB_GC_CR_UNLOCK(lev) rb_gc_cr_unlock(lev, __FILE__, __LINE__)
+#define RB_GC_VM_LOCK_NO_BARRIER() rb_gc_vm_lock_no_barrier(__FILE__, __LINE__)
+#define RB_GC_VM_UNLOCK_NO_BARRIER(lev) rb_gc_vm_unlock_no_barrier(lev, __FILE__, __LINE__)
+
 #if USE_MODULAR_GC
 # define MODULAR_GC_FN
 #else
@@ -57,12 +64,12 @@ size_t rb_obj_memsize_of(VALUE obj);
 bool ruby_free_at_exit_p(void);
 void rb_objspace_reachable_objects_from_root(void (func)(const char *category, VALUE, void *), void *passing_data);
 
-MODULAR_GC_FN unsigned int rb_gc_vm_lock(void);
-MODULAR_GC_FN void rb_gc_vm_unlock(unsigned int lev);
-MODULAR_GC_FN unsigned int rb_gc_cr_lock(void);
-MODULAR_GC_FN void rb_gc_cr_unlock(unsigned int lev);
-MODULAR_GC_FN unsigned int rb_gc_vm_lock_no_barrier(void);
-MODULAR_GC_FN void rb_gc_vm_unlock_no_barrier(unsigned int lev);
+MODULAR_GC_FN unsigned int rb_gc_vm_lock(const char *file, int line);
+MODULAR_GC_FN void rb_gc_vm_unlock(unsigned int lev, const char *file, int line);
+MODULAR_GC_FN unsigned int rb_gc_cr_lock(const char *file, int line);
+MODULAR_GC_FN void rb_gc_cr_unlock(unsigned int lev, const char *file, int line);
+MODULAR_GC_FN unsigned int rb_gc_vm_lock_no_barrier(const char *file, int line);
+MODULAR_GC_FN void rb_gc_vm_unlock_no_barrier(unsigned int lev, const char *file, int line);
 MODULAR_GC_FN void rb_gc_vm_barrier(void);
 MODULAR_GC_FN size_t rb_gc_obj_optimal_size(VALUE obj);
 MODULAR_GC_FN void rb_gc_mark_children(void *objspace, VALUE obj);
diff --git a/gc/mmtk/mmtk.c b/gc/mmtk/mmtk.c
index 9e4ee9f3de..c318c6fe48 100644
--- a/gc/mmtk/mmtk.c
+++ b/gc/mmtk/mmtk.c
@@ -129,7 +129,7 @@ rb_mmtk_block_for_gc(MMTk_VMMutatorThread mutator)
     struct objspace *objspace = rb_gc_get_objspace();
 
     size_t starting_gc_count = objspace->gc_count;
-    int lock_lev = rb_gc_vm_lock();
+    int lock_lev = RB_GC_VM_LOCK();
     int err;
     if ((err = pthread_mutex_lock(&objspace->mutex)) != 0) {
         rb_bug("ERROR: cannot lock objspace->mutex: %s", strerror(err));
@@ -173,7 +173,7 @@ rb_mmtk_block_for_gc(MMTk_VMMutatorThread mutator)
     if ((err = pthread_mutex_unlock(&objspace->mutex)) != 0) {
         rb_bug("ERROR: cannot release objspace->mutex: %s", strerror(err));
     }
-    rb_gc_vm_unlock(lock_lev);
+    RB_GC_VM_UNLOCK(lock_lev);
 }
 
 static size_t
@@ -927,7 +927,7 @@ rb_gc_impl_define_finalizer(void *objspace_ptr, VALUE obj, VALUE block)
 
     RBASIC(obj)->flags |= FL_FINALIZE;
 
-    int lev = rb_gc_vm_lock();
+    int lev = RB_GC_VM_LOCK();
 
     if (st_lookup(objspace->finalizer_table, obj, &data)) {
         table = (VALUE)data;
@@ -940,7 +940,7 @@ rb_gc_impl_define_finalizer(void *objspace_ptr, VALUE obj, VALUE block)
             for (i = 0; i < len; i++) {
                 VALUE recv = RARRAY_AREF(table, i);
                 if (rb_equal(recv, block)) {
-                    rb_gc_vm_unlock(lev);
+                    RB_GC_VM_UNLOCK(lev);
                     return recv;
                 }
             }
@@ -954,7 +954,7 @@ rb_gc_impl_define_finalizer(void *objspace_ptr, VALUE obj, VALUE block)
         st_add_direct(objspace->finalizer_table, obj, table);
     }
 
-    rb_gc_vm_unlock(lev);
+    RB_GC_VM_UNLOCK(lev);
 
     return block;
 }
@@ -966,9 +966,9 @@ rb_gc_impl_undefine_finalizer(void *objspace_ptr, VALUE obj)
 
     st_data_t data = obj;
 
-    int lev = rb_gc_vm_lock();
+    int lev = RB_GC_VM_LOCK();
     st_delete(objspace->finalizer_table, &data, 0);
-    rb_gc_vm_unlock(lev);
+    RB_GC_VM_UNLOCK(lev);
 
     FL_UNSET(obj, FL_FINALIZE);
 }
@@ -982,7 +982,7 @@ rb_gc_impl_copy_finalizer(void *objspace_ptr, VALUE dest, VALUE obj)
 
     if (!FL_TEST(obj, FL_FINALIZE)) return;
 
-    int lev = rb_gc_vm_lock();
+    int lev = RB_GC_VM_LOCK();
     if (RB_LIKELY(st_lookup(objspace->finalizer_table, obj, &data))) {
         table = rb_ary_dup((VALUE)data);
         RARRAY_ASET(table, 0, rb_obj_id(dest));
@@ -992,7 +992,7 @@ rb_gc_impl_copy_finalizer(void *objspace_ptr, VALUE dest, VALUE obj)
     else {
         rb_bug("rb_gc_copy_finalizer: FL_FINALIZE set but not found in finalizer_table: %s", rb_obj_info(obj));
     }
-    rb_gc_vm_unlock(lev);
+    RB_GC_VM_UNLOCK(lev);
 }
 
 static int
diff --git a/object.c b/object.c
index fbd2f5d557..8e924b4e6a 100644
--- a/object.c
+++ b/object.c
@@ -83,6 +83,7 @@ static VALUE rb_cFalseClass_to_s;
 #define id_init_dup         idInitialize_dup
 #define id_const_missing    idConst_missing
 #define id_to_f             idTo_f
+static ID id_instance_variables_to_inspect;
 
 #define CLASS_OR_MODULE_P(obj) \
     (!SPECIAL_CONST_P(obj) && \
@@ -733,11 +734,17 @@ rb_inspect(VALUE obj)
 static int
 inspect_i(ID id, VALUE value, st_data_t a)
 {
-    VALUE str = (VALUE)a;
+    VALUE *args = (VALUE *)a, str = args[0], ivars = args[1];
 
     /* need not to show internal data */
     if (CLASS_OF(value) == 0) return ST_CONTINUE;
     if (!rb_is_instance_id(id)) return ST_CONTINUE;
+    if (!NIL_P(ivars)) {
+        VALUE name = ID2SYM(id);
+        for (long i = 0; RARRAY_AREF(ivars, i) != name; ) {
+            if (++i >= RARRAY_LEN(ivars)) return ST_CONTINUE;
+        }
+    }
     if (RSTRING_PTR(str)[0] == '-') { /* first element */
         RSTRING_PTR(str)[0] = '#';
         rb_str_cat2(str, " ");
@@ -752,13 +759,15 @@ inspect_i(ID id, VALUE value, st_data_t a)
 }
 
 static VALUE
-inspect_obj(VALUE obj, VALUE str, int recur)
+inspect_obj(VALUE obj, VALUE a, int recur)
 {
+    VALUE *args = (VALUE *)a, str = args[0];
+
     if (recur) {
         rb_str_cat2(str, " ...");
     }
     else {
-        rb_ivar_foreach(obj, inspect_i, str);
+        rb_ivar_foreach(obj, inspect_i, a);
     }
     rb_str_cat2(str, ">");
     RSTRING_PTR(str)[0] = '#';
@@ -791,17 +800,47 @@ inspect_obj(VALUE obj, VALUE str, int recur)
  *       end
  *     end
  *     Bar.new.inspect                  #=> "#<Bar:0x0300c868 @bar=1>"
+ *
+ * If _obj_ responds to +instance_variables_to_inspect+, then only
+ * the instance variables listed in the returned array will be included
+ * in the inspect string.
+ *
+ *
+ *     class DatabaseConfig
+ *       def initialize(host, user, password)
+ *         @host = host
+ *         @user = user
+ *         @password = password
+ *       end
+ *
+ *     private
+ *       def instance_variables_to_inspect = [:@host, :@user]
+ *     end
+ *
+ *     conf = DatabaseConfig.new("localhost", "root", "hunter2")
+ *     conf.inspect #=> #<DatabaseConfig:0x0000000104def350 @host="localhost", @user="root">
  */
 
 static VALUE
 rb_obj_inspect(VALUE obj)
 {
-    if (rb_ivar_count(obj) > 0) {
-        VALUE str;
+    VALUE ivars = rb_check_funcall(obj, id_instance_variables_to_inspect, 0, 0);
+    st_index_t n = 0;
+    if (UNDEF_P(ivars)) {
+        n = rb_ivar_count(obj);
+        ivars = Qnil;
+    }
+    else if (!NIL_P(ivars)) {
+        Check_Type(ivars, T_ARRAY);
+        n = RARRAY_LEN(ivars);
+    }
+    if (n > 0) {
         VALUE c = rb_class_name(CLASS_OF(obj));
-
-        str = rb_sprintf("-<%"PRIsVALUE":%p", c, (void*)obj);
-        return rb_exec_recursive(inspect_obj, obj, str);
+        VALUE args[2] = {
+            rb_sprintf("-<%"PRIsVALUE":%p", c, (void*)obj),
+            ivars
+        };
+        return rb_exec_recursive(inspect_obj, obj, (VALUE)args);
     }
     else {
         return rb_any_to_s(obj);
@@ -4600,6 +4639,7 @@ void
 Init_Object(void)
 {
     id_dig = rb_intern_const("dig");
+    id_instance_variables_to_inspect = rb_intern_const("instance_variables_to_inspect");
     InitVM(Object);
 }
 
diff --git a/prism/templates/lib/prism/visitor.rb.erb b/prism/templates/lib/prism/visitor.rb.erb
index a1eac38dc4..b1a03c3f1a 100644
--- a/prism/templates/lib/prism/visitor.rb.erb
+++ b/prism/templates/lib/prism/visitor.rb.erb
@@ -34,7 +34,7 @@ module Prism
   #
   #     class FooCalls < Prism::Visitor
   #       def visit_call_node(node)
-  #         if node.name == "foo"
+  #         if node.name == :foo
   #           # Do something with the node
   #         end
   #
diff --git a/ractor.c b/ractor.c
index 56345d5670..177906ea1c 100644
--- a/ractor.c
+++ b/ractor.c
@@ -1658,10 +1658,9 @@ obj_traverse_replace_i(VALUE obj, struct obj_traverse_replace_data *data)
             if (d.stop) return 1;
         }
         else {
-            for (uint32_t i = 0; i < fields_tbl->as.shape.fields_count; i++) {
-                if (!UNDEF_P(fields_tbl->as.shape.fields[i])) {
-                    CHECK_AND_REPLACE(fields_tbl->as.shape.fields[i]);
-                }
+            uint32_t fields_count = RSHAPE_LEN(RBASIC_SHAPE_ID(obj));
+            for (uint32_t i = 0; i < fields_count; i++) {
+                CHECK_AND_REPLACE(fields_tbl->as.shape.fields[i]);
             }
         }
     }
diff --git a/re.c b/re.c
index 96a3cbeaa9..3cf99c1210 100644
--- a/re.c
+++ b/re.c
@@ -1666,7 +1666,7 @@ rb_reg_prepare_re(VALUE re, VALUE str)
     RSTRING_GETMEM(unescaped, ptr, len);
 
     /* If there are no other users of this regex, then we can directly overwrite it. */
-    if (RREGEXP(re)->usecnt == 0) {
+    if (ruby_single_main_ractor && RREGEXP(re)->usecnt == 0) {
         regex_t tmp_reg;
         r = onig_new_without_alloc(&tmp_reg, (UChar *)ptr, (UChar *)(ptr + len),
                                    reg->options, enc,
diff --git a/scheduler.c b/scheduler.c
index 80c0278933..11faca01d3 100644
--- a/scheduler.c
+++ b/scheduler.c
@@ -1061,9 +1061,8 @@ VALUE rb_fiber_scheduler_blocking_operation_wait(VALUE scheduler, void* (*functi
     operation->data2 = NULL;
     operation->unblock_function = NULL;
 
-    // If the blocking operation was never executed, return Qundef to signal
-    // the caller to use rb_nogvl instead
-    if (current_status != RB_FIBER_SCHEDULER_BLOCKING_OPERATION_STATUS_COMPLETED) {
+    // If the blocking operation was never executed, return Qundef to signal the caller to use rb_nogvl instead
+    if (current_status == RB_FIBER_SCHEDULER_BLOCKING_OPERATION_STATUS_QUEUED) {
         return Qundef;
     }
 
diff --git a/set.c b/set.c
index ed0ace4224..6dbfd535cf 100644
--- a/set.c
+++ b/set.c
@@ -528,6 +528,7 @@ set_i_initialize_copy(VALUE set, VALUE other)
 
     set_free_embedded(sobj);
     set_copy(&sobj->table, RSET_TABLE(other));
+    rb_gc_writebarrier_remember(set);
 
     return set;
 }
diff --git a/shape.c b/shape.c
index 668850cdd4..a7dff90ce3 100644
--- a/shape.c
+++ b/shape.c
@@ -1391,12 +1391,14 @@ static enum rb_id_table_iterator_result collect_keys_and_values(ID key, VALUE va
 static VALUE edges(VALUE edges)
 {
     VALUE hash = rb_hash_new();
-    if (SINGLE_CHILD_P(edges)) {
-        rb_shape_t *child = SINGLE_CHILD(edges);
-        collect_keys_and_values(child->edge_name, (VALUE)child, &hash);
-    }
-    else {
-        rb_managed_id_table_foreach(edges, collect_keys_and_values, &hash);
+    if (edges) {
+        if (SINGLE_CHILD_P(edges)) {
+            rb_shape_t *child = SINGLE_CHILD(edges);
+            collect_keys_and_values(child->edge_name, (VALUE)child, &hash);
+        }
+        else {
+            rb_managed_id_table_foreach(edges, collect_keys_and_values, &hash);
+        }
     }
     return hash;
 }
diff --git a/spec/ruby/core/file/birthtime_spec.rb b/spec/ruby/core/file/birthtime_spec.rb
index ff43aa7cef..f82eaf7cca 100644
--- a/spec/ruby/core/file/birthtime_spec.rb
+++ b/spec/ruby/core/file/birthtime_spec.rb
@@ -1,6 +1,11 @@
 require_relative '../../spec_helper'
 
 platform_is :windows, :darwin, :freebsd, :netbsd, :linux do
+  not_implemented_messages = [
+    "birthtime() function is unimplemented", # unsupported OS/version
+    "birthtime is unimplemented",            # unsupported filesystem
+  ]
+
   describe "File.birthtime" do
     before :each do
       @file = __FILE__
@@ -14,20 +19,20 @@ platform_is :windows, :darwin, :freebsd, :netbsd, :linux do
       File.birthtime(@file)
       File.birthtime(@file).should be_kind_of(Time)
     rescue NotImplementedError => e
-      skip e.message if e.message.start_with?("birthtime() function")
+      e.message.should.start_with?(*not_implemented_messages)
     end
 
     it "accepts an object that has a #to_path method" do
       File.birthtime(@file) # Avoid to failure of mock object with old Kernel and glibc
       File.birthtime(mock_to_path(@file))
     rescue NotImplementedError => e
-      e.message.should.start_with?("birthtime() function")
+      e.message.should.start_with?(*not_implemented_messages)
     end
 
     it "raises an Errno::ENOENT exception if the file is not found" do
       -> { File.birthtime('bogus') }.should raise_error(Errno::ENOENT)
     rescue NotImplementedError => e
-      e.message.should.start_with?("birthtime() function")
+      e.message.should.start_with?(*not_implemented_messages)
     end
   end
 
@@ -45,7 +50,7 @@ platform_is :windows, :darwin, :freebsd, :netbsd, :linux do
       @file.birthtime
       @file.birthtime.should be_kind_of(Time)
     rescue NotImplementedError => e
-      e.message.should.start_with?("birthtime() function")
+      e.message.should.start_with?(*not_implemented_messages)
     end
   end
 end
diff --git a/spec/ruby/core/file/stat/birthtime_spec.rb b/spec/ruby/core/file/stat/birthtime_spec.rb
index 5350a571aa..adecee15b0 100644
--- a/spec/ruby/core/file/stat/birthtime_spec.rb
+++ b/spec/ruby/core/file/stat/birthtime_spec.rb
@@ -3,6 +3,11 @@ require_relative '../../../spec_helper'
 platform_is(:windows, :darwin, :freebsd, :netbsd,
             *ruby_version_is("3.5") { :linux },
            ) do
+  not_implemented_messages = [
+    "birthtime() function is unimplemented", # unsupported OS/version
+    "birthtime is unimplemented",            # unsupported filesystem
+  ]
+
   describe "File::Stat#birthtime" do
     before :each do
       @file = tmp('i_exist')
@@ -18,7 +23,7 @@ platform_is(:windows, :darwin, :freebsd, :netbsd,
       st.birthtime.should be_kind_of(Time)
       st.birthtime.should <= Time.now
     rescue NotImplementedError => e
-      e.message.should.start_with?("birthtime() function")
+      e.message.should.start_with?(*not_implemented_messages)
     end
   end
 end
diff --git a/spec/ruby/core/kernel/inspect_spec.rb b/spec/ruby/core/kernel/inspect_spec.rb
index 1f9ce834ab..e60f7576c5 100644
--- a/spec/ruby/core/kernel/inspect_spec.rb
+++ b/spec/ruby/core/kernel/inspect_spec.rb
@@ -28,4 +28,34 @@ describe "Kernel#inspect" do
     end
     obj.inspect.should be_kind_of(String)
   end
+
+  ruby_version_is "3.5" do
+    it "calls #instance_variables_to_inspect private method to know which variables to display" do
+      obj = Object.new
+      obj.instance_eval do
+        @host = "localhost"
+        @user = "root"
+        @password = "hunter2"
+      end
+      obj.singleton_class.class_eval do
+        private def instance_variables_to_inspect = %i[@host @user @does_not_exist]
+      end
+
+      inspected = obj.inspect.sub(/^#<Object:0x[0-9a-f]+/, '#<Object:0x00')
+      inspected.should == '#<Object:0x00 @host="localhost", @user="root">'
+
+      obj = Object.new
+      obj.instance_eval do
+        @host = "localhost"
+        @user = "root"
+        @password = "hunter2"
+      end
+      obj.singleton_class.class_eval do
+        private def instance_variables_to_inspect = []
+      end
+
+      inspected = obj.inspect.sub(/^#<Object:0x[0-9a-f]+/, '#<Object:0x00')
+      inspected.should == "#<Object:0x00>"
+    end
+  end
 end
diff --git a/test/ruby/test_object.rb b/test/ruby/test_object.rb
index 7d00422629..9074e54df5 100644
--- a/test/ruby/test_object.rb
+++ b/test/ruby/test_object.rb
@@ -950,6 +950,19 @@ class TestObject < Test::Unit::TestCase
     assert_match(/\bInspect\u{3042}:.* @\u{3044}=42\b/, x.inspect)
     x.instance_variable_set("@\u{3046}".encode(Encoding::EUC_JP), 6)
     assert_match(/@\u{3046}=6\b/, x.inspect)
+
+    x = Object.new
+    x.singleton_class.class_eval do
+      private def instance_variables_to_inspect = [:@host, :@user]
+    end
+
+    x.instance_variable_set(:@host, "localhost")
+    x.instance_variable_set(:@user, "root")
+    x.instance_variable_set(:@password, "hunter2")
+    s = x.inspect
+    assert_include(s, "@host=\"localhost\"")
+    assert_include(s, "@user=\"root\"")
+    assert_not_include(s, "@password=")
   end
 
   def test_singleton_methods
diff --git a/test/ruby/test_set.rb b/test/ruby/test_set.rb
index 2bb7858eb2..3a8568762a 100644
--- a/test/ruby/test_set.rb
+++ b/test/ruby/test_set.rb
@@ -130,6 +130,12 @@ class TC_Set < Test::Unit::TestCase
     assert_equal(Set['a','b','c'], set)
 
     set = Set[1,2]
+    ret = set.replace(Set.new('a'..'c'))
+
+    assert_same(set, ret)
+    assert_equal(Set['a','b','c'], set)
+
+    set = Set[1,2]
     assert_raise(ArgumentError) {
       set.replace(3)
     }
diff --git a/test/ruby/test_zjit.rb b/test/ruby/test_zjit.rb
index 3b64887f92..47a9f6f7dc 100644
--- a/test/ruby/test_zjit.rb
+++ b/test/ruby/test_zjit.rb
@@ -205,6 +205,48 @@ class TestZJIT < Test::Unit::TestCase
     }, insns: [:opt_gt], call_threshold: 2
   end
 
+  def test_opt_empty_p
+    assert_compiles('[false, false, true]', <<~RUBY, insns: [:opt_empty_p])
+      def test(x) = x.empty?
+      return test([1]), test("1"), test({})
+    RUBY
+  end
+
+  def test_opt_succ
+    assert_compiles('[0, "B"]', <<~RUBY, insns: [:opt_succ])
+      def test(obj) = obj.succ
+      return test(-1), test("A")
+    RUBY
+  end
+
+  def test_opt_and
+    assert_compiles('[1, [3, 2, 1]]', <<~RUBY, insns: [:opt_and])
+      def test(x, y) = x & y
+      return test(0b1101, 3), test([3, 2, 1, 4], [8, 1, 2, 3])
+    RUBY
+  end
+
+  def test_opt_or
+    assert_compiles('[11, [3, 2, 1]]', <<~RUBY, insns: [:opt_or])
+      def test(x, y) = x | y
+      return test(0b1000, 3), test([3, 2, 1], [1, 2, 3])
+    RUBY
+  end
+
+  def test_opt_not
+    assert_compiles('[true, true, false]', <<~RUBY, insns: [:opt_not])
+      def test(obj) = !obj
+      return test(nil), test(false), test(0)
+    RUBY
+  end
+
+  def test_opt_regexpmatch2
+    assert_compiles('[1, nil]', <<~RUBY, insns: [:opt_regexpmatch2])
+      def test(haystack) = /needle/ =~ haystack
+      return test("kneedle"), test("")
+    RUBY
+  end
+
   def test_opt_ge
     assert_compiles '[false, true, true]', %q{
       def test(a, b) = a >= b
diff --git a/tool/fetch-bundled_gems.rb b/tool/fetch-bundled_gems.rb
index f50bda360a..b76feefd94 100755
--- a/tool/fetch-bundled_gems.rb
+++ b/tool/fetch-bundled_gems.rb
@@ -24,20 +24,22 @@ next unless n
 next if n =~ /^#/
 next if bundled_gems&.all? {|pat| !File.fnmatch?(pat, n)}
 
-if File.directory?(n)
-  puts "updating #{color.notice(n)} ..."
-  system("git", "fetch", "--all", chdir: n) or abort
-else
+unless File.exist?("#{n}/.git")
   puts "retrieving #{color.notice(n)} ..."
-  system(*%W"git clone #{u} #{n}") or abort
+  system(*%W"git clone --depth=1 --no-tags #{u} #{n}") or abort
 end
 
 if r
   puts "fetching #{color.notice(r)} ..."
   system("git", "fetch", "origin", r, chdir: n) or abort
+  c = r
+else
+  c = ["v#{v}", v].find do |c|
+    puts "fetching #{color.notice(c)} ..."
+    system("git", "fetch", "origin", "refs/tags/#{c}:refs/tags/#{c}", chdir: n)
+  end or abort
 end
 
-c = r || "v#{v}"
 checkout = %w"git -c advice.detachedHead=false checkout"
 print %[checking out #{color.notice(c)} (v=#{color.info(v)}]
 print %[, r=#{color.info(r)}] if r
diff --git a/variable.c b/variable.c
index 6d0e9832e7..a54bebcec0 100644
--- a/variable.c
+++ b/variable.c
@@ -1228,19 +1228,10 @@ gen_fields_tbl_bytes(size_t n)
 }
 
 static struct gen_fields_tbl *
-gen_fields_tbl_resize(struct gen_fields_tbl *old, uint32_t n)
+gen_fields_tbl_resize(struct gen_fields_tbl *old, uint32_t new_capa)
 {
-    RUBY_ASSERT(n > 0);
-
-    uint32_t len = old ? old->as.shape.fields_count : 0;
-    struct gen_fields_tbl *fields_tbl = xrealloc(old, gen_fields_tbl_bytes(n));
-
-    fields_tbl->as.shape.fields_count = n;
-    for (; len < n; len++) {
-        fields_tbl->as.shape.fields[len] = Qundef;
-    }
-
-    return fields_tbl;
+    RUBY_ASSERT(new_capa > 0);
+    return xrealloc(old, gen_fields_tbl_bytes(new_capa));
 }
 
 void
@@ -1253,7 +1244,8 @@ rb_mark_generic_ivar(VALUE obj)
             rb_mark_tbl_no_pin(fields_tbl->as.complex.table);
         }
         else {
-            for (uint32_t i = 0; i < fields_tbl->as.shape.fields_count; i++) {
+            uint32_t fields_count = RSHAPE_LEN(RBASIC_SHAPE_ID(obj));
+            for (uint32_t i = 0; i < fields_count; i++) {
                 rb_gc_mark_movable(fields_tbl->as.shape.fields[i]);
             }
         }
@@ -1290,7 +1282,7 @@ rb_generic_ivar_memsize(VALUE obj)
             return sizeof(struct gen_fields_tbl) + st_memsize(fields_tbl->as.complex.table);
         }
         else {
-            return gen_fields_tbl_bytes(fields_tbl->as.shape.fields_count);
+            return gen_fields_tbl_bytes(RSHAPE_CAPACITY(RBASIC_SHAPE_ID(obj)));
         }
     }
     return 0;
@@ -1299,21 +1291,12 @@ rb_generic_ivar_memsize(VALUE obj)
 static size_t
 gen_fields_tbl_count(VALUE obj, const struct gen_fields_tbl *fields_tbl)
 {
-    uint32_t i;
-    size_t n = 0;
-
     if (rb_shape_obj_too_complex_p(obj)) {
-        n = st_table_size(fields_tbl->as.complex.table);
+        return st_table_size(fields_tbl->as.complex.table);
     }
     else {
-        for (i = 0; i < fields_tbl->as.shape.fields_count; i++) {
-            if (!UNDEF_P(fields_tbl->as.shape.fields[i])) {
-                n++;
-            }
-        }
+        return RSHAPE_LEN(RBASIC_SHAPE_ID(obj));
     }
-
-    return n;
 }
 
 VALUE
diff --git a/variable.h b/variable.h
index a95fcc563d..54b7fc5461 100644
--- a/variable.h
+++ b/variable.h
@@ -15,7 +15,6 @@
 struct gen_fields_tbl {
     union {
         struct {
-            uint32_t fields_count;
             VALUE fields[1];
         } shape;
         struct {
diff --git a/zjit/src/codegen.rs b/zjit/src/codegen.rs
index 0dbe815c71..e32534b283 100644
--- a/zjit/src/codegen.rs
+++ b/zjit/src/codegen.rs
@@ -275,6 +275,8 @@ fn gen_insn(cb: &mut CodeBlock, jit: &mut JITState, asm: &mut Assembler, functio
         Insn::PatchPoint(_) => return Some(()), // For now, rb_zjit_bop_redefined() panics. TODO: leave a patch point and fix rb_zjit_bop_redefined()
         Insn::CCall { cfun, args, name: _, return_type: _, elidable: _ } => gen_ccall(jit, asm, *cfun, args)?,
         Insn::GetIvar { self_val, id, state: _ } => gen_getivar(asm, opnd!(self_val), *id),
+        Insn::SetGlobal { id, val, state: _ } => gen_setglobal(asm, *id, opnd!(val)),
+        Insn::GetGlobal { id, state: _ } => gen_getglobal(asm, *id),
         Insn::SetIvar { self_val, id, val, state: _ } => gen_setivar(asm, opnd!(self_val), *id, opnd!(val)),
         _ => {
             debug!("ZJIT: gen_function: unexpected insn {:?}", insn);
@@ -317,6 +319,24 @@ fn gen_setivar(asm: &mut Assembler, recv: Opnd, id: ID, val: Opnd) -> Opnd {
     )
 }
 
+/// Look up global variables
+fn gen_getglobal(asm: &mut Assembler, id: ID) -> Opnd {
+    asm_comment!(asm, "call rb_gvar_get");
+    asm.ccall(
+        rb_gvar_get as *const u8,
+        vec![Opnd::UImm(id.0)],
+    )
+}
+
+/// Set global variables
+fn gen_setglobal(asm: &mut Assembler, id: ID, val: Opnd) -> Opnd {
+    asm_comment!(asm, "call rb_gvar_set");
+    asm.ccall(
+        rb_gvar_set as *const u8,
+        vec![Opnd::UImm(id.0), val],
+    )
+}
+
 /// Compile an interpreter entry block to be inserted into an ISEQ
 fn gen_entry_prologue(asm: &mut Assembler, iseq: IseqPtr) {
     asm_comment!(asm, "ZJIT entry point: {}", iseq_get_location(iseq, 0));
diff --git a/zjit/src/hir.rs b/zjit/src/hir.rs
index 86e87d72ac..47b961badf 100644
--- a/zjit/src/hir.rs
+++ b/zjit/src/hir.rs
@@ -392,6 +392,11 @@ pub enum Insn {
     Defined { op_type: usize, obj: VALUE, pushval: VALUE, v: InsnId },
     GetConstantPath { ic: *const iseq_inline_constant_cache },
 
+    /// Get a global variable named `id`
+    GetGlobal { id: ID, state: InsnId },
+    /// Set a global variable named `id` to `val`
+    SetGlobal { id: ID, val: InsnId, state: InsnId },
+
     //NewObject?
     /// Get an instance variable `id` from `self_val`
     GetIvar { self_val: InsnId, id: ID, state: InsnId },
@@ -459,7 +464,7 @@ impl Insn {
             Insn::ArraySet { .. } | Insn::Snapshot { .. } | Insn::Jump(_)
             | Insn::IfTrue { .. } | Insn::IfFalse { .. } | Insn::Return { .. }
             | Insn::PatchPoint { .. } | Insn::SetIvar { .. } | Insn::ArrayExtend { .. }
-            | Insn::ArrayPush { .. } | Insn::SideExit { .. } => false,
+            | Insn::ArrayPush { .. } | Insn::SideExit { .. } | Insn::SetGlobal { .. } => false,
             _ => true,
         }
     }
@@ -625,6 +630,8 @@ impl<'a> std::fmt::Display for InsnPrinter<'a> {
             Insn::DefinedIvar { self_val, id, .. } => write!(f, "DefinedIvar {self_val}, :{}", id.contents_lossy().into_owned()),
             Insn::GetIvar { self_val, id, .. } => write!(f, "GetIvar {self_val}, :{}", id.contents_lossy().into_owned()),
             Insn::SetIvar { self_val, id, val, .. } => write!(f, "SetIvar {self_val}, :{}, {val}", id.contents_lossy().into_owned()),
+            Insn::GetGlobal { id, .. } => write!(f, "GetGlobal :{}", id.contents_lossy().into_owned()),
+            Insn::SetGlobal { id, val, .. } => write!(f, "SetGlobal :{}, {val}", id.contents_lossy().into_owned()),
             Insn::ToArray { val, .. } => write!(f, "ToArray {val}"),
             Insn::ToNewArray { val, .. } => write!(f, "ToNewArray {val}"),
             Insn::ArrayExtend { left, right, .. } => write!(f, "ArrayExtend {left}, {right}"),
@@ -982,6 +989,8 @@ impl Function {
             }
             &NewRange { low, high, flag, state } => NewRange { low: find!(low), high: find!(high), flag, state: find!(state) },
             ArrayMax { elements, state } => ArrayMax { elements: find_vec!(*elements), state: find!(*state) },
+            &GetGlobal { id, state } => GetGlobal { id, state },
+            &SetGlobal { id, val, state } => SetGlobal { id, val: find!(val), state },
             &GetIvar { self_val, id, state } => GetIvar { self_val: find!(self_val), id, state },
             &SetIvar { self_val, id, val, state } => SetIvar { self_val: find!(self_val), id, val, state },
             &ToArray { val, state } => ToArray { val: find!(val), state },
@@ -1012,7 +1021,7 @@ impl Function {
         assert!(self.insns[insn.0].has_output());
         match &self.insns[insn.0] {
             Insn::Param { .. } => unimplemented!("params should not be present in block.insns"),
-            Insn::ArraySet { .. } | Insn::Snapshot { .. } | Insn::Jump(_)
+            Insn::SetGlobal { .. } | Insn::ArraySet { .. } | Insn::Snapshot { .. } | Insn::Jump(_)
             | Insn::IfTrue { .. } | Insn::IfFalse { .. } | Insn::Return { .. }
             | Insn::PatchPoint { .. } | Insn::SetIvar { .. } | Insn::ArrayExtend { .. }
             | Insn::ArrayPush { .. } | Insn::SideExit { .. } =>
@@ -1063,6 +1072,7 @@ impl Function {
             Insn::DefinedIvar { .. } => types::BasicObject,
             Insn::GetConstantPath { .. } => types::BasicObject,
             Insn::ArrayMax { .. } => types::BasicObject,
+            Insn::GetGlobal { .. } => types::BasicObject,
             Insn::GetIvar { .. } => types::BasicObject,
             Insn::ToNewArray { .. } => types::ArrayExact,
             Insn::ToArray { .. } => types::ArrayExact,
@@ -1568,7 +1578,8 @@ impl Function {
                 | Insn::Test { val }
                 | Insn::IsNil { val } =>
                     worklist.push_back(val),
-                Insn::GuardType { val, state, .. }
+                Insn::SetGlobal { val, state, .. }
+                | Insn::GuardType { val, state, .. }
                 | Insn::GuardBitEquals { val, state, .. }
                 | Insn::ToArray { val, state }
                 | Insn::ToNewArray { val, state } => {
@@ -1635,6 +1646,7 @@ impl Function {
                     worklist.push_back(val);
                     worklist.push_back(state);
                 }
+                Insn::GetGlobal { state, .. } |
                 Insn::SideExit { state } => worklist.push_back(state),
             }
         }
@@ -2355,6 +2367,10 @@ pub fn iseq_to_hir(iseq: *const rb_iseq_t) -> Result<Function, ParseError> {
                     break;  // Don't enqueue the next block as a successor
                 }
 
+                // These are opt_send_without_block and all the opt_* instructions
+                // specialized to a certain method that could also be serviced
+                // using the general send implementation. The optimizer start from
+                // a general send for all of these later in the pipeline.
                 YARVINSN_opt_nil_p |
                 YARVINSN_opt_plus |
                 YARVINSN_opt_minus |
@@ -2371,6 +2387,12 @@ pub fn iseq_to_hir(iseq: *const rb_iseq_t) -> Result<Function, ParseError> {
                 YARVINSN_opt_length |
                 YARVINSN_opt_size |
                 YARVINSN_opt_aref |
+                YARVINSN_opt_empty_p |
+                YARVINSN_opt_succ |
+                YARVINSN_opt_and |
+                YARVINSN_opt_or |
+                YARVINSN_opt_not |
+                YARVINSN_opt_regexpmatch2 |
                 YARVINSN_opt_send_without_block => {
                     let cd: *const rb_call_data = get_arg(pc, 0).as_ptr();
                     let call_info = unsafe { rb_get_call_data_ci(cd) };
@@ -2425,6 +2447,18 @@ pub fn iseq_to_hir(iseq: *const rb_iseq_t) -> Result<Function, ParseError> {
                     let send = fun.push_insn(block, Insn::Send { self_val: recv, call_info: CallInfo { method_name }, cd, blockiseq, args, state: exit_id });
                     state.stack_push(send);
                 }
+                YARVINSN_getglobal => {
+                    let id = ID(get_arg(pc, 0).as_u64());
+                    let exit_id = fun.push_insn(block, Insn::Snapshot { state: exit_state });
+                    let result = fun.push_insn(block, Insn::GetGlobal { id, state: exit_id });
+                    state.stack_push(result);
+                }
+                YARVINSN_setglobal => {
+                    let id = ID(get_arg(pc, 0).as_u64());
+                    let exit_id = fun.push_insn(block, Insn::Snapshot { state: exit_state });
+                    let val = state.stack_pop()?;
+                    fun.push_insn(block, Insn::SetGlobal { id, val, state: exit_id });
+                }
                 YARVINSN_getinstancevariable => {
                     let id = ID(get_arg(pc, 0).as_u64());
                     // ic is in arg 1
@@ -3702,6 +3736,35 @@ mod tests {
     }
 
     #[test]
+    fn test_setglobal() {
+        eval("
+            def test = $foo = 1
+            test
+        ");
+        assert_method_hir_with_opcode("test", YARVINSN_setglobal, expect![[r#"
+            fn test:
+            bb0(v0:BasicObject):
+              v2:Fixnum[1] = Const Value(1)
+              SetGlobal :$foo, v2
+              Return v2
+        "#]]);
+    }
+
+    #[test]
+    fn test_getglobal() {
+        eval("
+            def test = $foo
+            test
+        ");
+        assert_method_hir_with_opcode("test", YARVINSN_getglobal, expect![[r#"
+            fn test:
+            bb0(v0:BasicObject):
+              v3:BasicObject = GetGlobal :$foo
+              Return v3
+        "#]]);
+    }
+
+    #[test]
     fn test_splatarray_mut() {
         eval("
             def test(a) = [*a]
@@ -3807,6 +3870,84 @@ mod tests {
     }
 
     #[test]
+    fn opt_empty_p() {
+        eval("
+            def test(x) = x.empty?
+        ");
+        assert_method_hir_with_opcode("test", YARVINSN_opt_empty_p, expect![[r#"
+            fn test:
+            bb0(v0:BasicObject, v1:BasicObject):
+              v4:BasicObject = SendWithoutBlock v1, :empty?
+              Return v4
+        "#]]);
+    }
+
+    #[test]
+    fn opt_succ() {
+        eval("
+            def test(x) = x.succ
+        ");
+        assert_method_hir_with_opcode("test", YARVINSN_opt_succ, expect![[r#"
+            fn test:
+            bb0(v0:BasicObject, v1:BasicObject):
+              v4:BasicObject = SendWithoutBlock v1, :succ
+              Return v4
+        "#]]);
+    }
+
+    #[test]
+    fn opt_and() {
+        eval("
+            def test(x, y) = x & y
+        ");
+        assert_method_hir_with_opcode("test", YARVINSN_opt_and, expect![[r#"
+            fn test:
+            bb0(v0:BasicObject, v1:BasicObject, v2:BasicObject):
+              v5:BasicObject = SendWithoutBlock v1, :&, v2
+              Return v5
+        "#]]);
+    }
+
+    #[test]
+    fn opt_or() {
+        eval("
+            def test(x, y) = x | y
+        ");
+        assert_method_hir_with_opcode("test", YARVINSN_opt_or, expect![[r#"
+            fn test:
+            bb0(v0:BasicObject, v1:BasicObject, v2:BasicObject):
+              v5:BasicObject = SendWithoutBlock v1, :|, v2
+              Return v5
+        "#]]);
+    }
+
+    #[test]
+    fn opt_not() {
+        eval("
+            def test(x) = !x
+        ");
+        assert_method_hir_with_opcode("test", YARVINSN_opt_not, expect![[r#"
+            fn test:
+            bb0(v0:BasicObject, v1:BasicObject):
+              v4:BasicObject = SendWithoutBlock v1, :!
+              Return v4
+        "#]]);
+    }
+
+    #[test]
+    fn opt_regexpmatch2() {
+        eval("
+            def test(regexp, matchee) = regexp =~ matchee
+        ");
+        assert_method_hir_with_opcode("test", YARVINSN_opt_regexpmatch2, expect![[r#"
+            fn test:
+            bb0(v0:BasicObject, v1:BasicObject, v2:BasicObject):
+              v5:BasicObject = SendWithoutBlock v1, :=~, v2
+              Return v5
+        "#]]);
+    }
+
+    #[test]
     fn test_branchnil() {
         eval("
         def test(x) = x&.itself